AS94412 3-31“ -I_. TEXAS AIIIIIEUEIURAI EXPERIMENT SIATIIIN AGRICULTURAL AND MECHANICAL COLLEGE OF TEXAS W. B. BIZZELL, President BULLETIN NO. 267 OCTOBER, 1920 DIVISION OF CHEMISTRY THE RELATION OF THE PHOSPHORIC ACID OF THE SOIL TO POT EXPERIMENTS B. YOUNGBLOOD, DIRECTOR COLLEGE STATION, BRAZOS COUNTY, TEXAS STATION STAFF T ADMINISTRATION B, Younennooo, M. _S., Director Cass. A. Feunza. Chief Clflk A. S. WARE. Secretary _ _ A. D. JACKSON, Ezeerutive Assistant CHARLES Sosouu, Technical Assistant VETERINARY SCIENCE ‘M. FRANCIS. D V. M., Chic] _ H. SCHMIDT, D. V. M., Veterinarian _ D, H. BENNETT, V. M. D... Veterinarian CHEMISTRY G. S. FRAPS, Ph. D., Chief; State Chemist S E. Asnumr. M. S., Assistant Chemist S. Lonnmn. B. S., Assistant Chemist J. B. SMITH. B. S., Assistant Chemist WALDO WALKFR. Assistant Chemist FIORTICULTURE H. Nizss. M. S., Chief _ W. S. HOTCHKISS. Horticulturist ANIMAL INDUSTRY J. M. Jonas, A. M., Chief; Sheep and Goat Investigations. J. B. McNULTY, B. S.. Dairiyman R. M. Smmwooo, B. S., Poullruman , Animal Husbandman in Charge of Swine I nvesligations A. BRFWl-"R, B. S., Assistant Animal [lus- ENTOMOLOGY M. C. TANQUARY, Ph. D., Chief; State Ento- molngis» H. J. Beimirmn. B. S.. Entomologist H. B. PARKS, A niculturist C. S. RUDE, B. S.,_Assistant Entomologist AGRONOMY A. B. Cowman, B. S.. Chief A. H. Lennon, B. S., Agronomist E. W. GEYER, B. S., Agronomist — ————, Agronomist PLANT PATHOLOGY AND PHYSIOLOGY J. J. TAUBENI-IAUS. Ph. D., Chief FEED CONTROL SERVICE F. D. FULLER, M S.. Chief ' S. D. PEARCE. Executive Secretary FORESTRY E. O. SIECKE. B. S.. Chief; State Forester PLANT BREEDING E. P. l-Iuunenr. Ph. D., Chief FARM AND RANCH ECONOMICS A. B. Cox, Ph. D., Chief SOIL SURVEY ‘"\V. T. CARTER, Jn.. B, S ..Chief T. M Rusnmznn. B S . Soil Surveyor bfllldmfl" H. W. HAWKER, Soil Surveyor SUBSTATIONS NO- l- Beflville. Bee Count)’ No. 8. Lubbock, Lubbock County I. E. COWART, M. S., Superintendent No. 2. Troup. Smith County W. S. Horcmnss. Superintendent No. 3. Angleton, Brazoria County E. B REYNOLDS, M. S.. Superintendent Beaumont, Jefferson County A. H. Pnmciz, B. S.. Superintendent No. 5. Temple, Bell County D. T. KILLOUGH, B. S., Superintendent Ne. 6. Danton. Denton County C. H. MCDOWELL. B. S., Superintendent No. ur, Dickens Coun 7. S ty _ B. E. ICKSON, B. S.. Superintendent tAs of October 1, 1920. B E. KARPER, B. S., Superintendent No. 9. Pecos, Reeves County V. L. CORY, B. S., Superintendent No. l0. (Feeding and Breeding Substation) College Station. Brazos County _ L. J. McCALL, Superintendent No. ll. Nacngdoches» Nacogdoches County . Superintendent **No. l2. Chillicothe, Hardeman County A. B. CRON, B. S., Superintendent V. E. HAFNER, B. S., Scientifir Assistant Ne. l4. Sonora. Sutton-Edwards Counties E. M. PETERS, B. ‘S., Superintendent ‘In cooperation with the School of Veterinary Medicine, A. 8: M. College of Texas. "In cooperation with the United States Department oi Agriculture. CONTENTS. PAGE Introduction . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Previous Work . . . . . . . . . . . ._ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Method of Work. .\ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Relation of Crops to Active Phosphoric Acid . . . . . . . . . . . . . . . . . .. '7 Relation of Successive Crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 8 What Shall Represent the Fertility . . . . . . . . . . . . . . . . . . . . . . . . . .. 11 Groups of High, Medium and Low Production . . . . . . . . . . . . . . . .. 11 Method of Chemical Analysis of the Soil . . . . . . . . . . . . . . . . . . . . .. 16 Relation of Crops to the Chemical Composition of Soils More or Less Productive Than the Average . . . . . . . . . . . . . . . . . . . . . . . .. 16 Relation of Crops to Surface or Subsoil . . . . . . . . . . . . . . . . . . . . . 19 Relation of Total Phosphoric Acid . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Relation of the Nitrogen Content . . . . . . . . . . . . . . . . . . . . . . . . . . .. 21 Relation of Acidity of Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Relation of Bases to Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 23 Relation of the Composition of the Soil to the Phosphoric Acid Taken Up by Crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Relation of the Active Phosphoric Acid and the Total Phosphoric Acid to the Needs of the Soil for Phosphoric Acid . . . . . . . . . . . . . 31 Statistical Results of the Study of the Phosphoric Acid Removed from the Soil by Crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 34 Phosphoric Acid Dissolved by Successive Extractions . . . . . . . . . . .. 38 Correction of Acid for Lime Removed . . . . . . . . . . . . . . . . . . . . . . . .. 39 Discussion of Individual Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 y Details of Pot Experiments. . . . .~ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Summary and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 [Blank Page in Original Bulletin] BULLETIN No. 267. OCTOBER, 1920. THE RELATIQN OF THE PHOSPHORIC ACID OF THE SOIL TO POT EXPERIMENTS. BY G. S. FRAPs. \ One of the most important problems of agricultural chemistry is to determine the relation between the chemical analysis of the soil and the need of the soil for plant food. The problem is a complex one, as a number of factors enter into the matter. In previous b-ulletins, it has been shown that there is a relation between the active phosp-horic acid of the soil and the results in pot experiments. This bulletin car- ries the subject further and deals with the relation bet-ween the phos- phoric acid, the chemical composition, and the results of pot experi- ments. Other bulletins have considered the phosphoricacid, the potash, and the humus of the soil. PREVIOUS WORK. Bulletin 126 (1909) contained a study of the active pho-sphoric acid of soils, and showed that the quantity of phosphoric acid extracted from a soil by crops grown in the pot experiments, on an average, increased regularly with the amount of active phosphoric acid extracted" from the soil by N/5 nitric acid. It was pointed out that the soil may pro- vide sufficient phosphoric acid for large field crops, and yet respond to fertilization with phosphoric acid in pot experiments, for the reason that conditions in the pot may favor a larger growth of the plant than conditions in the field. It was stated in Bulletin 126 that the-plant food