BXAS AGRICULTURAL EXPERIMENT sums 1.51m NO. 28s NOVEMBER, 1921 DIVISION OF CHEMISTRY lation of Soil Nitrogen, Nitrification and * Ammonification to Pot Experiments B. YOUNGBLOOD, DIRECTOR STATION, BRAZOS COUNTY, TEXAQ "i v08 BOBCKMANN-JONEB 00., Pnmmaav, AUSTIN, mus 1921 A154-1121-4M-L STATION STAFFT ADMINISTRATION ENTOMOLOGY B. YOUNGBLOOD, Ph. D.,_Director M. C. TANQUARY, Ph. D., Chief; State CHARLES A. FELKER, Chief Clerk - Entomologist A. S. WARE, Secretary _ _ H. J. REINHARD, B. S., Entomologist A. D. JACKSON, Executive Assistant L. R. WATsoN, A. M., Apiculturist CHARLES GORZYCKI, Technical Assistant C. S. RUDE, B. S., Entomologist M. P. HoLLEMAN, JR., Assistant Chief Clerk IAIEARDZQEHIOIIEIOQéSI . . LEx, ueen ree er VETERINARY SCIENCE AGRQNOMY *M_ F , D_ V_ M” ch" A. B. CoNNER, B. S., Chief; Crops H_ Scififif, D_ v_ S” Vatelrel-{larian A. H. LEIDIGH, B. S., Agronomist,_Soils J. J. REID, D. V. M., Veterinarian E. BGREYNoLns, M. S., Agronomist, Small rains E. GEYER, B. S., Agronomist, Farm Sup. CHEMISTRY mlendml KRAPS, PR/i 1%., ihieflt stgtéhChenltist PLANT PATHOLOGY AND PHYSIOLOGY . . sRuRY, . ., ssis an emis - S. LOMANITZ, B. S., Assistant Chemist J' ‘L TAUBENHAUS’ Ph’ D" Chief J. B. SMITH, B. S., Assistant Chemist COTTON BREEDING G. F. EREEMAN, D. Sc., Chief HORTICULTURE _ FARM AND RANCH ECONOMICS H- NESS» M- 5» Chlef A. B. Cox, Ph. D., Chief W. S. HOTCHKISS, Horticulturist SOIL SURVEY ANIMAL INDUSTRY “g (Pilelgflle Jlg- Chief . _ _ . . A KER, oi _ rveyor '1' Migvzlgltlliziétghivl" Ch'ef' ‘Sheep and Goat H. V. GEIE, B. S., Soil Surveyor R. M. SHERWOOD, B. S., Poultry Husband- FEED CONTROL SERVICE man B. YOUNGBLOOD, Ph. D., Director G. R. WARREN, B. S., Animal Husbandman _ _ _ _ _ F. D. FULLER, M. S., Chief Inspector in charge of Swine, Investigations S. D. PEARCE, Inspector J. L. LUSH, Ph. D., Animal Husbandman ~ J. H. RoGERs, Inspector (genetics) W. H. W001), Inspector SUBSTATIONS No. 1. Beeville, Bee County No. 8. Lubbock, Lubbock County I. E. CowART, M. S., Superintendent R. E. KARPER, B. S., Superintendent No. 2. Troup, Smith County W. S. HOTCHKISS, Superintendent Ne" 9' Peeee“ Reeves Gem“? V. L. CoRY, B. S., Superintendent No. 3. Angleton, BrazoI-ia County V. E. HAENER, B. S., Superintendent No. 10. College Station, Brazos County (Feedmg and Breeding Substatlon) No. 4. Beaumont, Jefferson County L_ J_ MCCALL’ Superintendent A. H. PRINcE, B. S., Superintendent No. ll. Nacogdoches, Nacogdoches County N°' 5' TemPlei Be“ Cmlnt? G. T. McNEss, Superintendent D. T. KILLOUGH, B. S., Superintendent **No. 12. Chillicothe, Hardeman County Ne- e- -D°“'°“' Denm" Cum‘? A. B. CnoN, B. S., Superintendent C. H. McDowELL, B. S., Superintendent No. l4. Sonora, Sutton-Edwards Countiel Ne- 7' SP“- Diekens Ceum?’ E. M. PETERS, B. S., Superintendent B. E. DICKSON, B. S., Superintendent ’ D. H. BENNETT, V. M. D., Veterinarian fAs of Noveinber l, 1921. _ _ *In cooperatgon wIth School of Veterinary Medlcme, A_. and M. College of Texas. **In cooperatlon wIth United States Department of Agriculture. CONTENTS. PAGF Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Method of Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Relation of the Crops to the Total Nitrogen of the Soil . . . . . . . . . . . '7 Relation of the Different Crops. . .\ . . . . . . . . . . . . . . . . . .- . . . . . . . . . . . 8 Relation of Surface Soil to Subsoil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Acid Soils Compared with Non-Acid Soils . . . . . . . . . . . . . . . . . . . . . . . 14 Relation of Composition of Soils to Nitrogen Withdrawn by the Crops 16 Correlation Between the Nitrogen Content of the Soil and the Nitro- gen Taken Up by the Crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Relation of Production of Nitrates to the Results of the Pot EX- periments . . . . . . . . . . . . . . . . . . . . . . . . . . .' . . . . . . . . . . . . . . . . . . . . . 21 Extensive Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~ . . . . . . .. 24 Relation of Nitric Nitrogen to Nitrogen Removed by First Crop. . . . 24 Correlation Between the Amount of Nitrogen Taken Up by the First Crop and the Amount of Nitrogen Available in the Soil. .' . . . . . . . 27‘ Correlation of Soils Grouped by Total Nitrogen . . . . . . . l . . . . . . . . . .' 29 Effects of Cropping Upon Nitrate Production in the Soil . . . . . . . . . . 32 Correlation Between the Nitrogen Removed in Cropping and De- crease in Nitric Nitrogen Made Available in the Soil . . . . . . . . . . . 36 Relation of Nitric Nitrogen Available After Cropping to the Nitrogen Removed by the Third and Fourth Crops . . . . . . . . . . . . . . . .» . . . . . . 36 Correlation Between the Nitrogen Taken Up by the Third Crop and the Nitric Nitrogen Available After Cropping . . . . . . . . . .3 . . . . . .. 38 Production of Ammonia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Preliminary Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Determination of Ammonia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Production of Ammonia Nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Correlation Between Ammonia and Nitric Nitrogen Available in the Soils and the Nitrogen Removed by the First Crop . . . . . . . . . . . . . 43 Irregular Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . = . . . . . 44 Summary and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . l . . 49 BULLETIN No. 283. NOVEMBER, 1921. RELATION OF SOIL NITROGEN, NITRIFICATION AND AMMONIFICATION TO POT EXPERIMENTS BY G. S. FRAPS. V It has been shown in a previous bulletin of this Experiment Station t-(No. 151 of 1912) that the nitrogen withdrawn from the soil by crops tin pot experiments increases, on an average, with the total nitrogen of the soil. Yet it is well known, as pointed out in Bulletin 151, that the fquantity of nitrogen taken from the soil by crops depends, to a con- isiderable extent, upon other factors than the total nitrogen of the soil. iThe object of this bulletin is to study these relations, especially the relation between nitrate formation, or nitrification, and the nitrogen fremoved by‘ crops in pot experiments. p, In Bulletin 151, referred to above, 332 pot experiments were con- sidered. It was found that there was a relation between the number ._' crops found deficient in nitrogen in pot experiments and the total nitrogen of the soil. The weight of the crops grown without nitrogen {added to the soil increased with the nitrogen content of the soil up- to the ggroups .06-.18 per cent., when it remained nearly the same; but the ipercentage of'nitrogen in the crops increased, so that the quantity of itrogen withdrawn by the crops increased with the percentage of nitro- in the soils. The importance of estimating the nitrogen in the props in such work was brought out, since the dry weight of the crop, gconsidered without knowledge of its composition, was misleading. The percentage of totalnitrogen in the soil was thus an average in- Qdication as to the fertility of the soil with respect to nitrogen. When it. sufficient number of soils were tested, the average amount of nitrogen Wthdrawn by crops was in proportion to the total nitrogen of the soil. ‘i his relation may not appear when only a few soils are studied; so the tudy of a large number of soils, as in Bulletin 151, was necessary. f While the above is true on an average, yetthere are soils which de— 'ate decidedly from the average", either above or below, and it is de— "rable to ascertain, if possible, the causes of such deviations in the pot Qxperiments, and devise methods for following them and anticipating hem, if possible. After the soils have been arranged in groups accord- f?“ t0 total nitrogen content, other characteristics may be studied, such relation of surface to subsoil, acidity, and length of time the soil has @- in cultivation. While plants can take up organic nitrogenous compounds (Fraps, rinciples of Agricultural Chemistry, pages 161, 219) as well as nitrates ; d ammonia, it is probable that cultivated plants absorb most of their Ytrogen in the form of ammonia or nitrates, and the importance of “I study of the quantity and formation of nitrates and ammonia is ' enerally recognized. Extensive studies of nitrification and ammonifi- etion are being made from a variety of points of view by a number of orkers. The object of our work is to study the relation between nitri- cation and ammonification and the nitrogen removed from the soil by 6 TEXAS AGRICULTURAL EXPERIMENT STATION. crops in pot experiments, with a view to a method for further separatio of soils with similar total nitrogen content but different nitrogen r .5 sponse to crops. _ » In Bulletin 259 we showed that the average quantity of nitrates p p duced by the method there described increased with the total nitrog of the soil, and, on an average, fairly constant percentages of nitroger? were converted into nitrates during the first twelve weeks. But the, were wide variations in the individual soils; some did not nitrify Q all, while the nitrification of others was much higher than the averag The addition of carbonate of lime to soils which failed to nitrify caus nitrification to take place.’ The nitrification of the organic matter various soils was found to vary from 3.5 to 37 per cent. and the nitri qj ing capacity from 2 to 232. Soils with unusually low nitrification we " mostly subsoils, and those with unusually high nitrification were als mostly subsoils. These and some other details presented in Bullet’? 259 will be further considered in connection with the results presen w; in this bulletin. ! METHOD OF WORK. The method used for the pot experiments is described in Bullet 12'?’ and 145. In this work, pots of 5000 gins. soil were used, and r; ditions of dicalcium phosphate for phosphoric acid and sulphate o potash for potash were made to the soils to be tested for nitrogen =0; ficiency. Pots to which phosphoric acid, potash, and nitrogen as nitra ‘I of ammonia were added, were used for comparison. No allowance w "a made for nitrogen in the seed, which would amount for corn to approxi mately .0225 gm. or 4.5 parts per million of the soil, and for sorgh t‘ .0150 gm. or 3 parts per million. The roots always were left in the po Nitrates were determined in 500-gm. portions of the soils placed i; percolators, and percolated at the beginning of the experiment and eve i four weeks thereafter, usually for twelve weeks, as described in Bullet, 259. The method for ammonia will be described on a later page. i‘ ,3. Table 1. Relation of average of four crops to nitrogen of soil. ‘i ‘Q Average weight » Corn Per gm. per crop Nitrogen Nitrogen Nitrogen possibil- ‘ cent ———-—————-———— per cent per crop per ity of N0. of, nitrogen ' in crops gm. million nitrogen soill . in soil KPN KP per crop per crop Group -1_, Series 13, 0—.020 per cent nitrogen . . . . . . . . . . . . . . . . . . . . . . .015 26.0 6.9 .73 .0463 9.3 12.4 Group 2, Series 9, 14, 15, 26, 31, .021- .040 per cent nitrogen . . . . . . . . . ' .033 25.4 7.4 .72 .0495 10.0 13.3 Group 3, Series 8, 12, 16, 22, 25, 32, 45, . .041—.060 per cent mtrogen. . . . .050 29.8 8.5 .69 .0546 10.9 14.5 Group 4, Series 18, 33, .061—.080 per \ cent nitrogen . . . . . . . . . . . . . . . . . .069 25 .8 8.6 .77 .0635 12. 7 16.9 V Group 5 Series 3, 34, 21, .081-. 100 per cent nitrogen . . . . . . . . . . . . . . . . . .092 32.3 13.2 .74 .0909 18.2 24.3 a Group 6, Series 6, 20, .101-120 per ' K- cent nitrogen . . . . . . . . . . . . . . . .. .111 _ 39.8 16.2 .72 .1205 24.1 32.1 » " Group 7, Series 7, 19, .121—.140 per ’ cent nitrogen . . . . . . . . . . . . . . . .. .131 33.8 13.0 .76 .0978 19.6 26.1 s; Group 8, Series 35, .141-. 160 per cent nitrogen . . . . . . . . . . . . . . . . . . . . .. .152 36.0 17.9 .77 .1483 29.7 39.6 _ _ Group 9, Series 5, over .160 per cent 1 nitrogen . . . . . . . . . . . . . . . . . . . . . . . 194 34.8 21.3 .84 .1973 39.5 52.2 RELATION OF SoIL NITROGEN, Euro, TO Por EXPERIMENTS. 7 l. RELATION OF THE CROPS TO THE TOTAL NITROGEN OF THE SOIL. Table 1 gives the average results of four crops on each soil, the. soils ing arranged according to their nitrogen content. The difference tween the groups is .02 per cent. soil nitrogen. The first group pntains soils with 0 to .02 per cent. soil nitrogen but only four soils are ound in this group. The second group, containing .021 to .04 per "j. oups may be seen in the last column of this table. l. The average crops with the complete fertilizer, KPN, are less for H soils containing less than .08 per cent. nitrogen (Groups 1 to 4) ' n they are for the soils containing more than this amount of nitro- The soils containing more than .08 per cent. nitrogen seem to y<- on an average, better adapted to the production of larger crops, en though all receive a complete fertilizer. I‘ The average weight of the crops which receive phosphoric acid and tash, but no nitrogen, increases with the percentage of nitrogen in g.- soils, with the exception of Group '7, containing .12-.14 per cent. “trogen, and including 12 soils. The difierence between Group 3, ntaining .041-.060 per cent. nitrogen and Group 4 (.061-.08) is not r‘ eat. . The average per cent. of nitrogen in the four crops is somewhat riable, although it is highest with Group 9, containing the largest lrcentage of nitrogen in the soil. The average weight of nitrogen removed by the four crops increases 'th the percentage of nitrogen in the soil, with the excep-tion of roup 7, containing .121-.140 per cent. nitrogen. The nitrogen re- oved per million of soil per crop increases in the same way, as it is _erely the same figures expressed in a different way. This also refers J the corn possibility of the nitrogen per crop. This is the amount corn which could be grown on two million pounds of the soil, if it ed all of the nitrogen removed by these crops to advantage, and used .5 pounds nitrogen for a bushel of corn. The corn possibility varies om 12.4 to 52.2 bushels per two million pounds of soil, which is the eight of an acre to the depth of about 7 inches. Table 2. Relation of average crops to nitrogen of soil, compared with previous work. Corn possibility I Gm. nitrogen Parts per million bushels per Number of per crop per crop 2,000,000 lbs. soils Bull. This Bull. This Bull. This Bull This 151 work 151 work 151 work 151 work 1. Nitrogen in soil 0—.O20 .0284 .0463 5.7 9.3 8 12.4 9 - 4 2. Nitrogen in soil .021-.040 .0471 .0495 9.4 10.0 12 13.3 17 55 3. Nitrogen in soil .041—.060 .0681 .0546 13.6 10.9 18 14.5 27 54 4. Nitrogen in soil .061—.080 .1207 .0635 24.1 12.7 32 16.9 13 30 5. Nitrogen in soil .081—. 100 .0995 .0909 19.9 18.2 26 24.3 12 23 6. Nitrogen in soil .101—.120 .0991 .1205 19.8 24.1 26 32.1 5 9 7. Nitrogen in soil . 121-. 140 . 1404 .0978 28.1 19.6 37 26.1 9 12 8. Nitrogen in soil .141—. 160 .1183 .1483 23.7 29.7 31 39.6 7 7 9. Nitrogen in soil .161 up. . . . . . . . . . . .1973 . . . . . . . . 39.6 . . . . . . . . 52.2 . . . . . . . . 8 9. Nitrogen in soil .161 to .180 . . . . . . . . . . . . . . . . . . . . . . . .. .2145 . . . . . . .. 42.9 56 . . . . . . .. 3 . . . . . . .. 10. Nitrogen in soil .181-.200 .4170 . . . . . . . . 83.4 . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . 11. Nitrogen in soil .221 up... .2995 . . . . . . .. 59.9 ... . . . . . . . . . . . . . . . . . . . .. 2 . . . . . . . . ‘nt. nitrogen, contains 55 soils. The number of soils in the other- reported. The results of Groups 2, 3, and 5 are much closer. " and the last. This causes larger differences between the nitrogen . 8 TEXAS AGRICULTURAL EXPERIMENT STATION. Table 2 compares the average results of this work with previo work published in Bulletin 151. As could be expected, the ave quantities of nitrogen withdrawn per crop are not identical with u,“ published in the previous bulletin" for all crops. The amount >7‘ drawn by Group 1, containing .021—.040 per cent. nitrogen is mud less in the results published in Bulletin 151 than for the work Nitrogen removed in parts per million of the soil is a different w, of expressing the grams nitrogen removed per crop, and the corn I._ sibility in bushels per two million pounds of soil. When the corn‘ p‘ sibilities are compared, comparatively close agreement is noted wi Groups 2, 3, 5, 6, 8, and 9. It is, of course, impossible to expect 1w agreement. 1 These results confirm the conclusions in Bulletin 151, that the .5,‘ age size of thecrop, and the nitrogen withdrawn from the soil in i‘; experiments, increases with the total nitrogen of the soil. a a RELATION or THE D1FFERENT CROPS. The average results of the first crops (corn) are given in Table 5 If this table is compared with Table 1, it is seen that the first c ' is much larger than the average crop. In Group 1 the weight of first crop- without nitrogen is nearly three times that of the aver crop. These differences are smaller with the succeeding groupsf that Group 9 is only 50 per cent. larger than the average. There =1 also wide differences in the percentage of nitrogen in the crops. A average nitrogen content is smallest with the first " group and larg‘ with the last group, and increases almost regularly between the fi moved by the crops, whether expressed in weight of nitrogen, or pa per million of soil, than between the weights of the crop-s. While weight of the first crop in Group 9 is only 50 per cent. more than ' average, the amountof nitrogen withdrawn by the crop is more 1:5 twice the average. t. i Table 3. Average relation of the first crop, corn, to the soil nitrogen. Per cent Weight Weight nitrogen Weight Nitrogen KPN KP in KP nitrogen parts per crop gm. crop gm. crop gm. million Group 1. 