TEXAS AGRICULIUIIAL EXPERIMENT STATION BULLETIN NO. 178 A SEPTEMBER, 1915 DIVISION OF CHEMISTRY Effect of the Additions on Availa- bility of Soil Phosphates POSTOFFICE: College Station, Brazos County, Texas E AUSTIN, TEXA VON BOECKMANN-JPlNES Co.. RINTERS 1.? 5 [Blank Page in Original Bulletin] A138 915-10m TEXAS AGRICULTURAL EXPERIMENT STATION (BULLETIN NO. 178. SEPTEMBER, 1915. DIVISION OF CHEMISTRY Effect of the Additions on Availa- bility of Soil Phosphates BY G. S. FRAPS, Ph. D., CHEMIST 1N CHARGE; STATE CHEMIST POSTOFHCE: COLLEGE STATION, BRAZOS COUNTY, TEXAS fl@~ AUSTIN, TEXAS VON BOECKMANN-JONES CO., PRINTERS, 1915 AGRICULTURAL AND MECHANICAL COLLEGE OF TEXAS W. B. BIzzELL, A. M., D. C. L., President TEXAS AGRICULTURAL EXPERIMENT STATION BOARD OF DIRECTORS . P1P“ G4 . S. WILLIAIvIs, Paris......... E BATTLE, Marlin ...... .. BREIHAN, Bartlett....................... . KUBENA, Fayetteville................... 0 ............ .. . F ék. MILLER, JR., AmarIll f: > OHN I. GUION, President, Ballinger .... .. . .............. .. . J. HART, Vice President, San Antonio ............. .. . H. ASTIN, Bryan ................................................. .. DAVIDSON, Cuero ............................................. .. . ........................ ..Term expiresll9l9 .......... ..Term expires 1919 ....... ..Term expires 1919 ....... ..Term expires 1917 .... ..Term expires 1917 .... ..Term expires 1917 .... ..Term expires 1921 .... ..Term expires 1921 . . . . . . . . ..Term expires 1921 MAIN STATION COMMITTEE L. J. HART, Chairman J. S. WILLIAMS \V. A. MILLER, JR. GOVERNING BOARD, STATE SUBSTATIONS P. L. DowNs, President, Temple .......................... .. CHARLES RooAN, Vice President, Austin... W. P. HOBBY, Beaumont .......................................... .. J. E. BOOG-SCOTT, Coleman .................................... .. .................................................... ..Term expires 1921 ............................................ ..-........Term expires 1919 . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..Term expires 1917 ....................................... . Term expires 1917 *STATION STAFF ADMINISTRATION B. YOUNGBLOOD, M. S., Director A. B. CQNNER, B. S., _Vice Director CHAS. A. FELKER, Chief Clerk A. S. WARE, Secretary DIVISION OF VETERINARY SCIENCE M. FRANcIs, D. V. S., Veterinarian in Charge _ _ H. SCHMIDT, D. V. M., Veterinarian DIVISION OF CHEMISTRY G. S. FRAPS, Ph. D., Chemist in Charge; State Chemist R. H. RIIJGELL, B. S., Assistant Chemist FRANK HODGES, B. S., Assistant Chemist W. T. P. SPRoTT, B. S., Assistant Chemist DIVISION OF HORTICULTURE H. NEss, M. S., HorticuIturist_ in Charge W. S. HOTCHKISS, Horticulturist DIVISION OF ANIMAL HUSBANDRY J. C. BURNs, B. S., Animal Husbandman, Feeding Investigations. J. M. JoNEs, A. M., Animal Husbandman, Breeding Investigations DIVISION OF ENTOMOLOGY F. B. PADDOCK, B. E., Entomologist in Charge; State Entomologist _ O. K. COURTNEY, B. S., Assistant Ento- mologist DIVISION OF AGRONOMY A. B. CoNNER, B. S., Agronomist in Charge A. H. LEIDIGH, B. S., Agronomist H. H. JoEsoN, B. S., Agronomist _ LoUIs WERMELSKIRCHEN, B. S., Agronomist DIVISION OF PLANT PATHOLOGY AND PHYSIOLOGY F. H. BLODGETI‘, P_h. D., Plant Pathologist and Physiologist in Charge N. D. ZUBER, B. S., Fellow. "DIVISION OF FARM MANAGEMENT REx E. WILLARD, M. S., Farm Management Expert in Charge DIVISION OF POULTRY HUSBANDRY R. N. HARVEY, B. S., Poultryman in Charge DIVISION OF FORESTRY J. H. FosTER, M. F., Forester in Charge; State Forester DIVISION OF FEED CONTROL SERVICE JAIvIEs SULLIVAN, Executive Secretary CHAS. A. FELKER, Chief Clerk . H. RoGERs, Inspector W. H. W000, Inspector T. H‘. WoLTERs, Inspector L4 S. D. PEARCE, Inspector W. M. WICKES, Inspector T. B. REESE, Inspector SUBSTATION NO. 1: Beeville, Bee County E. E. BINFOHD, B. S., Superintendent SUBSTATION NO. 2: Troup, Smith County W. S. HOTCHKISS, Superintendent SUBSTATION NO. 3: County N. E. WINTERS, B. S., Superintendent SUBSTATION NO. 4: County H. H. LAUDE, B. S., Superintendent SUBSTATION NO. 5: Temple, Bell County A. K. SHORT, B. S., Superintendent SUBSTATION N0. 6: County T. W. BUELL, B. S., Superintendent SUBSTATION NO. 7: Spur, Dickens Count; R‘. E. DICKSON, B. S., Superintendent Lubbock, Lubbocl Angleton, Brazoria Beaumont, JetTeI-son Denton, Denton SUBSTATION NO. 8: County V. L. CoRY, B. S., Superintendent SUBSTATION NO. 9: Pecos, Reeves Count} J. W. JACKSON, B. S., Superintendent SUBSTATION NO. 10: (Feeding and Breed ing Substation) College Station, Brazo: County T. M. REDDELL, Superintendent SUBSTATION NO. 11: Nacogdoches, Nacog doches County G. T. McNEss, Superintendent _ D. T. KILLOUGH, B. S., Scientific Assistan **SUBSTATION NO. 12: Chillicothe, Harde man County R. W. EDWARDS, B. S., Superintendent CLERICAL ASSISTANTS STATION J. M. ScIIAEnEL, Stenographer W. F. CHRISTIAN, Stenographer ELIZABETH WALKER, Stenographer J. L. COTTINGHAM, Stenographer C. L. DURsT, Mailing Clerk *As of October l,’ 1915 FEED CONTROL SERVICE DAISY LEE, Registration Clerk E. E. KILBURN, Stenogra her WILLIE JOHNSON, Tag C erk **In Cooperation with. the United States Department of Agriculture. TABLE OF CONTENTS. PAGE. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Description of the Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Weights of Crops Secured . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . t . . . 8 Phosphoric Acid Removed by the Crops . . . . . . . . . . . . . . . . . . . . . . .. 9 Phosphoric Acid Content of the Crops . . . . . . . . . . . . . . . . . . . . . . . .. 10 Composition of the Soil After Growing the Crops . . . . . . . . . . . . . . 10 Acknowledgment . . . . . . . . . . . . . . . . . . .t . . . . . . . . . . . . . . . . . . . . . . . . . 11 Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-15 Summary and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 15 [Blank Page in Original Bulletin] Etfect of Additions on Availability of Soil Phosphates. BY G. S. FRAPS. PH. D., CHEMIsT IN CHARGE; STATE CHEMIST. It ha.s been known for some time that lime and organic matter, in a general way, have a tendency to make the plant food of the soil more available. It has been claimed that manure app-lied With rock phosphate renders the phosphoric acid more available, but this, on the other hand, has been disputed (see Hartwell, Bulletin No. 151, Rhode Island Experiment" Station). The Writer has been able to find few facts on record in the literature referring to the action of lime on soil phosphates. Wheeler (Rhode Island Bulletins) has pointed out that an acid soil which responded to phosphoric acid before liming, after liming did not respond to phosphatic fertilizers. In experiments on different. forms of phosphates, lime often increases the effect of the phosphate (Rhode Island Bulletin No. 118). It is, however, difficult to distinguish between the improvement of soil conditions due to the use of the lime, and increase in availability of the phosphate. Liming injuriously affects the phosphoric acid of the soil, rendering it less solu- ble according to B. Schulze (Experiment Station Record 16, 32). Application of alkaline substances (lime, potassium carbonate) ex- erts an unfavorable influence on the assimilation of soil phosphoric acid according to lVI. Niagaolza. (Experiment Station Record 16, 556). Lime increased the phosphoric acid taken from the soil phosphates by oats, but it decreased that taken from bone meal or tricalcium phos- phate (Soderbaum, Experiment Station Record 14, 951). Lime exerts a retarding and injurious influence upon the availabil- ity of the phosphoric acid of organic manures to rice (in fish scrap, . bone, rice bran, rape cake). M. N agaoka (Experiment Station Record 16, 554.). A number of investigators find that lime decreases the phosphoric acid taken by crops from bone meal or rock phosphate, including Kell- ner, Nagaoka, Soderbaum, and Mooers. The observations with respect to the action of lime on soil phos- phates are contradictory. This may be due to the character of soil phosphates; the lime may exert a depressing effect. when the phosphoric acid is in the form of tricalcium pho-sphate, and it may have a favor- able action when the phosphoric acid is in the form of mono-calcium or di-calcium phosphate or united to iron or aluminium. This matter is of considerable importance in soil chemistry. As pointed out in Bulletin No. 1.26 of this Station, the needs of soils for phosphatic fertilizer in pot experiments are, on an average, related to their content of active phosphoric acid. As there also pointed out, there are decided deviations "from the average in various soil individ- (S TEXAS AGRICULTURAL EXPERIMENT STATION. uals. The quantity of phosphoric acid taken up by the crops may be affected by the lime, vegetable matter, o-r other soil constituents. If such is the case, deviations from the average may be due on the one hand to deficiency of favoring soil ingredients, or, on the other hand, to ‘larger favorable quantities. 'l‘hus two soils containing the same quantity of active plant food might supply differing quantities of phos- phoric acid to plants on account of deficiency of favoring substances in the one and a favorable quantity in the other. The quantity of lime and vegetable matter would thus be a factor to be taken into considera- tion along with the active phosphoric acid. The matter is also of practical importance. If addition of lime or vegetable matter increases the quantity of phosphoric acid which plants may take from the soil, such addition would be equivalent to the use of a phosphatic fertilizer, at least to a limited extent. Phosphates must, however, eventually’ be supplied to replace those removed from the soil, since the low quantity of phosphates must in time reduce the pro- ductive powers of the soil. DESCRIPTION OF THE EXPERILIENTS. The experiments here described were undertaken for the purpose of studying the effect of