withdrawn from the soil by the plant depends upon the form of combination of the plant food, its protection or nompyotection by incrusting particles, the action of weathering agencies upon it, and the nature of the plant. The composition of the soil extract depends upon the quantity of the phosphate exposed to the solvent, the solubility of the phosphate under the conditions ofthe extraction, the solubility of any material which may protect phosphate from the action of the sol- vent, and the fixing power of the soil for phosphoric acid from the sol- vent. Fifth-normal nitric acid dissolved phosphate of lime completely, but dissolved only to a slight extent the iron and aluminum phosphates which usually occur in the soil. It apparently distinguishes between these two classes of compounds. But N/5 nitric acid may not dis- tinguish between different phosphates which have unequal values to plants. ‘Soils absorb phosphoric acid in solution from N / 5 nitric acid, and other solvents, so that the amount of phosphoric acid in the extract does not necessarily represent the total amount present and soluble in the solvent. This fact complicates the problem decidedly, since the fixing power of the soil for phosphoric acid must enter into consid- 6 Texas Acarctrnrunan EXPERIMENT STATION. eration. A port-ion of the phosphoric acid dissolved by N/5 nitric acid comes from the highly insoluble iron and aluminum phosphates. Limestone soils may contain phosphates which are protected by the carbonate of lime from the roots of plants, but which are exposed to solution when the carbonate of lime is dissolved by the solvent. It is ditficult to allow for the effectspof phosphates protected by in- crusting material, and for fixation by the soil, in considering the rela- tion of the active phosphoric acid of the soil to pot experiments, and needs of the soil in the field. A soil with a high. fixing power may really contain large amounts of active phosphoric acid but the extract may contain only a small amount. In Bulletin 1'78 (1915) it was shown that the presence of carbonate of lime may increase the quantity of phosphoric acid taken up from phosphates of the soil in; pot experiments. The presence of carbonate of lime-, or of vegetable matter, may bring about diiferences in the quantity of phosphoric acid assimilated by plants from soils containing equal quantities of active phosphoric acid. The addition of carbonate of lime caused an increase in the quantity of the phosphoric acid taken up equal to three to seven bushels per acre per crop of corn, while the vegetable matter in three cases caused a gain in phosphoric acid taken up equal to- two or three bushels of corn per acre. Bulletin 212 (1917) deals with the availability to corn and sorghum of the phosphoric acid of rock phosphate, which is chiefly in the form of phosphate of lime. There were very decided variations in the value of rock phosphate in different soils.- The average recovery of phos- phoric acid from rock phosphate in 21 experiments was 9111.1 per cent. This work is of significance in connection with the fact that the active phosphoric acid of the soil is believed to come chiefly from phos- phates of lime. The first crop removes 5.8 per cent., on an average, of the phosphoric acid from rock phosphate. The phosphoric acid of rock phosphate thus has a. low availability to corn and sorghum. The influence of large quantities of rock phosphate upon the amount of phos- phoric acid taken from the soil is being studied. . Bulletin“ 126, referred ‘to above, showed that the active phosphoric acid of the soil is, on an average, related to the deficiency of the soil forlphosphoric acid in pot experiments, but there were deviations from the average, and the object of the present bulletin is to ascertain, if possib-le, the causes of the deviation. METHOD OF WORK. The object of the present work is to ascertain the relation between the phosphoricacid in the soil and the results of pot experiments. For the purpose of this work, the samples of the soil were divided in series according to the contents of active phosphoric acid. Two portions of 5000 grams each of the soil were Weighed out in galvanized-iron pots, and one portion received a complete fertilizer, consisting of dicalcium phosphate, ammonium nitrate, and sulphate of potash. The other pot received only nitrogen and potash. The amount of soil on hand in most cases did not permit the planting of duplicate pots. Two crops were grown each. year, the first crop being corn and the second crop being sorghum. As a rule, four crops were grown for the purpose of the ex- periment, although a larger number of crops was grown in some cases. The pots were kept in a green house, or in plant houses consisting of RELATION or PHOSPHORIC A011) on SorL TO Por EXPERIMENTS. 7 small frame houses with glass tops, and canvas tops and sides. 'After' harvest, the crops »Were~ dried, weighed, and subjected to analysis. Each series of soils was- kept under the same conditions as far as possible, and treated alike. As stated above, the soils ‘of each series contain the same quantity of active phosphoric acid. Detailed results of the experiments are given in Table 28. RELATION OF CROPS TO ACTIVE PHOSPHORIC ACID. Table 1 shows the average relations of the active phosphoric acid t0 the average results of the pot experiments. The total weight of the four crops, grown in the pots which did not receive phosphoric acid, increases with the active phosphoric acid content of the soil, with the Table 1.—Average results of four crops on the soils. B; m may 3;? m S. 1'52 m Si: ha Om Q QE a f: T: as s... as ,<_> ==., M» M; =2 a 2;. ca) hgq O UC- Qd 0;; u- o [-14 5r- ,_, ‘i0 ‘:0 ‘i: gag 9 Q91 s om 9m 0"‘ 01-. 0 Q P u Z“ i-Y-v- :25 4:” no n5 Q.%° o $75’ 8 f3 a Q5‘ °~=~ ‘M8 °- '° =2 “t. Z8 Z62 3° '33 83s 5'28. a U £17" J J Q 5 < M 2 M n. n. n. u Z Series 131, 29 . . . . . . . . . . . .. 7.3 113.1 28.0 7.0 0546 .0136 2.7 8.6 18 ------ ~ 12212:; as 12-2 are as 4s GTIES . . . . . . . . . . . . . . . .. . . . . . . . Series 28 . . . . . . . . . . . . . . . . . 34.8 138 .3 103 .8 25 . 9 2562 .0640 12 .8 41 .0 8 Serles 17 and 27 . . . . . . . . .. 