0—.020 nitrogen . . . . . . . . . . . . . 25.0 19.3 .57 .1200 24.0 Group 2.- .021—.040 nitrogen . . . . . . . . . . . . . 36.4 18.0 .62 0.1136 22.7 Group 3. .041—.060 nitrogen . . . . . . . . . . . . . 37.3 19.8 .59 0.1190 23.8 Group 4. .061-.080 nitrogen . . . . . . . . . . . . . 27.9 17 .9 .87 0.1340 26.8 Group 5. .081—. 100 nitrogen . . . . . . . . . . . . . 33.6 25.0 .89 0.2055 41.1 Group 6. . 101-. 120 nitrogen . . . . . . . . . . . . . 37.1 26.9 .96 0.2505 50.1 Group 7. . 12l—.140 nitrogen . . . . . . . . . . . . . 36.5 24.3 ' .86 0.1994 39.9 Group 8. .141—. 160 nitrogen . . . . . . .' . . . . . . 39.3 33.2 .95 0.3200 64.0 Group 9. Over .160 nitrogen . . . . . . . . . . . . . 34.3 33.9 1.32 0.4407 88.1 The averages of the first crops without fertilizer do not increase =, regularly with the soil nitrogen as the averages of four crops. r is the case also with the nitrogen taken up by the crop, although n‘ relation in this case is more regular. The average weights of the fi RELATION or SoIL NITROGEN, Ere, T0 Por EXPERIMENTS. 9 rops without nitrogen, and the nitrogen withdrawn by the first crops, {are not in as close relation to the average nitrogen of the soil as is the ‘average of four crops. - The ratio of the crop with the complete fertilizer to the crop with phosphoric acid and potash only is given in the last column. Group- 1 9's out of relation t0 the others. With Group 2, the weight of the crop .ithout nitrogen is 49.5 per cent. of the weight of the crop with the j omplete fertilizer. This ratio decreases almost regularly with the ther groups until in the last group (Group 9) the crop without nitro- Ten is 98.8 per cent. of the crop with complete fertilizer. Table 4. Average relation of the second crop, sorghum, to the soil nitrogen Per cent Weight Weight nitrogen Weight Nitrogen Ratio KPN KP in KP nitrogen parts per KPN:PK crop gm. crop gm. crop gm. million 100 to a "u, "L, " ‘ p 1. 0—.020 nitrogen . . . . . . . . . . . . . 20.1 2.6 .87 .0250 5.0 _ 12.9 ¢ p2. .021—.040 nitrogen . . . . . . . . . . . .. 24.6 3.9 .85 0.0357 7.0 15.9 v _p 3. .041—.060 nitrogen . . . . . . . . . . . .. 26.9 4.0 .79 0.0313 6.3 14.9 -- p 4. .061—.080 nitrogen . . . . . . . . . . . .. 25.1 5.8 .87 0.0477 9.5 23.1 r I p 5. .081—.100 nitrogen . . . . . . . . . . . . . 27.6 13.0 .86 0.0701 14.0 47.1 - I p 6. .101—.120 nitrogen . . . . . . . . . . . . . 35.6 12.1 .68 0.0758 15.2 34.0 n 7. .121—.140 nitrogen . . . . . . . . . . . .. 29.1 10.9 .83 0.0866 17.3 37.5 r - p 8. .141—. 160 mtrogen . . . . . . . . . . . .. 35.4 13.8 .83 .1227 24.5 39.0 - p 9. Over .160 nitrogen . . . . . . . . . . . .. _ 39.7 23.3 .69 0.1517 30.3 58.7 Q Table 4 gives the average results of the second crop, which was sor- hum. The average weights with complete fertilizer in the first five oups were decidedly below those of the last four. The weights of he crop-s without nitrogen are below the average of four crops. The .y'f‘ference is greatest with the first three groups, which are less than walf the average of four crops. With the other groups, the differences re not so great. The differences between the first crop and the second rop are quite large. With soils containing from 0 to 0.020 per cent. itrogen, thesecond crop is about one-seventh of the first crop-. With In soils containing the greatest amount of nitrogen, Group 9, the g: crop is about two-thirds of the first crop. imilar differences are observed when the weights of nitrogen re- ces are not the same, however. In Group 1 the nitrogen removed Vy the second crop is one-fourth of the first, while the weight of the op is one-seventh. With Group 9, the amount of nitrogen removed y the second crop is one-third of the first, but the weight of dry atter is two-thirds of the first crop. i The ratios of the crops with comp-lete fertilizer to crops with no trogen are wider for the second crops than for the first. While the , st crop in Group 2 (.021-.040 per cent. soil nitrogen) averages 49.5 ily 15.9 per cent. While the first crop in Group 9, containing over 6 per cent. nitrogen, is 98.8 per cent. of the crop- with the complete rtilizer, the ratio of second crop is only 58.7. j There is thus a decided falling off from the first crop to the second i p, both in the amount of the crop and the amount of nitrogen taken oved, or nitrogen in parts per million are compared- These diifer- a ‘- cent. of the crop with complete fertilizer, the second crop averages * 10 TEXAS AGRICULTURAL EXPERIMENT STATION. from the ‘soil. The average relations between the total nitrogen of the soil and the nitrogen removed by the crops are closer for the second crops than for the first crops. The growth of the first crop apparently removes the" more available nitrogen and this varies in soils containing the same total nitrogen. After the more available nitrogen has been removed by the first crop, the average nitrogen removed by the second crop is more nearly in proportion to the total nitrogen of the soil‘. 80 i-awrnye crop j- crop EZED-Jifivro, 70 mndmrmp . I‘ 5,, n, 1 § a fi . 5:0 K 3’. .540 8~ \ Q30 s Q u 5” T‘: 10 a -;I 1;. §‘ o, . . :1 .5» O ~02 .04- .06 .08 J0 .12 Per emf mrrvg en in soul Figure 1—Relation of nitrogen in soil to nitrogen removed by crops. This seems to be the explanation for the difierences between them two crops. It is quite possible that drying the soil and otherwise pre- paring it in the laboratory has rendered part of the soil nitrogen mor active, and enabled it to produce a larger first crop than would ha ‘ been the case had the soil been placed in the pot in a damp conditi” as it was taken from the field. There is evidence from other investi- 7 gations that this may be the case. Table 5. Average relation of the third crop, corn, to the soil nitrogen. Per cent Weight Weight nitrogen Weight Nitrogen Ratio KPN KP 1n KP nitrogen parts per KPN:PK crop gm. crop gm. crop gm. million 100 to _ Arrangement Group 1. 0—.020 nitrogen . . . . . . . . . . . . . 33.0 3.6 - 63 .0222 4.4 10.9 Group 2. .02l—.040 nitrogen . . . . . . . . . . . . . 32.2 4.8 58 0.0276 5.5 14.9 Group 3. .041—.060 nitrogen . . . . . . . . . . . . . 34.4 6.9 58 0.0397 7 .9 20.1 Group 4. .061-.080 nitrogen . . . . . . . . . . . . . 29.7 7. 3 61 0.0468 9.4 24.6 Group 5. .081-. 100 nitrogen . . . . . . . . . . . . . 36.9 8.6 58 0.0498 10.0 23.3 Group 6. . 101-. 120 nitrogen . . . . . . . . . . . . . 45.9 11.1 52 0.0567 11.3 24.2 Group 7. .121-.140 nitrogen; . . . . . . . . . . . . 37.3 11.8 58 0.0698 14.0 31.6 Group 8. .141—.160 nitrogen . . . . . . . . . . . . . 36.8 15.4 59 0.0878 17.6 41.8 Group 9. Over .160 nitrogen . . . . . . . . . . . . . 37.5 15.8 64 .1130 22.6 42.1 RELATION or SorL NITROGEN, Ere, TO P01‘ EXPERIMENTS. 11 Table 6. Average relation of the fourth crop, sorghum, to the soil nitrogen. - Per cent _ . Weight Weight nitrogen Weight Nitrogen Ratio KPN KP in KP nitrogen parts per KPN:PK crop gm. crop gm. crop gm. million 100 to Group 1. 0—.020 nitrogen . . . . . . ..?. . .. 26.2 2.2 86 .0180 3.6 8.4 Group 2. .021—.040 nitrogen . . . . . . . . . . . . . 18.7 2.8 81 0.0211 4.2 15.0 Group 3. .041—.060 nitrogen . . . . . . . . . . . . . 20.6 3.2 81 0.0283 5.7 15.5 Group 4. .061-.080 nitrogen . . . . . . . . . . . . . 20.4 3.6 73 0.0253 5.1 17.6 Group 5. .081—. 100 nitrogen . . . . . . . . . . . . . 31.1 6.2 61 0.0383 7.7 19.9 Group 6. .101—.120 nitrogen . . . . . . . . . . . . . 40.4 14.6 70 0.0989 19.8 36.1 Group 7. .121—.140 nitrogen . . . . . . . . . . . . . 32.1 4.9 78 0.0354 7.0 15.3 Group 8. .141-. 160 nitrogen . . . . . . . . . . . . . 32.3 9.1 69 0.0626 12.5 28.2 Group 9. Over .160 nitrogen . . . . . . . . . . . . . 27.8 12.2 72 0.0837 16.7 43.9 Tables 5 and 6 contain the results of the third crop of corn and the fourth crop of sorghum. In the first four groups, the Weights of the third corn crop are larger than the weights of the second sorghum crop, but the plants contain smaller percentages of nitrogen, so that the amount of nitrogen taken up is less for the third crop of corn than for the second crop of sorghum. With the last five groups, the weight of the corn crop averages less than the weight of the second sorghum crop, and the amount of nitrogen removed is decidedly less for the third crop of corn than for the second crop of sorghum. The differ- ences between the second crop and the third crop are much less than the differences between the first crop and the second crop. The weights of the fourth crop of sorghum are less than the Weights of the second crop of sorghum, or the third crop of corn. Here again the differences are not as great as between the first and second crops. Table 7. Comparison of four crops, (first crop 100), grown on soils grouped by nitrogen content. Weight of PK crops Nitrogen in crops Ratio KPN:KP Crop Crop Crop Crop Crop Crop Crop Crop Crop Crop Crop 1 2 3 4 2 3 4 1 2 t 3 4 Arrangement. .0—.020 nitrogen.... 100 13.5 18.7 11.4 20.8 18.5 15.0 77.2 12.9 10.9 8.4 .021—.040 nitrogen...- 100 21.7 26.7 15.6 31.4 24.3 18.6 49.5 15.9 14.9 15.0 .041—.060nitrogen.... 100 20.2 34.8 16.2 26.3 33.3 23.8 53.1 14.9 20.1 15.5 .061-.080 nitrogen... 100 32.4 40.8 20.1 35.6 34.9 18.9 64.2 23.1 24.6 17.6 .081-. 0nitrogen.... 100 52.0 34.4 24.8 34.1 24.2 18.6 74.4 47.1 23.3 19.9 .101—.10nitrogen... 100 45.0 41.3 54.3 30.3 22.6 39.5 72.5 34.0 24.2 36.1 .121—.140nitrogen.... 100 44.9 48.6 20.2 43.4 35.0 17.8 66.6 37.5 31.6 15.3 . .141—.160 nitrogen... 100 41.6 46.4 27.4 38.3 27.4 19.6 84.5 39.0 41.8 28.2 Group 9. .161—.180nitrogen....\ 100 68.7 46.6 36.0 34.4 25.6 19.0 98.8 58.7 42.1 43.9 Table '7 contains a comparison of the four crops and gives the weights of the crops without nitrogen, the nitrogen in the crops compared with the first crop as 100, and the ratio of the crops with the complete fer- tilizer to the crops without nitrogen. This table brings out clearly the relation between the first crops and the succeeding crops. The weights of the second crop of Group 1 is only 13.5 per cent. of the first crop, and the fourth crop is 11.4 per cent. of the first crop, while for Group 9, the second crop is 68.7 per cent of the first crop and the fourth crop is 36 per cent of the first crop. The diiferences are not so great when the nitrogen in the crops is considered. The nitrogen of the second crop of Group 1 is 20 per cent. of the first crop, while that of Group 9 is 34.4 per cent. The nitrogen removed by the fourth 12 TExAs AGRICULTURAL EXPERIMENT STATION. crop of Group 1 is 15 per cent. of that removed by the first crop, an that of Group 9 is 19 per cent. ' It is evident. that different conclusions may be drawp concerni i the deficiency of soils for nitrogen in pot experiments depending whether only one crop is considered, or whether the averages of seve successive crops are taken. If one crop only is considered, the will seem to give larger crops and yield greater quantities of nitrog». than if several crops are grown. 3- To illustrate further: the four soils containing 0 to 0.020 per cen? nitrogen of Group 1 gave up in the first crop, on an average, 24 pa “A nitrogen per million of soil, which is equivalent to 32 bushels of co j; to the acre of two million pounds. The average corn possibility HE. four crops is 12.4 bushels, while the corn possibility of the second cro would only be 6.7 bushels per two million pounds. The soils of Grou 9, containing over .16 per cent. nitrogen, gave up 88 parts per millio to the first crop, equal to a corn possibility of 117 bushels; the c0 1S. possibility for the average of four crops is 52 bushels and that for th second crop is 40 bushels. This is for an acre of soil about '7 inche ‘ deep. It would be twice this for 14 inches of soil, and three -.:~,. this for 21 inches of soil. \ ‘i A soil may appear deficient in nitrogen in pot experiments and ye not appear deficient in the field. The requirements of the crop in =,_ pot experiments may exceed the field possibility, limited by soil deptr or by moisture, soil condition, insect pests, or other circumstances. , Any conclusion as to the need of these soils for nitrogen would; therefore, vary to some extent with the number of crops considered; In our opinion, the results of the first crop are better than the pro-l duction of the various soils in the field would justify. The results}, of the second crop are probably lower, on account of the high quantities 2N of nitrogen withdrawn by the first crop-. ‘f Another fact brought out in this work is the importance of esti-s mating the amount of nitrogen in the crops in work of this kind, and of basing the opinion of the results of the pot experiment upon the, amount of nitrogen taken out, and not upon the total weight of th- dry matter. This is best illustrated by some individual tests, wh' are accordingly given in Table 8. It is seen from the examination g; this table that crops nearly the same weight of dry matter may vary decidedly in content of nitrogen, and therefore in the amount of nitrogen withdrawn from the soil. Table 8. Variation of nitrogen in certain crops. - l, Weight Weight Per cent Grams Nitrogen KPN KP nitrogen nitrogen per million ‘ " crop gms crop gms. in crop in crop by the crop 4; Soil 875, first crop, corn . . . . . . . . . . . . . . . . . . . 15.9 19.6 2.66 .5214 104.3 a Soil 875, second crop, sorghum . . . . . . . . . . . . . 32. 6 20. 7 0. 53 .1097 21.9 Soil 877, first crop, corn . . . . . . . . . . . . . . . . . . . 11.8 10.0 2.42 .2420 48.4 Soil 877, third crop, corn . . . . . . . . . . . . . . . . . . 20.9 13.4 0. 71 .0951 19.2 Soil 879, first crop, corn . . . . . . . . . . . . . . . . . . . 11.9 20.5 1.56 .3190 63.9 Soil 879, third crop, corn . . . . . . . . . . . . . . . . . . 46.3 3.4 0.59 .0201 4.0 Soil 897, first crop, corn . . . . . . . . . . . . . . . . . . . 48.9 33.5 0.59 .1976 39.5 Soil 962, first crop, corn . . . . . . . . . . . . . . . . . . . 14.7 21.5 1.12 .2408 48.2 Soil 962, third crop, corn . . . . . . . . . . . . . . . . . . 15.6 4.5 0.54 .0243 4.9 Soil 1056, first crop, corn . . . . . . . . . . . . . . . . . . . 47.4 38.9 0.66 .2567 51.3 Soil 3334, first crop, corn . . . . . . . . . . . . . . . . . . . 42.9 20.5 0.41 .0841 16.8 Soil 7613, first crop, corn . . . . . . . . . . . . . . . . . . . 32.1 13.1 2.00 .2620 52.4 l RELATION or Son. NITROGEN, Era, T0 Por EXlPERIMENTS. 13 YWith soil 8'75, the first and second crops are nearly the same in eight, butthe nitrogen is 104.3 and 21.9 parts per million. The _l- t crop of _corn on soil 8'77 weighs less than the third crop, but the t crop removed over twice as much nitrogen. The first crop on 3334 is much larger than on soil 7613, but three times as much ‘trogen is removed by the crop from soil 7613. Table 9. Relation between total nitrogen in soil and that removed by four crops. Per cent Per million Per cent nitrogen removed by of soil in soil four crops mtrogen removed p 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .015 37.2 25 p 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .033 40.0 12 p 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .050 43.6 9 p 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .069 50.8 7 p 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .092 72.8 8 p 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .111 96.4 9 . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .131 78.4 6 p 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .152 108.8 7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . - . . . . . . . . . . . . . . . . . . . . . .. .194 158.0 8 Table 9 shows the relation between the average percentage of nitro- gen in the soil, the parts per million of nitrogen removed by four rops, and the percentage of soil nitrogen removed by the first crop. 5 he four crops removed 25 per, cent. of the total nitrogen present in the first group of soils and 12 per cent. of the total nitrogen present ‘in the second group of soils. These quantities are evidently unusually "high, but the nitrogen in the seed (3 to 4.5 parts per million per crop) uld account for part of this nitrogen. With the other groups, the nitro- gen removed by the four crops is 6 to 9 per cent. of the total nitrogen of the soil. The amount of nitrogen given up to a single crop would ‘thus average 1% to 2 per cent. of total nitrogen of the soil, but might fr much larger when the soil is first placed under cultivation. RELATION OF SURFACE SOIL TO SUBSOIL. y, Table 10 contains a comparison of the surface soils and the subsoils ,- groups. The weight of the first crop without nitrogen, the weight of the second crop without nitrogen, the average weight of all crop-s ithout nitrogen, and the average nitrogen removed per ’million by all crops are given. In almost every group the surface soils produce on- an average better than the subsoils. In some cases the differences are small but in other cases the differences are quite large. Group 6 the only apparent exception, but only one subsoil is present in this group. On an average the nitrogen of surface soils is better taken up by the crops than the nitrogen of subsoils. " O 14 TEXAS AGRICULTURAL EXPERIMENT STATION. Table 10. Surface soils and subsoils. Surface _ Subsoil soil’ ' ‘f; Group 1. 