carbonate of lime and vegetable matter upon the assimilation o-f the soil phosphates by plants. Precipitated carbonate of lime was used, and ground corn cobs, sawdust, and starch, were used for organic materials. These were selected for the reason that they contain only traces of phosphoric acid. The selection was not alto- gether fortunate, especially the starch, since it set up a fermentation that injured the first crops grown in its presence. Description of Soils. No. 894—--Depth 0"--6". This is Norfolk fine sandy loam. It was taken from the farm of J. M. Pluperts, Nacogdoches, Texas. No. 895—Depth 0”-12”. This is Lufkin fine sand. It was taken from the farm of F. M. Smith, one mile north of Lufkin, Angelina county, Texas. ' No. 1145—Depth 12/522". This soil is Lufkin fine sand. It was taken from the farm of F. M. Smith, Lufkin, Angelina county, Texas. No. 992—Depth 0”-]2”. This soil is Orangeburg fine sandy loam. The sample was taken at Jacksonville, Cherokee county, Texas. No. 993—Depth 0"-12". This soil is Orangeburg clay. The sam- ple was taken from the farm of J. F. Burgess, Nacogdoches, Nacog- doches county, Texas. No. 1144. This soil is Norfolk fine sandy loam. The sample was taken at Jacksonville, Cherokee county, Texas. EFFECT or ADDITIONS ON AVAILABILITY OF SoIL PHOSPHATES. 7 TABLE I—COMPOSITION OF THE SOILS. ~ 1 Norfolk Lufkin iOrange- Orangc- Norfolk Lufkin fine fine , burg burg fine fine sanciy sandy l fine clay. sandy sand. loam. loam. sandy loam. loam. Nacog- Nacog- doches AngelinaCherokee doches Cherokee Angelina County. CountylCounty. County. County. County. Surface surfacelSurface Surface Surface Subsoil 894 , 993 1145 895 992 1144 Percent- Phosphoric Acid . . . . . . . . . . . . . . . . . . .04 .03 .15 .05 .09 .01 Nitrogen . . . . . . . . . . . . . . . . . . . . . . . . .07 .06 .04 .05 .06 .07 Potash . . . . . . . . . . . . . . . . . . . . . . . . . . .27 .08’ .59 .22 . . . . . . . . .09 Lime . . . . . . . . . . . . . . . . . . . . . . . . . . .. .06 .14, .29 .11 .17 .13 Magnesia . . . . . . . . . . . . . . . . . . . . . . . . .04 .23 .27 .02 .11 .21 Alumina and Oxide of Iron . . . . . . .. 3.33 1.93 16.10 . . . . . . .. 0.91 3.62 Insoluble and Soluble Silica . . . . . . . . 94.35 95.50 76.96 93.54 97.24 92.22 Loss on Ignition . . . . . . . . . . . . . . . . . . 1.50 2.09 5.42 1.48 . . . . . . . . 2.74 Moisture . . . . . . . . . . . . . . . . . . . . . . . . .27 .66 1.08 .45 . . . . . . . . 1.76 Parts per Million—- Active Phosphoric Acid . . . . . . . . . . . 15.4 27.8 1.50 15.6 32.0 23.7 Active Potash . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167.5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acidity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300 . . . . . . . . . . . . . . . . . . . . . . . . 200 I The chemical composition of the soils is given in Table 1. Details 0f the Ercp-erimentsr-Tllhe quantity of soil used in the experi- ments was 5 kilograms. The additions were made at the rate of 25 grams per pot, equal to 0.5 per cent., or five tons per acre based 0n two million pounds to the depth of seven inches. The double addition of calcium carbonate (2021) was at the rate of 50 grams per pot of soil, or ten tons per acre. The humate was prepared by precipitating am- monium humate with calcium chloride and Washing by decantation, then filtering. The amount used approximately corresponded to 20 grams humic acid per pot. The additions were made at the time of planting, and mixed thoroughly with the soil. Water was added three days before planting. All of the substances added were finely divided and the calcium carbonate was in the form of precipitated chalk. No additions of phosphoric acid were made to the soil, but additions of potash and nitrogen were made as described. First Crop, U0rn.—In each pot five grains of corn were planted, weighing 1.8 to 1.9 grams, seed being taken from a single ear of corn. One gram of sulphate of potash in 10 c.c. of water and one gram nitrate of soda in 1.0 c.c. of water were added before planting. In ad- dition, 1 gram potassium sulphate in 200 c.c. water was added to soil 1145 on May 1 ; 1 gram ammonium nitrate in 200 c.c. water was added to soil 1145 on May 4; one-half gram each of nitrate of ammonia and sulphate of potash were added to soils 992, 895, 1145, on June 1. Second Crop, Millet, 1908.-After the corn had been harvested, the pots were dug up, one gram each of sulphate of potash and ammonium nitrate added and % gram millet planted. The millet did not do so very Well on any of the pots, as it went to seed before making a good growth. 8 TEXAS AGRICULTURAL EXPERIMENT STATION. Third Crop, flI-ustardr-After harvesting the millet, the pots were dug up, one gram each of sulphate of potash and nitrate of soda were put in and one-half gram mustard planted. The mustard was killed by a. freeze and harvested at that time. Fourth Crop, Corn, 1909.