48.3 115.4 78.0 19.5 1635 .0409 8.2 26.2 16 exception of series 28. The average weight per crop increases in a. sim- ilar way. The same is observed with respect to the grams of phosphoric acid removed by the crop, and also in parts per million of soil. The corn possibility of the phosphoric acid is based on the assumption that 40 bushels of corn require 25 pounds of phosphoric acid, and that it is removed from the surface '7 inches of the so-il, which weighs two million pounds per acre. The corn possibility varies from 8.6 bushels with soils containing O to 1O parts per million of active phosphoric acid, to 26.6 bushels for soils containing 40 to 60 parts per million. Table 2.-—Average corn possibility of different tests in bushels per acre. Group 1 2 3 4 5 6 7 8 9 Phosphoric acid content of soil . . . . . . . . . . . . . . . . .. 0-10 10.1— 21-30 31.l— 40.1— 60.1— 80.1— 100.1— 320- 20 4O 60 80 100 190 420 Average corn possibility, ulletin 126 . . . . . . . . .. 4.5 12.5 20.8 19.7 24.4 26.5. 22.0 52.5 60.7 Maximum corn possibility, letin 126 . . . . . . . . . . 9 31 36 37 42 59 39 101 94 Standard o_f interpretation, Bulletln 1 . . . . . . . . . . Average four crops, Series . 8.6 14.4 18.0 41.0 26.2 . . . . . . . . . . . . . . . . . . . . . . .. Avera-ge {liiéé cicps; ‘seas; 4-47 10.2 15.2 20.2 44.8 21.2 . . . . . . . . . . . . . . . . . . . . . . .. 8 TEXAS AGRICULTURAL EXPERIMENT STATION. These average results are compared in Table 2 with the figures from Bulletin 126, and also the revised table based upon later work and pub- lished in Bulletin 161. The experiments described in Bulletin 126 include some in which the plant suifered from adverse conditions. The results of this series of experiments are therefore somewhat lower than the results of the later experiments. The relation between the other two series of ex- periments is remarkably close, considering the nature of the Work. RELATIONS OF SUCGESSIVE CROPS. Table 3 contains the average results of the first crop, which was corn. Table 4 contains the average results of the first and second crops combined. Table 5 contains the average results of the first, second, and third crops combined. Table 6 contains the fourth crop by itself. The average weights of the first and second crop-s combined per crop are slightly less than the average of the first crop. The average weights of the first, second, and third crops are slightly less than the average of the first and second crops. ‘There is a decided falling off in weight of the fourth crop, as it is only about one-half the weight of the first crop. It is a question whether, or not, the growth of two crops alone would not give as good results as the growth of four crops. There is such a large falling oif with the fourth crop that it would be probably better to discontinue growing it, except fo-r special work. The third crop» (corn) is usually a. good one but it would appear from the results here given that except for special work the first two crops might be sufficient. However, the results of the four crops are not always the same as the results of the first two crops. Table 3.—Average results of the first crop (corn). Active _ Phosphoric Phosphoric Crop Crop Phosphoric Acid per Acidper KN KPN Acid ' ion Million gm. gm. gm. per pot of soil Series 13 and 29 . . . . . . . . . . . . . . . .. 7.3 8.2 3 .0193 3.9 Series 4, 14, 30, 47 . . . . . . . . . . . . . . 14.8 13.8 34 9 .0298 6.0 Series 36 . . . . . . . . . . . . . . . . . . . . . . . 25.1 19.0 3 3 .0493 9.9 Series 28 . . . . . . . . . . . . . . . . . . . . . . . 34.8 31 .0 37 0 .0878 17.6 Series 17 and 27 . . . . . . . . . . . . . . . .. 48.3 25.7 7 .0623 12.5 Table 4.—Average results of the first and second crops. Active Phosphoric KPN KN KN Phos horic Phosphoric Acid per Total gm. Total gm. per crop Aci per Acid per Million gm. crop gm. Million Series 13 and 29 . . . . .. 7.3 43.6 16.9 8 5 .0178 3 5 Series 4, 14, 30, 47.... 14.8 62.4 28.8 14.4 .0323 6 4 Series 36 . . . . . . . . . . . . 25.1 56.1 33.1 16 6 .0384 7 7 Series 28 . . . . . . . . . . .. ' 34.0 67.2 57.2 28.6 .0801 16 0 Series 17 and 24 . . . . .. 48.3 50.0 45.4 22.7 .0539 10 8 RELATION or PHosPHomo A011) or S011. r0 Por EXPERIMENTS. 9 Table 5.-—-Average results of three crops. Active ' Phosphoric KPN KN KN Phosphoric Phosphoric Acid per Total gm. Total per per average Acid per Acid per Million crop gm. crop gm. crop gm. Million Series 13 and 29 . . . . .. 7.3 84.7 25.2 8 4 .0159 3 2 Series 4, 14, 30, 47.... 14.8 96.0 38.7 12 9 .0283 3 7 Series 36 . . . . . . . . . . .. 25.1 87.0 43.4 14 5 .0315 6 3 Series 28 . . . . . . . . . . .. 34.8 118.2 83.0 27 7 .0696 14 0 Series 17 and 27 . . . . . . 48.3 88.3 .9 22 6 .0474 8 5 Table 6.—-Results of the fourth crop. Active _ _ Phos horic KPN KN Phosphoric Phos horic Aci per crop gm. crop gm. Acid gm. Aci_ _per Million Million Series 13 and 29 . . . . . . . . . . . . . . . . . 7.3 17.0 3 5 .0079 1 6 Series 4, 14, 30, 47 . . . . . . . . . . . . . . 14.8 20.2 8.0 0168 3 3 Series 36 . . . . . . . . . . . . . . . . . . . . . . . 25.1 32.9 12.5 .0172 3 4 Series 28 . . . . . . . . . . . . . . . . . . . . . . . 34.8 29.5 20.6 .0475 9 5 Series 17 and 27 . . . . . . . . . . . . . . . .. 48.3 17.1 10.6 .0220 4 4 The conclusion is the same whether We consider the first crop alone, the first and second crops combined, the first three crops combined, or the fourth crop alone, or all four crops combined, or Whether we con~ sider the size of the crop"? or its phosphoric acid contents. This con- clusion is that on an average the. size of the crop-, or the amount of phosphoric acid taken up, is related to the active phosphoric acid of the soil. Series 28 does not fit in well with the others, but produces a larger crop in proportion to the quantity of active phosphoric acid in the soils. There are eight soils in this series. The active phosphoric acid in these soils appears to» average unusually high in crop-producing capacity. Table No. 7 contains the ave-rage results by series. Series No. 27 and series No. 28 are not so Well in line with the other results. Series 2'7 is too low, while series 28 is too high. '10 TEXAS AGRICULTITIIAI. EXPERIMENT STATION. 22. 888.. N88N. .22. .888. 82. 8.2. 28. 8888. 888... 28. 8N8. 888.. N2... 88. 82... 288. 888” 2.8. 888. ......... ::........ .82 88018.8“ 828888888 85.20 88... 888... 88. 828. NN8. 28. 28. 888 28. 888. . . . . . . . . . . . . . . .. . . . . . :8 .82 880128“ 2.888.888 “.520 888. 82.... 8N8... 28. 28. 28. 28. 888M .88. .88. . . . . . . . .. . . . . . . . . . ....N .82 82.01.28“ 828888888 “E20 8888. 888... 888... 888. 8N8. 888... 888... 888 .28. 88. .. . . . . . ... .. . .... . .12 .82 88012....“ 828882.88 “.820 8N. 8N. 8N. 88.. 