110-211-3m TEXAS AGRICULTURAL EXPERIMENT STATIONS BULLETIN NO. +55- L30 CHEMICAL SECTION, FEBRUARY, 1911 TECHNICAL BULLETIN Qrganic Phosphoric Acid of the Soil BY G. S. FRAPS, Chemist POSTOFFICE College Station, Brazos County, Texas. C Austin Printing Comoany Austin. Texas 1911 __g_ TEXAS AGRICULTURAL EXPERIMENT‘ STATIONS. Governing Board. Q(Board~of Directors A. & M. College.) W. A. TRENCKMANN, President . . . . . . . . . . . . . . . . . . . . . . . . . . . .Austin JOHN I. GUION, Vice-President . . . . . . . . . . . . . . . . . . . . . . . . . ..Bal1inger WALTON PETEET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Fort Worth CHAS, DAVIS . . . . . . . . . . . .. . . . . . . . . . . . . . .‘ . . . . . . . . . . . . .Steel’s Store L. J. HART . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .San Antonio DR. J. ALLEN KYLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Houst0n > R. L. BENNETT............... ED, R. KONE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Austin President of College. _ R. T. MILNER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Col1ege Station Station Ofiioers. H. H. HARRINGTON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Director J, W. CARSON . . . . . . . . . .Assistant to Director and State Feed Inspector M. FRANCIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Veterinarian G. S. FRAPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1. . . .Chemist J. C. BURNS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..Animal Husbandry H. . . ......Horti'culturist RAYMOND H. POND . . . . . . . . . . . . . . . . . . . . . . . . . . . .Plant Pathologist WILMON NEW-ELL . . . . . . . . . . . . . . . . . . . . . . . . ._ . . . . . . . . .Entomologist H. L. McKNIGHT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Agriculturist N. C. HAMNER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Assistant Chemist J, B. RATHER . . . . . . . . . . . . . . . . . - ~ . . . . . . . . . . . . . .Assistant Chemist J. B. KELLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Assistant Chemist C. W. CRISLER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Chief Clerk A, S. WARE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Stenographer STATE AGRICULTURAL EXPERIMENT STATIONS. Governing Boarot His Excellency Governor O. B. COLQUITT . . . . . . . . . . . . . . . . . . . . .Austin Lieutenant Governor A. B. DAVIDSON . . . . . . . . . . . . . . . . . . . . . . ..Cuer0 . Commissioner of Agriculture Hon. E. R, KONE . . . . . . . . . . . . . ..-Austin Director of Stations. H. H. HARRINGTON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..College Station Superintendents of Stations. A. T. POTTS, Beeville Station . . . . . . . . . . . . . . . . ..'.Beeville, Bee County W. S, HOTCHKISS, Troupe Station . . . . . . . . . . . ..Troupe, Smith County A. L. PASCHAL, Lubbock Station . . . . . . . . . ..Lubbock, Lubbock County J. T. CRUSE, Fort Worth Station . . . . . . . ..Fort Worth, Tarrant County H. C. STEWART, Pecos Station . . . . . . . . . . . . . . ..Pec0s, Reeves County T. W. BUELL, Denton Station . . . . . . . . . . . . . . . .Denton, Denton County ‘i-ifi Temple Station . . . . . . . . . . . . . . . . ..Temp1e, Bell County I. S. YORK, Spur Station . . . . . . . . . . . . . . . . . . . . . .Spur, Dickens County A. L. HARRIS, Angleton Station . . . . . . . . . . .Ang1eton, Brazoria County J. K. FITZGERALD, Beaumont Station. . . . .Beaumont, Jefierson County NOTE—The main station is located on the grounds of the Agricultural and Mechanical College, in Brazos County. The postoifice address is College Station, Texas. Reports and bulletins are sent free upon appli- cation to the Director, TABLE OF CONTENTS. I Page. introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .' . . . . . . . . . 5 Qmmonia-Solublc Phosphoric Acid . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Solubility of Phosphates in Ammonia . . . . . . . . . . . . . . .. 6 Fixation of Phosphoric Acid from Ammonia . . . . . . . . . . 7 Effect 0f Ratio of Soil t0 Solvent in Extraction 0f Phos- phoric Acid by Acid and Ammonia . . . . . . . . . . . . . . 7 I Other Soil Constituents Dissolved by Ammonia . . . . . . . . '8. ‘_ A Solution of Fixed Phosphoric Acid . . . . . . . . . . . . . . . .10 rmation of Ammonia-Soluble Phosphoric Acid . . . . . . . . . . . . . . . .11 i‘ phoric Acid Dissolved by Ammonia from Ignited Soils . . . . . . .13 . osphoric Acid Dissolved by Ammonia, With and Without Ex- traction With Acid ..................................... . .14 ative Solubility of Phosphates in Acid and in Ammonia . . . . . . . .16 t ect of Ignition on Solubility of Phosphates . . . . . . . . . . . . . . . . . .18 ition-Soluble Inorganic Phosphoric Acid in the Soil . . . . . . . . . . . .20 ition-Soluble and Ammonia-Soluble Phosphoric Acid . . . . . . . . . .21 ‘tion-sohihio Phosphoric Acid in Texas Soils. . ._ . . . . . . . . . . . . . .25 gposedMethods for Estimation of Organic Phosphoric Acid. . . .28 clusions of Stewart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..3'0 irony and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..32 ect of Ignition on Other Soil Constituents . . . . . . . . . . . . . . . . . ..l9 i __4_ AVAILABLE BULLETINS. The following is a list of Bulletins of this Experiment Station avail- able for distribution. The others are out of print. Any of these Bul- letins Will be sent free of charge. Requests should be directed to the Director of the Experiment Station, College Station, Texas: 79 96 97 98 100 105 107 108 109 111 112 113 114 115 119 120 121 123 124 126 128 129 131 132 133 Cotton Breeding. Commercial Fertilizers and Poisonous Insecticides, 1906-07. Kaffir Corn and Milo Maize for Fattening Cattle. Summary of All Bulletins from No. 1 to No. 94, inclusive. Chemical Composition of Some Texas Soils. Notes on Forest and Ornamental Trees. Commercial Fertilizers and Poisonous Insecticides, 1907-08, Winter