-—'l‘he pots were dug up and one gram of sulphate of potash and one gram of nitrate of soda added to each. Five grains corn, Weighing 1.8 to 1.9 grams, were planted March 8, 1909, and the crop was harvested June 9, 1909. One gram ammonium nitrate was added May 14, 1909. After this crop was harvested, the soils Nos. 894, 895, and 1145 were registered for analysis. Soils Nos. 992, 993, 1144 were used in continued tests. ' Fifth Crop, Kafir, 1909.—'l‘he p-ots were dug up, no addition made, and 1 gram kafir planted on June 14, and harvested on August 5, 1909. Soil No. 992 was registered for analysis. Sixth Crop, Mustard.—On soil No. 993 and 1144 only. No addi- tions were made; planted November 21, harvested December 22 on ac- count of freeze, one gram mustard seed having been planted. i8eeenth Crop, Com, 1910.—Two grams nitrate of soda were added to all pots after they had been dug up, and five grains planted, weight 1.45 to 1.55 grams. Harvested June 1'7, 1910. The plants-did very poorly and the experiment was discontinued after the harvesting of this crop, all of the pot-s of the two soils being registered for analysis. WEIGHTS OF CROPS SECURED. Weights of crops secured are given in Tables 6, '7, 8, 9, 10, 11, with summary in Table 2. Inspection of this Table 2 shows a gain due to the lime in every case, except with the double amount on soil No. 894. The minimum gain is about 20 per cent. of the original crops, and the maximum gain nearly 80 per cent. An examination of the detailed tables shows that while the effect of the lime on the first crop may be slight, its effect increases with subsequent crops. TABLE 2-—-GAIN OF DRY MATTER OF CROP IN GRAMS DUE TO ADDITIONS- Gain Gain Gain Gain Number by o 4 Originalt Gain b by by by 2 Ca. Starch. Sawdust. Cobs. Crops. Laboratory CroD y Number. Weight. Ca. 894 . . . . . . . . . . .. 40.0 22 1 O O O 1.8 4 895 . . . . . . . . . . .. 52.8 11 8 11.2 O . . . . . . . .. O 4 1145 . . . . . . . . . . .. 16.7 13 5 16.9 0 . . . . . . . .. 2.7 4 992 . . . . . . . . . . .. 53.2 20 4 21.9 8.2 . . . . . . . .. 17.2 5 993 . . . . . . . . . . .. 21.5 . . . . . . . .. 16.5 14.6 11.2 1.0 7 1144 . . . . . . . . . . .. 77 O . . . . . . . . . . . . . . . . .. O 1.2 2.9 7 Starch pro-duced gains on two soils, sawdust on two, and corn cobs on five. However, five of these gains are so small that they may be almost disregarded. Soils Nos. 992 and 993 responded to the organic matter. The organic matter in many cases reduced the size of the first crops, especially the starch. This may be seen by referring to the de- tailed tables. EFFECT or ADDITIONS ON AVAILABILITY OF SoIL PHOSPHATES. 9 PHOSPHORIC ACID REMOVED BY THE CROPS. Tables 12 to 17, inclusive, show the phosphoric acid removed from the soil, and Table 3 is a summary of the results. TABLE 3——GAIN OF PHOSPHORIIg DUE TO ADDITIONS IN GRAMS R . In Gain Gain Gain Gain Gain Number Laboratory Original by by by by by of Number. Crop. Ca. 2 Ca. Starch. Saw ust. Cobs. Crops. 894. . . . . . . . . . . . . .0880 .0434 .0072 . .0225 .0060 .0203 4 .1123 .0059 .0234 0 . . . . . . . .. 0 4 1145 . . . . . . . . . . . . . .0370 .0309 .0357 0 . . . . . . . . . .0097 4 992 . . . . . . . . . . . . . .1423 .0498 .0538 .0256 . . . . . . . . . .0539 5 993 . . . . . . . . . . . . . .0559 . . . . . . . . . .0369 .0286 .0260 0 7 1144 . . . . . . . . . . . .. .1876 . . . . . . . . . . . . . . . . .. .0127 .0020 0 7 Carbonate of lime causes a gain in phosphoric acid taken up in all cases. The gain ranges from 5 per cent. on soil No. 895 with a single application of lime to nearly 95 per cent. on soil No. 1145 with the double application of lime. Except in two instances, the gains are con- siderable. ' Starch causes four gains out of six, two of which a.re small; sawdust, all three are gains, two small; corn cobs, three gains out of six, two small. Soils Nos. 894, 1145, 992 and 993 responded to the organic matter, while 895 did not respond well and Nos. 1144 and 1145 only a little. TABLE 4—CORN POSSIBILITY OF PHOSPHORIC ACID REMOVED IN BUSHELS PER ACRE, AVERAGE PER CROP. -Corn Increase Due to Gain. Total _ Possibility Laboratory Orig- No. PhOSphOTIC 0f Active Number. inal. Saw- Crops. Acid. Phosphoric Ca. 2 Ca. Starch dust. Cobs. Acid of soil 894 . . . . . . . . . . .. 14 7 1 3.5 1 3.3 4 .04 12 95 . . . . . . . . . . . . 18 1 3.8 0 . . . . . . 0 4 .03 . 18 1145 . . . . . . . . . . .. 6 5 5.8 0 . . . . .. 1.5 4 01 18 992 . . . . . . . . . . .. 18 2 6.4 6.8 3.2 0 6.8 5 .15 12 993 . . . . . . . . . . .. 5 2 . . . . .. 3.4 2.6 2 4 0 7 .05 12 1144 . . . . . . . . . . .. 