0—.020 Nitrogen. ' ‘ _Number of ‘soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . “ 0 4 Group 2. .021—.040 Nitrogen. _ , Number of S01lS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 32 First crop KD gm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ._ . . . . . .. 20.8 15.8 Second crop KD gm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 2.9 Average all crops KD gm . . . . . . . . . . . . . . . . . . . . . . . ¢ . . . . . . . . .. 9.0 5.8 Nitrogen per million—_average all crops . . . . . . . . . . . . . . . . . . . . . . 11.03 8. 63 Group 3. .041—,060 Nitrogen. Number of soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 17 First crop KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.8 17.7 Second crop KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 3.3 Average all crops KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9. 1 8.0 Nitrogen per million——average all crops . . . . . . . . . . . . . . . . . . . . . . . 11.41 9.99 Group 4. .061—.080 Nitrogen. ' Number of soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 22 First crop KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22. 1 16.0 Second crop KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1 5.1 Average all crops KD. . . . . _. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 10.9 7.8 Nitrogen per million-average all crops . . . . . . . . . . . . . . . . . . . . . . 12.73 13.04 Group 5. .081—.100 Nitrogen. _ umber "of soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 15 First crop KD . . . . . . . . . . . . . I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.1 23.9 Second crop KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.5 6.1 , Average all crops KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.8 15.3 Nitrogen per million—average all crops . . . . . . . . . . . . . . . . . . . . . . . 19.45 17.49 Group 6. .101—.120 Nitrogen. Number of soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 1 First crop KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.0 29.9 Second crop KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.0 5.0 Average all crops KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.6 18.8 Nitrogen per million-average all crops . . . . . . . . . . . . . . . . . . . . . . 20.98 22.78 Group 7. .121—.140 Nitrogen. Number of soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2 First crop KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.4 13.7 Second crop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.5 4.0 Average all crops KD . . . . . . . . . . . . . . . ; . . . . . . . . . . . . . . . . . . . . . . 14. 1 6.8 ~ Nitrogen per million—average all crops . . . . . . . . . . . . . . . . . . . . . . 21.22 10.57 Group 8. .141—.160 Nitrogen. Number of soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2 First crop KD . . . . ..' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 34.9 28.9 Second crop KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.1 10.5 Average all crops KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18. 3 15.7 a Nitrogen per million—average all crops . . . . . . . . . . . . . . . . . . . . . . 32.80 20.63 Group 9. Over .160 Nitrogen. ‘ » Number of soils . . . . . . . . . . . . . . . . . . . . . . . . . . . ; . . . . . . . . . . . . . . . 7 . 1 First crop KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34.9 26.7 Second crop KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.3 9.0 Average all crops KD . . . . . . . . . . . . . . . . . . . . . . . . . .- . . . . . . . . . . . . 21.0 12.2 Nitrogen per million—average all crops . . . . . . . . . . . . . . . . . . . . . . 39.05 18.58 Average by groups-First crop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 .0 21.6 l! Second crop-.." . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 11.6 5.7 Average all crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.2 11.3 Nitrogen per million. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.1 15.21 ACID SOILS COMPARED WITH NON-ACID SOILS. Table 11 contains a comparison of acid soils and non-acid soils. The acidity Was determined by the Veitch method. In some groups the results are decidedly in favor of the non-acid soils; in other cases there is little difference, and in others the acid soils produce better. In about half the groups the non-acid soils do better, and in about the a other half there is little or no difference, or the acid soils do better. Some of the groups do not contain enough of the two kinds of the soils l to make satisfactory averages. On an average by groups, the non- acid soils produce better than the acid soils. RELATION OF SoIL NITROGEN, Ecru, TO PoT EXPERIMENTS. .15- Table 11. Comparison of acid and non-acid soils. Acid soil Non-acid SO 0-.020 Nitrogen. Number of soils . . . . . . . . . . . . . . . r . . . . . . . . . . . . . . . . . . . . . . . . . . . First crop KD gm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Second crop KD gm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Average all crops KD gm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nitrogen per million——average of all crops . . . . . . . . . . . . . . . . . . . . Subsoils .021—.040 Nitrogen. Number of soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . First crop KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Second crop KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Average all crops KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nitrogen per million-——average all crops . . . . . . . . . . . . . . . . . . . . . . Subsoils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .041—.060 Nitrogen. Number of soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . First crop KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Second crop KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Average all crops KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nitrogen per million—average all crops . . . . . . . . . . . . . . . . . . . . . . .061—080 Nitrogen. Number of soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . First crop KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Second crop KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Average all crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nitrogen per million-average all crops . . . . . . . . . . . . . . . . . . . . . . Subsoils . . . . . . . . .' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .081-. 100 Nitrogen. Number of soils . . . . . . . . . . . . . . . . . . . . . . . . ., . . . . . . . . . . . . . . . . . . First crop KD . . . . . . . . . . . . . . . . . . . . . . . . .1 . . . . . . . . . . . . . . . . . . . Second crop KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Average all crops KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nitrogen per million—average all crops . . . . . . . . . . . . . . . . . . . . . . ubso' .101-.120 Nitrogen. Number of soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . _ . . . . . . . . . . . First crop KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Second crop KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Average all crops KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nitrogen per milli0n—average all crops. . . . . . . . . . . . . . . . . . . . . . Subsoils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .121-.140 Nitrogen. Number of soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . First crop KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Second crop KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Average all crops KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . _ Nitrogen per million—average all crops . . . . . . . . . . . . . . . . . . . . . . Subsoils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .141-.160 Nitrogen. Number of soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ., . . . . . . . . . . Group 1. '~'|® o @ OOUI~I@ "J - - - - - . - - - - - - . . - . - . . . . . . - - - - - . . . . . - . . . . . - - ¢ - - . - Group 6. mawm * . Qcow o Group 7. qwwm w l-il-ll-‘b? @i-*i-5C)3 l-ll-‘ifi B:& l-il-l & Q w@pppm wpgggq wggggw wwmazm 3m»§$ $5Q»§§ wguwgw ghma ... .... .... Group 8. midi-no v-u-u-nté L0H n-A ' o omwwu» cwpqgm wqggmw wwumgm §m»§w Eqmmza ~mm~§~ First crop KD. . . . .- . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Second crop KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Average all crops_KD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . - .0 Nitrogen per million-average all crops . . . . . . . . . . . . . . . . . . . . . . . . Over .160 Nitrogen. _ _ Number of soils . . . . . . . . . . . . . . . . . . . .- . . . . . . . . . . . . . . . . . . . . . . . Group 9. Average by groups. First crop KD. gm . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Second crop KD gm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Average all crops KD gm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nitrogen per million—average all crops . . . . . . . . . . . . . . . . . . . . . In considering the effect of the acidity on the crop growth it is difficult t0 tell how much of this effect is due to being a subsoil and how much is due to acidity. The acidity may be one of the characters of the subsoil which decrease the growth compared with the surface soil. For this reason all of the acid soils in Groups 2, 3, and 4 were grouped into surface soils and subsoils. The averages are given 1n a Table 12. These are all acid soils. 16 p TEXAS AGRICULTURAL EXPERIMENT STATION. Table 12. Comparison of acid subsoils and acid surface soils. . Nitrogen First Second Average per million Number Per cent crop gm. crop gm. all crops average averaged nitrogen KD KD gm. all crops KD Group 2. . . . . . . . . . . . . . . . . . . . . . .. 10 .034 18.0 2.0 5.9 7.45 soil . . . . . . . . . . . . . . . . . . .. 3 .035 17.0 3.6 7.0’ 7.76 Group 3. ..................... .. 5 .046 20.2 3.4 7.6 13.23 soil . . . . . . . . . . . . . . . . . . .. 6 .042 18.8 4.8 8.5 9.17 Group4. . . . . . . . . . . . . . . . . . . . . . .. 3 .067 13.0 1.3 4.4 4.55 soil . . . . . . . . . . . . . . . . . . .. 3 .068 25.4 7.2 10.7 14.66 When the first crop is considered, the surface soil averages decidedly better than the subsoil with one group; a little better with another; and not as well with a third. When the second crop is considered, the surface soils average better than the subsoils in all three groups. With the average of all crops, the surface soils average better than the subsoils in all groups. When the nitrogen removed is considered, the surface soil is decidedly better than the subsoil in one group, there is little difference in another group, and the subsoil is better than the surface soil in the other group. c These averages are not at all conclusive. While the surface soils seem to give up nitrogen better than the subsoils on an average, and non-acid soils average better than acid soils, yet subsoils are erratic, and some may be much better than the corresponding surface soil, while others may be much poorer. RELATION OF COMPOSITION OF SOILS TO NITROGEN WITHDRAWN BY THE - ' CROPS. Table 13 shows the average relation of the chemical composition of the soils to the nitrogen withdrawn from four crops. The soils are arrangedin groups according to the amount of nitrogen taken up by the four crops grown on them. For example, Group 1 contains soils which yield less than .030 gm. nitrogen to the four crops. Group 2 contains soils which yield .0301-.0490 gm. nitrogen to four crops. Table 13. Average relation of composition of soil to nitrogen withdrawn by four crops. Gm. KD Gm. N i a _ a E crop crop a 3 g :3 3 ~'-"~ 8 F ° ° 5 3 a a s J5 w *3 a - .5 a 2 "r. g ‘i c, is? s Group Limits Z c,‘ i Q i Q, g g .2 "5 "5 '9 2 o 2 o Q-l C1‘ 2 “Z3 u I-< g _ o g3 o g9 a 8 .... é B ‘g Q +1 a +> a m‘ .5 u) -'__ a 5 .3 3 .2 i’ ‘=3 '5 .2 #3 5 e n. in <1 a. <1 <1: < .4 Z Z Z Group 1 0—.0300 . . . . . . .. .034 11.7 4.3 .0556 0244 24.4 1.5 0.20 11.2 0 18 Group 2 0301-.0490 . . . . . . .. .050! 15.4 6.5 .0804 .0383 63.6 25.5 2.82 31.1 28 31 Group 3 0491-0675 . . . . . . . . .066 20.7 9.2 1256 .0568 90.8 18.5 1.26 41.8 22 11 Group 4 0676—.0865 . . . . . . .. .075 26.8 11.4 1690 .0776 103.4 16.6 2.77 49.2 11 6 Group 5 0866—.1050 . . . . . . .. .074 31.1 13.6 2242 .0954 96.0 27.7 5.02 65.0 11 7 Group 6 1051-—.1240 . . . . . . .. .098 26.7 14.8 2161 .1136 81.7 12.9 -1.59 62.7 ' 6 5 Group 7 1241—.1430 . . . . . . .. .093 25.1 14.1 3242 .1298 32.4 28.4 2.25 112.0 3 1 Group 8 1431—.1615 . . . . . . .. .096 33.4 16.4 .3436 .1515 48.2 36.2 2.92 105.9 2 2 Group 9. 1616—.1800 . . . . . . .. . 121 25.3 16.0 .3644 .1688 89.3 23.0 1.42 113.4 7 1 Group 10. .1801—.2796 . . . . . . . . .127 35.7 22.1 .5366 .2337 160.5 19.4 .77 141.5 7 2 w. .. <., . ,3 m RELATION or SoIL NITROGEN, ETQ, TO Po'r EXPERIMENTS. 17 The average percentage of nitrogen in the soil increases with the amount of nitrogen taken up by the four crops, except with Groups 5, 7, and 8. , - The weight of the first crop, in grams, increases up to the fifth group, and is then irregular. The average weight of the four crops in grams increases with the amount of nitrogen taken up by the crops except Groups '7 and 9. The amount of nitrogen taken up by the first crop increases with the average nitrogen taken up by the four crops, with the exception of Group 6. The increase i.s not in the same proportion as the aver- age of the four crops. The active phosphoric acid increases from 24 parts per million in the first group to 90 parts per million in the_third group, and is then irregular, decreasing to 36 parts per million in Group 7- and 48 parts per million in Group 8. No regular relation is to be observed. The acid consumed is lowest with the first group, after which it is irregular. The lime is lowest with the first group, after which it is irregular. The nitrification increases with the amount of nitrogen taken up by the crops, with the exception of Groups 6 and '7, which are out of line. These nitrification data are the results published in the previous bulletin, No. 259, and constitute the quantity of nitric nitrogen produced in the soil during a period of twelve weeks, not in- * eluding the nitric nitrogen present in the soil at the beginning of the experiment. CORRELATION BETWEEN THE NITROGEN CONTENT OF THE SOIL AND THE NITROGEN TAKEN UP BY THE CROPS. Mathematical methods are used in studying the correlation between various characteristics in biological work. The degree of correlation between two organs cannot be secured by measuring a single pair only. It is the correlation in the long run which must be considered, and the biologist must deal with masses and with averages. In'Bulletin N0. 267 of this Station, the correlation factor R between total phosphoric acid of the soil and the average phosphoric acid taken up by» four crops, was found by Humbert to be .4495. Between active phosphoric acid and the phosphoric acid taken up by four crops, the factor R was found to be .5656. The methods used for the study of correlation are well adapted to certain kinds of chemical work, for the reason that they not only show the average results but also the relation between the results. The correlation between the total nitrogen of the soil and the nitro- gen taken up by four crops (average per crop) is given in Table 14. TEXAS AGRICULTURAL EXPERIMENT STATION. H H H H N H N N N N N N N N T 2 NN HN HNN HN N N Hmmmmmg. Hwann Hm fix Hp .. Wm. .. .. . . . . . . . . . . .. . .... . . . . . . . . . .»..H. In. . N . . . . . . . . . . . . . . . . . . . . . . . . .. .H .... .. .. . .. . .. . .... m: HWHTWH wit? PM HRH. Gm ...» mwflwwfl. Hm U...H.....H.:wwrmmwn..mmmmmmmwMp ..wwf.m . . . . . . . . . . . . . .. N .... .. .. . H H H . . .. H . 1m .. . . . . . . . .. . . .... .. H .. H . ... ... .. .. .. . . . . .. .. . . . . . . .. .. . . . . . . . . . H .. . . H ... . . . . . . . H .... .. . .. H .. . . . . . . . . . . .. .. . . . . . . .. H H . . .. . .... .... .. . H . N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . H H N H H . . H H .. . . .... .... .. . H H H . .. H. .. . . . . . .. . . H N .... .. .. . H N N H . . . . . . . . . . .. . H H N .... .. H H H H H . . . . . . . . . . . . . . . . N H .... .. H N .. H. H .. .. . . . .. . . . . . .. H .. .. H H N H N H .. .. . . . . . . . . . . .. . . . ... H . N H .... .. N N N N .. .. .. . . . . . . . . . . .. . .. .. .. H .. .... .. N N N N N N H . H .... N N N H NHN. NNN. NNN. NHN. NNN.. NNH. NNH. NS. NNH. NNH. NHH. NNH. NNH. NHH. NNH. mg. NNH.. N8. NNH.. NNH.. NE. NNH.. NNH.. N8. dew E cmwobmZ 18 Nacho .53 3 Umivaokflowouumfl uwNNoNNHN v.8 mo» H: cmwobi HEB c386: NHENH GOBQTPHOU .3 QEHNH (10.10 Kq paAovrxxax 1198010,»; RELATION OF SoIL NITROGEN, Ere, TO Potr EXPERIMENTS. 