227-A210-6M-L1 8O TEXAS AGRICULTURAL EXPERIMENT STATION B. YOUNGBLOOD, DIRECTOR COLLEGE snnou, BRA/ZOS COUNTY, TEXAS BULLETIN N0. 355 MAY, 1927 DIVISION OF CHEMISTRY RELATION OF THE POTASH REMOVED BY CROPS TO THE ACTIVE, TOTAL, ACID- SOLUBLE, AND ACID-INSOLUBLE POTASH OF THE SOIL AGRICULTURAL AND MECHANICAL COLLEGE OF TEXAS 'T. O. WALTON, President STATION STAFFT ADMINISTRATION: *B. YOUNGBLOOD, M. S., Ph. D., Director A. B. CONNER, M. S., Acting Director R. E. KARPER, B. S., Acting Vice-Director J. M. SCHAEDEL, Secretary M. P. HOLLEMAN, JR., Chief Clerk J. K. FRANCKLOW, Assistant Chief Clerk CHESTER Hices, Executive Assistant C. B. NERLErrE. Technical Assistant VETERINARY SCIENCE: "M. FRANcIs, D. V. M., Chief H. SCHMIDT, D. V. M., Veterinarian J. D. JoNEs, D. V. M., Veterinarian CHEMISTRY: G. S. FRAPs, Ph. D., Chief; State Chemist S. E. ASBURY, M. S., Assistant Chemist WALno H. WALKER, Assistant Chemist VELMA GRAHAM. Assistant Chemist ADAH E. STuRms, B. S., Assistant Chemist E. C. CARLYLE, B. S., Assistant Chemist R. O. BRooKE. M. S., Assistant Chemist T. L OGIER, B. S., Assistant Chemist J. G. EvANs. Assistant Chemist HORTICULTURE: W. B. LANHAM, M. A., Chief H. NEss. M. S., Berry Breeder RANGE ANIMAL HUSBANDRY: J. M. JoNEs, A. M., Chief; Sheep and Goat Investigations J. L. Lusa, Ph. D , Animal Husbandman; Breeding Investigations ‘ W. H. DAMERoN. B. S., Wool Grader ENTOMOLOGY: F. L. TnoMAs, Ph. D., Chief; State Entomologist _ H. J. REINRARI), B. S., Entomologist W. L OWEN, JR., M. S., Entomolo ist S. E. McGREcoR, JR., Acting Chie Foulbrood Inspector Orro IVIACKENSEN, Foulbrood Inspector GILLIs GRAHAM, Foulbrood Inspector AGRONOMY: ' E. B. REYNOLDS, M. S., Chief A. B. CONNER, M. S., Agronomist; Grain Sorghum Research R. E. KARPER, B. S., Agronomist; Small Grain Research P. C. IVIANGELSDORF, Sc. D., Agrontmist; Corn and Small Grains D. T. KrLLoucR. M. S., Agronomist; Cotton Breeding E. C. CusmNc. B. S., Assistant in Crops P. R. JOHNSON, Assistant in Soils PLANT PATHOLOGY AND PI-IfYSIOLOGY: C J. J. TAUBENI-IAUS, Ph. D , Chi FARM AND RANCH ECONOMICS: L. P. GAREARn, M. S., Chie ‘B. YOUNGBLOOD, S., P . D., Farm and Ranch Economist G. L. CRAWEQRD. M. S., Marketing Research Specialist V. L. CoRv, M. S., Grazing Research Botanisi '**T. L. GASTON, JR., B. S., Assistant, Farm Records and Accounts ***J. N. TATE, B. S., Assistant, Ranch Records and Accounts RURAL HOME RESEARCH: JEssiE WIIITACRE, Ph. D., Chief SOIL SURVEY: '**W. T. CARTER, B. S., Chief H. W. IIAWKER, Soil Surveyor E. H. TEMPLIN, B. S., Soil Surveyor T. C. BEiTcR. B. S., Soil Surveyor BOTANY: H. NEss, M. S., Chief PUBLICATIONS: A. D. JAcKsoN, Chief SWINE HUSBANDRY: _ FREn IIALE, M. S., Chief DAIRY HUSBANDRY: , Chief POULTRY HUSBANDRY: _ R. M. SRERwooD, M. S., Chief "'**AGRICULTURAL ENGINEERING: MAIN STATION FARM: G. T McNEss, Superintendent APICULTURAL RESEARCH LABORATORY: (San Antonio) _ _ _ H. B. PARKS, B. S., Apiculturist in Charge A. H. ALEX, B. S., Queen Breeder FEED CONTROL SERVICE: F. D. FULLER, M. ., hi S. D. PEARcE, Secretary J. H. ROGERS, Feed Inspector W. H. W000, Feed Inspector K. L. KIRKLAND, B. S., Feed Inspector W. D. NORTHCUTI‘, JR., B. S., Feed Inspector SUBSTATIONS ‘No. I, Beeville, Bee County: R. A. HALL, B. S., Superintendent No. 2, Troup, Smith County: W. S. HoTcuKiss, Superintendent ‘No. 3. Angleton, Brazoria County: R H. STANSEL, M. S., Superintendent No. 4, Beaumont, Jefferson County: R. H. WYcRE, B. S., Superintendent ‘No. 5, Temple, Bell County: H. E. REA, B. S., Superintendent Ne. 6, Danton, Denton County: P. B. DUNKLE, B. S., Superintendent ‘No. 7, Spur, Dickens County: R. E. DICKSON, B. S., Superintendent ‘No. 8 Lubbock, Lubbock County: D. JoNEs, Superintendent FRANK GAmEs, Irrigationist and Forest Nurseryman No. 9, Baimorhea, Reeves County: J. J. BAYLEs, B. S., Superintendent No. l0, Feeding and Breeding Station, near Colle e Station, Brazos County: R. M. HERWOOD, S , Animal Husband- man in Charge of Farm ' L. J . McCALL, Farm Superintendent No. l1, Nacogdoches, Nacogdoches County: H. F. MoRRls, M. S., Superintendent ‘"*No. 12, Chillicothe, Hardeman County: J. B. Qumav, B. S., Superintendent ***J. C. STEPHENS, M. A., Junior Agronomist No. I4, Sonora, Sutton-Edwards Counties: E. W. THOMAS, B. S., Superintendent W. L. BLAcK, D. V. M., Veterinarian V. L. CORY, M. S., Grazing Research Botanic-t *"‘O. G. BABCOCK, B. S., Collaborating Entomologist O. L. CARPENTER. Shepherd No. I5, Weslaco, Hidalgo County: W. ll. FRIEND, B. S., Superintendent M. McPnAiL. B. S., Entomologist No. I6, Iowa Park, Wichita County: E. J. WILsQN, B. S., Superintendent’ Teachers in the School of Agriculture Carrying Cooperative Projects on the Station: W. ADRIANCE; M. S., Associate Professor of Horticulture W. BILSING, Ph. D., Professor of Entomology P. GROUT, M. S., Professor of Dairy Husbandry P. LEE, Ph. D., Professor of Marketing and Finance SCOATES, A E., Professor of Agricultural Engineering H. P. SMITH, B S., Associate Professor of Agricultural Engineering TAs of May l, 1927 ‘On leave. ‘*Dean, School of Veterinary Medicine. "**In cooperation with U. S. Department oi Agriculture. ****In cooperation with the School of Agriculture. SYNOPSIS The object of this Bulletin is to trace the relation between the analysis of the soil for potash in several forms, and the amounts of potash taken up by plants in pot experiments, for the purpose of aiding in the interpretation of the results of soil analyses. The active potash, the total potash, the acid- soluble potash and the acid-insoluble potash are studied. The amount of active potash is found to be more closely related to the results of the pot tests than are any of the other forms of potash, though all have some relation both to the pot tests and to one another. The estimation of active potash is believed to give the best idea of the possible deficiency of the soil for potash at the present time. Statistical methods are used in the discussion. TABLE OF CONTENTS PAGE Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Soil potash as related to the plant . . . . . . .' . . . . . . . . . . . ._ . . . . . . . . . . . 6 Soil potash as related to the solvent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Method of Work . . . . . . . . . . . . . . . . . . . . . . A . . . . . . . . -; . . . . . . . . . . . . . . 7 Statistical methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Methods of analysis . . . . . . . . . . . . . . . . . . . . . . . _ . . . . . . . . . . . . . . . . . . 8 Relation of potash removed by crops to soil analysis . . . . . . . . . . . . . . 8 Relation of active potash to potash removed by cropping . . . . . . . . . . 9 Statistical relations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 10 Calculation of the relation of the active potash to the potash removed by the crop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Relation of calculated values to observed figures . . . . . . . . . i . . . . 12 Relation of acid-soluble potash to the crop . . . . . . . . . . . . . . . . . . . . . . . 141 Relation of total potash to the crop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1'7 Relation of acid-insoluble potash to the crop . . . . . . . . . . . . . . . . . . . 4 . 23 Relation of the active, acid-soluble, and total potash to one another. . 23 Summary of correlation factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Corn possibility of soil potash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2'7 Detailed methods of analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Active potash and acid consumed . . . . . . . . . . . . . . . . . . . . . . . . . . 2'7 Acid-soluble potash in soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Total potash in soils . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Summary and conclusions . . . . . . 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . i. 32 References . . . . . . . . . . . . . . . . . . . . . _ . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 BULLETIN N0. 355 MAY, 192'?