82. 82. 8.8N. 82. 8N. 82. . . . . . . . . . . . . . . . . . . . . . .8 .82 89.0128“ 2.8888888 .82. 5.. N2. 82. 8.. 82. 8N. 8N. 2N. 22 .2. 82. . . . . . . . . . . . . . . . . . . . . . .8 .82 820128“ 2.888.888 .88 $8 8N. 8N. 8N. .2. . 8NN. 8N. 8N. 82. 8N. 82. .. . . . . . . . . . . . . . . . .N .82 82012..“ 828888888 .88 s“. 8N. 2N. 2N. 2N. _ 2N. 8N. 2N. 8N 88.. 8N. . .. .. . . . . . . . . . . . z. ...2 820128“ 2.8888888 2.8 .88 N822 2.82 88.88. 2.82. 88.8 88.88 8.82 88.82 88.82 82.2 . . . .. 25.2. N82 2.2 N88N 88.8 8N2 88.2 2.88 88.2 88.82 8.8 .. . .......2..2 88.828.818.82 820 88.2.8 N82. 8.2. 88.28 8...8N 2.88 88.88 8.88 8N8... 88.8 .. . . . . . . . .. 12.22 8.5018 .82 820 8.8N 8.8N 2.88 88.8 8.8 8.8.8. 28.2 8N8 88.88 88.2 .. . 1.52.22 E=88...81N...2 880 N288 28.8.. 8.8 88.8 2.8 888N 88.88 8.8.. $.88 8.8N . .. . .. E1282 8.8.20 8801. .82 820 28.2 8.8 8.8.88. 88.88 88.8 8N8... 88.8.. 8.8 N88N 8.8N .. . 8.8 888.2 88.8 N82 8... 8.8 82.2 88... 8.8 8N... .. :22 58.888.818.82 880 88.8. 8.8N 8.8N 88.2 88.8 88.... 8.2 8.2 88.8 88.8 .22 E8018 .82 820 8.8N 88.8. 8.8N 2.2 8N8 8N2 88.2 2.2 8.8 Es :22 E=88...81N...2 820 2.NN 8.828 8.8 88.2 8.2 88.2 88.2 8.8 88.8 88.... .. . .. E8 328012.82 8S0 8.8.. 88...... 8N.88 2.8N 88.2 88.2 2.2 88.2 8N2 8N8 .. 2.8888888 82.3 . 8N 2 8N 88 2. 88 2 8. 8N 8. $8.888 82.88 . .8283 >2 82:80.. 88225818 038B RELATION OFPHOSPHORIG Aorn or, S011. TO PoT EXPERIMENTS. 11 It has already been pointed out in this and previous bulletins that some soils are unusually high in their crop-producing power for the amount of active phosphoric acid present and some are unsually low; that organic matter and lime affect the amount of phosphoric acid withdrawn; that.the phosphoric acid of "rock phosphate is unequally taken up from different soils. It is the object of the present bulletin to ascertain the cause of these variations, if possible. WHAT SHALL REPRESENT THE FERTILITY. The question as to which results best express the fertility of the soil with respect to phosphoric acid, is open to discussion and differences of opinion. Should the weightsof the crops be used, or the relative weight of the crop with complete fertilizer to that without phosphoric acid? Should the first crop, or the first plus the second, or four crops be used; should the phosphoric acid removed be used instead of the weight of the crops? These are the questions which arise. When the different methods give the same results, as occurs with a number of the soils, there is no question, but when the different methods give rise to different results, the case is different. GROUPS OF HIGH, LOWV, AND IVIEDIUIW PRODUCTION. In order to study the relation between the chemical composition and other properties of the soil, it was decided to arrange the soils in three groups within each series as follows: The first group consists of those 25 per cent. or more below the average of the group. The second group consists of those within 25 per cent. of the average of the group. The third group consists of those 25 per cent. or more above the average of the group. The series are arranged according to the amount of active phosphoric acid. i Since there is some variation in the yields of the crops from the dif- ferent tests on the same soil, and the amount of phosphoric acid with- drawn by the crops, there would be some difference in the grouping of the soils according to the method adopted in arranging them. In order to study this, the soils were arranged in three groups above men- tioned, according to the following several ways: (a) The weight of the first crop; (b) the Weight of the second crop added to the weight of the first crop; (c) the weight of phosphoric acid taken up by the first crop; (d) the weight of phosphoric acid taken up by the second crop added to that taken up by the first crop; (e) the total Weight of the four crops; (f) the total weight of the phosphoric acid taken up by the four crops. A In most cases the grouping is the same no matter which of the above methods was used. For the purposes of this work, the soils were finally arranged according to the total quantity of phosphoric acid taken up by the crops, with the exception of two soils. Soils Ho. 968 and 5969 were placed in the first group for the reason that all of the results excepting the total phosphoric acid placed them in this group. 12 TEXAS AGRICULTURAL EXPERIMENT STATION. NNNM ~02 E S8 wwwm 3w ism NQNU Nmm< E E2 BE. m3... 5% wot. E 3:. mmmm Sam 2B NQNU NU E2 E2 , . mwfi 8B ~25 $2 mwS 2:. £3 S: SQ. Ea... . . . . . . . . . . . . ,. . .82: s E8 :5 mm @2226 $0.2!» 9.80 E3. . wmmh E qfimh >mN~ E 3E E wNQ. mwww E ma? no 3Q. ma» $8 GE EQ. E E m8... Mano E52. mmmm mm? EE 2:2 EE E kg EE m3 E2 . $9 mu fiQ. mu E 2Q E mmfi... mmm< muE E5 w? $2M £8 E8 5:. . . . . . . .. R3 8:. .. EZ 2 E 3E o8 SE BNQ. £8 $5 . .. .. . . . .. wmQ. 2% $5 .35 95... 2% £3 fiQ. Qzw Qa E2. 3mm . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . .25?“ =£E§l~ 9.20 E~< . . . . . . . . . . . . . .. . . . . . . . . . . . . ... m5... . . No . . . . . . . . . . . . . . .. ....:E~m . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . ....SQ .. . . . . .. ......:€m¢ E2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . :9“? xxx. . . . . . .::......1@.Q. QVEE . . . . . . .. . . . . . . . mama? Mano? . . . . . . .. 2% . . . . . . .. $3 2:. 5% 3Q fiQ. $3 QQ. . .. 3Q. .. . . . . .. mum.“ qmfi .52. £2 QQ 2% $3 5% Em SS Ema 3Q. a3... mfia QQ. 3m . . . . . . . . . . . . . . 58E 5 E8 s; mm “afiezwaozmlfi A580 S 5 Ma 3 t. 3 S q aw 2 mfism .396 3 uv>oEo~ Eon oioanwoza @9962» no woman mnnoumvlfiw 01in. RELATION or PHOSPHORIC A011) or SOIL TO Pots EXPERIMENTS. 13 Table 8 shows the soils arranged according to the phosphoric acid removed by four crops, and it also shows the differences that would occur if the other arrangements were used. When a letter and figure is given below the soil number, it shows that if arranged according to method A, B, C, D, E, or F, as the case might be, the soil would be changed to group 1, 2, or 3, as noted. For example, soil 992 (series 4, group 2), would be placed in group 1 if the weight of the first crop alone were considered. Soil 937 (series 4, group 2) would be placed in the third group if the weight of the first crop (A), the weights of the first and second crops (B), and the phosphoric acid in the first crop (_ C) , were considered. It is interesting to consider what change-s would occur if the total phosphoric acid taken up by the first and second crops were considered, instead of the phosphoric acid taken up by the four crops. This would involve the following changes. In series 4 soil 913 would be moved from group, 2 to group 3. In series 13, 14, 17, 28 there would be no change. In series 27 soil 7252 would be moved from group 1 to group 3, and soils 970 and 7240 would be moved from group 2 to group 1. In series 29 soil 7255 would be moved from group 1 to group 3. In series 30 soil 7266 would be moved from group 2 to gro-up 1, and soil 7228 from group 2 to group 3. In series 36 soil 7708 would be moved from group 3 to group 2.’ In series 47 soil 9277 would be moved from 2 to group 3, and soil 91-83 would be moved from group 3 to group 2. There would be change in the grouping of 10 out of the 95 soils or about 10 per cent. This cannot be considered a large percentage. We can also consider what changes would be caused if the arrange- ment were based on the weight of the first two crops. In series 4 soils 937 and 913 would be changed from the second group to the third group. In series 13 soils 4596 and 3362 would be moved from the first group to the second group. In series 14 so-il 6884 would be moved from first group -to the second group. In series 17 soil 5943 would be moved from the third group to the second group. In series 27 soils 970 and 7240 would be moved from the second to the first group, and soils 7159, 7265 and 6883 from the second group to the third group. Soil 7107 would be moved from the third group to the second group. In series 28 soil 6976 would be moved from the first group to the second. In series 29 soil 7120 would be moved from the second group to the third gro-up. In series 30 soil 7666 would be moved from the second group to the first group, and soil 7228 from the second group to the third group. In series 36 soil 7708 would be moved from the second group to the third group. In series 47 soil 9279 would be moved from the second group to the third group, and soils 9183 and 9331 would be moved from the third group to the second group. There would b-e movement in the position of twenty-one soils, or about 22 per cent. of the soils under study. The consideration of the weight of first and second cro-p would, therefore, involve about twice as many changes as the considera- tion of the phosphoric acid removed by these crops. The phosphoric acid taken up seems to be a less variable condition than the weight of the crop, even though there is added the analytical error involved in the determination. It is evident from the above discussion that the grouping based upon the first two crops would be different in a number of cases from those based upon four crops. Sometimes the soils- produce better the 14 TEXAS AGRICULTURAL EXPERIMENT STATION. first. year than they do the second, and less often the crops are poor the first year and much better the second year. As already pointed out, and as shown in Table 1, the results of series 28 are out of line with the others. Another method of arranging the results is with respect to the cal- culated average phosphoric acid that should be Withdrawn by the crops based upon the active phosphoric acid present, rather than on the actual average of each series. This method requires that all of the crops should be grown under the same conditions, which is not, exactly the case, since even when the "crops are grown at the same time, they are not under exactly the same conditions. See Table 9. Table 9.—Method of arranging according to calculated phosphoric acid. Group 1 2 l 3 4 ’ 5 Active phosphoric acid . . . . . . . . . . . . . . . . . . . . . 0-10 10-20 20-30 30-40 40-60 Assumed corn possibility, bushels. . . . . . I . . . . 10 15 20 25 30 Parts per million phosphoric acid from soil. . .. 3.1 4.7 6.2 7.8 9 .4 Grams per pot of 5000 gm., average . . . . . . . . . .0155 .0235 .0310 .0390 .0470 25 per cent below, per crop . . . . . . . . . . . . . . . . . .0116 .0176 .0233 .'O292 _.0357 25 per cent above, per crop . . . . . . . . . . . . . . . . . .0194 .0294 .0387 .0498 .0587 Table 10 shows the arrangement in groups based on the calculated hospho-ric acid removed by the four crops. The small figure with some of the other figures shows the variations from the grouping based upon the average phosphoric acid of the series‘. Thus in series 13 soil 3611 would appear in group 2 if the grouping were in accordance with the average, instead of appearing in group 1. Soil 5969 would appear in group 3. 15 RELATION OF PI-IOSPHORIO A010 OF SOIL T0 P01‘ EXPERIMENTS. A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. mvfih . . . . . . .. . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. w~_> ........ . ................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..~w-> ........ ........ .............; . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. wmwm ................ ................ . . . . . . . . . . . . .. “mam . . . . . . . . . . . . . . .. .... .. . . . . . . .. . . . . . . . .. . . . . . . . . . . . . . . . . .. mmmm ................ .... waw ........ ....... sfihm . . . . . . . . . . . . . . ..~>-h ................ .......mmmm ........ ........¢¢@m mmmh . . . . . . ..~@@@@ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .... BOMB mfimm. mwmmm ~fimh . . . . . . . . . . . . . . . . wwwfi fifiwfl . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . .O.~QE n0 uGQO hofl MN UWNuQ/N 0>OQ< . . . . . . .. .. ........ ................ wwmh ....... . . . .. . . . . . . .. .............. ................ >m~> ........ ... ................ . . . . . . . . . . . . . . . . . . . . . . . _ . . . . . ..~ ........ wmmh ........ ........ ....... ........ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. mmmb ........ ........ ............... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 . . . . . . .. mm~> ....... ........ ................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. _w~» . . . . . . . . . . . . . . ..»~mN> . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . .. whmm ........ ~@_> ................ o~_> ........ . . . . . . . . . . . . . . . . . . . . . . .. mama ........ wmwh ........ .........~¢~» ....... . . . . . . . . . . . . . . . . . . . . . . .. ¢§m> ........ @m@@ .....