19 The maximum group content only is given in the headings of the table; thus the second column includes soils with .016-.025 per cent. nitrogen. The coefficient of correlation R as calculated by the method given in Davenport’s Principles of Breeding, page 465, for the above itable is .653i.029. If there is a perfect correlation, R would be 1. If there is a perfect negative correlation, R would be —1. If there is no correlation, R would be 0. The nearer R approaches +1 or -‘-—1, the closer the correlation. a There is a closer correlation between the total nitrogen of the soil and the nitrogen taken up in the four crops than the total phosphoric acid of the soil and the phosphoric acid taken up by the four crops, ~or the active phosphoric acid, and the phosphoric acid taken up by the four crops, since .653 represents closer correlation than .47 or .57. The correlation between the total nitrogen of the soil and the nitro- gen taken up by the first crop is given in Table 15, and the factor R as calculated from this table is 5811.033. Our previous discussion leads us to expect that there would be a closer relation between the total nitrogen of the soil and the average nitrogen taken up by four crops than between the total nitrogen of the soil and the nitrogen taken up by the first crop, and this is shown correct by the correlation coefficient. ‘ H4 @ \—< TEXAS AGRICULTURAL EXPERIMENT STATION. gggpqngqpmmax-ywav-amcv-uv-lOfififl - . ¢ - u . ¢ - . - . . ¢ . - - 1 - . . . - . . a. 0a coon: on n u - . - . .- - ‘ . - -. . . - - .- . - - ~ .- - . - - .- - . | . .- ¢ ¢- ~ . - . Q . ¢ . . . a . OIOI --. »-»- -.~. - . - - - - . - - . - - » - ¢ - - ~ - . - . - - - . u . - . . . - - - . - - 0 B . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . H .. . .. Q - . - o - - - ¢ - ¢ . - . - - ¢ - u-u-o ¢ --¢.¢|-..¢- ¢n u I .0. o no .@-n- . . . . . . .. .. . . . . . .. .. . . . . .. .. .. . .. . . . . . . . . . . . . . .. H m . . . . . . .. H . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . .. H . . . . . . . . . . . . . . . . . . .. H .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . H .. . . . . . . . . . . . . . . . . . . . . . . . .. .. H . . . . .. . . . . . . . . . . .. H . . . . .. H . . . . . . . . . . . . .. .. . . H H .. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. H . .. . . . . . . . . . . . . . . . . . . . . . H H .. . . . . . . .. w . . . . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . .. - . . . - . - - - - ~ . - . . - - . - . - . - . . . . - . - - - | - . ~ - | . ~ . - - - - ¢ - - ~ - - a - . . . . . . . . - . - - - . - . . . . . . . . . . . . . » . - . . - - - . . . . - - Q . . . . . - - . . - . - . - . - . . . - . . - - ¢ - . . - - . ~ . - . - . n . | - . . - . - . - . . . . . - - - - u - ~ . - - - . - . - . ~ . . . . . - . - . - . - . - . - - - . Q - ¢ - . . . - » - - . . - - . - ‘ . . » . - . - . - - 1 - . ¢ - - - . . . - - ¢ . ~ - . . . . . . u - o - - » n - ¢ - - ~ - - - - Q - - - - » - - . . . . . . . . ¢ . . . ¢ - . - ¢ - - . u . - . . - ¢ . . . - . - - ¢ - - - . . o - a . n . - - - - I . Q - u - - - . - Q . - . - - - - - . - - - . - O H . . . . . . . . . . .. . . . . . . . . . . .. H . . . . . . . . . . . . . . . . .. H U.“ UHmm....w:H.. - - - - - - - - - - - - u - Q . » - . - ~ . n » - - ¢ - 0 - - . » - - - . . . . . . . - » - . - » ~ | . - . - . - . - . | ¢ . - - . Q Q Q . n - u - Q - u . Q - o - - . . - ¢ » » . . - - ~ ~ - | a ¢ . a . - ¢ ¢ - O . - - - - ¢ - . . - ~ . . ¢ . - - c . > - | | - - » » - Q - - . - - | - - . . - - | . ~ . - - o - - - - - 0 . ‘(i010 qsxg u; 1193014; N Hafifi. 3H. m8. mHH. ma. mo» E HHowoHHHZ 20 doHu HEHH QHHH >§ @9683 HHowobHHH H28 m8 2H» Ho HHowoHHHHH H83 aookfifi cofifiwm 2H8. HBHEQHHHHO .2 QHHFH. RELATION on SoIL NITROGEN, Era, TO Potr EXPERIMENTS. 21 RELATION OF PRODUCTION OF NITRATES TO THE RESULTS OF THE POT EXPERIMENTS. Samples of the soils used in the pot experiments were placed in per- colators andrsubjected to nitrification. To 500 gms. of the soil, 0.2 gm. dicalcium phosphate and 0.2 gin. potassium sulphate were added, these additions having been made in the same proportions to the soils in the pot experiments. The percolation and nitrification were then carried out as described in Bulletin 259, page 10. . One series of these experiments was run exactly parallel with the pot experiments. The soils were weighed out, percolated on the date that the pots were planted, and then every four weeks thereafter. Other samples of the same soil were weighed out, water added in quan- ' tity equal to one-third the saturation capacity of the soil, and water added every other week to replace loss in weight. When the corn in the pots was harvested, these soils in the percolators were percolated and the nitrogen determined. The water conditions were, of course, not the same as in the pot experiments, for the reason that the plants were continually withdrawing the water from the pots, and more had to be added, while in the percolators water was lost only by evaporation, and there was much less variation. 1 The nitrogen present as nitrates at the beginning of the experiment was added to the quantity found during the test, and the total repre- sents the nitrogen as nitrates which could be placed at the disposal of the plants if the process of nitrification in the pots should be exactly the same as the process of" nitrification in the percolators. Table 16 shows the results of five series of these experiments. The soils were run in groups containingsimilart quantities of total nitrogen. Table 16. Relation of nitrogen removed by crops to nitric nitrogen formed in parts per million. Removed by One Found in percolation _ I epercola- Per lcent Soil N0. Total tlon when Total nitrogen Corn Sorghum corn cut 0 to 8 8 to 16 0 to 16 in soil . . weeks weeks weeks 7350 . . . . . . . . . . . . . .. 16.4 3.4 19.8 13.0 12.7 5.1 17.8 .024 7345 . . . . . . . . . . . . . .. 20.1 7.9 28.0 19.1 19.0 14..1 33.1 .039 7348 . . . . . . . . . . . . . .. 16.1 3.7 19.8 12.8 12.6 7.6 20.2 .029 7715 . . . . . . . . . . . . . .. 11.1 4.2 15.3 1.1 6.3 5.1 11.4 .032 7706 . . . . . . . . . . . . . .. 18.9 8.3 27.2 23.0 19.1 15.0 . 34.1 .038 7707 . . . . . . . . . . . . . .. 14.6 4.2 18.8 11.4 13.0 7.1 20.1 .027 7344 . . . . . . . . . . . . . .. 14.5 2.8 17.3 13.1 12.5 6.9 19.4 - .037 7156 . . . . . . . . . . . . . .. 71.4 5.1 76.5 47.4 66.0 19.3 85.3 .037 7253 . . . . . . . . . . . . . .. 9.4 4.6 14.0 12.6 7.0 -3.8 10.8 .026 7164 . . . . . . . . . . . . . .. 7.8 1.6 9.4 12.9 9.4 1.8 11.2 .038 7231 . . . . . . . . . . . . . .. 31.0 4.5 35.5 13.3 12.5 7.2 19.7 .028 Average . . . . .. 21.0 4.6 25.6 16.36 17.3 8.5 25.8 .032 7340 . . . . . . . . . . . . . .. 15.8 4.5 20.3 11.1 15.5 15.1 30.6 .066 7171 . . . . . . . . . . . . . .. 28.5 12.5 31.0 29.0 34.7 17.7 52.4 .075 5947 . . . . . . . . . . . . . .. 24.1 9.1 33.2 28.7 34.8 17.8 52.6 .066 5647 . . . . . . . . . . . . . .. 24.2 5.4 29.6 23.4 29.0 13.8 42.-8 .062 7615 . . . . . . . . . . . . . .. 11.4 8.7 20.1 13.9 25.3 20.3 45.6 .064 7616 . . . . . . . . . . . . . .. 13.5 5.0 18.5 9.1 14.8 11.0 25.8 .064 7158 . . . . . . . . . . . . . .. 11.6 4.8 16.4 12.9 18.7 _ 10.0 ‘ 28.7 .065 7632 . . . . . . . . . . . . . .. 23.0 5.5 28.5 19.2 31.6 14.5 46.1 .064 Average . . . . .. 21.4 9.3 30.7 19.6 25.2 20.6 45.8 .066 ' nitric nitrogen found by the percolation at the beginning of the experi’, 22 TEXAS AGRICULTURAL EXPERIMENT STATION. Table 16. Relation of nitrogen removed by crops to nitric nitrogen formed in parts. per million—Continued._ n Removed by One Found in percolation percola- _ Per A Soil No. Total tion when Total w '9 - Corn Sorghum Ocorn cut 0 to 8 8 to 16 0 to 16 in mil‘; weeks weeks weeks ' 982 . . . . . . . . . . . . . .. 44.5 18.2 62.7 1.7 1.7 55.8 57.5 7614 . . . . . . . . . . . . . .. 36.4 26.6 63.0. 6.0 3.1 3.1 6.2 .. 7358 . . . . . . . . . . . . . .. 31.6 8.3 39.9 20.8 21.4 3.7 25.1 l 7360 . . . . . . . . . . . . . .. 147.0 20.9 167.9 51.4 125.4 18.8 144.2 .095 7339 . . . . . . . . . . . . . .. 14.0 11.8 25.8 12.5 20.5 23.1 43.6 7229 . . . . . . . . . . . . . .. 33.7 12.6 46.3 45.0 40.6 27.1 67.7 .091 869 . . . . . . . . . . . . . .. 41.8 40.7 82.5 30.3 15.9 .66 22.5 5960 . . . . . . . . . . . . . .. 58.1 12.9 71.0 29.2 50.8 27.8 78.6 5959 . . . . . . . . . . . . . .. 36.6 22.3 58.9 36.1 59.4 22.8‘ 82.2 .093 7116 . . . . . . . . . . . . . .. 29.4 11.0 40.4 25.9 34.7 18.7 53.4 .09. ‘ 7352 . . . . . . . . . . . . . .. 31.2 7.2 38.4. 18.7 36.9 13.7 50.6 .0831 7127 . . . . . . . . . . . . . .. 25.5 12.0 37.5 17.8 40.5 31.4 71.9 .082 5939 . . . . . . . . . . . . . .. 32.0 22.3 52.3 30.9 78.9 47.0 125.9 Average . . . . .. 43.1 17.4 60.3 27.1 44.0 20.3 64.3 . . . . . . 7161 . . . . . . . . . . . . . .. 27.5 7.2 34.7 24.5 29.8 25.4 55.2 .147; 7613 . . . . . . . . . . . . . .. 52.4 21.0 73.4 p 19.6 22.8 37.8 60.6 .140‘ 7356 . . . . . . . . . . . . . .. 43.9 14.3 58.2 37.8 64.3 36.8 101.1 .1483 7223 . . . . . . . . . . . . . .. 27.5 4.3 38.8 38.8 49.6 28.8 78.4 1.1681- 3342 . . . . . . . . . . . . . .. 41.1 12.9 54.0 18.5 55.5 37.3 92.8 .151 Average . . . . .. 38.5 11.9 51.8 27.8 44.4 33.2 77.6 .151 7621 . . . . . . . . . . . . . .. 26.3 6.8 93.1 33.1 25.3 16.8 42.1 .044 ' 7351 . . . . . . . . . . . . . .. 27.3 6.5 33.8 21.8 19.9 15.2 35.1 ‘.056 ' 7619 . . . . . . . . . . . . . .. 18.3 5.4 23.7 20.5 20.1 13.7 33.8 .059 Y 7622 . . . . . . . . . . . . . .. 23.5 3.6 * 27.1 11.3 16.1 0 16.1 .052T 7342 . . . . . . . . . . . . . .. 23.2 5.7 28.9 12.3 18.4 19.4 37.8 .055‘; 7709 . . . . . . . . . . . . . .. 17.6 7.6 25.2 12.9 20.0 12.5 32.5 .044 7239 . . . . . . . . . . . . . .. 18.9 8.6 27.5 21.6 20.4 20.7 41.1 .048 3f 7226 . . . . . . . . . . . . . .. 36,1 7.9 44.0 40.4 20.7 13.2 33.9 .057 1 7354 . . . . . . . . . . . . . .. 17.6 3.1 20.7 4.2 0 0.4 0.4 .058 7349 . . . . . . . . . . . . . .. 21.6 5.4 27.0 24.7 21.6 11.6 33.2 .0421 7343 . . . . . . . . . . . . . .. 17.4 4.7 22.1 17.3 11.7 8.8 19.5 .055 71 . . . . . . . . . . . . . .. 19.2 4.6 23.8 22.3 25.6 12.1 37.7 .052 7 Average . . . . .. 22.3 5.8 28.1 20.2 19.9 13.1 33.0 .052 7347 . . . . . . . . . . . . . .. 20.4 12.0 32.4 21.4 25.6 21.2 46.8 .065 p 7714 .......... .. 18.5 16.9 35.4 l 44.9 I 45.2 y 29.0 74.2 .064 9.; When the nitric nitrogen found by one percolation at the end of th period of growth of the corn, about two months, is compared with th ment, plus that found every four weeks thereafter, for eight weeks; the agreement is found to be remarkably close in the first two sets? but as the quantity of nitrates produced becomes larger, the differences become wider. Larger quantities of nitrates, as a rule, are produced when several percolations are made than when only one percolation ' ‘ made at the end of the experiment. This does not occur with all soils, for with some soils the reverse occurs, as with soil 869. With other soils there is not a great difference. However, there are large differ- ences with some of the soils. Soil 7360 produces 51.4 parts per million nitrogen as nitrates when allowed to remain to the end of the experi- ment, and 125.4 parts per million when percolated at the beginning of; the experiment, at the end of four weeks, and at the end of eight weeksh This may be compared with 147.0 parts per million removed by the: corn crop». Soil 3342 produced 18.5 parts p-er million in the one per- colation, and 55.5 when the three percolationswere made. This may; be compared with 41.1 removed by the corn crop. 1 i RELATION OF SoIL NITROGEN, Enid, TO P01‘ EXPERIMENTS. 23 i1 From these results the conclusion is drawn that the percolation at ‘riods of four weeks is better than a single percolation. A similar mparison between percolation and jars is given on page 7 of Bulletin _9, and it is found that decidedly less nitrates were present in the . l: rs. This is in accord with our general knowledge that products of terial action hinder bacterial growth, and removal of these products “vives their action. There is also the possibility of denitrification. On an average, the amount of nitrogen removed by the crop is re- arkably close to the amount of nitrates produced in eight weeks. i his is best shown when the averages for the groups are compared. f With the first group the corn takes up 21.0 parts per million, and We nitric nitrogen is 17.3 parts per million. In the second group, pie corn takes up 26.3 and the nitric nitrogen is 19.9 parts p-er million. ‘in the third group the corn takes up» 21.4 and the nitric nitrogen is i; 5.2 per million. In the fourth group- the corn takes up 43.1 and the 13:: 'tric nitrogen is 44.4. In the last group, the corn takes up 38.5 and he nitric nitrogen is 44.4 per million. Much larger diiferences are found when we compare the nitrates roduced in the period from eight to sixteen weeks, with the amount "51 nitrates taken up by the sorghum crop which followed the corn. ‘he amount of nitric nitrogen produced is twice as much as the nitro- en removed by the sorghum with three of the sets. With the fourth t, the amount of nitrogen taken up by the sorghum is nearly equal o the amount of nitric nitrogen formed in the percolators. In the fifth et, the amount of nitrogen taken up by the sorghum is about one- third the nitric nitrogen in the percolators. The variations between the individual tests are much more decided ithan between the averages discussed above. In a number of the ex- periments theagreements between the amount of nitrogen removed by fthe corn, and the amount of nitric nitrogen available in eight weeks, Iis remarkably close. In other tests,the differences are much wider, Land vary both ways. This may be seen by considering Table 16. With a number of the soils the amount of nitric nitrogen produced . ikin the percolators is less than the amount taken up by the crops. This is the case with soils 7715, 7231, 7354, 7343, 982, 7614, and 869. Soil » i 7354 did not nitrify, but the corn crop took up 17.6 parts nitrogen iper million from the soil. Either the conditions for nitrification were more favorable in the pots in which the corn was growing, or the corn took up its nitrogen in other forms than nitrates in these particular pots. The writer is inclined to believe that the difference is due to iconditions of nitrification, and that the growing crop favorably in- .fluenced the process with these particular soils. Perhaps the removal process of nitrification, or perhaps the moisture conditions were more . favorable. The behavior of soil 982 is evidence that such is the case, j for it produced only 1.7 parts per million of nitric nitrogen in the first eight weeks, but more favorable conditions caused it to produce 55.8 parts per million in the second eight weeks, while the amount of nitro- l’ gen taken up by the corn crop was 44.5‘ parts per million of soil. f There are other soils in which the amount of nitric nitrogen pro- » duced is decidedly in excess of the nitrogen taken up- by the corn crop-. s Soil 7714 produced 45.2 nitrogen as nitrates, but the corn crop» took I ;.of nitrates and ammonia by the growing crop favorably influenced the _ differ in this respect. Nitrogen per million Available nitric nitrogen Weight crops, gm. ’ Per cent Number * Group based on ' Per cent Per cent _ . " nitrogen aver- nitrogen removed In In Per taken taken First Second 1n soil aged by first crop first second Total million by first by first crop crop crop crop of -so1l crop two f - crops * Group 1. 0-8 6.31 14.60 20.91 43.4 14.6 48.2 7.6 7.2 .058 5 Y; Group 2. 8.1—16 12.68 5.15 17.83 23.2 - 54.7 76.8 13.0 2,8 _.044 50 - Group 3. ‘16.1—24 19.35 6.12 25.47 33.3 58.1 76.5 17.2 3.9 .052 47 Group 4. 241-32 27.76 - 8.01 35.47 44.6 62.3 80.2 23.7 4.9 .073 20 y. Group 5. 32.1—40 35.34 14.33 49.67 49.9 70.8 99.5 . 27.4 8.4 .087 16 ' Group 6. 40.1—48 43.66 11.14 54.80 69.9 62.5 78.4 26.9 7.8 .107 10 i; Group 7. 48.1—64 54.94 11.86 66.80 ~ 57.2 96.1 116.7 29.6 8.1 .062 14 Group 8. Over 64 94.74 29.13 123.87 124.5 76.1 99.5 36.4 20.7 .121 17 24 TEXAS AGRICULTURAL EXPERIMENT STATION. up only 18.5. Soil 7615, produced 25.3, but the corn crop took up onl“ 11.4 parts per million. Soil 5959 produced 59.4 and the corn took u 36.6. Soil 5939. produced 78.9, and the corn crop took up 32.0. 