‘ RELATION OF THE POTASH REMOVED BY CROPS TO THE ACTIVE, TOTAL, ACID-SOLUBLE, AND ACID-IN SOLUBLE POTASH OF THE SOIL G. S. FRAPS This Bulletin is a report of progress on a study of the relation be- tween the chemical analysis of the soil and the properties of the soil. Previous bulletins have reported work on phosphoric acid, nitrogen, and potash and the results secured have been applied in other bulletins dealing with the composition and properties of typical Texas soils. This Bulletin is one of the series dealing with soil potash. Bulletin 145 discusses the active potash of the soil and its relation to pot experi- ments; Bulletin 190, the effect of additions on the availability of soil potash; Bulletin 284, the availability of potash in some soil-forming minerals; Bulletin 325, the effect of cropping upon the active potash of the soil. This Bulletin deals with the relation of the active potash, the total potash, the acid-soluble potash, and the acid-insoluble potash to the crops grown on the soils in pot experiments, their potash content, and the amount of potash removed by the crops. The object is to ascertain more closely, if possible, the relation between the analysis of the soil and the ability of the soil to furnish potash for crops. As shown in Bulletin 145, there is a close relation between the active potash of the soil and the potash taken up by crops. The active potash lost by cropping as shown by chemical analysis of the soil before and after cropping, is also closely related to the amount of potash removed by the crops, as shown in Bulletin 325. The bulletin here presented carries the study further, and other bulletins are in preparation relating to soil potash dissolved by other solvents. ' HISTOBICAL Active potash and phosphoric acid were usually studied together. Gerlach (1) concluded from several hundred experiments on dilute solvents for two years with 16 soils, that 1 per cent citric acid best served to indicate the needs of the soil for phosphoric acid. There were, how- ever, exceptions» Dyer (2) found the root acidity of 100 plants to vary from 0.34 with Solanaceae to 3.4 with Rosaceae and to average 0.91 per cent. He applied 1 per cent citric acid to soils of the Rothamsted Experiment Station and found the results with potash and phosphoric acid in accordance with the history and properties of the samples. He con- cludes that a soil containing less than .01 per cent potash or phosphoric 6 BULLETIN NO. 355, TEXAS AGRICULTURAL EXPERIMENT STATION acid soluble in this solvent is usually in need of a corresponding fertilizer. The American Association of Official Agricultural Chemists (3), through various Referees, undertook studies of citric acid and other solvents. Nitric acid 0.2 N with correction for neutralization Was adopted as official for several years, but was eliminated in revising the methods in 1917, a serious mistake in the opinion of the writer. The Experiment Station at Halle (5), Germany, used Weak citric acid. Liebscher (6) obtained results in accordance with those of Dyer. The Massachusetts Experiment Station ('7) obtained results which did not correspond with the yield of crops. Sap-acidity of wheat (8) Was found to be equal to 0.48 per cent citric acid, While that of clover Was 1.02 per cent. Hall and Plymen (9) tested 1 per cent citric acid, equivalent hydrochloric acid, acetic acid, and Water saturated with carbon dioxide, on 19 soils. The 1 per cent citric acid gave results most nearly in agreement with the recorded history of the soil, though there is evidence that the same interpretation cannot be placed on results obtained from all types of soils. Cousins and Hammond (10) found Dyer’s method unsatisfactory on the highly calcareous soils of Jamaica, unless the acid was corrected for the lime present, and then the results agreed with the known pro- ductiveness. Kudashey (11) recommends % per cent oxalic acid and reports re- sults on 62 samples of soils. The Dyer method agreed with field tests on clay soils but not with other types of soils (12). Moore (4) compared the quantity of potash and phosphoric acid extracted from the soil by dilute acids, with the quantity removed by crops from the soil, regardless of the deficiencies of the soils for any particular plant food. On the basis of this work he proposed the use of .02 normal hydrochloric acid. Buler (13) states that Water containing carbon dioxide gives better results than dilute acids. He regards soil containing less than 0.015 per cent potash soluble in carbonated Water as deficient. Ingle (14) found in pot experiments that extraction with 1 per cent citric acid makes the soil less productive for crops at first, but the active plant food is gradually restored. Fraps (15) found a close relation between the active potash of the soil and the potash taken up by crops. The active potash lost by cropping was also shown to be closely related to the potash removed by the crops. SOIL POTASH AS RELATEDVTO THE PLANT The amount of potash removed by the plant depends upon a number of factors. The kinds of potash compounds in the soil and the relative amounts, are both important, but are by no means the only factors. In POTASH REMOVED BY CROPS TO ACTIVE, TOTAL, ETC., POTASH OE SOIL 7 pot experiments efforts are made to eliminate all other variables; yet this cannot be done completely. The factors which affect the potash removed by plants in pot experi- ments include the quality and quantity of the different potash com- pounds in the soil, the kind of plant; conditions of growth, such as temperature, water supplied, and time of growth; the relation between the number of plants and the quantity of soil, and others. Both the chemical character and the physical character of the soil are also of effect. If the soil has a poor water capacity or assumes a poor physical condition, the growth of the plant will be retarded and the amount of potash taken up by the plant may be low. Plants may make a small growth, but at the same time take up a high percentage o_f potash; so analysis of the plant is always necessary. Underfield conditions more variables enter into play, making the connection between field growth .and pot results quite difficult to cor- relate. Natural variations in the soil in the field are of considerable effect. The depth of the surface soil and the depth and character of the subsoil and seasonal conditions including temperature and moisture conditions, affect the amount of plant food absorbed. The ratio of plant growth to soil available is also of significance. SOIL POTASH AS RELATED TO THE SOLVENT The potash dissolved by solvents from the soil depends upon several groups of factors. The more important ones are as follows: (1) The nature of the solvent, including the strength of solvent, the time of contact, the temperature, and ratio of soil to solvent. These are discussed to some extent in Bulletin 145. (2) The relative abundance of the potash-bearing compounds in the soil. Absorbed potash, and minerals such as leucite or phillipsite give up 15 to 60 per cent of their potash to 1.2 nitric acid; biotite and glauconite less than 10 per cent; and microcline and orthoclase prac- tically none, as shown in Texas Bulletin 145. (3) The solubility of soil materials which protect or enclose potash minerals. (4) The power of the soil to fix potash under the conditions of the experiment. This varies with the solvent used. As shown in Texas Bulletin 145, this factor is not of great importance with potash when 0.2N nitric acid is used. METHOD OF WORK The pot experiments were carried out as described in previous bulle- tins. The dry soil was passed through a sieve and 5000 grams placed in pots which had already had gravel placed in them. Dicalcium phosphate and ammonium nitrate were added to the no-potash pots. The pots were Watered and corn or other seed planted. The pots were kept in a greenhouse and watered three times a week, or oftener if 8 BULLETIN NO. 355, TEXAS AGRICULTURAL EXPERIMENT STATION necessary. Two crops were grown in succession, corn being usually the first, sorghum or kafir the second. The crops were harvested, dried, Weighed, and the potash determined in them. The pots were kept in a greenhouse, and grown during the summer, when the temperature sometimes became quite high. It was realized that this high temperature would affect the results, but it could not be avoided. The results must be considered as comparative, not absolute, for under lower temperatures and other different conditions, different amounts of potash Would have been taken up by the plants. The amount of potash taken up under more moderate temperatures Would probably be lower. The conditions were kept similar as nearly as possible. STATISTICAL METHODS Statistical methods are used in genetics, economics, and other studies as an aid to unravel factors operating in complex conditions. These methods are applicable to soil studies and have been used in previous bulletins. The results secured will be discussed in connection with the subject matter. METHODS OF ANALYSIS The active potash was estimated by solution in 0.2N nitric acid, digesting 5 hours at 40°. No correction Was made for the neutralization of the acid by the bases. The total potash was estimated by the Lawrence-Smith Method. The acid-soluble potash is that dissolved by 1.115 hydrochloric acid by the Hilgard method. The acid-insoluble potash is the difference between the total potash and the acid-soluble potash. The detailed methods are not available elsewhere and are given at the end of this Bulletin. RELATION OF POTASH REMOVED BY CROPS TO SOIL ANALYSIS The average results arranged according to the potash removed by two crops in 329 experiments are given in Table 1. In this table, if two or more pots of the same soil were used, the results were averaged before being used to prepare the table. As the potash removed by the crops increases, there is generally an increase in the active potash, the total potash, and the acid-soluble potash. Until the potash removed by the crops exceeds 600 parts per million of the soil, the active potash increases regularly. After this there is a decrease in the active potash. Until the potash removed by two crops exceeds 300 parts per million, both the total potash and the acid-soluble increase regularly, after which it is irregular with a tendency to increase. These are discussed more fully below. In interpreting the results of the chemical analysis of the soil, it is POTASH REMOVED BY CROPS TO ACTIVE, TOTAL, ETC., POTASH OF SOIL 9 necessary to judge the possible crop production or deficiency from the analysis. For this reason, it was considered more important to arrange the results according to the analyses than according to the crops, though such arrangements involve more Work and more tables. Table 1.