17 . . . . . . . . . . H1 1.1 02 0 7 . . . . . . . . . . . . . . . . . . .. Table 4 shows the phosphoric acid removed in terms of the “corn possibility” in bushels per acre, based on a weight of two million pounds soil per acre to the depth of '7 inches, and a. requirement of 0.625 pounds phosphoric acid per bushel of corn. One bushel corn would require .0015 grams phosphoric acid "per pot of 5000 grams of soil. The effect of the lime has been to decidedly increase the assimila- tion of the phosphoric acid. The gain expressed in corn is 3 to 7 bushels per acre, with two exceptions. Addition of carbonate of lime to these soils clearly increased the assimilation of phosphoric acid by the crops. The gain due to the vegetable matter on three of the soils is 2 to 3 bushels. Thus, the phosphoric acid absorbed by plants from the soil depends not only upon the forms of phosphoric acid in the soil, but also on the 10 " TFEXAs AGRICULTURAL EXPERIMENT STATION. presence of other substances, such as carbonate of lime and organic matter. Soils Nos. 895 and 1145 are acid, but the carbonate of lime has no greater effect up-on their phosphoric acid than on soils Nos. 992 and 993, which are not acid. It will require further investigations t0 trace the relation between the character of the soil and the effect of lime upon its phosphoric acid. It is of course impossible to state defi- nitely whether the phosphoric acid was rendered more available, or whether the crops took up more phosphoric acid, because conditions were made more favorable by the additions. The effect, however, is the same; namely, through the aid of the additions made to the soil, the plants secured more phosphoric acid. PHOSPHORIC ACID CONTENT OF THE CROPS. The phosphoric acid. content of the crops grown on various soils with the various treatments, expressed in percentages, is shown in Tables 18 to 23, inclusive. No particular relations can be traced in these per- centages, as there is little variation. When the crop was unusually low, it usually contained a higher percentage of phosphoric acid. This may be noted especially with soil No. 895—corn, 1909, pot 9, starch. The crop weighing 5.3 grams contains 0.38 per cent. phosphoric acid, while the crop in pot 1, 21.9 grams, contains 0.19 per cent. COMPOSITION OF THE SOILS AFTER GROWING THE CROPS. After the crops had been grown as described, the contents of the pots were mixed and subjected to analysis. The results a.re given in Table 5. TABLE 5—-PHOSPHORIC ACID IN PARTS PER MILLION IN SOIL AFTER CROPS WERE GROWN. 894 895 1145 992 993 1144 Original, before growing crops . . . . . . 15.4 27.8 23.7 15.0 15.6 . . . . . . . . After growing cr0ps—add1tion O. . . . 16.3 23.8 20.4 11 .9 15.7 37 O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 27.0 18.5 11.9 . . . . . . . . . . . . . . .. Ca . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 15.2 27.3 15.1 11.2 . . . . . . . . . . . . . . .. Ca . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 25.6 15.2 12.5 . . . . . . . . . . . . . . .. 2Ca . . . . . . . . . . . . . . . . . . . . . . . . . . .. 15.9 26.6 19.9 5.0 28.7 . . . . . . .. 2 Ca . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 26.9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Cobs . . . . . . . . . . . . . . . . . . . . . . . . . . .. 15 2 25.0 18 7 . . . . . . .. 11. 39 0 Cobs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 26.0 25 5 12.5 . . . . . . . . . . . . . . .. Starch . . . . . . . . . . . . . . . . . . . . . . . . .. 13 5 25.0 27.0 10.0 12 7 35.6 Starch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 25.0 24.0 8.5 . . . . . . .. 38.1 Sawdust . . . . . . . . . . . . . . . . . . . . .. 12 3 . . . . . . . . . . . . . . . . . . . . . . .. 10 9 . . . . . . .. Removed by crops, no addition per million . . . . . . . . . . . . . . . . . . . . .. 17 22 7 28 _ 11 37 The additions of carbonate of lime, etc., had practically no eifect upon the quantity of active phosphoric acid remaining in the soils at the end of the experiment. There is a slight increase with the starch on soil 1145, and with the carbonate of lime on soil No. 993, but the differences are almost in the limit of error. The phosphoric acid removed in the cropping also has had practi- cally no effect upon the active phosphoric acid. Although 17 parts per million phosphoric acid have been removed by plants from soil No. 894, Earner or ADDITIONS 01v AVAILABILITY or SoiL PHOSPHATES. 11 the cropped soil contains practically the same active phosphoric acid as the uncropped. A slight decrease appears with soils Nos. 1145 and 992, but practically Within the limit of error. As pointed out in Texas Bulletin No. 126, active phosphoric acid of about 10 parts per million is probably derived from a large quantity of diflicultly soluble phosphates of iron and alumina, and not from a small quantity of the more easily soluble phosphates of lime. The active phos- phoric acid in the soils used in these experiments varies from 15 to 2'7 parts per million, and thus a considerable portion of it results from the highly insoluble iron and aluminum phosphate. The plants have evi- denty drawn upon the total phosphoric acid, rather than upon the active phosphoric acid. ACKNOWLEDGMENT. Laboratory xvork, pot tests, and other Work involved in the investi- gations in this bulletin, have been participated in by Messrs. E. C. Car~ lyle, J. B. Kelly, T. L. Ogier, and perhaps other members of the stalf. TABLE 6—WEIGHT IN GRAMS OF CROPS GROWN ON SOIL NO. 894. _ _ Corn l Millet Mustard Corn _ Additions and Pot Numbers. 