1f 7356 produced 64.3 and the corn took up 43.9. Either the corn cro did not take up all the nitrates formed,- or the nitrification conditio’ were more favorable in the percolators than in the pots in which if; corn was growing. It could hardly be expected that the corn cro would completely exhaust the nitrates of the soil, for such is not usuall the case. Wright (Soil Science, 1920, 258) found large proportio‘ of nitric nitrogen left in the soil after growing various crops. NITRIFIGATION OF MANY SOILS. After the preliminary work discussed above had been completed, large number of soils on other portions of which pot experiments ha_ » been made, were placed in percolators, and nitrified for three u; of four weeks each. To the nitric nitrogen already present in ii, = soil, and extracted by the first percolation, was added that formed duri i ing the experiment, and this total is the amount under discussion inf this bulletin. The growing crops have at their disposal the amount of nitrogen already present in the soil as well as that formed during the period of the growth. Bulletin 259 was a study of the production off nitrates in soils, and for this reason the nitrogen present in the soil at th beginning of the nitrification was not considered. The two bulletins The soils were arranged in groups differing .02 per cent. in total‘; nitrogen content. The work was carried on during the late springij and early summer, when the weather was warm. As shown in Bul-j letin 259, weather conditions no doubt influence the production of» nitrates. - RELATION OF NITRIC NITROGEN TO NITROGEN REMOVED BY FIRST CROPS. The soils were arranged in groups differing 8 parts per million in the amount of nitrogen removed by the first crop, and the averages are given in Table 1'7. The average nitrogen taken up by the first crop . ranges from 6.31 parts per million in Group 1 to 94.74 parts per mil- i, lion in Group 8. The available nitric nitrogen in parts per million ’ is given in the table. By available nitric nitrogen we here mean the p, Table 17. Average relation of nitrogen in first crop to nitrification and weight of crops. p RELATION or SoIL NITROGEN, Era, TO P01‘ EXPERIMENTS. 25 ic nitrogen removed by the percolation at the beginning of the f]. ification, added to that removed at the end of the four weeks, at 4 end of eight weeks, and at the end of twelve weeks. _ jlVith the exception of Groups 1 and '7, the amount of available ic nitrogen increases regularly with the amount of nitrogen taken ‘l? by the first crop. The available nitric nitrogen in Group 1 is much igerthan the amount of nitrogen removed by the first crop-, but this a its the second crop, shown in the secondcolumn, to remove more y ogen than any crop up to Group 8. It would appear from these l a a lts that the crops grown on the soils of Group 1 were limited by ‘in other condition than the amount of nitrates in the soil. l A he table shows that there is a distinct relation between the average ount of nitrates formed in the soil and the average amount of 1-15‘! crop - i-IVi-Zhicropps l F/yi? I 5o (o do 90 no 1/0 1:0 15g no av I60 no in 1.9a 20o Ava/livfi/e fli/r/c n/froye/‘I i Figure 2.——Relation of nitrogen removed by crops to available nitric nitrogen produced by soil. A gen removed by the first crop. The first crop was used as the of comparison for the reason that it has at its disposal approxi- ly the same quantity of nitric nitrogen as was extracted from the lators. The period of growth of the second and subsequent crops all much larger than the nitrification tests in the percolators. ghe amount of nitrogen removed by the first crop, divided by the ant of nitric nitrogen in the soil, expressed in percentages, is given gi table. Fourteen per cent. of the nitric nitrogen was removed 15;‘: first crop in Group 1, 54.7 in Group 2, and 96.1 in Group '7. percentages removed by the other groups vary from 58.1 to 76.1. jehese figures also show the differences between Group 1 and the ' This is the way in which the analyses would be considered, if one we 3 26 TEXAS AGRICULTURAL EXPERIMENT STATION. other groups. In the first group the nitric nitrogen was taken up bf the first crops to a much smaller extent than with the other grou The nitrogen in parts per million taken up by the second crop ‘ shown in the table. The first group is out of line with the othe, on account of the excess of nitrates left by the first crop. The amo I of nitrogen taken up by the second crops beginning with the seconi group increases from 5.15. to 59.13 parts per million, and the increi is regular with the exception of Groups 6 and 7. ' ‘ The total nitrogen taken up by the first and second crops combin, is also shown in the table. This may also be compared with the nit i nitrogen secured during the nitrification tests. It must again be r called that the two crops were growing in periods of about four month while nitrification occupied a period of about three months. Ti amount of available nitrates formed was not, therefore, the same ;_ that which can be taken up» by the two crops, since a longer time L nitrification was permitted the soil on which the crops were growin The percentage of the available nitrates removed by the first a, second crops combined as given in the table, varies from 48.2 to 116., Group No. 1 is lowest. Excluding Group 1, which is not normal, variation is from 76.5 to 116.7 per cent. - i; The average weight of the crops is alsogiven in the table. The increase with the nitrogen removed by the crops in the first cro though not in the same proportion, with the exception of Group The number of soils averaged is given in the last column. There = ‘ only five soils in the first group. ._ The soils were also arranged in groups according to the quantity u nitric nitrogen secured during the nitrification tests of twelve .0 attemp-ting to draw conclusions from the analytical work. The ave I; age of the soils arranged in this way is given in Table 18. The ave age nitric nitrogen produced varies from 4.6 parts per million ' Group 1 to 178.4 parts per million in Group 12. The nitrogen r; moved by the first crop varies from 16.36 to 110.89 in Group 12. ‘ T‘ average amount of nitrogen removed by the first crop increases wit the average amount of available nitric nitrogen present in the so'_ with the exception of Group 1, including 11 soils. The amount w nitrogen removed by the crops in Group 1 greatly exceeds the amoun in the soil. In other words, nitrification did not occur in the per_cf lators so as to form nitrates equal to the nitrogen removed by th: crops. This is true to a certain extent of Group 2, although not =; great as Group 1. The average amount of nitrates removed by the first crop, divide by the nitric nitrogen formed in the soil (including that present l’ the beginning) is also shown in the table. A corresponding figxi was given in Table 17, but ihere the soils are arra11gc.d_ according the nitrogen removed by the first crop, while here they are arrange according to the nitric nitrogen available in the soil. The first cro of Group 1 took up 355 per cent. of the nitrates produced in the sol The first crop with Group 2 took up 118.5 per cent. of the nitrates pr duced in the soil. With the other groups the percentage of nit f nitrogen removed by the first crop varies from 46.1 to 74.5. é F. g. e1 ‘ i. . RELATION or SOIL Nrtrnoenn, Ere, TO Porr EXPERIMENTS. 27 Table 18.. Relation of nitric nitrogen to nitrogen removed by crops in parts per million and weight of crops 1n grams. Percentage _ Nitrogen Weight of crops of available Avarl- per million in gm. nitric nitrogen Num 070 able removed ber N. nitric aver- Group limits based in nitro- First By first aged on nitric nitrogen soil gen First Second and First Second By first and 1n soil crop crop second crop crop crop second crop crop Group 1. 0-10 .041 4.6 16.36 2.94 19.30 14.3 1.8 355.6 419.5 11 Group 2. 10 1-20 038 15.2 18.00 ' 4.65 22.65 16.9 2.6 118.5 149.0 29 Group 3. 20 1—30 049 24.7 18.40 6.36 24.76 15.3 3.5 74.5 100.3 27 Group 4. 30 1-40 O55 34.4 21.76 7.37 29.13 19.6 4.7 63.3 84.7 34 Group 5. 40 1-50 057 44.9 27.60 6.81 ' 34.41 21.2 4.3 61.5 76.6 27 Group 6. 501-60 079 55.4 34.03 11.98 46.01 25.9 7.5 61.4 83.1 11 Group 7. 60.1—70 103 67.1 36.65 14.55 51.20 25.9 7.7 54.6 76.3 10 Group 8. 70.1—80 085 73.5 50.22 18.71 68.93 24.2 12.5 68.3 93.8 9 Group 9. 80.1-100 .131 90.3 53.47 16.52 69.99 32.4 12.0 59.2 77.5 7 Group 10 100.1—120 .086 102.2 47.13 21.10 68.23 21.8 13.0 46.1 66.8 7 Group 11 120.1—140 .170 130.2 65.11 36.31 101.42 30.5 25.1 50.0 77.9 5 Group 12 140.1—180 .133 178.4 110.89 50.55 161.44 35.7 20.2 62.2 90.5 6 The amounts of nitrogen taken up by the second crop, and by the first and second crops p combined, are also given in the table. With the exception of Groups 5 and 9, the nitrogen removedby the second crop increases regularly with the nitric nitrogen available in the soil. A regular increase of the nitrogen taken up by the first and second crop combined is to be seen in the table, with the exception of Group 10, which is a little out of line. The total nitrogen taken up by the four crops likewise increases regularly with the nitric nitrogen avail- able in the soil. ' The nitric nitrogen available in the soil, divided by the nitrogen taken up by the first and second crops, is likewise shown in the table as percentage of available nitrogen taken up- by the first and second crops combined. With Group 1, this is 419.5 per cent, with Group 2, 149.0 per cent., and with Group 3, 100.3 per cent. With the other groups it varies from 66.8 to 93.8. CORRELATION BETWEEN THE AMOUNT OF NITROGEN TAKEN UP BY THE FIRST CROPS AND THE AMOUNT OF NITRATES AVAILABLE IN THE SOIL. The correlation discussed in connection with the total nitrogen of the soil is probably the most satisfactory method of comparing results of this kind. A correlation table showing the relation between the nitric nitrogen of the soil and the nitrogen taken up by the first crop, is given as Table 19. 28 TEXAS AGRICULTURAL EXPERIMENT STATION. (I010 qsxg Kq pazxome: uafiolqm cwHH o c c H c o o m m m H m w. H w w H w H w HH v m HH 2 wH mm wH c .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. H ..H . o .. c . . . . . . . . .. H .H .. . . . . . . .. o w H w . o H . . ..H H .H . . . . . . .. H .H . . . . . . .. m H ....H H .H m H ..H . H. H H w . w ..H w H H . ....H . . w . ..H ..H 1w H H H H a . H H H H 2w ..H a . DIN ...H .. w H H wH m .m H .H m m wH . m m w w m H m». .H In H 12m m w w w HA. H ..H ....H w a m vm .H H ..H a a m2 a: wwH owH EH wwH a: m2 omH 3H wwH N2 5 Q9 H.HH woH N2 8 8 Huw w» NH. a. 3 H1.“ wH. NH. 3 ow wzom E cwwobm: m-nmmagfl do~§fiw .3 32:5... nwmaufia HEQHS we awmouza “ab? wwimai. 63am. acmwaHoboO 5H wink RELATION oFTSoIL NITROGEN, Euro, T0 Potr EXPERIMENTS. 29 \ The coefficient R has also been calculated from this table with the result that R:.708i.025.~ Table 15 shows the correlation between the total nitrogen of the soil and the nitrogen removed by the first crops, and the factor R for this table is .581i.033. There is thus a closer correlation between the nitrogen taken up by the first crop and the nitric nitrogen produced in the soil under the conditions of the Work here described than there is between the total nitrogen of the soil and the nitrogen removed by the first crop. The correlation between the nitrogen removed by four crops and the total nitrogen of the soil R is 0.653. ' The-determination of the amount of nitrates produced by the soil presents a method of forming an opinion as to the amount of nitrogen in the soil available to plants. Some of the soils are out of line, and deviate widely from the average, and soils of this character require further study. ' CORRELATION OF SOILS GROUPED BY TOTAL NITROGEN. It seemed-possible that there might be a closer correlation between the available nitric nitrogen of the soil and the nitrogen removed by the first crops, if the soils were first grouped by total soil nitrogen, since there was also a correlation between the total nitrogen and the nitrogen removed by the first crops. Only two groups of soils contained a sufficient number of soils to make a test, and even these were not large enough. Table 20 is a correlation table for 56 soils, showing the relation be- tween the available nitric nitrogen of the soil and the nitrogen re- moved by first crops on soils containing .041—.060 per cent. total nitrogen. 30 TEXAS AGRICULTURAL EXPERIMENT STATION. ww H w o o w w o H m o H H w w w w wH HH v H“ H . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. H . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IwoH o . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ImoH o . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Zwm w . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . _ . . . . . . . . . . . . . . . . . . . . . . . IQC® w . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IHw w . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1w» o . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . _ . . . . . . . . . . . IQ. H . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. H . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..ww o . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . low w . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . H H H . . . . . . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ilfim w . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. w .. .. H . . . . .. . . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IwH. w . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. .. .. . . . . .. H . . . . .. . H H . . . . . . . . . . . . . . . . . . . . . . . . . . Imw H . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . .. H . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Iww m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . .. . .. H . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. H . . . . . . . . . . . . . . . . . . . . . . . . . Iow w . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . .. m w . . . . . . . . . . . . . . . . .. H wm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...H . . . . .. H . . . . .. m w w Hw m w ..wH HH H . . . . . . . . . . . . . . . . . . . . . . V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. m . . . . .. H H w H. w . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. w ofi HHH woH a: wm 2.. aw w» m» ww ww fi x wH~ Q ww 8 HQN wH NH w dwmohfin H.300 .38 8n wwfHmw. waHaHawaou mac» no no.8 2.6 .5 UQ>OHH$H nwwohnmn H55 :8 2H» we nowohfizn 35E oHnaHHa>< mHHow aH cwwosmn 0H3? vHnmmm>< c1010 qsxg u; uogmm 19d 1133010,; sHnflH. coHwaHwboO dw QEFH. 31 RELATION OF SQIL NITROGEN, ETC, TO P01: EXPERIMENTS. ‘ Fcq-lbbdiv-INP-ifiv-Iv-iv-l IN v-n-o u‘: HC¢¢Q¢¢¢¢¢QQQ¢N¢¢Q o Nmaziw 2?. . . . . . . . . . . -$}4 . . . . . . . . . . low N .H . . . . ........Q© 1w .~ . . . . . . . . . . Zvm .4; mmmmfiumw mm in w . . . . . . . . . . II € . . . . . . . . . . . .. ..O0 Olfi w m IN . . . . . . . . . . Iva w. 1w m m. m . . . . . . . . . . Iww 0.. In . . . . . . . . IZNH X .. . . . . . . . . . . 1w. m3 $3 2:. Efi m: m3 $2 o3 s; m2 Q2 8H .5 w: m2 m2 8 8 aw 2v E 8. fi. 3 § anew mo nvwoam: or»? Bnamafifl duwogpi <83 0:3 8a aaffiwo. mnmmfiunoo mmom no. no.8 .36 3 v3.35: .5258 wan m3 we nowoaza 2.5? manama>< 63am. aomafiwbaO .3 20am. 32 TEXAS AGRICULTURAL EXPERIMENT STATION. Table is a correlation table- for 52 soils, containing .041—.060 per cent. total nitrogen. a é if‘ 4 "1 >3? '2 In the correlation for all 180 soils (Table 19) between the available} nitric nitrogen and the nitrogen taken up by first crops: The coefficient R is 17081025. In the correlations for 56 soils with .02-—.040 per cent. total nitrogen: it The coeficient R is .40'7—*_—.0'73. In the correlation of 52 soils with .041-——.060 per cent. total nitrogen: The coefficient R is .556i.064. The correlation is closer with soils containing .041—-.060 per cent.’ total nitrogen than for soils with .021——.040 per cent. total nitrogen, but not so close for all the soils. The difference is probably due in part to the number of soils taken, since one soil far‘ out of line may affect the coefficient decidedly when ~ only a small number are used. » k .3” ("pea Ih;_;_1‘"f.j:< ‘ l,’ ...: In the examination of Tables 15 and 16 we found that crops grown on soils in Group 1, Table 15, did not take up the nitrates of the soil as well as the other crops. scattered through the other groups. It is possible that some similar crops are In Table 16 we found that. a? “'14” f‘ number of the soils, especially in Groups 1 and 2, and probably some in Group 3, took up much more nitrates from the soil than were - formed in the nitrificationexperiments. These soils were exceptional as compared with the others, and require further study, and are dis- cussed at the end of this bulletin. EFFECTS OF OROPPING UPON NITRATE PRODUCTION IN SOILS. After the pot experiments had been completed, the soils used were passed through a sifter, the roots were removed, and portions of the soils cropped were subjected to the nitrification at the same time and under Y the same conditions as a portion of the original soil. The objection of a this work was to ascertain what effect the cropping had upon the nitro-_ gen remaining in the soil as regards production of nitrates, and if nitrification tests would show the nitrogen removed by cropping. The averages for the groups arranged according to the available nitrates or1g1nally found 1n the so1l are g1ven 1n Table 22. The ar- i Table 22. Relation of nitrates produced before and after cropping in parts per million. Nitrogen “Decrease” Groups limits based Per cent Nitrate nitrogen removed divided by on nitrate nitrogen nitrogen by four nitrogen Number in original soil in soil. Before After crops by crops averaged cropping cropping Decrease per cent Group 1. 