Bur Clover. Alfalfa. Texas Fever. - Nature and Use of Commercial Fertilizers. Spray Calendar. Composition of White Lead and Paints. Fertilizer Test With Onions. Infectious Anaemia of the Horse. ‘Corn and Cotton Experiments for 1908. Report of Progress at the Troupe Sub-Station. Commercial Fertilizers and Poisonous Insecticides, 1908-09. The Pecan-Case Bearer. . Active Phosphoric Acid and Its Relation to the Needs of the Soil for Phosphoric Acid in Pot Experiments. Cottonseed Meal as Human Food. Studies of the Ammonia-Soluble Organic Matter of the Soil. Hog Feeding Experiments. Co-operative Forage Crop Work, Commercial Fertilizer. c First, Second, Fourth, Fifth, Eighth, Ninth, Tenth, Eleventh, Thirteenth Annual Reports. ORGANIC PHQSPHORIC ACID OF THE SOIL. By‘ G. S. Fraps. The phosphoric acid may be present in the soil as phosphates of lime, phosphates of iron and aluminum, and in organic forms. The unprotected phosphates of lime are soluble in fifth-normal nitric acid. The basic phosphates of iron and aluminum are less easily soluble in fifth-normal acid, more soluble in more concentrated acids. (See Bulletin No. 126 of this station for a study of the phosphates soluble in dilute acids.) The presence of the inorganic phosphates, and their varying forms of combination and solubility, render a study of the organic phosphates a difficult matter. For the purposes of soil chemistry, Weak compounds of phosphoric acid with organic bases, or phosphates which are merely absorbed by organic sub- stances, are of little more significance than compounds of phosphoric acid With inorganic bases, or phosphates absorbed by inorganic sub- stances. If the P04 ion can dissociate from the compound, the or- ganic or inorganic character of the remainder of the compound is not A of great significance. Ethereal salts of phosphoric acid, or substances which contain phosphorous as a constituent of the molecule, are of more importance. Those organic phosphorous compounds which exist in the soil may possibly be members of four groups: (a) Those partly soluble in Water. (b) Those insoluble in Water, but soluble in dilute acids. (c) Those insoluble in ‘dilute acids but soluble in ammonia. (d) Those insoluble in all of these solvents. These groups "exist in plants, and their existence in the soil i_s merely a matter of quantitative occurrence in plant or animal resi- dues, and persistence under the action of the bacterial agencies of the soil. The bacteria themselves may give rise to such bodies. AMMONIA-SOLUBLE PHOSPHORIC ACID. The phosphoric acid which is extracted from the soil by ammonia, after previous extraction with dilute acids, has been held by many chemists to be in organic combination. It has been pointed out in an article by the author (American Chemical Journal,_1908, page 579) that ammonia dissolved phosphoric acid from basic iron and aluminum phosphates, and that the phosphoric acid fixed by the soil from Water solution increases the ammonia-soluble phosphoric acid. Since the phosphates of iron and aluminumare present 1n the soil and are not removed completely by the preliminary extrac- tion with acid, the ammonia-soluble phosphoric acid can not be as- sumed to be entirely of organic origin. That is to say, this solvent __6__ , does not afford us a method for estimating the organic phosphoric acid of the soil. If it were possible t0 determine the proportion which is organic, and that which is inorganic, the solvent might be of serv- ice, but this proportion would have to be determined for each soil or group of soils, and even then the ammonia-soluble organic phos- phoric acid would n01; necessarily be the total organic phosphoric acid, since some of the latter may be insoluble in ammonia, or be ex- tracted by the acid. SOLUBILITY OF PHOSPHATES IN AMMONIA. Some estimations (in addition to those in the article referred to above) of the solubility of phosphates in ammonia are presented in Table 1. A The quantity of phosphate containing 0.10 gram phosphoric acid was allowed to remain in contact with 2000 cc of 4 per cent am- monia for 24 hours, being shaken from time to time. The amount of phosphoric acid used would correspond to 100 grams soil containing 0.1 per cent phosphoric acid in contact with 2000 cc ammonia, or a ratio of 1 gram soil to 20 cc ammonia. The phosphates of lime are; little soluble. The phosphates of iron and of aluminium are more easily decomposed, especially wavellite and vivianite. TABLE 1. SOLUBILITY OF PHOSPHORIO ACID OF MINERAL PHOSPHATES IN AMMONIA. Laboratory i Percentage Number ' ' _; Dissolved 245 Apatite, Phosphate of Lime .............................................. --; 2.8 710 Apatite ___________________________________________________________________ _-1 3.8 727 Apatite __________________________________________________________________ _-T 1.2 239 Phosphorite, Phosphate of Lime __ I 6.0 713 Phosphorite _____________________________________________________________ --‘ 1.6 729 Phosphorite ____________________ __ - 3.6 716 Variscite, Phosphate of Alumina- —- -— y 8.0 240 Wavellite, Phosphate of A1umina____ 1 44.4 238 Ferric Phosphate ____ __ 100.0 241 Vivianite Phosphate of Iron (ierrous)___ 1 98.4 712 {Vivianite _ 69.9 733 =Vivianite _________________________________________________________________ __ 79.0 242 lTripilite Phosphate of Iron and Manganese ‘ 3.6 719 iTripilite _______________________________________ __ 8.7 724 lTripilite _ __ 1.2 714 Dufrenite Phosphate oi Iron _____________________________________________ __ 15.7 728 Dufrenite _- 8.7 The solubility of the phosphoric acid of several minerals in‘ am- monia of ‘different strengths is given in Table 2. The methods were the same as those used in preceding work. Table 2. Solubility of phosphoric acid of mineral phosphates in ammonia of different strengths: ' TABLE 2. SOLUBILITY OF PHOSPHORIO AOID OF MINERAL PHOSPHATES IN AM- MONIA OF‘ DIFFERENT STRENGTHS. ‘ l i i a Ferric 1 Vivianite ‘y Wavellite {Phosphate l per cent 3 per cent l per cent i‘ ‘ ‘ . i 0 1 per cent ammonia __________________________________________ __ 49.0 ’ 29.8 ; 89.5 0 5 per cent ammonia_____ __ __ “j 81.6 ‘ 30.0 1 96.9 1.0 per cent ammonia__ ..