—Soi1s arranged according to potash removed by_ two crops, averaged if more than one pot of the same S011 Potash Removed Acid by Two Crpps— Potash in Average Active Total Soluble Number Per Milhon 2 Crops Per Crop Potash Potash Potash Averaged of Soil p. m. p. m. p. m. Per Cent Per Cent 0- 5O . . . . . . . . . . . .. 42 21 66 .43 .07 14 51-100 . . . . . . . . . . . . . 77 39 85 ’ .59 .11 57 101-150 . . . . . . . . . . . . . 122 62 128 .79 .23 55 51-200 . . . . . . . . . . . . . 173 87 164 .99 .29 45 201-250 . . . . . . . . . . . . . 226 113 244 1 .17 .46 35 51-300 . . . . . . . . . . . . . 270 135 306 1 .53 .65 15 301-400 . . . . . . . . . . . . . 347 174 349 1 .43 .63 30 401-500 . . . . . . . . . . . . . 433 217 352 1 .30 .61 14 501-600 . . . . . . . . . . . . . 539 270 801 1 .89 .93 7 Over 600 . . . . . . . . . . . . 665 333 628 1 .79 1 .14 RELATION OF ACTIVE POTASH TO POTASH REMOVED BY CROPPING The average results of the experiments arranged according to the active potash of the soil are given in Table 2. Each pot is included separately though there are sometimes more than one pot of the same Table 2.-Averages of soils arranged by active potash. Active Weight Weight Potash Potash Potash Active Potash Potash No. Potash First Second in 1st in 2nd Two Potash in 1st in 2nd Aver- Per Crop Crop Crop Crop Crops Soil Crop Crop aged M11. gm. gm. p. m. p. m. p. m. p. m. p. m. p. m. a. 6 25- 50 26.4 17.1 43.3 17.8 61.2 4O .83 .53 27 50- 75 28.6 21.7 47.1 29.6 76.7 62 1.09 .75 46 75-100 32 .0 21.4 69 .4 32 .5 99 .7 88 1.23 .84 41 100-125 38.7 20 .0 85 .6 35 .4 120 .2 110 1 .66 .93 30 125-150 33.1 22.1 101.6 48.6 149.5 136 1.74 1.13 37 150-175 32.2 20.9 110.0 44.7 153.7 163 1.74 1.22 16 175-200 36.3 27.4 139.1 61.6 194.5 189 2.05 1.12 16 200-225 34.9 26.8 171.5 56.8 226.0 211 2.65 1.22 15 225-250 32 .7 27 .3 190 .9 88.1 273 .0 241 3.11 1.76 19 250-275 33 .1 25 .5 201.6 81 .1 280 .9 259 3 .41 1 .74 10 275-300 30.1 26.2 171.9 118.4 257.6 288' 3.02 2.24 6 300-325 31.8 33.0 243.0 112.6 338.5 317 3.74 1.80 7 325-350 3O .0 26 .1 234 .5 9O .4 325 .0 338 3 .97 1 .87 5 350-375 26.1 22 .9 231.2 88 .0 319 .2 364 4.69 2 .31 6 375-400 30 .0 29 .5 209 .7 98 .6 332 .3 390 3 .62 2 .00 4 400-425 37 .9 36 .7 254 .0 100 .0 354 .0 405 3 .33 1.36 2 425-450 32 .7 22 .8 288 .0 74 .0 362 .0 438 4 .42 1 .78 3 450-475 32 .4 26 .3 259 .0 98 .0 357 .0 463 4 .44 1 .93 -2 475-500 28 .7 11 .2 229 .0 67 .0 244 .0 488 4.23 2 .97 1 500-525 40 .1 26 .0 379 .0 72 .0 451 .0 524 4 .73 1 .38 4 525-550 36 .0 30 .5 293 .0 151.0 444 .0 535 4 .20 2 .43 4 550-575 26 .9 42.2 248 .0 166 .0 414 .0 568 4.78 2 .12 1 600-625 41.1 . . . . . . .. 193 .0 . . . . . . .. 201.0 601 . . . . . . . . . . . . . . . . 1 625-650 46 .8 34 .9 491.0 174 .0 665 .0 628 5 .52 - 2 .50 1 725-750 34.8 . . . . . . . . 338.0 . . . . . . . . 450 .0 736 . . . . . . . . . . . . . . . . 1 775-800 23.2 29.6 199.0 132.0 331.0 791 4.28 2.24 4 1000-1409 30 .8 31.1 383 .0 180 .0 563 .0 1207 6.23 2 .90 1O BULLETIN NO. 355, TEXAS AGRICULTURAL EXPERIMENT STATION soil. The number of samples in the groups exceeding 575 parts active potash per million is not satisfactory for proper averages, but there also are some groups below which do not contain enough samples. Weight 0f CIOD- While the average Weight of the crop is a little lower at first, no regular relation can be traced between these weights and the active potash of the soil. The correlation coeflicient, r, for the weight of the first crop and the active potash is —|— .045 i .055, or prac- tically none at all. These facts indicate that the Weight of the crop alone cannot be correctly used to study the potash of the soil. P61‘ 66111; DOtaSh ill ¢I'OD- The average percentage of potash in the crop increases with the active potash in the soil. This applies both to the first and the second crop. The percentage of potash in the second crop is less than in theifirst, decidedly so in many cases. Usually the first crop was corn, the second sorghum, both grown the same year. The difference may be i11 part due to the nature of the crop, in part to the fact that the first crop has removed some of the active potash. y A The average percentages of potash in the first crop (corn), range from 0.87 to 6.23 per cent, and in the second crop (sorghum), from 0.52 to 2.97 per cent. These results show that estimates of the avail- ability of potash minerals or of soil potash based upon weights of the crop alone are open to serious question, to say the least. The correlation coefficient, r, for the percentage of potash in the first crop and the active potash in the soil is + .194 i .053. This is a low correlation. Pfltflsh taken 11D by the CYOD- The amount of potash taken up by the crop, expressed in parts per million of the soil, is given for the first crop, the second crop, and for the two combined. There is a close relation between the active potash in the soil and the amount of potash taken from the soil by crops. While the active potash is not the only factor involved, it is certainly an important one. The potash taken up by the first crop is larger than that taken up by the second. It is believed that the potash taken up by the two crops represents the ability of the soil to give up potash a little better than either the first crop or the second crop alone. Statistical Relations The correlation coefficient for the active potash in the soil and the potash taken up by the first crop is + .742 i .019. The correlation coefficient for the active potash and the potash taken up by two crops is 0.794 i .014. In both cases the correlation is high, but the two crops give a better correlation than the first crop. It is believed that this is due to the tendency of the second crop to equalize variations in the first crop due to seasonal or other conditions. POTASH REMOVED BY CROPS TO ACTIVE, TOTAL, ETC, POTASH OF SOIL l1 Calculation 0f the Relation of the Active Potash t0 the Potash Removed by the Crops The question of the degree of accuracy With Which it is possible to estimate the potash removed by crops in pot experiments from the active potash is a matter of considerable importance. The relation of the potash take11 up by crops to potash in the soil under field conditions is also of great importance, but is a more diflicult problem and is not dis- cussed here. It must be remembered that the amount of potash removed by crops in pot experiments is not an absolute measure of the availability of the potash in the soil, since the growth of the crops is afiected by other factors than the quantity of available potash. It is the best measure We have at the present time, however. a The relations between the average amounts of potash removed by the crops and the active potash in the soil are shown graphically in Figures 1 and 2. The averages are grouped in both curves quite regularly up to about 450 parts per million of active potash, beyond which the points are more scattering. The number of samples of soils containing more than 450 parts per million were in many of the groups insufficient for fair averages, and this fact prevents the formation of a correct opinion Q gi m % i’ . ‘o’ \) § o §§§ ‘t? F/yl. Q Q "~ t, y’~9f.'7j.< .. 3T1 N3 wwm .. NN 3w mww mofilooofi . . . . 2w . .. NE .. . .. 3m ooofilmhm . .. how .. . Em mwmlomm . . .. Now .. ... . .. 3w . . ommlmNm . . . . . . . . .. . . . . .. .. .. . won . . . .. . . .. oww . mNmloom .. .. IR . . . . .. . .. .. .. . Wuwm . ... . .. own .. .. .. oomlmhw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . m . . mmw mhwlomw . . . . . . . . .. NB . . hmm omw|mNw I . . . . . . . . . . . . . . . . .. mom . . . . . . . . .. .. . . . . . .. mmm . . . . . mNwloow . . . . . . . . . . . . .. . .. . wNN wmm 1mm .. . . EH wmm m2 oQwImR. .. IIIH IN . . . . . .. . . . . .. mwm . . . . .. . . . . . . . . . . . . awn . . . . . . . . _. mhhlomu .. . . . . .. mw m2 09. .. . . .. . . w 0% wwm 007mm» . .4 . . . . . . . . ... .. . fiNm . .. . SA,“ mNnlooN. . . . . . . . . . . m5 . hmm. oomlmnw .. .. . . . . . . . . .. Nom .. . 5m . mhwlomw . . . . . . . . .. m5] omw mow . .. .. . . ma] mNm 3v omwlmNw . . . . . . . . . . . whN n30 8N . . . mNfi wfim m2 mNwloow . . . . . . . IA .. . . . . . . . 3v .. m?“ oowlmwm . . . . . . . . Io 3 N“. .5 E0 w? Nw hNN hm mow 3N mfifomm . . . . é . . . . >| DU 3% N. NN w wmN mmN ommlmNm . . . . - ¢ u - . ~ u - - n - ¢ n . I - a q q n n - - u . u - - - .? . . . . . n21: new EN . . Nm fiwN mNN oomlmnw . . . . . . . . . . . . mm Nam 5m oN mm NH QN mmN @5703 . . . . .m . a - - - - . - - - - - - - - - - - - - . - . . - - - . . . . . . . - . - u .N 2 E m mmm Em m. N. wl omN wmN mmToow . . . . . . .0 I hm 2 Q». Nmm 3 ww mwl mmN 2N 00.70% . . . . . . . . . d NN C. o mNm 2m ... 