10 . . . . . . . . . . .. .041 4.6 10.7 --6.1 26.56 0 11 Group 2. 10.1-20 ........ .. .033 15.2 14.7 0.5 30.21 1.7 20 Group 3. 20.1-30 ........ .. .040 24.7 15.0 3.3 33.75 20.1 27 Group 4. 30.1-40 . . . . . . . . .. .055 34.4 22.7 11.7 43.00 20.0 34 Group 5. 40.1-50 ........ .. .057 44.0 25.0 10.3 47.03 40.3 27 Group 6. 50.1-60 . . . . . . . . .. .079 55.4 24.6 30.8 67.61 45.5 11 Group 7. .1- ........ .. .103 07.1 24.0 42.5 74.35 57.2 1o Group 8. 70.1-80 . . . . . . . . .. .085 73.5 30.1 43.4 88.78 50.0 9 Group 0. 30.1-100 ....... .. .131 00.3 40.4 40.0 00.42 50.2 7 Group 10. 100.1-120 ....... .. .030 102.2 37.7 04.5 113.40 50.0 7 Group 11. 120.1—140 . . . . . . . .. .170 130.2 41.6 88.6 146.92 60.3 5 Group 12. 1401-130 ....... .. .133 173.4 51.4 127.0 177.00 71.5 0 183 RELATION or SorL NITROGEN, Ere, TO Poi: EXPERIMENTS. 33 rangement of this table is the same as in Table 18, and some of the figures of Table 18 are repeated for the purpose of comparison. The nitric nitrogen produced in the soils after the four crops have been grown is shown in the table. In Group 1, the nitric nitrogen produced after cropping is greater than the nitric nitrogen available in the original soil. This confirms our previous conclusion concern- ing the soils of this group, namely, that nitrification takes, place better in these soils carrying the crops than in the soils in the percolators. In Group» 2, the nitrification produced after cropping is not much different from that produced before cropping. With the other groups, i there is a decided decreasein the nitric nitrogen produced in the soil which had been cropped. The amount of this decrease increases reg- ularly with the amount of available nitrates originally produced in the soil. - - /\//0/1 fi x O Q 5,0 yen producf/on per m/ 8 m F” é.‘ flecrease fr? fl/fr/c‘ fl/f/"o N. p Q 40 A a}: 12o as? l 20o 2'40 N [fro fen removed é/cm/w M/Jdr/s per m/W/m O Figure 3.—Relation of nitrogen removed by crops to decrease in nitric nitrogen produced after cropping. The differences between the available nitric nitrogen before cropping and the available nitric nitrogen after cropping show the effect of the cropping upon the soil as measured by the nitrification method. In the first group, composed of 11 soils, 4.6 parts per million of nitric nitrogen were available in the soil before cropping. After the removal of 26.56 parts per million of nitrogen by the crops, the croppedsoil produced 10.7 parts per million of nitric nitrogen, or more than be- fore cropping. The second group» of soils also averages little or no loss. With the other groups there is closer relation between the de- crease in the amount of nitric nitrogen produced and the total nitrogen removed by cropping. p The last column shows what percentage the decrease in available nitric nitrogen is of the nitrogen removed in cropping. In Group 2, 34 TEXAS AGRICULTURAL EXPERIMENT STATION. the average decrease is only 1.7 per cent. of the nitrogen removed. With Groups 3 and 4, the decrease is 26 per cent., and with the remain- ing groups the decrease ranges from 40.3 t0 71.5 of the amounts re- moved by the crop-s. The cropping of the soil has, therefore, a decided effect upon the soil nitrogen as shown in the production of nitrates, and this effect can be followed by nitrification tests such as these de- scribed here. In Table 22 the soils were arranged according to the nitric nitrogen produced in the soil. In Table 23 the soils are arranged in groups according to the nitrogen removed by the four crops, expressed in parts per million of soil. Table 23. Average relation of total nitrogen removed by crops to nitrogen before and after cropping. “Decrease” Nitrogen - Nitric nitrogen divided ' Nitro- Num- Groups based on per million First crop by total gen ber nitrogen removed removed nitrogen Before After nitrogen in soil of soils by four crops by crops per million cropping cropping Decrease per cent Group 1 0-20 . . . . .. 14.97 10.13 17.2 13.4 3.8 25 .045 1 Group 2 20.1-40.. . 29 82 15.79 28.6 17.7 10.9 36 .046 73 Group 3 40.1-60. .. 48 57 24.96 38.7 23.5' 15.2 31 .065 41 Group 4 60.1-80.... 69 83 42.94 60.2 27.5 32.7 47 .076 25 Group 5 80.1-100... 89 04 45.77 66.6 28.5 38.1 43 .079 10 Group 6 100.1-120... 106 07 58.23 102.8 45.2 57.6 . 54 .131 7 Group 7 120.1—140... 132 60 73.35 74.2 25.5 58.7 44 .084 5 Group 8 1401-180. .. 181 33 73.23 140.6 42.6 l‘ 95.5 59 .128 4 Group 9. 180.1-200... 191.97 126.70 149.5 51.8 ; 5 96.7 50 .157 4 Group 10. 210.1-220. . . . 218.09 104.35 138.3 V” 35x8‘, “i; 38.0, 36 .185 2 The average nitrogen removed by the four crops is given in one column. The nitrogen removed by the first crop is also given. The available nitric nitrogen is given under the head of “nitric nitrogen before cropping.” With the exception of Group 7, these increase with ‘the amount of nitrogen removed by the crops. The nitric nitrogen formed in the nitrification test after the cropping, plus that present in the cropped soil before the test began, is given in the next column heading “after cropping.” ~ This increases regularly up to the sixth group, after which it is irregular, but in the irregular groups there are not enough soils to form good averages. The decrease inthe available nitric nitrogen in the soil before cropping and after cropping, is shown in another column, headed “decrease.” This decrease becomes larger as the quantity of nitrogen removed by the crops gets larger. The relation is regular with the exception of Group» 10, which contains only two soils. ' The decrease expressed in percentage of the nitrogen removed by the four crop-s is given in another column. This decrease varies from 25 to 59 per cent. of the nitrogen removed by the crop. This method has, therefore, permitted us to trace the effect of cropping upon the nitrogen of the soil. The cropping has decreased the nitrogen which can be converted into nitrates. With many of the soils the relation is fairly constant. 35 RELATION OF SolL NITROGEN, ET0., TO POT EXPERIMENTS. ‘ fi2ggg22:%@©NNm@@##@N@@#'3 v-d v-l NW N -Aflfifi -wmmmww -Nbwfifi _ :m@$mN:#' - CO <0 C0 - v-l v-i O Q v N v-l uogmm 13d squad ‘sdoxo Xq POAOUIBJ uafiongu 112401, %'¢@MN-N# m2 m; o3 $2 N2 wfi 5 ¢fi w: m: m2 m: 2: 8 2 w» xw 3 E Nb 8 $ 3 S S ma“ w“ 3 £ N” mm QNQK 3 mfi w w wwabow awwoan: vwgzn 5 omaohuofl dosmfl 3Q 3.8a 5 396 we wogflfi cwwofimc was 9.353 otfia E wmamzowfi $3.9m nomufiwfiov ém Scam. 36 TEXAS AGRICULTURAL EXPERIMENT STATION. CORRELATION BETWEEN THE NITROGEN REMOVED IN CROPPING AND DE- i CREASE IN NITRIFICATION MADE AVAILABLE IN THE SOIL. The correlation between the nitrogen removed by the crops and the decrease in nitrification of the soil has been worked out by the methods already described. The correlation table is Table 24. The correlation coefficient R is .680j—_.029. This shows a good correlation between the i two factors. Crops which produced more nitrate nitrogen after cropping than they did before cropping are not included. - The correlation between the nitric nitrogen available in the soil and A the‘ nitrogen removed by the first crop R is 0.708:.25. RELATION OF THE NITRIC NITROGEN AVAILABLE AFTER CROPPING TO THE NITROGEN REMOVED BY THE THIRD AND FOURTH CROPS. It was considered that there might perhaps be a relation between the amount of nitrogen removed by the third and fourth crops and the amount of nitric nitrogen produced in the nitrification experiment made after the soils had been cropped. The soils were accordingly arranged in groups according to the nitric nitrogen available after cropping, and averages taken. The results are given in Table 25. With the exception of Groups 1, 6, and 9, the nitrogen removed by the third crop is in the same order as the nitric nitrogen available after crop- ping. The nitrogen removed from the soils of the first group by the Table 25. Relation of nitrogen removed by third and fourth crops to nitrate nitrogen produced ' after cropping, in parts per million. Produced Nitrogen removed by Per cent A.. __ ‘ nitmtes after cropping after nitrogen cropping Crop 3 i Crop 4 in soil Group 1. 0-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4.7 4.9 3.0 .069 Group 2. 6.1—12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9.6 4.2 3.7 .039 Group 3. 12.1-18 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 15.3 6.3 4.3 .044 Group 4. 181-24 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 20.2 9.0 4.6 -050 Group 5. 241-30 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 26.7 10.2 7.2 .080 Group 6. 30.1-36 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 31.9 9.3 9.8 .067 Group 7. 36.1—42 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 39.1 13.4 5.3 .102 Group 8. 42.1-48 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 45.9 15.7 10.8 .154 Group 9. 48.1-54 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 50.1 11.2 7.5 .094 Group 10.. 54.1-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 65.8 24.1 17.1 .156 third crop is equal to the nitrogen available after cropping, but with the other groups the third crop removed about two-fifths to one-fourth of the nitrogen available after cropping. It is seen that the nitrogen taken up by the third crop is not as much as the nitrification test would lead us to infer. The first crop exhausted the nitric nitrogen‘ much more closely. The nitrogen removed by the fourth crop in- creases with the nitric nitrogen available, with the exception of Groups '7 and 9. The nitrogen taken up by the crop varies from two-thirds to about one-seventh of the nitric nitrogen available after cropping. It would appear that the conditions in the pots for nitrification for the third and fourth crops are not as favorable as they are in the per- colation jars after cropping. It is possible ~that breaking up» the soil and preparing it for the percolators placed it in a more favorable con- dition for nitrification than it was in the pots. Table 26. CorrelationlTable. Nitrogen taken up by third crop and nifiraté nitrogen produced after cropping. RELATION OF SOIL NITROGEN, ETC, TO P01‘ EXPERIMENTS.’ 3'7 wiodoieddwiodoiedddodcieddgodoidc$$odoi’ <94 . . . -== "‘ ' : : g‘ 0° F‘! 'I—1 X q v-i a ~ o 0 -~ $2.‘ : : : g - o g0 ._. : : "" 1"‘ N j: F‘ II ' 0% Z o 1"“ : : . 1"‘ ‘*1 111 o o o c: v-lv-l - -o1 v-l u: w ~-m~- wwm m 5 -M--QNN m -MN§©NNfi-----fi w g9 . . . . . . F4 3Q . . . ,_| ‘ .qqq-un|gqqg~qqq q-qq-q . . . . . . . . . . . q-q Q; q»: . . . . . . . . . . . . . . 5y -waaw~vv~~ m m - ~ - v flmmww-~~----fi o gq . . . . . cq H -flu m 38 TEXAS AGRICULTURAL EXPERIMENT STATION. CORRELATION BETWEEN THE NITROGEN TAKEN UP BY THE THIRD CROP AND THE NITRIC NITROGEN AVAILABLE AFTER CROPPING. Table 26 shows the correlation between the nitrogen taken up by the third crop and the nitric nitrogen found in the nitrification test after cropping. p The coefficient of correlation calculated from this table, R, is .538i.O36. PRODUCTION OF AMMONIA. Some of the soils reported in Bulletin 259 did not nitrify, and the question arose whether ammonia wasvproduced in these soils to a greater extent than in soils in which nitrification occurred. The ques- i tion also arose whether the ammonia nitrogen in the soil, added to the l‘ nitrate nitrogen, would not be a better measure of the nitrogen avail- p ability than the nitrate nitrogen alone. For these reasons the study " of the formation of ammonia nitrogen was taken up in connection. with the formation of nitric nitrogen. Preliminary W0rk.—--It was ‘desired to conduct the ammonia work i: parallel with nitrification work by making an estimation of ammonia f in the filtrates on which the nitrates were determined. While it was . recognized that all the ammonia would not be removed from. the soil by the water, it was at the same time considered that the ammonia left l‘ behind would be either removed at a subsequent percolation, or else converted into nitrates and then removed. In order to ascertain the amount of ammonia which would be re- _~ tained by soils, two portions of the same soil were placed in percolators and one sample percolated with water, the other with very dilute am- I monium chloride. .The ammonia was determined by the colorimetric method described below. The soils were percolated with (a) distilled j water, (b) with ammonia solutions containing about 2O parts per , million of ammonia nitrogen in the form of ammonium chloride, and > (o) with solutions containing about 50 parts per million of ammonia nitrogen. The results of this test are shown in Table 2'7. As was, to be expected, the percentage of ammonia nitrogen absorbed by the soils was. quite high. It is therefore to be expected that the ammonia removed by water " in percolating the soils in these experiments may not represent all of. j. the ammonia nitrogen formed in the soil, but possibly only a small percentage of it; but any ammonia left behind should eventually be Q recovered as nitrates. ' - After various preliminary work the following method was adopted for the ammonia nitrogen in soils. DETERMINATION OF AMMONIA. Reagents. Ammonia-free Water. A.—Acidify distilled water with sulphuric , acid and distill in a room free from ammonia, rejecting the first 100 ~ c.c. Preserve in glass-stoppered bottle. Ammonict-free lVaiter. B.——Add 10 c.c. sodium carbonate solution y RELATION 0F SoIL NITROGEN, Era, TO P01‘ EXPERIMENTS. (5 per cent.) to 1000 e.c. water. Preserve in glass-stoppered bottle. 10 e.c. and dilute to 1000 W 39 Evaporate about 750 e.c. and c001. Standard. Ammonium ChZomdo.—-Diss0lve 1.91 gms. ammonium chloride in 1 liter ammonia-free Water, A. 1 0.0.20.5 mg. N. Take ith ammonia-free Water A 0r B. 1 c.c.:.005 mg. N. Table 27. Ammonia nitrogen absorbed from solution by soils. Ammonia nitrogen in solution used 18.0 23.3 13.8 51.7 Ppm. in ab- Ppm. in % ab- Ppm. in % ab- Ppm. in % ab- solution sorbed solution sorbed solution sorbed solution sorbed 853 First percolate . . . . . . . . . . . . . . . . . 6.25 65.3 1.56 93.30 7.50 45.4 0.78 98.5 a 853 Second percolate . . . . . . . . . . . . . . . 1.38 92.3 2.53 89.20 0.83 94.0 1.63 96.9 855 First percolate . . . . . . . . . . . . . . . . . 3.17 82.4 . . . . . . . . . . . . . . . . 4.88 64.5 . . . . . . . . . . . . . . . . 855 Second percolate . . . . . . . . . . . . . . . 2 .00 88.9 . . . . . . . . . . . . . . . . 1.88 86 .9 . . . . . . . . . . . . . . . . 858 First percolate . . . . . . . . . . . . . .. 14.50 19.4 10.00 57.00 12.50 9.1 19.00 63.8 858 Second percolate . . . . . . . . . . . . . . . 12.25 31.9 10.00 57.00 9.38 31.8 23.50 55.2 - 876 First percolate . . . . . . . . . . . . . . . . . 7.00 61.1 4.75 79.60 6.25 54.5 3.50 93.3 876 Second percolate . . . . . . . . . . . . . . . 3 .00 83.3 4.25 81.29 6.25 56.1 5.88 88.8 923 First percolate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.25 81.29 . . . . . . . . . . . . . . . . 10.00 80.9 3 923 Second percolate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.69 88.43 . . . . . . . . . . . . . . . . 11.40 78.3 924 First percolate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.75 83.87 . . . . . . . . . . . . . . . . 1.40 97 .3 5 924 Second percolate . . . . . . . . . . . . . .. . . . . .. . . . . . . .. 1.33 94.28 . . . . . . . . . . . . . . .. 5.20 90.1 925 First percolate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.38 ‘ 81.16 . . . . . . . . . . . . . . . . 5.40 89.7 f; 925 Second percolate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.09 91.00 . . . . . . . . . . . . . . . . 8.00 84.8 933 First percolate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.38 81.16 5.10 62.9 3.75 92.9 933 Second percolate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.20 77 .63 5.25 61.8 6.00 88.6 936 First percolate . . . . . . . . . . . . . . . . . 6.88 61.8 . . . . . . . . . . . . . . . . 4.69 65.9 . . . . . . . . . . . . . . . . 936 Second percolate. . . . . . . . . . . . . . . 5.25 70.3 . . . . . . . . . . . . . . . . 4.38 68.1 . . . . . . . . . . . . . . . . i‘ 937 First percolate . . . . . . . . . . . . . . . . . 17.00 5.6 . . . . . . . . . . . . . . . . 10.00 27 .3 . . . . . . . . . . . . . . . . {.1 ~ 937 Second percolate . . . . . . . . . . . . . . . 7.50 58.3 . . . . . . . . . . . . . . . . 6.25 54.5 . . . . . . . . . . . . . . . . 941 First percolate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.50 67.74 18.00 . . . . . . . . 5.30 90.0 T 941 Second percolate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.75 66.67 8.75 40.0 20.00 61.9 is 942 First percolate . . . . . . . . . . . . . . . . . 8.13 54.8 1.00 95.70 6.50 52.7 4.60 91.0 i . 942 Second percolate . . . . . . . . . . . . . . . 5.88 67.3 6.75 70.99 7.50 45.4 6.00 88.6 969 First percolate . . . . . . . . . . . . . . . . . 5.50 69.4 2.69 88.43 4.00 70.9 3.25 93.8 969 Second percolate . . . . . . . . . . . . . . . 2. 76 84. 7 2 .56 89.00 2.50 82 . 6 4. 25 91.6 981 First percolate . . . . . . . . . . . . . . . . . 17. 00 5.6 . . . . . . . . . . . . . . . . 17.50 . . . . . . . . . . . . . . . . . . . . . . . . j 981 Second percolate . . . . . . . . . . . . . . . 