___________________..______-________-_-_i 87.6 1 29.4 i - 98.7 2 0 per cent ammonia __________________________________________ __§ 89.6 ; 36.0 v 100.0 4 0 per cent ammonia __________________________________________ _-\ 96.2 i 39.0 ; 100.0 _7_ Even ‘ammonia of one-tenth per cent exerts a decided solvent ac- tion upon these minerals. Ammonia dissolves phosphoric acid from the phosphates of iron and aluminium chiefly. None of the phosphates ordinarily found in the soil are completely decomposed by ammonia. Fifth-normal nitric acid, on the other hand, dissolves the phosphates of lime more easily than those of iron and aluminiua. FIXATION OF PHOSPHORIC ACID FROM AMMONIA. It has been shown by us that phosphoric acid may be fixed by soils from acid solution. The object of the work reported below was to ascertain if any fixation takes place from ammonia. TABLE 3. PHOSPHORIC ACID FIXED FROM AMMONIA SOLUTION. -1 Absorptive Laboratory ; Fixed from power Number i Description of Soil Ammonia from water I ' per cent per cent l l 336 ‘Susquehana fine sandy 10am ________________________________ ._ O 1 86.1 980 Orangeburg fine sandy loam 0 ] 53.2 958 lOrangeburg fine sandy 10am 18 l 87.1 1056 ;N0rf01k sand, 1-19 26 ‘i __________ __ 823 prangeburg fine sandy loam, 12-36 ________________________ -- 30 i 98.2 1590 iLufkin sandy 10am, 8-14 ' 62 84.1 825 jLufkin fine sandy 10am 73 88.9 The soil was extracted (once) with N/5 nitric acid, Washed thor- oughly, and dried. One portion of 100 grams of the soil received no additon, the other received 200 parts per million of phosphoric acid in the form of potassium phosphate. The portions were then digested with 1000 cc. of 1 per cent ammonia, shaking every half hour for the first four hours. After 24 hours, the solution was poured 0E, the clay precipitated with 10 grams ammonium chloride, and fil- tered off. Five hundred cubic centimeters were evaporated with the additon of 1 gram carbonate of lime, 10 cc concentrated nitric acid added when nearly dry, evaporated to complete dryness and ignited. The residue was taken up with 5 cc hydrochloric acid, evaporated and _ heated to dehydrate silica, redissolved in acid, filtered, and phosphoric acid determined (volumetric) as in soils. The results are presented in Table 3. From 0 to 62 per cent of theadded phosphoric acid was fixed. The soils selected had a high absorptive power forphosphoric acid. The error of analysis is greater in this work than in that with fifth-normal acid but the evidence shows that the soils may absorb phosphoric acid from ammonia solution as well as from acid solution. Pending some decision as to the significance of the ammonia-soluble phosphoric acid of the soil, we have not considered it necessary to go deeply into this matter of absorption. The fact that soils may fix phos- phoric acid from ammonia solution is, in my opinion, further evidence of the presence of inorganic ammonia-soluble phosphates in the soil. EFFECT OF RATIO OF SOIL TO SOLVENT ON EXTRACTION OF PHOSPHORIC ACID BY ACID AND AMMONIA. In this series of experiments, varying amounts of soil were digested _3_ With 1000 cc of N/5 nitric acid. The residues were washed thoroughly ' onthe filter paper, then Washed into glass-stoppered bottles with 1000 cc of 4 per cent ammonia. Phosphoric acid soluble in N /5 nitric acid, and that soluble in ammonia were determined by methods already de- scribed (see preceding section for method with ammonia). The re- sults of this series of experiments are shown in Table 4. The maxi- mum amount of “acid consumed” in any estimation was 20 per cent. None of the soils Were calcareous soils. TABLE 4. EFFECT OF QUANTITY OF SOIL IN EXTRACTION OF PHOSPHORIO ACID. i i Grams Soil Laboratory i r k 4 Number i lOgm 25gm 50gm 100gm 200gm i i Milligrams Phosphoric Acid per 100006 1056 jBy N/5 Nitric Acid ....................... -- 1.59 i 2.47 4.25 ‘ 6.75 *1212 1206 iBy N/5 Nitric Acid _______________________ __ 2.12 f 4.56 I 7.81 j 17.12 25.25 341 iBy N/5 Nitric Acid ______________________ __ .66 1 .25 i .37 1 .60 : .60 113s 13y N/5 Nitric Acid _______________________ __ .50 1 .50 .56 ; .67 1 .06 980 By N/5 Nitric Acid _______________________ -- .93 .93 , 1.00 _‘ 1.17 l 1.31 i 1 1 1 i ‘i . 1056 By 4 per cent Ammonia __________________ 0.s 2.16 , 2.70 i 6.50 g 15.06 1206 ‘By 4 per cent Ammonia __________________ __% 1.26 1.96 1 3.30 ‘ 6.60 | 9.10 341 By 4 per cent Ammonia ___________________ __j ______ __ 1.36 .50 i .40 1.30 1138 By 4 per cent Ammonia __________________ __‘ 0.50 0.30 ______ __; 0.76 i 1.40 980 By 4 per cent Ammonia __________________ __; 1.80 2.70 i 4.70 1 7.40 16.70 . l Parts Phosphoric Acid per Million 1056 iBy N/5 Nitric Acid _______________________ __‘ 160 99 85 1 68 = 61 1206 ‘By N/5 Nitric Acid ________________________ __= 213 183 . 156 - 159 126 341 iBy N/5 Nitric Acid _______________________ __i 65 10 s y 6 s. 1138 iBy N/5 Nitric Acid _______________________ __= 5O 20 11 9 5 980 iBy N/5 Nitric Acid _______________________ _, 93 38 16 12 7 i 3 l 1056 lBy 4 per cent Ammonia __________________ __; so s6 l 54 i 65 75 1206 iBy 4 per cent Ammonia __________________ "i 126 7s , 66 i 66 . 