2 NI. mNN 3w mwmlomm . . . 4.. 2 mm 2! 8m mNw mN m0 wfiln 5N mmN omwlmNw . . . . . . . . . S hN R. 5| wwN 0mm mN . 8 2W1 20m 2N mNwloom I6 3. 3 Z mwN wmN wN mm fiN m2 N: oowlmhN . . . . . . . . . .2 mm 8 1m]. omN fiwN wm we mNl. m: NoN fimuomw . . . . . . . . . .2 2. Na Q1 omN whN mm an wNl. 9: 22 omNlmNN . . . . . . . . . A.“ ~ mm wo SI moN wNN Nm w» NN|l om H N: mNNIQoN . . . . . . . . . .3 wN m... hi. S: m2 wH mN N| >2 02 ooNlm: .. . . . . .. A: QN 2. m R: 0.2 mN wN Z NNH 0: @5102 . . . . . . . .5 wN .5 .|| m3 02 wN hN m. m2 N2 8 TmNN . . . . . . . . . 0m mN mm N NN.“ oN~ “N vN N ww ww @702 . . . . . . . .3 mm mm Tl 3 02 mm 0N v m“. $ 007mb . . . . . . . . . be Q 3 T: w“. R. mm wfi w m... S‘ m» Ion . . . ilhN N0 NN 0| Nm 3 S. 2 0| ...». 2. on lmN o nothr/QQ 00$E>0Q 00:0 03E 0000b 00SB>0Q cofimtyofi 0on0 032 0000b Qiwwom mmom m0 omficwohom vhmwqmww IEED $0200 omwcoohvm 002.03% ABEQ -00? U 030043 000E: Z wnnohmv 3000 03h. E 0000 50E 05 5 don m0 025E $0 3.3m .325 ~00 E 05.0..“ “E202.” o5 0w 60200000 05 00 @5288 52.000 0200a 50b wofifisodwu mm 30.8 .3 0: 00x3 cmfioa o5 M0 momfifloflllm 050B 14 BULLETIN NO. 355, TEXAS AGRICULTURAL EXPERIMENT STATION The standard deviation which is expressed in _parts per million is irregular but tends to increase as the active potash increases. The percentile deviation is somewhat higher with the soils containing the smallest amounts of active potash. The average percentile deviation is about 30 per cent. This multi- plied by .67 gives about 20 per cent, which means that it is approximately an even chance there will be an average variation of 20 per cent, accord- ing to statistical theory. RELATION OF_ACID-SOLUBLE POTASH TO THE CROP The results of the experiments arranged by the acid-soluble potash of the soil are given in Table 4. The weights of the first crops are irregular, but a slight increase in weight of the second crop is found in the first part of the table. As the acid-soluble potash increases, there is a11 increase in the potash removed by both the first and the second crops, and by the two crops combined. There is also an increase in the active potash and i.n the total potash, showing that the quantity of these is related to the acid-soluble potash. The correlation coefficient between the acid-soluble potash of the soil and the potash removed by two crops is + .667 i .013. This is a high correlation, but not as high as —{~ .794 i .014 found for the active potash and the potash removed by two crops. The correlation coefficient between the acid-soluble potash and the active potash is + .761 i .019, or closer than for the acid-soluble potash and the potash removed by the crops. While the amount of acid-soluble potash in the soil is related to the potash removed by the crops, it is probable that this is due largely to the fact that an increase in acid- soluble potash is accompanied by an increase in active potash, and is thus largely to be ascribed to the active potash. The averages for the acid-soluble potash are plotted in Figures 3 and 4. The points seem to be arranged in two parallel lines up to about 0.6 per cent acid-soluble potash, after which they become scattering. No satisfactory curves were calculated from the data. Straight lines were plotted from observation up to 0.6 per cent acid-soluble potash, after which the writer assumes there is no further increase. The lines plotted are: (3) Potash removed by first crop: 60-}- 270 times acid- soluble potash (up to 0.6 per cent) OI‘ Y I 60 + 270x (4) Potash removed by two crops I 83 + 392 times acid- soluble potash up to 0.6 per cent a or Y: 83+ 392x POTASH REMOVED BY CROPS TO ACTIVE, TOTAL, ETC., POTASH OF SOIL l5 0 00.0 0v.0 v0.0 00.0 0.000 0.0v0 0.v0 0.000 0.00 0.00 000.0|000.0 0 00.0 00.0 00.0 00.0 0.000 0.000 0.000 0.000 0.00 0.00 000010000 0 00.0 00.0 0v.0 vv.0 0.000 0.000 0.0v0 0.000 0.00 0.00 000.0I000.0 0 00.0 00.0 00.0 00.0 0.000 0.000 0.000 0.000 0.00 v.00 000.0|000.0 0 00.0 00.0 00.0 00.0 0.v00 0.000 0.00 0.000 0.0 0.00 000.0I000.0 0 v0.0 00.0 00.0 00.0 0.000 0.000 0.00 0.000 0.0 0.00 000. 0I000.0 0 00.0 00.0 00.0 00.0 v.000 0.0v0 0.00 v.000 0.00 0.00 000. 0:000. 0 00.0 00.0 00. 0 00.0 0.000 0.000 0.000 0.000 0.00 0.00 000. I000 0 00.0 00.0 v0.0 00.0 0.000 0.000 0.00 0.000 0.00 0.00 000. I000 0 00.0 00.0 00.0 00.0 0.00v 0.000 v.0v v.000 0.00 0.00 000. I00v 0 0v.0 00.0 00. 0 00.0 0.000 0.0v0 0.00 0.000 0.00 0.00 00v. I00v 00 v0.0 0v.0 00.0 00.00 0.000 v.000 0.000 0.000 0.00 0.00 00v. I000 0 00.0 00.0 0v.0 00.0 0.v00 0.000 0.00 0.000 0.00 0.00 000. I000 00 00.0 00.0 00.0 vv.0 0.000 0.000 0.00 0.000 v.00 0.00 000. I000 0 00.0 00.0 00.0 00.0 0.000 0.v00 0.000 0.000 0.00 0.00 000. I000 00 00.0 00.0 00.0 00.0 0.000 0.000 0.0v 0.000 0.00 0.00 000. I000 00 00.0 00.0 00.0 vv.0 0.0v0 0.000 0.0v 0.000 0.00 v.00 000. I000 v0 00.0 00.0 00.0 00.0 0.000 0.000 0.00 0.000 0.00 0.00 000. I000 00 00.0 00.0 0v.0 00.0 0.000 0.000 0.0v 0.000 0.00 0.00 000. I000 00 00.0 vv.0 0v.0 00. 0 0.000 0.000 0.00 0.000 v.00 0.00 000. I000 00 00.0 00.0 00.0 v0. 0 0.000 0.000 0. 00 0.000 0.00 v.00 000. I000 00 00.0 00.0 00.0 00.0 0.000 0.v00 0.00 0.00 0.00 0.00 000. I000 00 00.0 00.0 00.0 00.0 0.00 0.00 0.00 0.00 0.00 0.00 00.0|0 0cm 5 0cm 5 Q50 0500 .5 .0 .5 .0 .5 .0 .5 .0 .50 .50 0060 .090 060.5054 523cm 5.00 5A0 0:550 5 0.05m 5 523cm 6.050 .050 .050 .050 .050 523cm 5205570 205cm 55cm 093cm 523cm 05004 95,0. 5 05050 5 050,0 5 05050 05E 205cm 500. 030,0. 05.0 5cm 005D 5on0 523cm 023cm 553cm 500.3,? 553$ 50¢ 52.550 05505-0000 0c 555cc 5.50 o» 0505.8“ 0505058 5cm 0c @ww$><|.0 0000.0 16 BULLETIN NO. 355, TEXAS AGRICULTURAL EXPERIMENT STATION g Q w‘ 31 6 ° § i3- ég <\l-\\_ Q 8 .5? H92. ‘"“ Q g )’=/5f}’“.00O4X? s 3i @ “Y? Q Q o N* Q 5 AC fi ve Po fash per/V/Y/fon. l l l i l I l l mo zoo J00 40o .500 60o 70o s00 Figure 2.—Relation'of _the active potash_in the s0il_ to the potash removed from the soll by two crops, w1th approxxmate curve. % w 8 g q" vuq o N§ Q \ . m ' F7525 ‘~—fi$y=aaraazx Q O O x g g w Q0 .0 018m o Q0 o 8Q Q o m. G Q Q Per Cenf O l l Af/o’ $0 ulb/e Ffofois/z. l a2 0.4 0.6 0.8 no /.2 1.4- Ac Figure 3.-—Relation of the acid-soluble potash in the soil to the potash taken up by two crops, w1th approxlmate curve. POTASH REMOVED BY CROPS TO ACTIVE, TOTAL, ETC., POTASH OF SOIL 17 RELATION OF OBSERVED TO CALCULATED VALUES FOR ACID- SOLUBLE POTASH " The relations between the potash removed from the soil by the first crop and by two crops, to the values calculated from the acid-soluble potash by the formulas just given, are shown in Table 5. The difference is that between the observed and calculated values. The standard deviation represents the variations of the results of the individual pot experiments from the calculated values for each group. The percentile deviation is the standard deviation divided by the cal- culated results, expressed as per cent. The average percentile deviation is 44 and 38, which is greater than about 30 per cent found for active potash. Examination of the table shows that prediction by means of acid- soluble potash is much less close than by means of active potash. This is confirmed by observation of Figures 3 and 4, and by the lower corre- lation between the acid-soluble potash and the potash removed by crops. RELATION OF TOTAL POTASH TO CROP The results arranged according to the total potash of the soil are given in Table 6. The weights of the crops are irregular. The potash with- drawn from the soil by the first crop, by the second and by the two crops combined, increases with the total potash of the soil. There is evidently a relation between the total potash of the soil and the potash removed by the crops. The active potash and the acid-soluble potash also increase as the total potash increases, showing that these three kinds of potash are related to one another. 18 BULLETIN NO. 355, TEXAS AGRICULTURAL EXPERIMENT STATION xi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V . . . . . . . . . . . . . . . V . . . . . . . . . . . . . . . . . . A . . . 2 N0 N0 000 0NN 0 2 0H 00N IN 11.000. T50; w mm 0.2 ~0| 00m :0 E. m: N011 omN NON . . . :03“. 7000.. _ 0. 0m. 02 05| 0mm 00m. E S; 00_| omN 0mm .000. 70mm 0 0 Nw S; m0| 0mm m? 0m >0 5| omN >0N . . ooN. 013;. 0 ... 0N #0 3 000 0mN m h 0 omN 0NN . . . . .03. T00. ~ N E a: 00~ 000 N0~ Ev t: h0~ 00N mfi . 000. ~|~N0. ~ N 0N 00 00 000 0hN 0m 00 2. 0mN ~0~ .0N0. T30. 0 0 0N 0N 000 000 8 00 00 00N 3i . . . . .000. I000. fi 00 mm 3|. 0mm 2N 0m 00 0N omN 00m . . . . .000 n30. m. 2. mm: E1 0mm 02. H0 o3 0001 omN 00m . . $0 l0“. m 0N 00 3. 000 0NN NN B 0m 00N 00~ .000 lfiNw. N 00 0: N‘ 0mm N00 2. #0 N 00N 0NN . . . . . 0NN. I~00. 0~ 0N mm nN 000 00m 00 00 0w 0mN 3N .000 I50. m 00 :0 mNl 00m 0N0 00 ~0 0~| 3N NmN .000. 13m. .3 N0 0: 001 m0N :0 i: 00N :1 02 00N ... :20. 1:0» m 0w 0: 0N amN vmN 00 N0 0N N0~ $0 .000. 1N0. Nfi 0m N0 2| 00N mmN Q >0 0T! 00H 00w 0N0. I000. 0~ 00 00 NN N~N 02 N0 00 0~ 03 02 .000. i000. 5 2. N»; ~01. 2: 0NN m0 5 NN] m2 m2 . . . . .000. IQN. 0N 3. 0m 0N m0~ 00A 0.». 00 2 >2 02 .....2&. I000. 0N mm. 0h mNl. N: 00~ m» 0n mNl. ~0~ 0Q .005 lfiNfl. 0N 0m m0 0 0: 0: 2. Q H 00 00 0N5 L00. 