1908 l 1908 1908 1909 Total. Gain. l 1--O . . . . . . . . . . . . . . . . . . . . . . . . . . .. 13.9 5.7t 5.9 14.5 40.0 . . . . . . .. 2——Ca. (Carbonate of lime) . . . . . . .. 13.2 6.31 10.5 32.1 62.1 22 1 3—2 Ca . . . . . . . . . . . . . . . . . . . . . . . .. 11.8 6.3 4.5 11.8 34.4 0 4—Cobs . . . . . . . . . . . . . . . . . . . . . . .. 11.1 6.6 10.1 14.0 41.8 18 5—Starch . . . . . . . . . . . . . . . . . . . . . .. 5.4 7.2 9.8 16.6 39.0 0 6—Sawdust . . . . . . . . . . . . . . . . . . . . .. 13.4 8.3 3.4 12.0 37.1 0 TABLE 7—WEIGHT CROPS ON SOIL 895. I _ Corn Millet Mustard Corn _ Additions. 1908 1908 1908 1909 Total. Average Gain. 1——O . . . . . . . . . . . . . . . . . .. 21.9 8.1 7.5 15.0 52.5 52.8 . . . . . . .. —O . . . . . . . . . . . . . . . . . .. 28.2 7.1 6.5 11.4 53 2 . . . . . . . . . . . . . . .. 3—Ca. (Carbonate of lime) 27.0 8.4 12.8 18.8 67 .0 64.6 11 8 4—Ca. . . . . . . . . . . . . . . . .. 26.3 6.5 12.7 16.6 62.1 . . . . . . . . . . . . . . .. 5—2 Ca . . . . . . . . . . . . . . .. 26.8 8.2 11.1 16.5 62.6 64.0 11 2 6—2 Ca . . . . . . . . . . . . . . .. 27.9 10.6 7.5 19.5 65.5 . . . . . . . . . . . . . . .. 7—~Cobs . . . . . . . . . . . . . . .. 22.5 8.0 12.5 12.0 55.0 50.0 0 8—Cobs . . . . . . . . . . . . . . .. 17.7 6.8 11.6 9.0 45.1 . . . . . . . . . . . . . . .. 9—Starch . . . . . . . . . . . . . .. 13.5 10.0 10.9 13.5 47.9 45.9 0 10——Starch . . . . . . . . . . . . .. 5.3 10.2 13.1 14.8 43.42 . . . . . . . . . . . . . . .. TABLE 8——WEIGHT OF CROPS GROWN ON SOIL NO. 1145. Corn , Millet Mustard Corn Total. Average. Gain. Additions 1908 1908 1908 1909 1——O . . . . . . . . . . . . . . . . . .. 7.4' 3.6 1.5 3.7 16.2 16.7 . . . . . . .. 2——O . . . . . . . . . . . . . . . . . .. 6.3 3.8 0.4 6.5 17.3 . . . . . . . . . . . . . . .. 3—-Ca (Carbonate oflime). 9.0 4.1 5.0 11.1 29.2 30.2 13 5 4—Ca . . . . . . . . . . . . . . . . .. 9.4 3.8 5.4 12.5 31.1 . . . . . . . . . . . . . . .. -5—-Cobs . . . . . . . . . . . . . . .. 5.2 4.2 3.3 7.4 20.1 19 4 2 7 6—Cobs . . . . . . . . . . . . . . .. 7.0 3.4 0.4 8.0 18.8 . . . . . . . . . . . . . . .. 7—Starch . . . . . . . . . . . . . .. 2.2 4.5 0.2 4.8 11.7 12.8 0 8—Starch . . . . . . . . . . . . . .. 3.2 3.4 1.1 6.2 13.9 . . . . . . . . . . . . . . .. 9-—2 Ca . . . . . . . . . . . . . . .. 10.2 3.8 9.0 10.6 33.6 33.6 16 9 12 TEXAS AGRICULTURAL EXPERIMENT STATION. TABLE 9-——WEIGHT CROPS IN GRAMS GROWN ON SOIL NO. 992. _ _ Corn Millet Mustard Corn Kafiir Total. Average. Gain. Additions. 1908 1908 1908 1909 1909 17.5 6.6 7.5 11.8 11.2 54.6 53.2 0 *17.5 1.6 6.5 16.8 9.3 51.7 . . . . . . . . . . . . . . .. 3—Ca......... 19.6 4.5 12.8 21.4 10.1 68.4 73.6 20.4 4—Ca......... 26.5 3.5 12.7 23.5 12.5 78.7 . . . . . . . . . . . . . . .. 5—2Ca . . . . . .. 25.3 5.7 11.1 21.5 11.5 75.1 75.1 21.9 6—2 Ca . . . . . .. 22.1 4.7 7.5 . . . . . . . . . . . . . . .. 34.3 . . . . . . . . . . . . . . .. 7——C0bs....... 26.7 6.3 12.5 14.4 12.3 72.2 70.4 17.2 8—Cobs....... 23.8 3.8 11.6 17.8 11.6 68.6 . . . . . . . . . . . . . . .. 9—Starch..... 22.5 4.2 10.9 15.0 7.0 59 6 61.4 8.2 10——Starch..... 16.1 4.9 13.1 16.8 12.2 63.1 . . . . . . . . . . . . . . .. *Assumed. TABLE 10——WEIGHT OF CROPS GROWN ON SOIL 993. . F" 1908 1908 I 1908 1909 1909 1909 1910 ' _ Additions. Corn. Millet. Mustard Corn. Kafiir. Mustard.’ Corn. Total. Gain. 1——O . . . . . . . .. 4.5 2.7 5.4 1.5 1.9 3.6I 1.9 21.5 . . . . . .. 2—Ca . . . . . . . . 6.3 1.7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-—2 Ca 6.3 2.3 7.5 8.0 5.2 2.6 5.8 37.7 16.5 4—Cobs . . . . .. 2.1 0.8 3.9 3.8 9.2 10 1.7 22.5 1.0 5—Starch..... 2.5 2.3 7.4 5.7 6.5 4.7 7.0 36.1 14.6 6—Sawdust... 6.5 2.9 5.1 8.5 6.2 3.5 . . . . . .. 32.7 11.2 TABLE 1l——WEIGHT OF CROPS IN GRAMS GROWN ON SOIL NO. 1144. 1908 1908 1908 1909 1909 l? 1909 1910 _ Additions. Corn. Millet. Mustard. Corn. Kaffir. Mustard. Corn. Total. Gain. ' I 1-—O..... 26.2 6.7 8.1 17.0 8.8 2.2 8.0 77.0 . . . . . .. 2—C0bs . . . . .. 35.7 3.8 4.8 19.0 6.1 3.5 7.0 79.9 2.9 3—--Starch..... 9.7 8.2 10.9 20.5 0.9 4.7 8.2 63.1 0 4—Sawdust... 26.9 4.0 8.1 19.6 8.9 2.0 8.7 78.2 1.2 TABLE 12—PHOSPHORIC ACID IN GRAMS EREMOVED BY CROPS FROM SOIL NO. 894. Additions to Pots. I Corn. Millet. Mustard. Total. Gain. I I ‘ O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0264 .0148 .0142 .0326 0880 . . . . . . . . Ca . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0277 .0239 .0284 .0514 .1314 .0434 2 Ca . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0224 0233 .0176 .0319 .0952 .0072 Cobs . . . . . . . . . . . . . . . . . . . . . . . . . . . . ‘ .0266 0251 .0237 0329 1083 .0203 Starch . . . . . . . . . . . . . . . . . . . . . . . . . . .0162 0245 0255 .0443 1105 .0225 Sawdust . . . . . . . . . . . . . . . . . . . . . . . . .0281} 0274 0099 .0290 0940 0060 TABLE 13—-PHOSPHORIC ACID IN GRAMS REMOVED FROM SOIL 895 BY CROPS. Additions. Corn. Millet. Mustard. Corn. Total. Average. Gain. 1—O . . . . . . . . . . . . . . . . . . .0405 0162 0158 .0405 1130 1123 0 2-——O . . . . . . . . . . . . . . . . . . .0451 .0149 0174 .0342 1116 . . . . . . . . . . . . . . .. 