‘.......... wmwh mwwam mwmh . . . . . . . . . . . . . . .. __m@ . . . . . . .. @@~h . . . . . . . . . . . . . . .. _~_> cmmm @@_» nacfim _@»@@ mmmm >§~@ . . . . . . . . . . . . . . .. mfia ..... . . . . . . .. mwww m<@m ~_¢~» mwo“> ~_mm@ . . . . . . .. Qwww ~>m_~ . . . . . . . . . . . . . .. qwwh QMG Zwmfim mwfimb mmwwmw . . . . . . . . hwmwm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .UMG.~Q>Q HO HGQU uOQ ... . . . . . . . . . . . . . . . . . . . . . . . . . . ..... . . . . .. . . . . . . . . . . . . .. ... . . . . . . ..~HH@m . .. . . . . . . . . . . . ... . . . . . . ..~@>~@ . . . . . . .. .. . . . . .. ........ . Nwmm . . . .. . . . . . . . . . . . . . . ..~m@m@ o¢~_ . . . . . . .. . . . . . .. ....... wamw Nmmh . . . . . . . . . . . . . ... ~w@_¢ ¢@_> . . . . . ..~>m@ . . . . . .. wmmv ~ww@ .. . . . . . . . . . . . . . . . .. mwma omww wwww mmfifl ....... whmm Nawwh Nmmmw . . . . . . . . . . . . . . .. <@.@ ¢@_> ~w_¢ mvmm mmmh fiwww 88 3Q . . . . . . . . 5S E2 3Q. ofim $5 mwfi m? . . . . . . . . . . . . . . . .. . . .22: S :8» :5 mm vwwhgzw asom >~ h~ mm @m “Q om wfi Q an m_ mwcum hacks .53 an v9.35»! Eon oiosamoan wowm-soiwo no woman mnsobwlkofl Bash. 16 TEXAS AGRICULTURAL EXPERIMENT STATION. The following differences are found in the table from the arrange- ment by averages (Table 8). In series 3 there are two changes, two in series 29, two in series 4, one in series 14, one in series 30, five in series 4'7, one in series 36, six in series 28, two in series 13, and two in series 2'7. There are thus twenty-four changes, or something over 25 per cent. The greatest number of changes occur in series 4.7 and 28. In series 4'7 the positions of the soils are lowered, while in series 28 the positions of the soils are raised. In series 28 three soils are shifted from the first series to the second series by basing the grouping on the calculated phosphoric acid. METHOD OF CHEMICAL ANALYSIS OF THE SOIL. The active phosphoric acid and active potash were determined by solution in fifth-normal nitric acid, without correction {for the‘ acid neutralized. They are expressed in parts per million. The acid con- sumed represents the percentage of the acid neutralized in the process of extracting the active phosphoric acid and potash. It represents the bases neutralized by the acid. It is expressed in percentage of the acid used. The nitrogen was determined by the usual method. The phosphoric acid absorbed represents the percentage of phosphoric acid taken from twenty milligrams of phosphoric acid in contact with one hundred grams of soil and 200 cc. of water. The acidity was deter- v mined by the Veitch method; lime by the Hilgard method. Active phosphoric acid extracted by five successive extractions with fifth normal nitric acid was made by washing the residue back into the extraction bottle and making another extraction, until five had been ~made. The phosphoric acid was determined separately in each ex- tract. Phosphoric acid soluble in cold 12 per cent. hydrochloric acid was determined before ignition, and after ignition. The difference is termed ' ignition soluble phosphoric acid, and is considered by some chemists to represent the phosphoric acid in organic combination. This may be the case to -some extent, but we have shown elsewhere that ignition will render some mineral phosphates soluble in acid. RELATION OF CROPS TO THE CHEMICAL COMPOSITION OF SOILS MORE OR LESS PRODUOTIVE THAN THE AVERAGE. Table 11 gives the average chemical composition of the soils used in these pot experiments, arranged in series according to the content of active phosphoric acid, and these series divided in groups according to the average phosphoric acid removed by the crops, the groups being based on those 25 per cent. or more below the average, 25 per cent. below to 25 per cent. above the average, and 25 per cent. or more above the average as previously described. Table 11 shows the average composition and the crop production of the soils based on the average for each series. A similar arrangement was made of the soils in the groups arranged by the calculated phos- phoric acid removed, and the results of this calculation are given in Table 12. 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HSS SSSS. »Soo. HSSS. SSS. S.» SSS. SS3 H.»m S.» SS SSH SSH S S.SH HS. SSS. SSS SSoo. SSS. HSSS. SSS. SS S.S SSS. SHHH S.»H S.» SS oHnS SHH o S.H SH. SSS. SSS SSoS. SSS. SSS. SS. SS S.S SSS. SSH. H..»S SSH »H 31o SSH o S.ooH HHSH HS. SS» SSSS. SSSS. oSSo. SSS. SSS S.H¢ SSS. SS3 HflS S . SH SH SHS SSH o S. H SH . SS. S. H.H SSSS. SSS. »Soo. SSS. S» S. SH SHSS. SSS SSS S.S . SH S13 HS S HSH HS. »»o. SSS »Soo. SSS. SSS. SSS. SS ».SH SSSS. ».SSH H.»S S.S SH HS|S S SSS ».» SS. »»o. SS» SSS. SHSS. oSoo. SSS. SH. SSH SSS. ».»SH SSS SS SH SSH SS o SS So. SSo. SSS SSS. o»Ho. SSo. »So. SS o.SH SSSS. SS3 SSS SS SH SH|o SS SSS SS HH. SS. SSS o»oS. SSS. SSoS. SHS. SS SS SHSS. S . S H SH S . S SH oHeS SS o S. H »S. SS. SS» SSS. S»S. SSS. SSS. S S . S »SS. S4.» HSS ».SH »H. oHuo SS o So SS. SS. S.HH. SHS. »SHS. S»oo. SS. S.»H SHSS. SSSH S.HH. S.HH H. SHS S»S o SS SH. SSS. S.» Sooo. »H.S. SSS. SHS. HS SSH $2. SSSH SHS S4. H. 31o SHS S SS »S. SSo. SSS HSoo. SS. ooHS. SSS. S» S.HH »SS. S.»SH SSS S.H v SSSH SSS o SSH SS.H SSS. SHS »Soo. »SS. 3S. S»S. SS SSH SSo. S355 SS8 5a SE5 .6.» S8 5S S8 8S c258 G353 E3 2mm 33.2w SHHFHM S358 SEES SS8 =5 SS8 .8 S» 4cm nomfinmm ._om SS3 8m =5 :5 3.5mm maoh. mnoé Q98 dZ 8.3a :5 BS S355 SS8 6a mom A~o3< 52a: .824 2g HSQB 8S5 S w>mpo< Scan .58 Sc .58 .8 SES mwivm JeQoQ JSSSQQ >£E¢< L50 25A. éazz SZSSSSH SEES SSH»? Sflmmog SASS? 022.4 3i. macho H€< vionnmoam S98 Ba HSSHEH :5 wiwmldwS. 8 S»SS.ISS S~HHOuUlwv=flmefloU|dH 03MB 27 RELATION OF PHOSPHORIC A011) OF SOIL TO POT EXPERIMENTS. 3.333 “m3. m.3 om3 v3 mmm 5m woo. 3.33 wm3o. womo. ommo. mmo. m: 93 Es .......vww:w>< 3..3m3 m.m3. 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To 3.3 o o3. m3. 8... o4.» $8. ovmo. .28. 3%. s. 93 t3 3a m? 32o 3. 3T3 mmm o o3. oo.3 2.... we .25. as. o33o. 3.33. m3. o.3 :8. 38w _ 3:8 B: 3:3 :23 3:2. .8: 3:8 .5: 53:38 :o3=38 3.33 2.33 w88w 882w :o3=38 :o3=38 3:3 3: 3:8 .393 36 3cm 53:2. 3cm 3:8 :23 .8: .5: 03:23: @395 @3395 3396 dZ @232: .633 .633 38:: 3:3 .633 8w b.5823 8.53:3 :33: 33.. 3:393. $833 n 9333i. $23: .88 3o 86.3 3o 8.53 mwiow 55G 39383 .3333: :8 @833 6.52 335x33 282w “paw: 2:2.» SE85 @233. 3.33.. n35 2i Qizgwcg: dob .8: .5358 :23 $.G:|3.mo3. o3 o§o.I.333 335:6 .8928.» 3 30$ 3o :o33:3@33|..3.o::33:oO|o3 v3.1.3. 28 TEXAS AGRICULTURAL EXPERIMENT STATION. N202 2.02.. w.w2 . . . . . . . .. 2.2.2 m2 . m.w2 00.2 220. 20.22. 2.2220 0220. $220. 