0v mm mm 2 m0 N0 Q 0N m 00 mm . . . . . .00. 0|0 3 00100600 comwwiwvfi 00:0 002.‘: 0000b saint/vi cofiwrwofl 00:0 000.2 0000b 22000.0 @000 25:03am 0.0000000 Lvmmfi -0200 Bisouhon- 0000530 1.50.00- -02.00 203000640 00 300.00 .0Z 300D 03F :0 00.00 3th 0.3 0S 000w 00 02:2: $0 300m .330 000 5 0:500 0000030 05 o0 A9300 2233-060 0:0 89C 03000300 mm 000$ .3 0: 00x3 i300 05 00 005000110 20mm. POTASH REMOVED BY CROPS TO ACTIVE, TOTAL, ETC, POTASH OF SOIL 19 3* $16 *;,_§ flyi- Q \ gJ-E Q r- 60¢Z70xi O 5* Qh-Qt Q C5 b o a ‘é "8 0Q)“ 0 Q "'1 o O o e Q G @ \ PerCehf Ac/o’ fio/ub/e Pofas/v. l l 0.1a oi4 0.1a sis /.'o /.'2 441 ze- Figure 4. Relation 0f the acid-soluble potash i1} the soil to the potash taken up by the first crop, wlth approximate curve. m ‘K fi-E a“ . ‘Q-‘k Q P.“ Q '\ \ |J\\ §_~g (E 7' 55f//Z/\:DQ Q Q 3-0. Q09 9 (D Q Q PekC-Qh/ Q I TOfO/ 100/‘05/7 0.5 1'0 A5’ 2&0 2'5 $0 G115 41.0 Figure 5.——Relation 0f total potash of the soil to potash removed by the first crop, with approximate curve. 20 BULLETIN NO. 355, TEXAS AGRICULTURAL EXPERIMENT STATION m 000.0 0v.N 00.0 00.0 00.0000 00.Nv0 00.000 00.Nmm 0m.NN v0.vN 00N I0v.N N 000.0 00.N N0.N mv.0 00.Nm0 00. 0N0 00.000 0m. 00m 0v0m 00.0m 0v.N I00.N N 000. m0N 00N 0m.0 00.0N0 00.mmm 00.000 00.000 N.0m 00.0N 0m.N I00.N 0 N00. 00N vm.N N00 00.000 0. 00N 0N.0m 00. 00N 0N.m0 00.0N 00.N I000 0 0v0. 0N.N 0m.N 00.0 00 00m 00.000 00.000 0m0NN 00.vN 00.0N 0m.N |0N.N .. 0 mv0. 00.N v0.0 m0.m 0v 00N 00.0NN 0000 0v.000 vN.00 00.0N 0N.N I00 N m 00v. 00.0 00.N Nv.0 0N v00 00 m00 00.N00 0N.00N 000m 00.0N 00N I00.0 N0 v00. 00. 0 00. 0 mm.m 0N~00N 0N~m0N mv.00 00000 vv.0N 00.0N 00.0 I00. 0 m v0. 0v.0 00.N 000 00.000 0v.0v0 0m. 000 00.0mm vN.0N 00.v0 00. 0| 0v. 0 0 0v. 0v.0 00.0 N0 m 00.0mm 00.000 00.N00 00 m0N 00.0N 0v.m0 0v.0I 00.0 N 0N0. N00 00.0 0N0 00 00N 00.00N 00.00 0.00N 0m mN 00.0N 00 0 I00.0 N0 N00. 00.0 00.0 00 m 00..00N 00 NON 00 00 0.0v0 000m N0.N0 00.0I 00.0 v0 vm. 0m. 0 00.0 09m 00.0vN N0m 00N 0000 0000 m0.vN 00.00 00. 0I 0m. 0 N0 m0. 0N.0 N00 00.N 0 NON 0N 00N N0.00 v 000 m0.0N 00.00 0m. 0I 0N.0 v0 0mm. 00.0 N00 Nv.N 00.m0N 0~0NN v0.0v 0.N00 00.vN N0.0N 0N.0I 00.0 0N 00. 00.0 00 0 m0.N . 00 00N 0 mNN 00.0v 0.v00 00.0N 00.0N 00.0 00.0 vN 0N. 00. 0N0 mN.N 0m 00N 00.m0N 00 00 N.000 m0.0N 00.00 00. 0I000. 0N 0m. 000. 00.0 0N.N 00 00N 0N.NON N0.N0 0.000 0v.NN 0m.0m 000. I000. vN NN. 0v. v0 0 0v.0 N0.m00 00.000 N000 m.000 0v.00 0v.mm 000 I00v. vN 000. m0. 000m N0.0 mv.0N0 0.Nm0 000m 0.000 00.0N 00.0m 00v I000. 0m 00. 0m 000. v0.0 00.,0N0 0.000 v0 vm 0.00 00.00 0m.mm 000 I000. 0N 000. 00. 00. vm 0 00.00 N0.N00 00mm 0.0v 0N.0N 000m 000. I000. 00 000. 00. 00.0 000 00.000 0.000 00.0N N.00 0m.0N 00.0N 000. I000. 00 00. m0N. 00v. 00v. mm.N0 0.Nv 00.0N 0.00 00.v0 vN.0m 000 I00N. m 000. v0. 00 0v0 mm 00 0.00 00.v0 0. 0m v0.v0 00.Nm 00N I000. 06w 5 .0500 50m 00cm 5 050 .050 .5 .0 .5 .5 .5 A0 .5 .0 .50 .50 500 5cm 0000.00.04 523cm .0060 .5 vacuum 5 050m 5 523cm .550 .0050 .050 .050 .050 523cm 5.05570 c5530 53cm 530cm 523cm o>00c< 95.0. 5 0:830 5 050m 5 055cm 005m 03cm. 10:04 03cm. 5on0 50m 5on0 Em 53cm 593cm 523cm 0.0003,? 5000c? 00930.0 0.3.3 c0 055cc...“ 0.00.5050 m00cm|u0 00.0mm. POTASH REMOVED BY CROPS TO ACTIVE, TOTAL, ETC., POTASH OF SOIL 21 Figures 5 and 6 show the relation between the total potash of the soil and the potash removed by the first crop and by two crops. The points are grouped regularly up to 1.5 per cent total potash, after which they become somewhat scattering. There is, however, more regularity for the total potash than for the acid-soluble potash. The curves used were drawn from observation and their equations are as follows: ' (5) Potash in first crop r: 33 + 117 times total potash of the soil or Y r: 33 + 117 X (6) Potash in two crops :2 22 + 1'74 times total potash of the soil or Y I 22 + 174 X The correlation coefficient between the total potash of the soil and the potash removed by two crops is + .662 i .023. This is less than for the acid-soluble potash, and much less than for the active potash. The correlation coefficient between the total potash and the active potash is + .630 i .038, and for the total potash and the acid-soluble potash + .792 i .020. It is again a question whether the relation of the total potash to the potash removed is due to the total potash itself, or to the relation between the total and the active potash. The relation of the calculated to the observed figures, with the standard deviation, is shown in Table '7. 8 Q__ V) D . §_G§ Fly! 6 Q 8 Qxgfiza/nx o V-LE k Q Pn-fiQ o o (L Q §‘__ (D g Pe/Cenf 75f0/ Pafdsh, - l l I : I I a5 1'0 15 .20 2.5 do a5 4.0 Figure 6.-—Relation of the total potash in the soil to the potash taken up by two crops, with approxlmate curve. 22 BULLETIN NO. 355, TEXAS AGRICULTURAL EXPERIMENT STATION w¢ > . - . - - . . . . ¢ . . . . . . . ¢ . . . - . . - . . . . - . . - . - . . ¢ . . . - . . . - . . - . . . . - | - . . - - . . - . - ¢ - . - - ' . . - - . . a u - 66 666 w“ 666 “Nw 6N 66 6N 666 N66 . . 66m NI 6“m N 6 . . . . . . . . . . . . . . . . . . .. 66]. 66w 6N6 N . 6w6 6w6 ......6“NI66.N N . . . . . . . . . . . . . . . . . . .. 66 6ww 666 6N6 6N6 666 ......66.NI6w.N N ww 666 6“6 66w N6N 66 N66 “66 666 66N . . . . . .6w.N I66.N 6 w6 6w6 6“ w6w ww6 66 N66 66 66N “NN . . . . . .66. N I6N.N 6 6w ““6 666 666 6NN 66 666 666 6“N 666 . .6N.NI 66 N 6 6w 666 6 .|I 666 w6w 66 666 6 66N 66N . . . . . .66. N |66.. 6 6 N6 666 66 ww6 66N 6w 666 66 6wN “66 . . . . . 66.6 I66 6 N6 6“ 6wN ww6| “N6 6“w 6 66 N6| 66N 666 . . . . . .66 6| 6“.6 6 . . . . . . . . . . . . . . . . . .. 66|I 666 666 “6l. 6NN 66N ......6“6I66.6 6 . . . . . . . . . . . . . . . . . . .. 6 N6N 66N 66 w6N 66N ......66.6I66.6 N “6 “66 N6 w“N N6N w6 666 “N 66N 6“6 . . . . . .66 6| 6w.6 N6 6w. “66 66II “6N N6N ww w6 6|! 666 666 . . . . . 6w 6| 66.6 “6 N6 wN6 6N| 66N 66N w6 “6 66 6“6 666 . . . . . .66. 6i 6N. 6 N6 66 666 6II NNN “NN 6w 6“. 66 666 N66 . . . . . 6N. 6| 66.6 “6 6w 666 66l. 66N wNN ww 66 6 666 6w6 . . . . . .66. 6| 66. 6 wN 66 66 “NII “66 w6N 66 6“ “I ww6 666 . . . . . .66. 6I666. “N w“ 6N6 66|| 666 N6N 66 N“ “I N66 666 .666. I666. 6N 6w 66 6 666 666 6w 6w 66 6N6 666 666. I66“. “N w6 6“ 6 666 N66 66 66 6 666 666 .66“. I666. “N 6w 66 66II 666 w66 .66 66 6 “6 “6 .666. I666. 66 66 66 66| 666 666 6w 66 6 66 66 .666. I66w. 6N 6N6 w66 66 66 666 666 66 66' w“ 66 66w I666. w6 Nw 6N 6| 66 N“ 66 wN N6 N6 66 .666 I66N. 66 66 6 6 6w 6w 66 6N 6N 66 66 .66N I666. 6 660666666066 6606666666066 00660 6.06666 6650b 660662.666 6606666666066 00660 6.062 6.6666016 2606 066.66.030.66 6.63.6636 0606,6666 6.06660 066666006066 6.63.6866 60.6.6666 6606660 626.36%? 666M360 66.66./6 .6 . 066060 026,6. 666 66060 696616 0666 666 .6600 60 6606:6666 .6066 F6666 666 06006 6066 666 6.666606 $662026 0666 06 660.3066 666.606 6660.66 6.066.606.6660 ww 666060 .666 6666 6.0.66.6 660666066 0666 60 6606.6@606n6|.“ 0666666. POTASH REMOVED BY CROPS TO ACTIVE, TOTAL, ETC., POTASH OF SOIL 23 The differences given are between the values calculated and those found. The standard deviation represents the variation of individual pot tests from the calculated values for each group, while the percentile deviation represents the same variation expressed in percentage of the calculated values. The average percentile variation is larger in the prediction from the total potash than that for the active potash, being about 45 per cent, as compared With about 30 per cent in theprediction from the active potash. RELATION OF ACID-INSOLUBLE POTASH TO THE CROP The acid-insoluble potash is the term applied to the quantity left When the amount of acid-soluble potash is subtracted from the total potash. The results arranged according to the acid-insoluble potash are given in Table 8. The results are more irregular than in the other tables, though there appears to be some tendency for the potash removed to increase as the acid-insoluble potash increases. The same tendency can be noted With the active potash, the total potash, and the acid-soluble potash. The correlation coefficient between acid-insoluble potash and potash removed by two crops is + .388 i .052. For acid-insoluble potash and active potash it is + .428 i .034. These coeflicients are much loWer than those previously secured. This indicates that the acid-insoluble potash is much less significant, in relation to crops, than the acid-soluble potash. It also indicates that the acid-soluble is more important than the total potash. A On account of the small degree of correlation, no attempt Was made to draw curves to show the relation of the acid-insoluble potash to the crops. RELATIONS OF THE ACTIVE, ACID-SOLUBLE AND TOTAL POTASH The active, acid-soluble, and total potash are all three related to the potash removed from the soil by crops, and they are also related to one another. This renders it a diflicult matter to decide how much each contributes to the potash removed by crops, and which of the relations observed are due to the condition of the potash in the soil and Which to the relation of one to the other. In other words, it is a question how much of the relation of the acid-soluble potash in the soil to the potash removed by the crops is due to itself, and how much to its association with the active potash, and the same holds for the total potash. An attempt has been made to separate these factors. For this purpose the relation of the three factors is assumed to be linear and to be as in Figure '7. The quantity of total potash is assumed to act directly upon the potash in the crops, and also through the acid-soluble potash and through the active potash. The amount of acid-soluble potash is as- sumed to act directly upon the crops, and also through the active potash. The amount of active potash is assumed to act directly. Other factors 24. BULLETIN NO. 355, TEXAS AGRICULTURAL EXPERIMENT STATION 0 H0.H 00. 