46 341 iBy 4 per cent Ammonia __________________ __; ______ -_ 54 , 10 4 j 7 1138 iBy 4 per cent Ammonia ______ -1 __________ __\ 50 12 i ______ __i 8 ; 7 cs0 [By 4 per cent Ammonia __________________ __i 1s0 10s g 96 = 74 s3 . , _ On examination of the table, We find that the concentration of the phosphoric acid in the solvent increases with the quanity of soil pres- ent, but that the parts per million of phosphoric acid extracted from the soil decreases as the quantity of soil increases. This observation holds for both the acid and the ammonia, and for all the soils, with the exception of No. 341, which behaves irregularly, possibly because the amount of extracted phosphoric acid is small. This behavior of soi1' phosphates towards ammonia is not what We should expect if we hold the theory that the ammonia merely combines with and extracts or- ganic phosphates. Two grams ammonia in contact With 100 grams soil, which is the smallest amount ammonia used per gram of soil, is sufficient to combine ‘with over 20 per cent “humic acid” to form “ammonium humate.” Hence an increased amount of ammonia is not necessary to form ammonium humate. The solution in ammonia takes place in a similar manner to the solution in acid. OTHER SOIL CONSTITUENTS DISSOLVED BY AMMONIA. In studying the acid-soluble phosphoric acid, We found the solution of considerable quantities of the soil, which sometimes takes place, might expose considerably more phosphoric acid to the solvent than is exposed to the roots of plants. We studied the solvent action of am- monia to see if it was 0f significance in this respect. __9‘__ *I1*\'vr-v~1r"es-" The iron and alumina, lime, and magnesia were determined in the ution obtained by the action of 1000 cc of 1 per cent ammonia 24 urs at room-temperature upon 100 grams residues, from different 'il treatments. The clay Was precipitated With ammonium sulphate, n the clear liquid used for the estimation, being first evaporated to ess and taken up With acid, The iron and alumina Were precip- ted With ammonia and the Weight corrected for the phosphoric acid ~ sent. The results are presented in Table 5. The quantity of material _'ch goes into solution is small, and We consider the exposure of soil osphates by solution of protecting material in the" ammonia to be ligible. The previous treatment With acid, however, exposes pro- ted soil particles, to the action» of the succeeding treatment with am- '_ia.' This has already been pointed out in Bulletin 126. More iron and alumina, lime, and magnesia, are dissolved from the p Which has been previously treated With Water, than from the e soil treated With acid. The amount of these materials dissolved ’ eases as the strength of theacid previously used, increases. The F» ts With the last tWo soils are not entirely in accord With these ‘ ments. n the other hand, the quantity of phosphoric acid dissolved by am- ia increases With the strength of the solvent Which previously acted n the soil. The ammonia dissolves least phosphoric acid from ex- _ tion With N/5 nitric acid, and still more from the residue from _ extraction With 1.8N nitric acid. Correction to the original Weight e soil Would modify this conclusion. This behavior of the soil as een Water and N/5 acid could be explained by saying that the acid _l decomposed organic calcium compounds, containing phosphoric a but this explanation Would not account for the different effect the tWo strengths of acid. The N/5 nitric acid is amply strong to mpose all calciuni organic bodies Which might be present. An- explanation Would be that the acids broke doWn or decreased size of the soil particles and removed protecting material, thus rding more surface for the action of the solvent. T: ' s. DISSOLVED FROM son, RESIDUES BY ONE PER GENT AMMONIA IN PARTS ~ g PER MILLION. i F8203 P1105. ratory ; D1118 Lime Magne- phoric ;~ ber 1 A1203 sium Acid 11o FAfter treatment with water -------------- -- 204 313 91 s6 "1 . N/5 Nitric Acid_____ 192 156 84 I 118 . l 1.8N Nitric Acid____ 101 ' 148 76 159 821 lAtter treatment with water --------------- -- 293 173 98 77 ; N/5 Nitric Acid_____ 223 156 80 87 , 1.8N Nitric Acid____ 163 127 j 65 107 e823 ;Atter treatment with water ------------- -- 157 292 i 137 5a j 1 N/ Nitric Acid---" 100 152 1 105 106 1.8N Nitric Acid____ 60 157 ’ 209 127 a After treatment with water .............. __ 85 403 112 5 N/5 Nitric Acid-____ 57 568 145 73 . 1.8N Nitric Acid_-__ 55 164 134 132 $32 After treatment with water ______________ __ 93 180 s3 97 -. N/5 Nitric Acid"--- 110 193 94 30 1.8N Nitric Acid_-__ 24 189 76 116 5: ere is a correction to be made on account of the solution of the during the previous treatment, as the Work is based upon 100 __10_ grams soil residue, not 100 grams soil. The correction is not lar _ however, for none of the soils used contain much material solubli in these strengths ofacid, and the correction would be in the dir i. tion of the conclusions just noted, ‘ SOLUTION OF FIXED PHOSPHORIG ACID. The objectof this work was to determine whether phosphoric acid presented to the soil in a soluble inorganic form, was fixed and held,‘ in part, so as not to be soluble in acids, but so as to be partly soluble in ammonia. ' In this experiment, approximately 200 mg. phosphoric acid in 100 cc Water Was brought in contact with 20, grams soil, 24 hours at room temperature. The quantity of phosphoric acid used was thus 1 per cent of the soil, or 10,000 parts per million. A portion of the solution was withdrawn and subjected to analysis and the results, expressed in percentages of the phosporic acid presented to the soil, are shown in column 2 of Table 6. We can compare these percentages with the “absorptive power” of the soil, namely, the percentage of 400 parts per million absorbed in 24 hours, shown in column 1. (Bulletin 126 contains description of this method.) With three of the soils, the percentage absorbed from the high amounts of phosporic acid used in this experiment are nearly the same as the fixing power, or a little lower. With the other soil, the difference is much greater. Only soils of unusually high absorptive power could be expected to absorb as large percentage of phosphoric acid from 10,000 parts per million, as from 400 parts per million. The absorption of several of the other soils is high, considering the large quantity of phosphoric acid used. TABLE o. EXTRACTION or PHOSPHORIC ACID BY AOI-D AND BY AMMONIA. v f => TE i E , i‘ 6,215 Percentage of phoJsphoric acid in soil L orator Q ‘ ° Q r tlgumbery 3E 5 Absorbed Extr’d ‘ Extr’d of 3011 f3 Q t QHEE , Total by j by , by Am- § Not <94 l O4 o Q4 ;_ Added Soil ‘1 Acid i monia 3 Extr’d 134 ______________ _; 74,2 l 66.2 l 1.012 0.670 0.633 .007 1 030 326 _____________ __‘ 68,2 63.7 , 1.012 0.645 v 0.591 .000 f 054 330 _____________ __ 86,7 1 71.9 l 1.012 0.728 K 0.690 .007 031 336 ______________ _, $6.1 . 