11.50 36.1 . . . . . . . . . . . . . . . . 8.00 41.9 . . . . . . . . . . . . . . . . -1125Firstperco]ate . . . . . . . . . . . . . . . .. 3.13 . . . . . . . . . . . . . . . . . .. i 1125 Second percolate . . . . . . . . . . . . . . . 3.08 83.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1267 First percolate . . . . . . . . . . . . . . . . . 10.50 41.7 3.17 86.40 15.50 . . . . . . . . 8.00 84.8 1267 Second percolate . . . . . . . . . . . . . . . 3.13 82.6 2.75 88.17 5.63 60.5 8.50 83.8 Solution used . . . . . . . . . . . . . . . . . . . . . .. 18.00 . . . . . . .. 23.3 . . . . . . .. 13.8 . . . . . . .. 51.7 . . . . . . .. g Standard Uolortmeter SoZutton.-—Use 10 e.c. Weak ammonium = chloride, about 90 of ammonia-free Water _ B and 4 e.c. Nessler’s solu- . tion, diluting to 100 e.c. 100 c.c.:.05 mg. N (5 parts per million on 10 gins. soil). iNessleris~ Solation.—Prepare by usual methods. Analytical Prooess.—Make percolate up to 200 e.c., take 20 e.c., add ‘i 2 gms. magnesium oxide and 80 e.c. ammonia-free Water. Distill off 50 e.c. Make up to 100 e.c. and take an aliquot. Dilute with am- monia-free water B. add 2 e.c. Nessler’s solution, and compare with lstandard. Take a larger or smaller aliquot according to the ammonia §§to be exp-ected. »g Make a blank determination, using 80 e.c. Water and 2 gms. mag- esium oxide. Distill off 50 e.c., dilute to 100 e.c. and take 50 e.c. a or the Nessler determination. 100 e.c. standard: 5 p. m. on 10 gms. soil (50 e.c.) :25 p. m. on 2 gms. soil (10 e.c.) fication would not be large, but that if soils containing larger amounts ? 4O TEXAS AGRICULTURAL EXPERIMENT STATION. PRODUCTION OF AMMONIA NITROGEN. Table 28 shows the production of nitric nitrogen, and of ammonia; nitrogen, in some soils which did not nitrify well, reported in Biilé letin 259. The soils were always percolated at the beginning of the nitrification work, and the amount of nitrogen recovered is shown the first column headed 0 under the head of nitric nitrogen, or monia nitrogen, respectively. The nitrification was conducted on fiv periods of four weeks each, and the ammonia determined in the fi three of these periods. With soils 1126, 4596, .4586, 7132, and 195p fair amounts of nitric nitrogen were formed during the last two periods; Table 28. Nitrate and ammonia nitrogen in soils in parts per million in successive periods of weeks. Nitrate nitrogen Ammonia nitrogen Removed by first crop C .- N) T'f . 3 4 5 Total 0 1 2 3 2.0 .0 0 1.1 . . . . .. 8.3 11.4 6.85 .66 .33 .14 7., 4.7 .3 .7 .8 . . . . .. 1.1 7.6 2.05 . .36 .15 .06 2.1 1.2 .0 .0 .0 0 .5 1.7 .41 .24 .03 .08 .6 .2 .0 .0 .2 . . . . .. .5 0.9 .96 .15 .15 .08 1. .0 .0 . . . . . . . . . . . . . . . . . . . . . . .. 0.0 .05 .08 . . . . . . . . . . .. . 13.9 .0 .0 .3 .0 .2 14.4 .17 .13 .06 .06 . .2 .0 .5 5.0 5.0 5.6 16.3 .58 .12 .05 .06 '°_ .0 .0 .5 r 5.7 7.4 3.4 17.0 1.76 .05 .01 .02 1. f .2 .0 .2 .2 .0 .3 0.9 2.58 .70 .23 .07 "I? .0 .0 .0 1.3 5.0 4.1 10.4 .20 .12 .0 .02 . 2.0 .3 .2 .7 .0 .5 3.7 1.42 .22 .0 .01 1.7 8.8 2.5 3.2 2.2 4.2 _ 21.7 1.40 .10 .01 .03 1. 5* The ammonia nitrogen recovered varies from .05 to 6.85 parts million in the first extraction before the nitrification had begun. The; ammonia produced during the regular nitrification periods was very} small, not much "more than one part per million for even the highes While there was some ammonia already present in the soil at t i‘ beginning of the test, there was little or no production of ammon” during the period of nitrification. Thedamount of ammonia presen A in most of these soils was comparatively small, and could practicall be left out of consideration. i The amount of nitrogen removed by the first crop» is also given in the table for such of the soils as were cropped. This also is not large but the ammonia formation does not throw any further light upon" the matter. With soil 2351, 7.7 parts per million of nitrogen was removed by the first crop, the total amount of nitric nitrogen formed was 1.7, while the ammonia nitrogen present and formed was 0.76 per million. The additional determination of ammonia nitrogen gave; . practically no additional information. With soil 3657, the amoun i: p of nitrogen removed by the first crop was 3.8 parts per million, amount of nitrate nitrogen formed was 0, and the amount of ammonia‘, nitrogen was .13. Here again the ammonia determination gave little.’ further information. - Itmight be objected to the above that the soils studied did not pro- . duce much available nitrogen anyhow for the crops, so that the total amount of available nitrogen that could be expected in the ammoni- RELATION or Son. NITROGEN, Ere, ro Potr EXPERIMENTS. 41 of available nitrogen were studied, more significant amounts of am- monia would be secured. On account of the above consideration, the ammonia nitrogen was determined in connection with the nitrification on 116 soils before cropping and about 117 soils after they had been cropped. The amount of ammonia nitrogen secured during the first period of nitrification was usually less than 0.1 parts per million. For this reason the ammonia determination was not made after the first period of four weeks. A list of these soils is given. in Table 29. Out of 233 soils there were 25 soils which produced more than .1 part per million of am- monia nitrogen during the first nitrification period of four weeks, and of these 25, 8 produced over 2 parts per million, and only 3 over 5 parts per million. i ' The figures in the first column of the table are for the first percola- tion, at the beginning of the experiment. Of the 116 soils before cropping, and 117 soils after cropping, only 2O soils before cropping and 1 after cropping contained more than 5 parts per million of the ammonia nitrogen. These are listed in Table 30. This includes both the ammonia nitrogen at the beginning of the experiment and that formed during the first percolation period. Table 30 also shows the nitric nitrogen produced during the nitrification of three periods of fourweeks each added to that originally present in the soil. It also ShOWs the amount of nitrogen removed by the first crop. ‘ Table 29. Soils which produced over 0.1 parts per million ammonia nitrogen in four weeks. _At_ End of begmmng four weeks 2350 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . _ . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2.94 .30 1934 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 0.11 0.37 3331 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 0.96 0.11 7090 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1.91 1.30 11028 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1.00 0.12 334 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 20.78 .12 6680 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3.62 4.80 7235 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6.92 1.33 7180 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2.27 1.63 3632 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5.58 0.15 6268 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4.94 2.32 7094 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 0.11 0.81 7113 . . . . . . . . . . . . . . . . . . . . . . . . . . _ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 0.25 7.32 7173 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 0.13 6.22 3412 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 0.15 1.12 7093 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 0.05 2.85 7256 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 0.06 0.88 7109 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 0.03 0.46 11095 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 0.06 0.88 11096 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 0.02 2.91 11097 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 0.05 0.52‘ 11098 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 0.02 0.63 11099 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 0. 0.17 11101 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 0.02 0.50 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7.92 3.65 6268 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4.77 15.40 With a few of these soils the addition of ammonia nitrogen to the nitric nitrogen explains why the first crop took up; more nitrogen than was present in the nitrates. For example, with SO11 981, the first crop took up 49.3 parts per million of nitrogen while the nitric nitrogen ' available was 49.9. If the nitric nitrogen-alone is considered, the first 42 TEXAS AGRICULTURAL EXPERIMENT’ STATION. crop apparently exhausts the available nitrogen completely, but if th ammonia nitrogen is taken into consideration, there is an excess y; about 13 parts per million of available nitrogen. With soil 894, the available nitric nitrogen is 72.9 and the nitrog taksp 7gp by the first crop '7 2.02. The ammonia nitrogen, howevej, 1S . . . . I With soil 1119, the available nitric nitrogen is 34.6, and the nit 1 gen removed by the first crop, 40.32. The ammonia nitrogen is 13.0 With soil 962, the available nitric nitrogen is 46.7 and the nitro taken up by the first crop, 48.16. The ammonia nitrogen is 5.63. With these four soils, the determination of the ammonia nitrog explains why the first crop should take up as much nitrogen as present as the available nitric nitrogen, or more. In these soils t available nitric nitrogen does not represent all of the available nits gen that is present in the soil. _ With the remainder of the 21 soils listed in Table 30, the determi; tion of the ammonia nitrogen throws no particular light on the matt A Table 30. Soils which contain ammonia nitrogen in excess of 5 parts per million. Ammonia nitrogen Nitric Nitr 14- Set _ _ nitrogen m n a‘ Beginning 4 weeks available 981 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 12.56 .07 49.9 59. ; 4689 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 8.03 .03 30.4 13. T 7250 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 8.09 .04 80.6 42. 1137 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 8.74 .01 75.3 11. " 1135 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 6,79 .02 38.3 26. 7129 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 8.24 .01 . . . . . . . . . . . . . . . . . . . . . . 11015 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 86 22.34 .03 894 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 87 21.56 3.21 72.9 72. 7112 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 87 11.23 .03 33.1 23. 334 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 90 20.78 0.12 267.9 84. 7235 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6.92 1.33 71.9 38. 7232 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 6.10 0.08 24.9 13. 7089 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 29.92 0.09 58.9 14. _ 1119 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 94 12.91 0.10 34.6 40. 7175 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 9.65 0.03 38.6 19. 7095 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 99 6.07 0.01 19.8 12. 1119 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 101 7,92 3,65 . . . . . . . . . . . . . . . . . . . . . 962 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 93 5.52 .07 46.7 7128 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 5.25 .. 90 20.4 3632 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 5.58‘ .15 63.9 3361 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 5.02 .09 36.6 W \ Only one-sixth of the 117 soils contained more than 5 parts per l; lion of ammonia nitrogen at the beginning of the experiment, and v few of them i produced any ammonia nitrogen, or enough to req’ consideration. Of the 21 soils containing more than 5 parts per u: lion of ammonia nitrogen, only four were of any particular significant, iWith the others, the determination only decreased the percentage > total available nitrogen that was removed by the first crop. a . Fromi the above work we conclude that the determination of J monia during the process of nitrification as carried out by us? usually unnecessary. The determination of ammonia removed by l, first percolation might be of significance in particular cases, but us it is of little significance, and may be disregarded. . ‘- _ RELATION or SoIL NITROGEN, ETo., To PoT EXPERIMENTS. 43s ‘EELATIoN BETWEEN AMMONIA AND NITRIC NITROGEN AVAILABLE- IN THE SOILS, AND’ THE NITROGEN REMOVED BY THE FIRST onor. lfTlle object of this study was to ascertain whether the determination .a.mmonia nitrogen in addition to the nitric nitrogen gave better cor- Xtion between the total available nitrogen and the nitrogen removed the first crop than does the nitric nitrogen alone. For this pur- “ correlation Table 31 was prepared. Only 95 soils were avail- e for this work, which is half the number available for the correla- with available nitric nitrogen. a . Table 31. Correlation Table. Nitrogen removedlby first crop and ammonia and nitric nitrogen produced by soil " Nitrogen in first crop, parts per million 61218243036424854606672788490 3? E a»; E . . . . N. . . 1172917 6 5 4 6 3 2 0 4 O 0 1 . The correlation coefficient for the total available nitrogen (including ‘th the ammonia nitrogen and the nitric nitrogen) and the amount nitrogen removed by the first crop», R, is .698i.036. The corre- onding factor for the correlation between the nitric nitrogen avail- Yle and the nitrogen removed by the first crop, R, is .708-_l-_.025. There is thus a slightly closer correlation between the nitric nitrogen Qailable and the nitrogen removed by the first crop» than between the tal available nitrogen and the nitrogen removed by the first crop. jis, may be_ due to the fact that a greater number of soils was in- uded in the correlation table for the nitric nitrogen. But since ually as good- correlation can be secured by considering the nitric ‘itrogen alone, and since the amount of ammonia nitrogen produced lder the conditions of these experiments is usually small, we may Tfely conclude that the ammonia determination may be left out of ‘nsideration in work of this kind. Only in special cases need the termination of ammonia be made. ‘ . ‘x z. ~I 9° v-A <9 w-u-u-A U! wwccoooccor-i-h-wwi-immwwoomw-loowihm 44 TEXAS AGRICULTURAL EXPERIMENT STATION. IRREGULAR SOILS. There are two classes of soils with which the relation betweenh nitrate production and the amount of nitrogen taken up by the c is not sufficiently close. In one class, the amount of nitrogen taken by the crop is. much less than the amount produced in the nitrificani. test. In the other class, the nitrogen taken up- by the crops consi‘ ably exceeds the amount produced by the nitrification test. If i causes of these differences could be ascertained, and corrected, the relation between the nitric nitrogen produced in the nitrification t‘ and the amount of nitrogen taken up- by the crops would be m closer. The discussion of these soils has been delayed to the end a the bulletin for the reason that preceding Work might throw some upon the matter. Soils of the first group, which took up much less nitrogen in first crop than the amount of available nitrogen produced in the ni ; fication test, are shown in Group 1 in Table 17. The five soils of tf group- produced on an average 43.4 parts per million available nit i nitrogen in the nitrification test, while the first crops took up o» 6.31 parts per million. A similar relation is observed with Group i in Table 22. Table 32 contains the fivetsoils of Group 1, referred to above. examination of this table shows that only two of these five soils, 36 and 992, are decidedly out of line, and these are chiefly responsib for the irregular appearance of the group. Table 32. Soils of Group 1, Table 17, where firstprops take up less nitrogen than the soil contains _ mtnc nitrogen. Nitrogen per million Available KD crop gm. KDN % nitric first nitrog First Second Total nitrogen First Second crop in soil crop crop 1 and 2 per million crop crop gm. ~ 1 9184 subsoil . . . . . .. 6.30 1.62 7.92 23.1 6.3 1.3 29.9 .046 7164 subsoil . . . . . .. 7.78 1.62 9.40 14.5 7.4 1.0 40.4 .038_ 7132 Subsoil . . . . . .. 4.36 2.64 7.00 4.4 4.7 1.5 37.6 .045 3620 Subsoil....... 6.64 10.60 16.24 56.6 6.5 9.3 48.4 ‘.122 992 Subsoil . . . . . .. 6.50 56.54 62.04 118.7 13.0 22.8 29.9 .040 i Average . . . . .. 6.31 14.60 . . . . . . . . .. 43.4 7.6 7.2 . . . . . . . . .. .058 1;; Sample 3620 produced 56.6 parts per million of nitric nitrogen, but? the first crop took up only 6.64 parts per million, but in another poté experiment on the same soil the first crop withdrew 34.4 parts perf million of nitrogen. The difierence, then, is due rather to the error in the pot experiment. Soil 992 produced 118.7 partsper million nitric nitrogen and the? first crop took up 6.5 parts per million, while the second crop took.» up 56.5 parts per million. Unfavorable conditions in some way. pre-I vented the first crop- from utilizing the nitrogen, as shown by the sec- ond crop. ' "i The second class of soils is those from which the first crop removed r much more nitrogen than was formed in the nitrification test. This class is shown in the average of Group 1 of Table 18, and to a less extent in Group 2. In Group 1 the average available nitric nitrogen i i RELATION OF SoIL NITROGEN, ETo., To PoT EXPERIMENTS. 