0H.m 00.H 0m.0 0.000 0.00m 0.00H ~63 0.0m 00m 000.H|Hm0.H H m0.H 00. H0.m Hm.0 0.000 0.000 T. . . . 0.00m 0.0m 0.00 0m0.H|H00.H 0 00H H0. 00.m 00.H 00.m 0.H0m 0.0H0 0 00 0 mmm 0.0m 0 00 000.H|H00.H 0 00. H m0. 00.m m0. H 00.0 0.000 0.00m 0m0 0.00H 0. 0m 00m 000. H1H00. H 0 m0. H 00. 0H. m 0H.m 00.0 0. H00 0. 000 0. 00H 0. 00m 0.00 0 00 000. HIH00. H m 00H 00. H0.H 00. 00. 0.mmH 0.H0 0 0m 0.H0 0.0H 0.00 000.H|Hm0.H 0 0m. H 00. 00. H H0.m 00.0 0.m00 0.0mm 0. H0 0.0H 0. 0H m. m0 0m0. HlH0m. H 0 0m. H 00. 00. H 00. H 00. H 0. 0Hm 0. 0Hm 0.m0 0.00H H. 0m H. H0 00m. HlHom. H 0 0H.H 0H.H 00.m H0.m 0H.0 0.000 m.0Hm 000 m 00H H.0 H.0H 00m.H|HOH.H m 0H. H 00. 00. H 00. H 00. H 0.mHH 0.mHH 0.00 000 0.0H 0.00 00H. H|H00. H 0 00. H 00. 00. H 0H. H 00. H 0.00m 0.00m 0.00 m.00H 0.0m 0. 00 000. H|Hm0. H 0 00. 00. H0. H 00. H 0m.m 0.00m 0. H0m m.00 0 00H m.0H 0.00 0m0. H|H00. 0 00. H0. 00.H 00.H 0m.0 0.000 0.0m0 0 00 00mm H.0m m.00 000. IH00. 0 00. H0. 0H. H 00. H 0H. m H.0Hm 0. 0mm 0.00 H.00H 0. 0m 0.00 000. IH00. 0H m0. 0N. 00. H 00. H 00.m 0.m0m H.00m 0.00 0 00H 0.0m 0.m0 000 |H00. 0H m0. H0. 00. H 00. H HH.m m.00H 0.m0H 0.00 0.0mH m.0m 0.00 000. |Hm0. 0H 00. 00. m0. H 0m. H 00.m 0. H0m 0.00m H00 0.00H 0.00 0.00 0m0 IH00. 0H 00. 00. H0. H mH. H HH.m 0.0Hm 0. HHm 0.m0 m.00H 0.0m 0.00 000 IH00. 0H 00. 0m. m0. 00. H 00.m m.00m 0.0mm 0.00 0.00H 0.0m 0. H0 000 IH00. 0m 00. 00. H0. 00H 00.m 0 00m 0.0mm 0.00 0.00H 0.0m 0.00 000. IH00. 0m 00. 00. 00. mH. H H0.m 0. 00H 0.00H H.00 0.0mH 0. Hm 0.00 000 |Hm0. mm 00. 0m. 00. HH. H 00. H 0.00H m.00H 0.00 0.00H 00H 0.m0 0m0 IH00. mH 00. 0H. 00. 00. 00. H 0.0HH H.0HH 0.00 H.00 0.0m 0. H0 000 IH00. 0H 0m. 0m. m0. 00. m0. H m.00H 0.00H m.00 0.00 H.0H H00 000. lH0m. 0H mm. 0H. 00. 00. 0m. H 0.0HH 0.0HH 0.0m H. 00 0.0H 0. H0 00m IH0H. 0 0H. 00. 0m. 00. H0. H 0.00 m.0mH 0.mm 0.00 m.0H H.m0 00H 1HmH. 0 HH. 0H. H0. 00. H 0H.m 0. H0 0.00 0.0H 000 0mH 00m 0mH IH00. H H0. H0. m0. . . . . . . .. 0H.m 0.00m 0.00m 0. mm 0 00H 0 00 0 m0 00. l0 09.30% H500 mom E =00 E mom E 0E0 030 .E .0 .3 .0 .5 .0 .E .0 .80 .80 EvU Em J$>< 0on5 053cm nmfionH H5030 05E EwmLonH £0000 .0000 .030 dohu .0000 023cm 505:2 E04 064 13oF awmwonH 0.2.5.5 @234 oz/H. E E530 E fiEnH E 0:030 02TH @5335 0.60 pom E00 3m EoU 5m E00 5m EQU 5m EwwbonH 55cm 023cm 000000? 0000.5 064 .2220 oEEomnTEuw ER 0000020 vimfik. POTASH REMOVED BY CROPS TO ACTIVE, TOTAL, ETC., POTASH OF SOIL 25 72:7‘ 0/ A Ops 5901117 w“ D< p '\(D\ [Add 5O OfherC/“aos. C Ac f/ we Figure 7.—-7Assumed relations of the quantity of potash in thesoil in different forms to the quantity taken up by crops. 5 W besides the amounts of these kinds of potash in the soil influence the amounts in the crop, and these factors are represented by 0. The following solution was kindly furnished by Dr. J. L. Lush, Animal Husbandman. (16) r(AB) I d I .79 r(AC) I f—|—e.r(AB) I .63 r(BC) I e+f.r(AB) I .76 r(AD) I a+b.r(AB)+fc—l-ec.r(AB) I .62 r(BD) I a.r(AB)~+b+ec—]-fc.r(AB) I .67 r(CD) I fa+ea.r(AB)—|—eb+fb.r(AB)+c I .79 O I \/ 1-—r2(D.ABC) The values secured from the above calculations are as follows: a(total potash) I .189 b(acid-soluble potash): .013 c(active potash) I .669 O(other factors) I .520 If the assumption is changed to have the active potash and the acid- soluble potash act through the total potash (transposing “Total” and “Active” in Figure 7), the values secured are as follows: c (total potash) I0.194 b ( acid-soluble potash) IO.007 a(active potash) I .666 O(other factors) I .591 26 BULLETIN NO. 355, TEXAS AGRICULTURAL EXPERIMENT STATION Under either assumption the amount of active potash is decidedly the most important, total potash is of low importance, While acid-soluble is insignificant. “Other factors”- are decidedly more important than the amounts of either total or acid-soluble potash in the soil. The figures obtained apply only to the results as diagrammed. They do not check the conceptions of the causal relations existing between these variables. If the conception of those relations is correct the figures will measure the relative importance of those relations. If the con- ception of those relations is incorrect, or if the relations are far from linear, the figures will not reveal it unless they are manifestly absurd. These methods are useful primarily for measuring causes; not for de- ducing them in the first place. While this mathematical solution is dependent upon the correctness of the premises on which it is based, it affords evidence that is significant. Active potash appears to be the most important factor, and next to it come other factors than the quantity of potash in the soil. SUMMARY OF CORRELATION FACTORS Table 9 contains a summary of the correlation factors for purposes of comparison. Table 9.—Summary of correlation coefficients (all positive) Acid Acid Active Soluble Insoluble Total Potash in two crops . . . . . . . . . . . . . . . . .794 j; .014 .667 51.023 .388 i .052 .622 d; .023 Active potash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .761 :1; .019 .428 i .034 .625 d: .038 Acid soluble . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .792 d: .020 Total potash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .845 d; .012 . . . . . . . . . . . . Potash in first crop . . . . . . . . . . . . . . . .742 j; .019 Weight dry matter in first crop . . . . . . .045 :1; .055 Per cent potash in first crop. . . .. . . . .194 51.053 ESTIMATION OF ACTIVE POTASH PREFERABLE The amount of active potash is much more closely related to the potash removed by crops in the pot experiments here reported, than is the acid-soluble, the total, or the acid-insoluble potash. This is brought out by the high correlation factor (r), by the diagrams of Figures 1 and 2, by the standard deviation from the calculated figures, and by the path coefficient for active potash. The estimation of active potash is also to be preferred on analytical grounds. Since much larger quantities of soil can be used (80 grams) than in the other two methods (0.5 to 2.0 grams) a greater degree of accuracy can be secured in the work. The accuracy of the estimation of total potash leaves much to be desired when 0.5 grams isweighed out directly from the sample not previously ground to an impalpable POTASH REMOVED BY CROPS TO ACTIVE, TOTAL, ETC., POTASH OF SOIL 27 powder. The estimation of acid-soluble potash is also less accurate in percentage of the amount of potash determined, than is the estimation of active potash. The relations between the active potash and the potash removed by crops are most clearly brought out when a sufficient number of soils of widely varying potash contents are used. When a small number of soils is used, or when the potash content of the soils is close together, the relations may be obscured by other factors than the quantity of potash present. The mathematical discussion in a preceding section brought out the fact that the operation of other factors might be more significant than the net operation of the amount of either the total potash or the acid-soluble potash, though much less than for the active potash. CORN POSSIBILITY OF SOIL POTASH The comparison of the relative deficiency of phosphoric acid, nitrogen and potash in the soil, as brought out by chemical analysis, has been made in previous bulletins by means of the corn possibility. By corn possibility is meant the number of-bushels of corn that would be pro- duced from the plant food considered, from two million pounds of soil to the acre, if 0.625 pounds of phosphoric acid, 1.5 pounds of nitrogen or one pound of potash were required to produce one bushel of corn. This method is believed to bring out the relative deficiency of the soil more clearly than a direct comparison of parts per million of plant food, for the reason that there is considerable difference in the amounts of the three plant foods used by the same crop. i The corn possibility is used merely as a method of comparing the amounts of the different plant food present, and is not intended to designate what the soil will produce in the field. Other factors enter into field production. The figures for corn possibility for active potash based upon the results presented in this Bulletin, and the curve y: 15X-—.00(l4: X2 (Figure 2), are given in Table 10. They may be compared with the figures previously used. Since this curve represents two crops, the figures are divided by two. The use of the active potash is to be pre- ferred for the reasons already given. The corn possibility for acid-soluble potash may be secured by dividing by 2 the calculated values for two crops in Table 5. The corn possibility for total potash may be secured in the same way from Table 11. DETAILED METHODS OF ANALYSIS Active Potash and Acid Consumed Weigh 100 grams of soil into a dry 2% liter bottle. Heat the water bath to 40° C. Add exactly 1000 cc. 0.2N nitric acid, and place in the warm water bath. Keep the temperature of the bath constant at 40° for the five hours, shaking every half hour. Filter on a large double 28 BULLETIN NO.35& TEXAS AGRICULTURAL EXPERIMENT STATION Table 10.