42.1 a 1.012 0.426 0.371 .058 000 341 _____________ __‘ 98 .4 . 35 .2 . 1 .012 0. 356 0.298 . 031 027 829 _____________ __i 87,1 l 34.1 1 1.012 0.345 0.323 j .020 002 324 _____________ __ 71,4 1 59.8 j 1.012 0.606 0.574 1 .026 006 816 _____________ __ 56 . 4 , 32 .9 1 . 012 0. 333 0. 320 . . 011 002 817 _____________ __ 56.8 f 8.0 1.012 0.081 0.043 ~ .007 031 821 _____________ __ 44.7 l; 4.7 1.012 0.047 0.016 .015 016 823 _____________ __ 98.2 49.3 1 1.012 0.512 0.320 .168 024 825 _____________ __ 88.9 29.1 j 1.012 0.295 0.249 .020 026 We consider next the percentages (based on the soil) of phosphoric acid absorbed, and extracted by the different solvents. In extracting with acid, the 20 grams soil was left for 10 hours in contact with 250 cc of 1 per cent hydrochloric acid. The acid was then decanted through a filter, 200 cc acid added, and again decanted. The soil was then transferred to a funnel and washed with acid several times; As is seen by the table, this treatment extracted a large proportion of the fixed phosphoric acid. That is, the phosphoric acid fixed ap- -_-11_ pears to be chiefly in the form of acid-soluble phosphates. The absorbed phosphoric acid was not, however, completely extracted. The treatment with ammonia (4 per cent) was similar to that with acid. It followed the acid treatment, upon the same sample of soil. It will be noticed that the treatment with ammonia did not recover the-entire amount of fixed phosphoric acid. The experiment shows clearly, however, that the fixed phosphoric acid is not completely ex- tracted by acid, and that it is partly recovered in the succeeding treatment with ammonia. This experiment shows that the ammonia- - soluble phosphoric acid of the soil must be, in part, at least, of inorganic origin. According to this experiment, a large portion of the inorganic phosphoric acid added to the soil may be removed‘ by re- peated extraction with 1 % hydrochloric acid, a portion is recovered in the ammonia extract, and a portion remains in the soil. FORMATION- OF AMMONIA-SOLUBLE PHOSPHORIC ACID? In Bulletin 129, we reported the results of some experiments de- signed to ascertain whether the formation of ammonia-soluble or- ganic matter takes place in the soil. No production of such bodies was observed. It was found that when correction had been made for that added, the ammonia-soluble organic matter decreased, under the conditions of the experiment. The organic materials added to the soil after they had been ex- tracted with hydrochloric acid contained ammonia-soluble phosphoric acid. (See Table No. 13 of Bulletin 129, this Experiment Station.) The ammonia-soluble phosphoric acid was determined in this work, and the results will be reported here. The plan of the experiment was to mix 20 grams organic material with 500 grams of. soil, allow the mixtures to remain moist for 14 weeks or a year, dry, and subject them to analysis. A mixture of the original materials was prepared and subjected to analysis at the same time as the “humified” mixtures. (For full details see Bulletin No. 129 of this Station.) The soil was, of course, extracted with acid before being extracted with ammonia. The estimation of phosphoric acid was carried on with 100 cc of the ammonia extract, equivalent to two grams of soil. In dealing with such small quantities" of phos- phoric "acid, the error of analysis is. of course, not small. The re- sults presented ‘represent averages of two or more estimations, usu- ally made on different solutions and at different times. i An increase in ammonia-soluble phosphoric acid may be due to the combination of phosphoric acid with organic matter, to form products not soluble in dilute acids, but soluble in ammonia, or it may be due to the formation of phosphates of iron and aluminum which are not completely decomposed by dilute acids but which are partly or completely decomposed by ammonia. Hence, an increase of ammonia-soluble phosphoric acid does not necessarily signify an increase of organic phosphoric compounds. -12__ TABLE 7. PERCENTAGE or AMMONIA-SOLUBLE PHOSPHORIO ACID AFTERA“ RIOUS INTERVALS. a -‘- E i ‘ L b t ' A I 8 _ g a ora ory : =0 g Number of * I g , g g g I g E Soil. a ~ i 634-1 | “3_. “E y “ g less as 1 , v2 , v12 ; mOE mil 02H r ; sss Original mixtures _______________ -_! 01s .037 070 1 .023 021 a I Mixtures after 14 weeks ....... __‘ .018 1 .036 .048 i .028 021 . i Mixtures after 1 year __________ _-‘ .018 _ .040 .038 \ .020 l 020 805 Original mixtures _______________ __; .012 p .017 i .061 .018 .018 ‘ Mixtures after 14 weeks ______ __ .014 ‘ .015 1 .049 i .012 012 Mixtures after 1 year __________ _- .013 * .010 l .052 .012 .012 958 jOriginal mixtures _______________ __ .070 .137 ‘ .175 .078 .068 i Mixtures after 14 weeks ______ __ .080 .137 124 .065 .070 Mixtures afterl year __________ __; .077 .130 1 I120 .090 . .096 14 wks 1 year lAvcrage of increases where they j occur ___________________________ __l . a .014 ; ______ __, ______________ __@__-__ iAverage of decreases ____________ __' .008 .014 1 ______ __‘ ______________ __\____ ‘Net change ______________________ “@003 1-003 ______ _-; ______ __:__-_- iNumber of increases ______________ _1 5 p 6 § ______ n“ ______ __i ______ __‘____-* iNumber oi decreases ____________ __7 s i 9 i ______ __ Table 7 shows the results of the experiments with three soils, an" a number of mixtures. We find the addition of the organic materi increases the ammonia-soluble phosphoric acid by that Which is con tained in it. The increase is only