3—Ca . . . . . . . . . . . . . . . . . . 0405 . 0235 0105 . 0404 . 1149 1182 . 0059 I 4——Ca . . . . . . . . . . . . . . . . . .0447 0182 .0207 .0380 .1216 . . . . . . . . . . . . . . . . 5—2 Ca . . . . . . . . . . . . . . . . 0350 . 0343 . 0222 . 0396 .1311 1357 0234 6——2 Ca . . . . . . . . . . . . . . . .0391 .0278 .0266 .0468 1403 . . . . . . . . . . . . . . . . 7—Cobs . . . . . . . . . . . . . . . .0270 0160 0131 .0308 .0869 .0852 0 8—Cobs . . . . . . . . . . . . . . . .0283 0177 .0121 .0254 .0835 . . . . . . . . . . . . . . . . 9—Starch . . . . . . . . . . . . . .0230 .0210 .0213 .0330 .0983 .0965 0 10—Starch . . . . . . . . . . . . . .0207 .0226 0143 .0370 .0946 . . . . . . . . . . . . . . . . EFFECT ()F ADDITIONS ON AVAILABILITY OF SOIL PHOSPHATES. "13 TABLE I4——PHOSPHORIC ACID 11g GRAMS REMOVED BY CROPS GROWN ON OIL NO. 1 145. 1909 Corn. Millet. Mustard. Corn. Total. Average. Gain. 1—O . . . . . . . . . . . . . . . . . . . 0126 .0093 .0050 .0089 .0359 .0370 — 2——-0 . . . . . . . . . . . . . . . . . . . 0113 .0091 .0012 0166 .0382 3—Ca . . . . . . . . . . . . . . . . . . 0162 .0094 0100 0305 .0661| .0679 .0309 4-—Ca . . . . . . . . . . . . . . . . . . 0179 0106 .0149 .0263 .0697 5—-Cobs . . . . . . . . . . . . . . . . 0109 0100 .0089 .0167 .0465 .0467 .0097 6—Cobs . . . . . . . . . . . . . . . . .0133 0092 .0023 .0220 .0468 7—Starch . . . . . . . . . . . . . . .0040 .0104 .0008 0127 .0279 .0299 0 8—Starch . . . . . . . . . . . . . . .0048 .0095 .0025 .0149 .0317 2—Ca . . . . . . . . . . . . . . . . . . 1 0173 .0091 0198 .0265 .0727 .0727 .0357 TABLE 15-—PHOSPHORIC ACID IN GRAMS FROM SOIL 992. Additions. Corn. Millet. Mustard. Corn. Kaffir. Total. Average. Gain. 1—O . . . . . . . . . .0376 .0305 .0236 0342 .0303 .1462 1423 . . . . . . . . 2-—O . . . . . . . . . .0400 .0070 .0221 .0432 .0260 .1383 . . . . . . . . . . . . . . . . 3—Ca . . . . . . . . .0421 0176 .0442 .0535 .0283 .1807 .1921 .0498 4—Ca . . . . . . . . . .0504 .0105 .0432 .0705 .0288 .2034 . . . . . . . . . . . . . . . . 5——2 Ca . . . . . . . .0453 .0217 .0333 .0677 .0322 .2002 1961 0538 6——2 Ca . . . . . .. .0569 .0169 0184 . . . . . . . . . . . . . . .. 111921 . . . . . . . . . . . . . . .. 7—Cobs .0507 .0252 0375 .0432 .0344 .1910 1962 0539 8 Cobs . . . . . . . .0510 0137 .0348 .0752 .0267 .2014 . . . . . . . . . . . . . . . . 9-—Starch. . . . . .0484 .0160 0322 .0420 .0203 1589 1679 0256 10——Starch. . . . . 0403 .0191 0364 .0470 .0341 1769 . . . . . . . . . . . . . . . . TEstimated for Corn. TABLE l6—PHOSPHORIC ACID (GRAMS) FOR SOIL 993. Additions. Corn. Millet. Mustard. Corn. Kaffir. Mustard. Corn. Total. \ Gain l l l l O . . . . . . . . . . . .0081 .0059 0108 0056 .0061 0137 .0057 .0559 . . . . . . . Ca . . . . . . . . .. .0101 .0051 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2 Ca . . . . . . .. .0113 .0060 .0210 .0184 .0083 0104 .0174 .0928 .0369 Cobs . . . . . . . . .0036 .0020 0020 .0091 0175 .0038 .0051 .0431 0 Starch . . . . . . . .0033 .0046. 0155 .0118 0151 0188 .0154 .0845 .0286 Sawdust. . . . . .0111 0078 .0097 0200 0136 0140 .0057 *.0819 .0260 *Estimated. TABLE 17-—-PHOSPHORIC ACID IN GRAMS REMOVED FROM SOIL 1144. Corn. Millet. Mustard. Corn. Kaffir. Mustard. Corn. Total. Gain. O . . . . . . . . . . . .0459 .0288 .0227 0400 .0218 .0112 0172 1876 . . . . . . . Cobs . . . . . . .. .0615 .0190 .0108 0456 .0050 .0210 0161 .1790 0 Starch . . . . . . . 0204 .0377 .0343 .0482 .0165 .0282 0160 .2013 0127 Sawdust. . . . 0430 .0236 .0194 0500 .0220 0120 0196 .1896 .0020 TABLE I8—PER CENT PHOSPHORIC ACID IN CROP GROWN IN SOIL 894. Corn Millet Mustard Corn 1908 1908 1908 1909 O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 .26 .24 .21 Ca . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 .36 .27 .21 2Ca . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .19 .37 .37 .20 Cobs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24 .38 .24 .20 Starch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30 .34 .26 . 19 Sawdust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 .33 .29 .21 14. TEXAS AGRICULTURAL EXPERIMENT STATION. TABLE l9—-PER CENT PHOSPHORIC ACID IN CROP GROWN IN SOIL 895. Corn Millet Mustard 1908 1908 1908 1-—-O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 .20 .20 2-—O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 .21 ‘.21 3—Ca . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 .28 .19 4—Ca . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 .28 .18 5-2 Ca . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .14 .37 .19 6—Ca. S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .13 .33 .21 7—-—Cobs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 .20 .18 8—Cobs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 .26 .17 9--—Starch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 .22 .19 10—Starch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38 .24 . 