—Corn possibility of one crop for active potash in two million pounds soil Group (Active Potash) Bushels ' 1>er lkcre 25-50 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . .. 26 0.1-75 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . .. 38 75.1-100 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 50 100.1-125 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . .. 61 125 1-150 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 73 150.1—175 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 84 175.1-200 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . .. 94 200.1-225 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 105 225.1-250 . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 115 250 1-275 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 125 275.1—300 . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 135 300.1—325 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . 1. 144 325 1-350 , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 154 350.1-375 . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . .. 163 375.1-400 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 171 400.1—425 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 180 425 1-450 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 188 450 1-475 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 196 475 1-500 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . _ . . . . .. 204 500 1-525 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 211 525 1-550 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 219 550 1-575 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 226 575 1-600 . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . .. 232 600 1-625 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 239 625.1—650 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 245 650 1-675 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 251 675.1-700 . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 256 700.1-725 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 262 725 1-750 . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 268 750.1—775 . . . . . . . . , . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . , . . . . . . . .. 273 775.1—8 . . . . . . . . . . _ . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 277 800.1—825 . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 282 .825.1—850 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 286 850 1-875 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 290 875 1-900 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 294 900.1—925 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 297 925.1-950 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 301 950.1—975 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . .. 304 975.1—1000 up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . _. 306 fluted filter paper. When cold, measure 800 cc. into porcelain evaporat- ing dishes,.and save the remaining solution for the determination of acid consumed. Acid 6011811111911 Dilute 100 cc. with about 50 cc. distilled water and heat to boiling about one minute to expel carbon dioxide. Titrate with 0.1N sodium hydroxide and phenolphthalein. Make a blank on the original acid. Subtract the titration from the blank and multiply by 5. This gives the acid consumed in percentage of 0.2N nitric acid. Active Dotash- Evaporate 800 cc. of the filtrate in a large dish transfer to a small dish, add about 20 cc. hydrochloric acid and evaporate to complete dryness in a water bath. Dry thoroughly in an air bath, but do not heat hot enough to decompose the iron salts. Take up with hot Water and 5 cc. hydrochloric acid. Filter into an evaporating dish and Wash the filter and residue with hot Water. Add 15 cc. hydrochloric acid, evaporate to a small volume, add Water enough to make volume about 50 cc. and then add '7 cc. of platinum chloride solution (1 cc. I 1 per cent potash on 1 gram). Evaporate to dryness on a steam bath, or, if this is not possible, to a thick paste. It POTASH REMOVED BY CROPS TO ACTIVE, TOTAL, ETC., POTASH‘ OF SOIL 29 is not always possible to evaporate to dryness because calcium chloride is sometimes present. Remove and c001. If it is necessary to keep the material over night, either place the dishes in a special desiccator, or else evaporate again the water absorbed during the night. If the mass becomes black on account of reduction of platinum, add 3 cc. concentrated acid and 10 cc. con- centrated hydrochloric acid, cover with a watch glass until action has stopped, and again evaporate. Do not, however, mistake the color of iron salts for reduced platinum. Add 10 to 30 cc. acid alcohol (see below) stirring while adding. The quantity of alcohol to be used depends on the quantity of salts in the dish. If the mixture becomes very hot when the alcohol is added, which sometimes occurs, though seldom, add quickly 2O to 30 c.c. more alcohol. Stir well and break up lumps with a short stirring rod. Decant the liquid through asbestos in a gooch crucible. Wash three or four times with acid alcohol, or more if there is much material to be dissolved. Then wash by decantation with 95 per cent alcohol until the alcohol does not dissolve any more colored material. This will take 6 to 12 washes with the 95 per cent alcohol. All the platinum chloride must be removed, for any left will form insoluble ammonium platinum chloride in the next series of washings. Pour about 10 cc. ammonnium chloride solution on the material in the dish, stir well and allow to stand a few minutes to dissolve the im- purities. Pour 01f through the gooch crucibles, and Wash by decantation three times with ammonium chloride solution and as many more as is necessary to remove all the impurities from the yellow platinum salt. The salt should be kept in the dish as far as possible up to this point, as it is more difficult to wash out the impurities from the crucible. Transfer the yellow precipitate to the crucible with alcohol, carefully rubbing out the dish with a policeman, and wash in the crucible eight times with 95 per cent alcohol, being careful to wash all parts of the inside of the crucible, so as to wash out the ammonium chloride. Ex- amine the precipitate to see that it appears pure before stopping. Wash. the outside of the crucible with alcohol, dry in a steam oven 2-3 hours, and weigh within an hour. Report parts per million of active potash. The filtrate from the platinum is run into special flasks which are used for nothing else. The platinum salts are carefully saved. Save all platinum waste and mix nothing else with it. Acid-Soluble Potash in Soils Weigh 10 grams of soil into a small pyrex Erlenmeyer flask provided with a rubber stopper carrying a glass tube about 6 inches long. Add 100 c.c. hydrochloric acid 1.115 sp. gr. measured with a pipette, and digest 10 hours in a boiling water bath, shaking every hour. The diges- tion should be continuous, if possible. Dilute as soon as the digestion is complete with 100 c.c. water, and filter on an ashless filter paper. 3O BULLETIN NO. 355, TEXAS AGRICULTURAL EXPERIMENT STATION Wash the insoluble residue with hot water until free fro-m chlorides, at least 15 times. Combine the washings and the original solution, and evaporate in a porcelain dish on the steam bath. When nearly dry, add a few drops of nitric acid to oxidize the organic matter. Evaporate to complete dryness, and heat in air bath for 1 hour‘ at 120-130° to render silica insoluble. When cool, add a few drops of strong hydrochloric acid, sufiicient only to saturate the residue. Add 10 to 20 cc. of water, warm on the water bath until solution is complete, and the residue is colorless and free from iron and filter, washing 15 times with hot water into a graduated flask. Make the filtrate up to 500 cc. Combine the two filters and main residue, and after drying ignite in a weighed quartz crucible, over a Bunsen flame, for an hour or more; then complete by igniting to constant weight. Weigh and calculate percentage of in- soluble residue on Form 17 0. (This solution is used also for estimation of lime, magnesia, and iron and alumina.) Measure out 100 cc. of the solution into a porcelain dish, add 10 cc. concentrated hydrochloric acid and evaporate to dryness. Take up with water, add 2 cc. of platinum chloride solution (1 cc. I 1 per cent K20), and 2 or 3 cc. hydrochloric acid and evaporate on a water bath to dryness or a thick paste. It is not always possible to get the residue completely dry on account of the presence of calcium chloride, but it can be evaporated to a thick