slight with blood and excremen The ammonia-soluble phosphoric acid decreases as the material d a cays with all the mixtures of soil No. 895, (except phosphate) s; with two mixtures each of soil 895 and 958. With soil 958 there a three increases, and with soil 895, two increases, and one practicall unchanged. On an average, the ammonia-soluble phosphoric acid de- creases... No decrease is observed with the meat mixtures, soils 885 -and 958, the blood mixture with soil 885, and the excrement mixture with soil 885. Increases are noticed with the phosphate, soil 885 and 958, and with blood, and the excrement mixtures in soil 958. The cotton seed meal mixture loses the most ammonia-soluble phos- phoric acid. ~It is our opinion that the increased"ammonia-soluble phosphoric f acid (when any such increase occurs) is due to combination with in- “j organic soil constituents. The fact that such increase is greatest with the potassium phosphate mixture supports this opinion. TABLE 8. PERCENTAGE OF AMMONIA-SOLUBLE PHOSPHORIG ACID IN ORIGINAL ' MIXTURES AND AFTER DEOAYING A YEAR. i l i i . i . Original ‘ After Laboratory i Number Mixtures‘ 1 year s05 1x0 addition _______________________________________________ ____ _- .013 l ........ -- lSoil plus wheat bran _______________ _~_ ___________________________ _-; .090 4 .023 lSoil plus tankage _______________________________________________ _-i '.029 I .020 ‘Soil plus wheat shorts __________________________________________ _- .059 .028 {Soil plus corn chops ____________________________________________ Ml .032 4.023 lSoil plus bat guano ____________________________________________ __4 .035 .022 ‘Soil plus rice hulls ________________ _-.. ___________________________ _-j .059 .043 J Table 8 contains an experiment on soil 895 with several other or- ganic materials. The addition of the organic material involved an addition of ammonia-soluble phosphoric acid] The ammonia-soluble phosphoric acid decreased after “humification” for a year in all the mixtu-res. _13__ PERCENTAGE OF AMMONIA-SOLUBLE PHOSPHORIO ACID IN VARIOUS SOILS MIXED WITH MANURE. Soil plus Soil plus Excrement Soil I Excrement . After g y 1 year I .013 ' .013 .018 - .013 .020 .020 ____ __ i .038 1 .045 .054 .021 = .023 .020 A ( .013 ’ .013 .013 .31 "I \ ble 9 contains an experiment With excrement on several soils. -" "xcrement adds little ammonia-soluble phosphoric acid, as We , 'en, and has little effect upon that in the soil. In soil No. 821 i erve an increase of ammonia-soluble phosphoric acid. OSPHORIC ACID DISSOLVED BY AMMONIA FROM IGNITED SOILS. n 1 object of this Work Was to ascertain if soils contain inorganic [iarsoluble material. As We shall see later, the inorganic phos- likely to be soluble in ammonia, are rendered more easily in acid by ignition. experiment, the soil was first ignited, then treated as for paction of humus, first With acid, then With 4' per cent am- i_ The ammoniacal extract was filtered, and evaporated. direct. ults are presented in Table 10. i y 1 TABLE 10. DISSOLVED BY AMMONIA FROM IGNITED SOILS. i I i Phosphoric . acid solu- ble in > ' Loss on ammonia ,ry ' Ash ignition Phosphoric; before .1 inorganic (humus!) acid ignition per cent per cent ‘ per cent per cent Soil from Minnesota, Stevens county 1.75 .17 i .020 .068 Soil from Minnesota, Stevens county 1.76 .24 .010 .%9 Soil from Minnesota, Polk county- 1.21 .22 .015 .043 Soil from Minnesota, surface, Kilt- son county ______________________ __ 1.82 .30 .01 .066 Soil from Minnesota, surface, Mar- 1 shall county ____________________ __ 1.32 .32 ‘ .01 .073 Soil from Minnesota, Marshall _ ' county __________________________ _- 2.01 - .24 .01 .070 ~ t Wabash fine sandy loam _________ _-] 1.48 0.25 .005 a __________ __ Wabash fine sandy loam, 20_30_____1 1.70 .24 .01 l __________ __ Houston 10am, 0-12 _______________ "I 2.31 .27 .003 ~ __________ __ Wabash heavy clay_________..._______~ 2.17 .23 | .02 039 Wabash silt loam _________________ __ ‘ 2.63 .16 1 .03 , __________ __ Houston black clay _____________ __ i 2.22 _20 | .01 i __________ __ “ash” was in suspension in the ammoniacal solution, and ght on ignition, from 0.16 to 0.32 per cent of the ignited is is, of course-, due to Water heldby the clay but it illus- iowa soil may contain no organic matter, and yet ‘appear to :11 us. - - - jount of phosphoric acid in the liquid varied from 0.003 to i_ cent. Besides destroying the organic matter, the heat might" t‘ mineral phosphates. A ‘w’. .__.14:__ Other estimations of ammonia-soluble phosphoric acid in p; soils, and the conclusions drawn from them, will be given later. ' presence of ammonia-soluble phosphoric acid in the ignited so' our opinion is evidence of the presence of inorganic ammonia-sol phosphoric acid in the original soils, At the least, it is evidence the ammonia-soluble phosphoric acid of the. soil is not necessarily ganic in nature. 1 PHOSPHORIC ACID DISSOLVED BY AMMONIA, WITH AND WITHOUT F EXTRACTION WITH ACID. - In Table 5, we presented the results of a number of estimatio, phosphoric acid dissolved by ammonia from soils, after "extrae with water, with N/5 nitric acid, and With 1.8 nitric acid. The t v ment with acid increases the ammonia-soluble phosphoric acid, w‘ increase has been ascribed to organic phosphorous compounds, ' soluble in acid on account of the decomposition of compound _ lime or magnesia with organic acidic bodies. (See discussion belo. In order to test this pointfthe phosphoric acid dissolved frof number of ignited soils, with and without extraction with hy chloric acid was determined by us. Two portions of ten grams- soil each were weighed out and ignited. One portion was extrac directly with ammonia, the other extracted with 1 % hydrochl acid, and then with 4 % ammonia, as per the methods of the ciation of Official Agricultural Chemists. The ammonia solut: was made up to 500 cc, the clay in over 400 cc of the filtered soluti was precipitated