22.20. oo 0.00 2.202 .......0w0.20>< 2.222 2.2.22 0.0m om 21o mo o mm 02.20 ooo. 0.02 820. £020. m2o. 02.20. . . . . . . I www 20.02 0.2.2 2.220 :0 om 2-0 mo2 . . . . . . .. 0.2020 8.0 2N2. 0.200 02220. . 200020. 2002.20. mwo. 02 2.20 $2 o.2o2 22.222. 262 om 02-0 2 omw 0.20 .2. 08. 0.0m 2202020. 2.2220. mooo. ~20. . . . . . . . . 20.8 2.202 20.2.02 i020 2.2.0 om ~10 S. 0200 0.0 20. 222. 2.202. 0220. ommo. owoo. omo. ow 2.2 22.22 2 .8 0 .2020 20.2 om o2|o o2 o o.oo2 >2 .20 owo. 2.00 ooNo. 20220. oomo. woo. 20 20.2 22.2. wow 0.22. o.w2 om §|~2 2 o 20.20 22. $0. :00 220220. 00S. mooo. 2mo. 22.2 ~02 @2222. 22.022 2...... 20.20 om 2.20 o 2.2.2 mo. $20. 2.3 02.220 E8. om2o. 2.20. m0 2.2 2E2 2.202. :0 20.0 om $2.2 28 o o.2. 2.2. 2.020. mmw 20200. ow2o. o22o. omo. . . . . . . .. 2.222 ooo2 0.2022 2.22 2. . mm ww 2.|o S2 o 2am 2.2. Eo. 2.202 mwoo. 20.0220. 202020. wmo. .3 N. 2m 22.02. 2.202. 2.5 0.8 220 muo 2w o w.o o2. 220. 2.22 02220. oowo. 02.220. .020. 2 20.02. N22. 0.0202 2... 2.22 a o|o 200 o 0.202. 02 2.20. 0.200 202.220. 202.20. oowo. wmo. 2o 20.2.2. 2202. o . 202 o. o2. o. N2 2w ow|w 2w 208 o.2 wm. 2.3. 0.2.. 202.20. 22020. 22o. omo. N22 0 . 2. 2K2. w.mm2 m . .22 0.2.0 2.2 210 . . . . . . . $2. mm oo. 20220. 20.202 wwwo. 2022.20. ww2o. 2.20. o2 2.02 0202 2.22.2 20.5 2.02 2.2 To 0202 oow om .. . . . . .. .02. 0.02.. 2020220. 02.220. wwoo. 2220. S 2.52 2.52. 0.2.2 20.2020 2.0.202 m2 2-0 2 o 0.2. 20. 2E0. 20.200 $020. .2220. oooo. ooo. ow 0.202 2.202 o.w2 20.2020 0.02 m2 2T0 02 o mm m2. 202.0. 2.200 202.200. 00220 02.220. 20020. 200 0.20 220202 2.22 2.220 20.: 2. 2.20 2.2 o 0.22 2. 202. 20.20 2.220. 220. mm2o. woo. 2. @222 $22. 082.0% 2228 .222 2228 .222 2228 222 22200 222 22022228 22022228 2020.0 2.2M 220280 080.5 22022228 22022228 2228 222 2228 .222 200 20m 2202222202 20w .2228 .222 .222 .2022 202202222 220.20 220.20 220.20 .02 002200222 .222 .222 2008220 22200 .222 220w $200222... 22022222222 202022.. 2020.22 2020.2. 00820. m 02222022 2002222 22202 20 .2002 20 20.222 002.22% 2222202 22002022 222202022. -2200 0822 6.2.222 2002202222 22220 2222025 222E025 222203 0.222022. 20204 . 22020 20202.. 0200222200222 .2020 222 22022228 .222 $.2022|wmm2. 3 2.32 .|.>2 2222026 .000222022.0 02 220.20 20 2202202022120022222222001222 0320.2. 29 RELATION OF PH OSPHORI 1 A0113 OF S011. To P01? EXPERIMENTS. heee w.hee wee. eee e eee eew 5e. w.en ewee hene. wewe. ehe. 5 www axe. ......dw¢5>< fa eeh e.ee ew eve wew e eee ew. ene. eew hewe. neee. weee. hee. ee e.he eehe. ................wewe weee wene nwe. we e|e wwn e wwe he.e ewe. 5w weee. nhwe. heee. ene. ee e.ew ewww. . . . . . . . .hnen eehe ewne is. we e-e eee e e.eee ne we 2N. i.» wene. ewee. ewwe. hee. hee ewe. ewwn. ..............wnen newe nee e.ee. we eeue ee e n.h ew. eee. een wnee. weee. eeee. ewe. eee h.ww $8. :2 n.nee eew we eeae whe e e.eee weee ehe. w.nw eewe. wnne. eeee. eee. ehe e.ew eeee. e.ne.e hwe e.he we eene 8e e wee 5e ewe. 5w ewee. eewe. eeee. ene. wh n.ew weee. n.eee n.hw 5e he i. eee e n. e ne. eee. eew 2.2.. eeee. $5. e5. eee e . 2. whwe. 3.5 eew n.we he w|e eee e h.w we. n5. h.ew weee. nhee. he5. wwe. nee hwe. weee. hee 5:. e.he.e eelh wee e e.ee we. nee. e.hw weee. ewee. heee. ewe. we eee. hnee. i: 52 hwe. he eee ehe e e.e ee. hee. we weee. wnee. 2.5. eee. eee e.ee eeee. e.ene e.eee ewe. he eue nne e e.w 5. ene. ewe eeee. eewe. eeee. hne. e3 w.wn wewe. e.ewe w; enw he i. a. e n.e we. wwe. e.ee eeee. neee. n+5. wwe. eee hwe. ewhe. w.hwe wee wew 3 eene nne e emw he. ewe. h.ee eeee. weee. heee. eee. ee eee eehe. e . eee n. eh e . ee S eeue 3e e h . ee nn. eee. e ee eeee. was. wwee. wee. eee e. ee eeee. mEEw e53 5Q e59. 5Q .55 5Q 58 5Q noeeeefl 52:5 Bu.» Zmve @555 552w caeeeefl 52:55 e55 5Q e59 5Q 5 eew 525$ eew e53 5Q 5Q 5Q BSQQ wQoS 55B Q98 dZ @555 5Q . 5Q 5E5 e58 5Q 5w A5054 noeeeswe 534 e54 eSPe. 85$ n @354 éQeQ .58 we .58 ea efie 815w eeQwme eewfioQ >223. -56 25A éefiz eafiiee 35w eew...» 22.5 e555 @354 23.. 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IU m. ...5 0:500 00 >50 0.0. 55 0 $0 0 0000 0 0000.0 N500. 000.0 F. 0.0 3 0000.0 . . . . . . . . . . . . . . . .. 0 0:550 05:00 05055 0055 .50 0055 .50 0055 .50 0055 .50 0055 .50 355.555 055:0 505.5 w 5:55 .50 -055 0055 .50 05m 05w 0200mm 05w 05050. 52.0 0.50 5:55 E55 00m 055550 0054 500d 5502 0500000 50.2w E54 5254 05 .5Z 2.800 05 .5 Z 525.0 . $500 .5055 0:50 0n 055-50 E55 515005500 3 00005555 05005.25 5:55 .05 0205500055 5m555><||.0m~5_n50. RELATION OF PHosPI-Ionrc A011) or SOIL TO Porr EXPERIMENTS. 31 Group No. 4, from .1055 to .1358 grams or 6.8 parts per million per crop. Group No. 5, from .1359 to .1658 grams or 8.4 parts per million per crop. Group No. 6, over .1658 grams phosphoric acid removed by four crops. The individual soils are shown in Table 19. ‘The average results of this arrangement are given in. Table 20. a The active phosphoric acid increases regularly with the average phos- phoric acid taken up by the four crops. The difference between group 5 and group 6 is not great, however. The total phosphoric acid is lowest for the first group and highest for the last group, but groups 2, 3, 4, and 5 contain nearly the same quantities of total phosphoric acid. The acid consumed is lowest in the first two groups, but is then irregular. The nitrogen increases regularly from the first group to the sixth group, with the exception of group 5. It has already been pointed out that in soils containing the same amount of active phosphoric acid, the plants seem to take up more phosphoric acid from the soils contain- ing more nitrogen. The relation is not regular. The lime is lowest for the first group and is then irregular. The acid-soluble phosphoric acid increases regularly with the first three groups, a.nd is highest with the sixth group, but groups 4 and 5 are irregular. The phosphoric acid dissolved after ignition, like the acid-soluble phosphoric acid in- creases with the first three groups, and is highest with the sixth group, but is irregular with groups 4 and 5. The ignition-soluble phosphoric acid increases up to the sixth group, with the exception of group 5, but the difference between group-s 3 and group 4 is very slight. The propor- tion of subsoils is largest in. the first group, next largest in the second, and is about the same for groups 3, 4 a.nd 5. It is smallest in group 6. There is a closer relation between the active phosp-horic acid and the results of the pot experiments, than between any other constituent and the