paste. Record on the report sheets the quantity of platinum solution used. Remove and let it become cold. Add 10 to 30 cc. acid alcohol accord- ing to the quantity of material in the dish. All except the potassium platinum-chloride should dissolve. Pour the acid alcohol through as- bestos in a gooch crucible. Wash again with acid alcohol by decantation, then with 95 per cent alcohol until the alcohol wash does not dissolve any more colored material. Pour the washings through the weighed gooch, but leave the precipitate in the dish as completely as possible. Six washings or more are necessary. Then pour on 10 cc. ammonium chloride wash, stir well, and allow it to stand a few minutes in order to dissolve the impurities. Pour off the wash liquor through the gooch. Wash three times with ammonium chloride by decantation, or as many more times as is necessary to remove all the foreign material, which is usually white in color. Transfer the potash salt to the gooch with 95 per cent alcohol and wash on gooch eight times with alcohol. Remerm ber that a concentrated solution of ammonium chloride has been used, and be careful to wash the sides of the crucible. Examine the precipitate carefully to see that it consists entirely of potassium platinum chloride. Dry in steam oven, cool in desiccator, and weigh. The first evaporation is to get rid of nitrates. If any nitrates are present, compounds are formed with the platinum which are not soluble, and vitiate the results. POTASH REMOVED BY CROPS TO ACTIVE, TOTAL, ETC., POTASH OF SOIL 31 Total Potash in Soils. Lawrence-Smith Method Weigh carefully 0.500 grm. and grind to a very fine powder in an agate mortar. Then mix with 0.5 grams ammonium chloride in a glass mortar by use of a spatula and glass pestle; add 4 grams (approxi- mately) O. P. calcium carbonate and mix thoroughly with the preceding mixture by use of a spatula and glass pestle. The mixture is then transferred to a platinum crucible, and inserted in an asbestos board so ’ that about one-thi.rd of the crucible isithrough the hole. Then heat a gently. A platinum cover is placed on the crucible, slightly to one side. When the ammonia has volatilized, increase the heat. The flame should be so regulated that the crucible will not be red more than one-half of the height of the fusing mass within the crucible. Heat to low redness for one hour. Place the crucible, lid, and contents while hot in about '75 cc. water in a 200 cc. beaker, crush the lumps and let stand over night or two hours. Crush lumps in crucibles; if crushed in a beaker, use a pestle, as a glass rod will often punch holes through the beaker. The material should be completely covered. Filter, and wash with hot water at least fifteen times. Evaporate the filtrate to about 50 cc. Filter into a 100 cc. porcelain dish and wash ten times with small amounts of hot water, each time allowing all of the water to run through before adding more, and washing the filter paper near the top. Discard the precipitate, which is carbonate of lime. Transfer the solution to a porcelain dish, make acid with hydrochloric acid and evaporate to about 50 cc., add 2 cc. of platinum chloride solu- tion (1 cc. I 1 per cent K20) and 2 or 3 cc. hydrochloric acid and evaporateon a Water bath to dryness. Record on your report sheets the quantity of platinum solution used. Remove and let cool. Add 10 to 15 cc. acid alcohol. All except the potassium platinum chloride should dissolve. Wash once with acid alcohol, then with 95 per cent alcohol by decantation until the alcohol wash does not dissolve any more colored material of any kind, pouring the washings through a Weighed porcelain gooch crucible, but leaving the precipitate in the dish as much as possible. When the soluble plat- inum salts have been washed out, pour on 10 cc. ammonium chloride wash, stir well, and allow it to stand a few minutes in order to dissolve the impurities. Pour off the wash liquor through the gooch. Wash three times with ammonium chloride by decantation, and as many more times as is necessary to remove all the foreign material. Transfer the potash salt to the gooch crucible with 95 per cent alcohol and wash on gooch eight times with alcohol. Remember that the concentrated solution of ammonium chloride must be washed completely from the inside and outside of crucible. Examine the precipitate carefully to see that it consists entirely of potassium platinum chloride. Dry in steam oven; cool in desiccator and weigh. Report the results as percentage of total potash (K20) in the soil. 32 BULLETIN NO. 355, TEXAS AGRICULTURAL EXPERIMENT STATION Acid fllwhol- Add 10 cc. C. P. concentrated hydrochloride acid to 100 cc. 95 per cent alcohol. SUMMARY AND CONCLUSIONS (1) The amount of potash removed from the soil by plants depends upon the amount of potash present, the forms of potash, kind of plant, conditions of growth and other factors. (2) The amount of potash removed from the soil by solvents de- pends on the amount of potash present, the form of the potash, kind of solvent, fixing power of the soil, conditions of the extraction, and other factors. (3) Methods of analysis are given for active potash, acid-soluble potash, and total potash in the soil. (4) When the results are arranged according to the potash removed by the crops, the active potash is found to increase regularly until the potash removed by the crop exceeds 600 parts per million of soil. The total potash and acid-soluble potash increase regularly until the potash removed by the crops exceeds 300 parts per million. (5) No relation could be traced between the weight of the crop and the active potash in the soil. (6) The average percentage of potash in the crops increases with the active potash in the soil. (7) The analysis of the crop for potash is always necessary when the availability of potash to crops is being studied, as the Weight of dry matter alone may give misleading results. (8) There is a close relation between the potash taken up by the crops and the active potash of the soil, the coefficient of correlation be- ing +3742 i .019 for the first crop and +3794 i .014 for the two crops. (9) Curves are drawn for the relation of the activevpotash to the potash removed by crops, and the percentile deviation from the cal- culated values shown to average about 30 per cent. (10) The acid-soluble potash is related to the potash taken up by the crops, the coeflicient of correlation being +1567 i .013 for two crops. The correlation between the active potash and the acid-soluble potash is +3761 i .019. (11) Curves are assumed and calculated values compared for the acid-soluble potash and the potash removed by crops, the average per- centile deviation from the calculated values being about 44 per cent. (12) The total potash is related to the potash removed by crops, the coeffioient of correlation between total potash and potash in two crops being +.662 i .023. It is also related to the active potash and to the acid-soluble potash, the correlation coefficients being +.630 i .038 and +3792 i .020, respectively. (13) Curves are assumed and calculated values compared for the total potash and the potash removed by crops, the average percentile deviation from the calculated values being about 45 per cent. POTASH REMOiVED BY CROPS TO ACTIVE, TOTAL, ETC., POTASH OF SOIL 33 (14) The acid-insoluble potash is less closely related to the potash removed by the crops than the others, the correlation coefficient between acid-insoluble potash and potash in tWo crops being +.388 i .052. (15) If it is assumed that the total potash and the acid-soluble potash act through the active potash as well as directly, the path co- efiicient for active potash is +669, for total potash —|—.189, for acid- soluble +013, and for other factors +520. (16) The active potash is most closely related to the results of pot experiments and is best adapted to show the needs. or strength of the soil as regards potash. (17) The corn possibility for potash is used to designate the number of bushels of corn that would be produced under the conditions of the pot experiments from the potash removed if it takes one pound potash for one bushel of corn. It is used to compare the relative deficiency of the soil in phosphoric acid, potash, or nitrogen. Revised figures for corn possibility for potash are given. a REFERENCES ‘» (1) Gerlach, Experiment Station Record 3, 208. (2) Dyer, Experiment Station Record 5, 1013, from Journal Chem. Society, 1894, 115. (3) Report of Referee on Soils, Bulletin 47, 49, 56, 67, 73, Division of Chemistry, United States Department of Agriculture. (4) Moore, Jour. Am. Chem. Soc., 1902, page 109. (5) Experiment Station Record 5, 471. (6) Experiment Station Record 7, 664. (7) Experiment Station Record 11, 508. (8) Experiment Station Record 11, 1018. (9) Experiment Station Record 13, 914. (10) Experiment Station Record 15, 335. (11) Experiment Station Record 17, 527. (12) Wannes, Experiment Station Record 18, 208. (13) Ann. Agric. de la Suisse, 1909, 161. (14) Chemisches Centralblatt, 1905, 1, 285. (15) Texas Bulletins 145, 190, 284, 325. ( 16) Wright, Journal Agr. Research 20, 557; Genetics 8, 239.