45 is 11.6, While the crop removes 16.36 parts per million, or 355.6 per cent. of the available nitrogen is removed by the crops. In Group 2 the available nitric nitrogen is 15.2, While the first crop removed 18.00 parts per million, and the percentage of available nitric" nitrogen re- - moved by the first crop is 118.5. Group 1 contains 11 soils, and Group 2 contains 29. -Another effect of these unusual features of the soils is shown in Group 1 and Group 2 of Table 22. After cropping, the amount of nitrification is larger than in the original soil. Ap- parently the cropping favorably affects the nitrification test. The ni- trate nitrogen before cropping in Group 1, Table 22, is <1.6Aparts per million, while after cropping it is 10.7. With Group 2 the nitrate nitrogen produced before cropping is 15.2, and after cropping 14.7. The crops removed 26 to 30 parts per million of nitrogenfrom the soil between these tWo tests. m 0 _.l_ T A T S T N E M m E P X E m U T L U O TL R G A S m T 46 ¢ - ¢ . - . . - .- ..-¢-..¢. q ¢-~.-.@w$%@>< owm wm. oSnwuo mm: wmw w m.w m.wS mwww ww.m wm.Sm. w.mS S.wS mw9 . . . . . ........So=m2S5 2i o S9 mSuw mm SwwS w 9m 9mm mwmm c9w mmmw 9Sm 9S Sm9 . . . . . . . . . . . .2325 mmmw o S9 mum mm 9cm w 9m 9S owmw ww.m o9wS 9mS 9mS wm9 . . . . . . . . . 5.5.5 22. o wS. mSuw m.S m.S w 9m 9Sm wwmw 69w mmmm 9m 9wS mm9 . . . . . . . . . E325 mmmm. o wSw wS|> 9mm 9mm w mm 9mS mwmw ww.m wSwm 9S. m.SS mm9 . . . . . . . . . . . ISgoD N5 o wm. mS|w 9m Em w 9m mwm ww.mw wm.w m9¢w 9mS 9mS wm9 . . . . . . . . . . . .1325 S5. mSm S. mSno m.S 9mm w m.w w.S owwm wmm. m9mS 9mS w.SS mw9 . . . . . . . . .....So=o:n5 ma: o wS. o1. mm.m 9cw w . 9m m.mw m9mw o: m9mm S.wm m.SS mw9 . . . . . .2525 wSw o 5. mSvm wdS 9w w 9m w.S No.5 mmdS c9mm 9m m.mS mw9 . . . . . . . . .....S2aooD mSm. .m nsoew - . . . . . 0-; -..». ..-...--. .-..¢.¢ ¢ .1 - é x¢% £.¢ cg. . -. 2a wS. wm|mS 9m m.» w m.o m.SS w9mS mS.S omw 9w 9oS mw9 . . . . . . . . S255 S: o mS. wmamS o2 w 9m 9S mmwm mS.w ooé 9w mm mw9 . . . . . . . . . . . 122:5 wwww 8m oS. mmuS 9n 9m m 9m m.mS m9mm o; wSmm m.S m.w wm9 . . . . . . .3525 mwwm mom mm. S|m 9o w.Sm w m.m 9m m9cm omw ww.m 9S S.w mm9 . .. ._ .. .285 mmfi wmw mm. wSnm . 9m m.mS w m.S 9w w9S ww.m m9w 9wS w.w mw9 . . . . . . . .335 mwSm. o mm. SmnS 9m ms w 9S 9w w9mm mS.w w9S w.w S.» wm9 . . . . . . . . . . . ..S§o2S5 wmwm. 8m mS. wmLmS 9S 9mm w m.m m.wS ommm m9w m9mS m.wS 9w mw9 . . . . . . . . . . . . .2525 ma» o mw. wmumS m.w mmm m 9m m.S w9cm ww.m w9S 9w 9S mm9 . . . . . . . .. S3225 wSww 8w w9 wm|mS 9w mdw m m.S 9wm w9mw cmm 2.5 9m w.S mw9 . . . . . . . . . . .6825 Sow 8o S. Smnw o 9m w m.S m.wS w9mm mmm wS.wS 9w 9o mw9 . . . . . . . . . . . 133225 26S. o mm. wmumS 9m m.S. m m.S m.wS wwéw oS.m w9wS S.mS 9c wm9 . . S2525 mmmw S nsoow 28o hon c258 Son no.8 no.6 wnooo no no.8 no.8 wflnnooo wfinnooo o2: Sooflsmaoo mOmm mnoho mo SEooom Swan Sfion. 288m SEE .253 ooowom mom E >222 . 26o 6m finomS wSoSS o>SSo< 232:2 . oowoéi 2m .285 “SM noSSSSE non oooomohn 28o oom nowobSZ oowomfln oSHSSZ #8» qommoouifin on». 8 22$ onouo ofi o» nowoufio v.82 SoSoSS mow? onwonw no mSSom mm oSnoB § .17 11s.... a 4'7 RELATIONMOF SOIL NITROGEN, Euro, TO PQT EXPERIMENTS. .....-.. . . . . . . .. Qw-é ¢ @.@ . . . . . . . . . ..Q@_QMQ>< 6 3. 3A. 5.5 m.3 w 5.6 w.3 66.5 w3.3 3.3 6.3 5.63 3.8. . . . . . . . ........_§5D 3333. 6 mm. 3am mm. wmm w 3m m.3 53.8 m; m3~3 m.33 33 mmo. . . . . . . .........3§5D mwm» 666 m3. mnc m.3 5.66 w w.m m.3 mwwm 6.6.5 mm m3 w.3 m.3 56. . . . . . . . . . .3650 33K 6 3. 6.6 3 6.6 w 3m 33 03.3 m3w mw.m3 6.6 w.3 .86. . . . . . . . . . . . ....3§5D 3.33. 6 3. omum 6.5 6.65 w 33 33 3.3m w3m w33 m.3. 33 656. . . . . . . . . . . . ....3§5D mmmm 6 ow. cmum 33 wmm w m.m :3 3mm. m3.m m33 3.mw 33 66. . . . . . . . . . . . ....3§5D 66: 6 m3 m3|c 3 w.m m 3.m 33 m3m3 m: 65.3.3 :3 33 66. . . . . . . . ..3§5D mwmm Q 3m. mmwom 33 Z5 w 3m 3.3 m3mm owm mw.3 33 33 wm3 . . . . . . . . . . . ....3§5D 3E3. 66w mm. m3|m Q33 33 m m.3 m.m3 w33 m3m wm.3 m.3 33 33 . . . . . . . . . . . ....3§5D 333. 6 3m. 3am 3m 3mm w w.m m.3 . m3wm mm.w mm.w3 33 m.3 56. . . . . . . . . . . . ....36=6D 8t 6 3. m31m w.3 m.3 w 3m 33 mmmm 66.5 3 .6 3.w3 33 656. . . . . . . . . . . . . . 2363533 m3» 6 3. m3|m 3 33w w 33 w.33 mmmm mm.w m3m3 m.3 m.w3 wm.3 . . . . . . . . . . . . . .3650 $3. 6 >3 31.3. 3 m.3m w m.3 3.33 66.55 omm 333 33 w.m3 £6. . . . . . . . . . . . . . .3659 66:. 6 m3. 66 m.3 3mm w 3. m.3 E56 3H3 m.3 33 6N6. . . . . . . . . . . . 1.35533 6w: 6 5. wm|m3 3m 3mm w 33 w.3. E53 m33 5....» 6.6 m.w3 mm3 . . . . . . . . . . . . . ..3§5D w33. wmw 33. 3am 3m 6.» w. 5.6 3m3 3.3 3.13 66.63 6.5 m.m3 66. . . . . . . . . . . .._§5D Q33. 6 33. wm|m3 3m 6.56 w m.m m.w3 w3wm E5 m333 3mm 3m3 33 . . . . . . . . . . . . . .3550 mwmm cmm 66. m3|m 66.3 33 w w.3 33 .633 66.6 65.6 3.3 333 666. . . . . . . . . . . 238533 3.33. 6 >3 wm|o3 m.3 m.3m w m.3 m.m3 3.3m w3.m $.33 m.3 m.3 mm3 . . . . . . . . . . ..3§5D 333. 6 w3 wmam m. m..33 w w.3 3w3 mwwm- mm.w m333 5.6 v: 333 . . . . . . . . . ......3§5D 662. m 3560 3866 36.3 8633338 6.3 Q96 3396 5.36.6 =6 .396 .396 33333366 33333936 6833 3668:6866 mOmm 5336.6 3o 68.8w 65.33 3666.3. 38666m 5.33 666.34 6.6.3633 33.5 :3 333.363. 6866 6.3 3333363 E633 636w. 633882 8636.338 8m .5896 3 8633338 .63 366636.23 6866 .63 . 863.6532 8636.663: 63.632 .3563 86336636338 Q50 Ow fldflu 236.6 03$ Ow QQMOHZQ P308 A023 5.336% m0 mmom 63.3.6.3. 48 TEXAS AGRICULTURAL EXPERIMENT STATION. The details of these groups are given in Table 33. In only one soil of Group 1, No. 7174, is the nitric nitrogen produced after cropping decidedly less than that producedbefore cropping. The amount of nitrogen taken up by the crop is slightly less than the amount of ‘nitric nitrogen produced in the soil, so that this soil need not be considered as an unusual soil. Soil 7132 gave up about the same amount of nitro- gen to the crop as was produced in the nitrification test, and the same is true with soil 7253, although both of these soils produced more nitrates after cropping than they did before cropping. If the soils of Group 1, producing less than 10 parts per million of nitric nitrogen, are considered, we find that of the 11 soils, 8 gave up more nitrogen to the first crop than is produced in the nitrification test, and 9 pro- duced decidedly more nitrates after cropping than they did before cropping. For some reason or another, these soils did not produce as much nitric nitrogen in the nitrification test as they should have produced. If we consider the soils of Group 2, producing 10 to 20 parts per million of nitric nitrogen in the nitrification test, we find that 9 give up more nitrogen to the first crop than found in the test, and 14 pro- duced more nitric nitrogen after cropping than they did before cropping.- The correlation between the nitric nitrogen produced in the nitrifi- cation test, and the nitrogen taken up by the first crop, is more im- portant than the decrease or increase in nitrate production caused by the cropping. - The soils of Group 2 are divided into two classes and each class is averaged separately. Class 1, unusual soils, includes those soils from which the crops take more nitrogen than was produced in the nitrifi- cation test, and Class 2, usual soils, includes those from which the crop-s took less than produced in the nitrification test. No particular feature of the analysis could be taken to distinguish between the soils here called unusual and those called usual. Some are acid and some are not acid. Many in both groups are low in lime, while two unusual soils contain 3.14 and 0.71 per cent. lime, respec- tively. Sometimes, in the nitrification work, the soils did not percolate well. Sometimes less percolate was secured than the 200 c.c. desired. In a few cases only 25 or 50cc. were secured; with still fewer, there were only a few drops. This matter was traced back to see if it would account for the soils termed “unusual.” It did account for three soils of Group 1 and one of Group 2, but soil 7253 of Group 2, classed as “usual,” also did not percolate well. However, these four soils (3657, 8818, 3338, and 7172) may be excluded on account of poor percolation. This reason could not apply to any of the others. It was pointed out in Bulletin 259 that carbonate of lime (1 per cent.) eliminated conditions unfavorable to nitrification, and increased nitrification, but that it might also eliminate natural differences be- tween soils. Table 34 shows the effect of carbonate of lime upon soils which did not nitrify well, which were listed in Table l4 of Bulletin 259, but the amount of nitric nitrogen is not stated in the same way. The nitric nitrogen present in the first percolation is added in the results given in‘ Table 34, as with all cases reported in this bulletin. But this was RELATION OF SoIL NITROGEN, Era, TO P01‘ EXPERIMENTS. 49 p134. Nitric nitrogen produced with and without calcium carbonate on soils which did not nitrify well. Total Total Nitrogen 4 weeks 28 weeks Available per- million no carbonate nitric taken by carbonate added nitrogen = first crop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4.0 62.2 11.0 e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 13.3 49.4 8 5 36.18 - . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1.5 43.0 10.7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 0.0 42.6 4.7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 0.5 27.3 0.9 18.14 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6.7 11.3 14.5 7.78 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2.1 185.2 14.9 the case with Bulletin 259, as it dealt with the production of ; ates- ' '7ith soils 2347 and 7090 there is a closer relation between the nitro- f: removed from the soil by crops and the nitric nitrogen produced er the carbonate of lime was added than that produced before it was i; _ With soils 1126, 2351, 3976, and 1138 the reverse is the case. matter requires further study, but from the results here reported iwould appear possible that the addition of carbonate of lime in the i ification tests might push the production of nitric nitrogen far 0nd the amounts that the first crops would take up- in the pot eriments, and thus the correlation would be poorer than without the “bonate of lime. i ' SUMMARY AND CONCLUSIONS. 1. This bulletin is the study of the relation of the total nitrogen the soil, the nitrogen available in the form of nitrates, and the rogen available in the form of ammonia, to the nitrogen removed ‘crops in pot experiments. a ' The average Weight of nitrogen removed by the four crops in- bases With the percentage of total nitrogen in the soil. . The first crop is much larger than the succeeding crop-s. The average weight of the second crop on the soil containing ‘if smallest amounts of total nitrogen is only 13.5 per cent. of the crop, and the fourth crop is 11.4 per cent., While for the soils hest in nitrogen, the second crop is 68.7 per cent., and the fourth u}. is 36.0 per cent. of the first crop. The differences are not so f; when the nitrogen removed is considered. . Conclusions as to the needs of the soils for nitrogen as deter- ed by pot experiments would depend upon the number of successive ‘s grown Without nitrogenous fertilizer. gays be determined in pot experiments of this kind. of the soil or 1% to 2 percent. per crop. f. the nitrogen of subsoils. Subsoils are erratic, and may be much or much poorer than the surface soils. . i On an average, non-acid soils give up- more nitrogen to crops Crops of nearly the same Weight of’ dry matter may vary con- v yrably in nitrogen content, and the nitrogen of the crops. should ‘ The four crops usually remove 6 to 9 per cent. of the total nitro- On an average, the nitrogen of surface soils is better taken up c 50 TEXAS AGRICULTURAL EXPERIMENT STATION. than acid soils, but many of the individual acid soils give up m0 nitrogen than the corresponding non-acid soils. . 10. Little relation could be found between the nitrogen taken u by the soil and the active phosphoric acid of the soil, or the ac" consumed, or the lime. 11. The amount of nitric nitrogen. present in the soil at the o; ginning of the experiment, added to that produced in the percolato ' during three periods of four weeks each, was compared with the nit o. gen taken up by the first crops. 5‘ 12. There is a close relation between the amount of nitrogen moved by the first crop, and the amount of available nitric nitrogei The nitrogen removed by the crops varies from 58.1 to 76.1 per ce'_ of the nitric nitrogen with the exception of some groups out of rel tion with the others. ' 4 i 13. The soils used in the pot experiments were subjected to simil nitrification tests after the crops had been grown on them, and results compared with the uncropped soils. ; 14. The effect" of cropping is clearly shown by the differences tween the nitrification before and after cropping. There is a relatio between the decrease i.n the nitric nitrogen formed and the amount u“ nitrogen withdrawn from the soil by the crops‘ grown upon it. 15. The nitrification test enables one to trace the effect of croppi upon the nitrogen of the soil. a 16. The relation between the nitrates produced after cropping an the nitrogen removed by the third and fourth crop, is not’ as close the relation between the nitrates available before cropping and t “l, nitrogen removed by the first crop. _ i - 1'7. Ammonia was determined by colorimetric methods in a numb of soils used in the-pot experiments. “ 18. Considerable percentages of ammonia may be absorbed and tained from the percolation, but these would later undergo nitrificatio: 19. The amount of ammonia nitrogen secured during the fi ~__' period of nitrification was usually less than .1 part per million, w‘ that the ammonia determination was not made after the first peri of four weeks. . l, 20. In 233 soils, half of which had been cropped, 25 soils produc more than .1 part per million of ammonia nitrogen during the fi :1" nitrification period of four weeks ; 8 of these produced over 2 parts ~.; million, and only 3 over 5 parts per_million. 21. Only 20 of the 233 soils had available more than 5 parts p million of ammonia nitrogen, including that originally present in t 1 soil. 22. With a few of the soils, the determination of ammonia nitroge ofiers some information, but with the majority of the soils the deter mination gives no particular aid. The determination appears to o: unnecessary as a rule. 'y 23. With some soils the amount of nitrogen taken up by the crop is much less than the amount produced in the nitrification test. Th'_ may be partly due to the unfavorable conditions during the pot exfi periments. Y‘ 24. The amount of nitrogen taken up by the crops from some‘ soilg considerably exceeds the amount produced by the nitrification test; l RELATION OF SoIL NITROGEN, Era, T0 Potr EXPERIMENTS. 51 These soils also produce more nitric nitrogen after cropping than they did before cropping. 25. Addition of carbonate of lime may increase the nitrification of some soils which produce less nitric nitrogen than the amount of nitro- gen taken up by the crops, but the amount of nitrates produced may also greatly exceed the amount of nitrogen taken up by the crops, so that there is no better correlation than before. This matter requires further study. 26. In the correlation between the nitrogen content of the soil and‘ the nitrogen taken up by the four crops as estimated by statistical methods, R is .653i.O29., 27. In the correlation between the total nitrogen of the soil and the nitrogen taken up by the first crop, R is .581i.033. 28. In the correlation between the amount of nitrogen taken up by the first crop and the amount of nitrates available in the soil, R is .708i.025. There is thus a closer relation between the nitrogen taken up by the first crop and the nitric nitrogen used than between the total nitrogen of the soil and the nitrogen removed by the first crop. 29. In the correlation for 56 soils with .021—0.04() per cent. total nitrogen between the available nitrogen of the soil and the nitrogen removed by the first crop, R is .40'7i.O74. 30. In the correlation for 52 soils with .O4=1—.O6O per cent. total nitrogen, between the nitric nitrogen and the nitrogen removed by the first crop, R is .556-|-.064. 31. In the correlation between the nitrogen taken up by the third crop and the nitric nitrogen found in the nitrification test after the cropping, R is .538+.036. 32. In the correlation between the nitrogen removed by the crops and the decrease in nitrification of the soil, R is .680+.029. 33. In the correlation between the total available nitrogen, that is, the ammofiia nitrogen plus the nitric nitrogen, and the amount of nitro- gen removed by the first crop, R is .698:+_—,.036 on 95 soils. The de- termination of ammonia gives no increased correlation over the de- termination of nitric nitrogen alone. I