pot experiments. Some of these relations may be incidental, and some may be associated with other properties of the soil. THE RELATION 'OF THE ACTIVE PHOSPHORIO ACID, AND THE TOTAL PHOSPHORIC ACID TO THE NEEDS OF THE SOIL FOR PHOSPHORIO ACID. It was pointed out in Bulletin 126 that the active phosphoric acid is related to the needs of soil for phosphoric acid in pot experiments. While the object of this bulletin is to ascertain if possible the reason why somewhat wide differences occur between soils co-ntaining the same quantities of active phosphoric acid, it is well, however, to point out the relation between the active phosphoric acid, the total phosphoric acid, and the needs of the soil for phosphoric acid, as shown in the results of the pot experiments presented in this bulletin. Table 21 gives the relation between the average active phosphoric acid and the parts per million of phosphoric acid removed by crops. The two run closely parallel, with the exception of group 6, which does not contain as much active phosphoric acid as it should. The per- centage of total phosphoric acid removed by four crops increases from group to group. It is lowest with the first group and increases up to the fifth group. Apparently the availability of the active phosphoric acid varies, since a greater amount of phosphoric acid is removed from 32 TEXAS AGRICULTURAL EXPERIMENT STATION. Table 21.—Relation between phosphoric acid in soil and removed by crops. Parts per million Per cent Per cent —————————————— Total Total _ Removed Phosphoric Removed Active by four Acid by four 1n soil crops in soil crops Groupl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 8.8 6.1 .030 2.0 Group2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 13.5 11.5 .041 2.7 Group3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 16.5 18.1 052 3.5 Group4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 26.5 24.1 .047 5.1 Group5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 37.9 30.1 .040 7.5 Group6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 38.3 49.3 .070 7.0 thesoil by the crops, when larger amounts of active phosphoric acid are present. Table 22 shows the average relations when the soils are arranged in groups according to the total phospho-ric acid present. The active phosph-oric acid is lowest with group 1 and highest with group 5, but groups 2, 3, .and 4 are nearly the same. The first crops increase regu- Table 22.-—Average relation of total phosphoric acid to results of pot experiments. Phosphoric Acid Weight of Phosphoric Num- Acid, gms. ber Total Active First Four removed aver- per per crop, crops, by four aged cent million gms. gms. crops Group 1——Be'.ow .020 per cent. . . tot . . . . . . . . . . . . . . . . . . .. 12 .017 15.9 14.6 .0673 Group 2—.021—.O40 per cent. . .. 46 .038 22.5 19.5 9 4 .1085 Group 3—.041—.060 . . . . . . . . . . 17 .049 22.7 21.2 60 0 .1286 Group 4—.061—.O80 . . . . . . . . . . .. 10* .060 17.4 11.3 38 8 .0869 Group 5—Over .080 . . . . . . . . . . .. 10 .126 26.1 17.8 .1669 larly with groups 1, 2, and 3, but group 4 is the lowest, and ghoup 5 is less than group- 2. The total weights of four crops is lowest with group 1, group 2 is a little larger, group 3 nearly the same as group 2, group 4 less than group 2, and group 5 is highest. The phosphoric acid removed by four crops increases regularly, with the exception of group 4. There is some relation between the to-tal phosphoric acid and the results of the pot experiments. ' Figure 1 shows the relation between the active phosphoric acid of each soil, and the pho-sphoric acid removed by four crops from it. Each soil is represented by a dot and the position of the dot shows the amount of active phosph-oric acid contained in it, an-d the amount of phosphoric acid removed by the crops. The figure shows that there is a. relation between the active phosphoric acid, and the phosphoric acid removed by the crops. Figure 2 represents the relation between the total phosphoric acid and the phosphoric acid removed by the crops in the same way. The relation is better for the active than for the total phosphoric acid. 33 amok. 50w he czrwkunt? Eon utozn uwoaa m5 3 zom on... mo Eon uiozamcaa .53 25 we coiabflalm Eswi E3 p222‘, 0&1 \o.2.k RELATION OF PHOSPHORIC A010 0F SOIL TO POT EXPERIMENTS. t. Q m» mo. w... mo. an a C . O o o o o a: o a . .. J . . .. . . 8 I O O OOO d a o pa. m U, O .. . U m . v . 2 w 0 Q0 0O O O I . O OO O O % I O O OO O0 0O o o o % - - . u , ./ a o DWI”, . m o d 0 I c. . mm wom- 0+. .303 E8 >5 c3m€fim>w Eva utosmwosa v5 3 2cm 23 Mo Eon 321x23 213m Ho cofifiomlfi “Kama $.66 u.>\3\kno._mu( QR Db Om, 0w O D Q N Q~ 1 . . a o a a a a o Own o O n o u one O 0O a O a n 0000 o0 u QOO: no a .0 n 0O a a can. n o c I Lao u I O O a a o a n n s o l - q o n 1a o a u » w n a r V5 Q d ‘Q ‘O v-u o '0 6 N N. . . . Idol: Fqpowwa; pp» a/nyckal/d Q '°. 2.. 34 TEXAS AGRICULTURAL EXPERIMENT STATION. STATISTICAL RESULTS OF THE STUDY OF THE PHOSPHORIG ACID REMOVED FROM THE SOIL BY CROPS. Dr. E. P. Humbert, Chief of the Division of Plant Breeding, has examined these figures by statistical methods‘with the results given belo-w. Tables 23 and 24, also prepared by Dr. Humbert, give the group arrangement according to this method. ’ The exact relationship (l) between the amount of phosphoric acid taken from the soil by four successive crops and the active phosphoric acid in the soil and also (2) the exact relationship between the amount of phosphoric acid taken from the soil by four successive crops and the total phosp-horic acid in the soil is here discussed. The figures upon which the discussion is based are taken from Table 19. In this ta.ble column 1 gives the amount of phosphoric acid removed from the soil by four crops in grams; column 2 gives the active pho-sphoric acid con- tained in the soil in which the crops were grown, in parts per million; column 4 gives the percentage total phosphoric acid contained in the soil. 35 RELATION OF PHOSPHORIC A011) OF S011, TO Pom EXPERIMENTS. mmHoHooHoooomoHvmwwHmHHmnmm HH H. Q Q o H H H. o H. H H N HHH m H HH m H H NH HH HH HmmHH E H N Nmq QN H N H HvmmH NH mHm NNwH NH mHHmmv wwuwnwwwmmuwwwwwwwwww ________._________.__ mm. Nm. 3. $2 Q. 3. .8 vm. Hm. wN. mN. mm. mfl. 2. mH. 0H. S. H5. mm. om. 5w 3i U». w»: mm. Nm. 0N. @N. MN. oN. “A. Al. 2. w? mo. No. 'su1e.1{) u; SGOJQ mod Xq uaqel pgov opzoqdsoqd ;o mnourv XLDEIFHHS JqoU 8m E =8 E 304 2§HN8HrH 130B .W>~P:.