19 11-—Hematite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .12 .15 .19 12-—Hernatite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 .26 .23 Corn 1909 TABLE 20—PER CENT PHOSPHORIC ACID IN CROPS GROWN IN SOIL 993. 1908 1908 1908 1909 1909 1909 1910 Corn. Millet. Mustard. Corn. Kaffir. Mustard. Corn. O . . . . . . . . . . . . . . . . . . . . .. .18 .22 .20 .38 .34 .35 .30 Ca . . . . . . . . . . . . . . . . . . . . . . 16 .30 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Ca . . . . . . . . . . . . . . . . . .. .18 .26 .27 .23 .16 .40 .30 Cobs . . . . . . . . . . . . . . . . . .. .17 .26 .23 .24 .19 .75 .30 Starch . . . . . . . . . . . . . . . . .. .13 .20 .21 .21 .24 . . . . . . .. .22 Sawdust . . . . . . . . . . . . . . .. .17| .27 .19 .24 .22 . . . . . . ..| . . . . . . .. TABLE 21—PER CENT PHOSPHORIC ACID IN CROPS GROWN IN SOIL 1144. 1908 1908 1908 1909 1909 1909 1910 Corn. Millet. Mustard. Corn. Kaffir. Mustard. Corn. I . . . . . . . . . . . . . . . . . . . . .. .18 .37 .28 .23 .25 .51 .22 Cobs . . . . . . . . . . . . . . . . . .. .18 .50 .23 .22 .27 .60 .23 Starch . . . . . . . . . . . . . . . . . . .21 .46 .30 .20 .39 . . . . . . . . .20 Sawdust . . . . . . . . . . . . . . . . . 16 .59 .24 .26 . 25 .53 .23 TABLE 22—PER CENT PHOSPHORIC ACID IN CROPS GROWN IN SOIL 992. 1908 1908 1908 1909 1909 Corn. Millet. Mustard. Corn. Kafiir. 1-—O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .22 .31 .32 .29 .27 2—-O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36 .34 .26 .28 3—Ca . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22 .28 .35 .25 .28 4—Ca . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .19 .36 .34 .39 .23 5-2 Ca . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 .38 .30 .29 .28 6—2 Ca . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .23 .36 .25 . . . . . . . . . . . . . . .. 7-—C0bs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 .35 .30 .27 .28 8—Cobs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 .36’ .30 .29 .23 9—Starch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22 .34 .30 .29 .29 10—Starch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25 .59 .27 .26 .28 Earner OF ADDITIONS ON AVAILABILITY on Son. PHOSPHATES. 15 TABLE 23-—PER CENT PHOSPHORIC ACID IN CROPS GROWN IN SOIL 1145. 1908 1908 1908 1 909 Corn. Millet. Mustard. Corn. 1—O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 0.26 34 .20 2—O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 18 0.24 .31 .33 3—Ca . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 0.23 .20 .22 4—Ca . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 0.28 .28 .21 5—C0bs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 0.24 .27 .22 6—Cobs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 0.27 .58 .24 7—Starch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18 0.23 38 .23 8—Starch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 0.25 23 .22 9—2 Ca . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17 0.24 .22 .13 SUMMARY AND CONCLUSIONS. 1. When nitrogen and potash are supplied, the addition of car- bonate of lime at the rate of 0.5 per cent. or five tons per acre increased the size of the crop and the amount of phosphoric acid withdrawn from the soil phosphates on the six soils tested in the pot experiments. The effect of the lime was small at first, but usually increased with succeed- ing crops. .2. The addition of starch, sawdust, or cobs had some effect on the crop in two soils but little with the other four soils. 3. With the six soils which gave up phosphoric acid equal to 5 to 18 bushels of corn per acre per crop, the addition of carbonate of lime caused an increase in the quantity of phosphoric acid taken up equal to 3 to '7 bushels per acre per crop. 4. The vegetable matter in three cases caused a gain in phosphoric acid taken up- equal. to two or three bushels corn per acre. 5. The presence of carbonate of lime or of vegetable matter may bring about differences in the quantity of phosphoric acid assimilated by plants from soils containing equal quantities of active phosphoric acid. 6. No relation can be traced between the additions and the phos- phoric acid content of the crops. When the crops are unusually small, the phosphoric acid content tisually runs higher than the average. '7. The additions of carbonate of lime or vegetable matter had prac- tically no effect upon the quantities of active phosphoric acid remain- ing in the soil at the ends of the experiments. 8. The phosphoric acid removed in the cropping also had practi- cally no effect upon the quantity of the phosphoric acid remaining in the soil at the ends of the experiments. The active phosphoric acid in the soils used varied from 15 to 2'7 parts per million. The phosphoric acid taken up by the plants was evidently drawn largely from the more insoluble phosphates.