with 2 grams ammonium chloride, the soluti filtered and 400 cc taken for analysis. The results are presen in Table 11. ' TABLE 11. PERCENTAGE EXTRAOTED BY AMMONIA FROM IGNITED SOILS WITH WITHOUT PREVIOUS EXTRAOTIONS WITH 1 PER CENT ACID. l ' i . . Laboratory i a _ ] - f Number g No acid ilAfter acid‘ Differ 328 ‘Blanco 10am ________________________ _; _______ __ .0025 l .0063 ‘ .0038; 330 Ilrawford stony c1ay_ _____________________ _- .0018 , .0127 - .0109 331 lSubsoil of 330--- ___ _____________________ __ .0025 .0069 ‘ 338 Wabash clay ___ _______________________ __ .0017 ; .0087 831 Laredo silty clay ______________________________ _- .0007 .0056 882 iWabash clay, 10-36 ____________________________ __ .0012 f .0056 341 (Susquehana fine sandy loam, subsoil ________ __ .0153 * .0215 344 Orangeburg fine sandy loam __________________ __ .0228 .0230 832 Orangeburg clay _______________________________ __ .0175 l .0200 845 Wabash silt 10am ______________________________ __ .0156 i .0256 869 iLaredo silty clay, 12-36 ________________________ __ .0006 ' .0076 876 Houston black clay, 10-36 _____________________ __ .0059 .0103 741 iMinnesota, Stevens county ____________________ __ .0025 ‘ .0069 744 iMinnesota, Kiltson county ____________________ __ .0038 % .0078 992 iOrangeburg fine sandy loam __________________ __| .0194 y .0450 Soils free from organic matter thusiyield more phosphoric s»: to ammonia after they have been extracted with hydrochloric ac than without such extraction. The difference is from 6 to 256 1f per million. As we shall see later, ignition has the effect of rend ing iron and aluminum phosphates more soluble in acid. The igni, soil. therefore, cannot contain as much phosphoric acid comb'~f_ with iron and aluminum as the original soil. and the presence __15__ ‘er amounts of iron and aluminum phosphates would allow a pos- ity for greater differences in the original soils than those pre- i d in Table 11 for ignited soils. 5| effect of the acid upon the soil may be to break up soil parti- f and thus expose more phosphates to the succeeding extraction 5| the ammonia. The acid may also dissolve substances Which fix Tpphoric acid from ammonia, and thus reduce the quantity ex- '_ d. It is probable, of course, that the acid decomposes organic ounds held insoluble by lime or magnesia in soils which have fbeen ignited, and by liberating the organic acid, renders it more soluble in ammonia, But the fact that ammonia dissolves phosphoric acid from a soil sample treated with acid than from not so treated, can not be considered as evidence of the organic ' e of the phosphorous so dissolved. _ wart (Bulletin 145, Illinois Experiment Station) asserts that ference between the phosphoric acid dissolved by a soil after ction with acid, and the same soil before extraction with acid ents phosphoric acid which must be organic. The following ted from him: “Attention should be called to the fact that when riginal soil was treated direct with ammonia, without previous‘ tion with hydrochloric acid, under conditions where the maxi- amount of inorganic phosphorous should be dissolved, only unds of phosphorous per two million pounds of soil, were ob- i ; yet, after the soil had been treated with hydrochloric acid to f the calcium, under conditions when the minimum amount of ic phosphoric acid would be dissolved by the ammonia, 510 of phosphorous per two million pounds of soil were obtained. ffierence between these two numbers, 278 pounds, unquestion- represents phosphorous which must have been derived from or- _isources. Now, since only 55 pounds of phosphorous is pre- Nted with the rnatiere no/ire by phosphoric acid, it would appear ..: the organic phosphorous associated with the precipitated e noire is only a small part of the organic matter in the soil.” ording to the work Stewart reports, the 55 pounds referred to last sentence were precipitated after a portion of the organic ihates had been decmnposcd by evaporation on a water bath, ‘e precipitated phosphorous in the undecomposed humic acids j be 149 pounds instead of the 55 pounds hegives. However, ,1 a matter of little importance, in comparison with the fact that ork shows as utterly untenable the assumption that the increase onia-soluble phosphoric acid “unquestionably represents phos- acid which must have been derived from organic sources.” j'dence is presented to show that it does come from organic i, but the fact is in itself‘ taken as evidence. If such reason- ‘Ids, then ignited soils contain organic phosphoric acid. erring back to the quotation just made from the Illinois Bulle- ‘Y find that the 278 pounds of “phosphorous” referred to may = ly organic, and partly inorganic, and that 149 pounds are “the organic phosphorous associated with the precipitated we nmlre is only a small part of the organic matter of the soil” (justified by the work done. - 'tated with the humic acids instead of 55. Hence the conclu- ' ._15_ RELATIVE SOLUBILITY OF PHOSPHATES IN ACID AND AMMONIA. The relative solubility of a number of phosphates in 15% hydrf chloric acid, and in ammonia, both With and Without previous e’ traction With hydrochloric acid, is presented in Table 12. In Work, an amount of material containing 0.1 gram phosphate i-l placed in 1000 cc glass stoppered bottle, 200 cc of 1 % hydrochlori‘ acid (made up by titration) Was added, shaken Well, and allowed stand over night. The liquid was then poured off through a filter’ filter and residue returned to bottle, and 200 cc acid added as before Three extractions Were made in this Way. The combined filtrati Were made up to 1000 cc and phosphoric acid determined in 200; cc of it. c" TABLE 12. SOLUBILITY OF PHOSPHATES IN ACID AND AMMONIA IN PERCENTAGES OF PHOSPHORIG ACID USED. l In4per ‘l In 1 per cent am- Directly cent hy- , monia 1 by am- i, Laboratory drochloric‘ after the ‘mania, no}, Number acid i acid 3 acid used ‘jg 716 ivariscite _______ __ ____ 11.; ; 12.5 34.9 .3 732 Variscite ______ __ ___- i 9- 3 -8 1-1 721 ‘Wavellite _________ -_. ............................ __l 9.8 37-1 39-8 726 ‘Wavellite ________________________________________ __' 12.4 40.7 3__-..-_..-_--.‘ 24o iWavellite ....................................... “l 12.1 36.6 * 37.5 ; 72s lDufrenite _____ _- __ 18.1 7.0 5 7.1 » 241 iVivianite 80.7 1.7 ‘. 91.1 J 733 ‘Vivianite _______________________________________ “l 100- l 0.5 i. 96-0 ' 242 ‘Tripilite ________________________________________ __ 100. ‘ 0.4 ; 1-9 i 719 Iripilite ____ ______ J 100. l 0.4 = 1.9 ., 724 ‘Tripilite ........................................ _-| 100. 1 0.2 1 1.5 , . After extracting the third time, residue and paper Were Washed, thoroughly and allowed to drain, Filter and paper Were returnedf to bottle, 1000 cc of 4 % ammonia, made up by titration, Were added,” and alloWed to stand 36 hours. It Was then filtered into a dry bottle, and 500 cc taken for the estimation of phosphoric acid. The extraction direct With ammonia Was made as described abovej the previous treatment With acid being, of course, omitted. . f It is seen from the Table 12, that the treatment With acid decom- poses vivianite and triplite completely, but only dissolves a portion of the phosphoric acid from Wavellite, variscite, and dufrenite. The ammonia has a much greater solvent action upon Wavellite, and on one sample of variscite, than the three extractions With acid. It_ is evident that the soil may contain basic phosphates of iron and alumi-,. num from Which all the phosphoric acid is not dissolved by the treat-p ment With acid preliminary to the extraction of humus, and that such inorganic phosphates are soluble in ammonia. Further, such phosphates may be dissolved to a greater extent by ammonia than by acids. Solubility in 12 % Hydrochloric Acid. This WorkWas similar to the preceding, .but the mineral containing 0.05 grams phosphoric acid.- Was extracted With 200 cc of 12 % hydrochloric acid, 24 hours at; room temperature. The liquid Was filtered and the residue Washed; with hot Water. The filtrate Was made up to 500 cc and 200 cc taken’; for estimation of phosphoric acid. Filter and residue Were digested; 34 3 H‘ i _17_' for 36 hours with i000 cc of 4 % ammonia and phosphoric acid determined in 500 cc of the filtrate. ' The results are presented in Table 13. The strong acid has a greater solvent power than the one per cent acid, but it does not dis- solve completely the phosphoric acid from the variscite, Wavellite, or dufrenite. Ammonia has a stronger solvent action on the Wavellite than has the acid, even though the wavellite has previously been ex- tracted with the acid. TABLE 13. PERCENTAGE OF PHOSPHORIC ACID DISSOLVED FROM MINERALS BY 12 PER CENT HYDROOHLORIO ACID AND BY AMMONIA (12 PER CENT). l ~ By hy- By hydro- By am- l ' r By hy- drochloric chloric acid monia ' Laboratory drochloric i acid after after acid after acid Number lacid direct‘ ignition (direct) direct l ‘ l 733 Vivianite _________________________ __l 99 1 ______________________ __‘i 1 714 Dufrenite __________________________ __l 10o 10o ___________ _i __________ __ 716 lVariscite __________________________ __; 26 100 ‘ 15 l 9 726_ lWavellite __________________________ __; 18 100 21 i 35 721 Wavellite ___________________________ _l 19 < 100 , 21 l 41 724 Tripilite __________________________ __ ‘ 100 : 100 __________ __l __________ __ 719 Tripilite ___________________________ __‘ 10o * 10o = __________ __l __________ __ 72s lDufrenite __-, ________________________ _l s6 l 96 = __________ __| 3 242 ‘Tripilite ___________________________ 10o l __________ __________ __i __________ -_ 732 lVariscite __________________________ __l 14 l __________ __1 l 50 240 Wavellite __________________________ __l __________ __ ‘ 10o lIIIIIIIIIIIl __________ _- l l = l Let us apply these results to the soil, An extraction with cold 12 Iper cent hydrochloric acid Would dissolve most of the dufrenite, Qpyivianite, and similar compounds. The phosphates remaining Would Fibe similar to viriscite and wavellite. The phosphoric acid of one ;sample of the variscite and both samples of Wavellite, is more easily fysoluble in ammonia than in 12 per cent hydrochloric acid. It follows gthat an extraction with ammonia which follows an extraction with i112 per cent hydrochloric acid might very conceivably extract more, Tginorganic phosphoric acid than a second extraction with the acid. A method for estimating the organic phosphorous of the soil has §been based upon the assertion that 12 per cent cold hydrochloric i-‘acid dissolves all the easily soluble inorganic phosphorous of the soil, land that a succeeding extraction with ammonia should extract no gimore inorganic phosphorous than a second extraction with the acid. [gAccording to this publication (Illinois Bulletin 145) “It would also em very ztnreasonable to suppose that dilute ammonia possessed as Z»; rong a solvent a power for inorganic phosphorous as does 12 per cent ydrochloric acid” (after the soil has once been extracted with the cid). The facts which caused the author to consider such a be- iavior toibe very unreasonable, are not presented, but the facts we "ve just detailed, on the contrary, would cause one tdbelieve that j ch a behavior would be the very one to expect. Hence the method lferred to above is based upon an assumption which is not justified ' the facts which we have in our possession, and in the absence of _ ect and positive evidence that this assumption is correct, we are a: tified in leaving it out of consideration. _ Table 10 also contains an extraction with 12 per cent hydro- hloric-acid which followed a similar extraction on the same ma- rial, and was in the same way. The acid dissolved less than the "u 0111a. i’ A—18- In considering‘ the bearing of this work further, we must remember that the phosphates used do not necessarily represent those which may be, or are, present in the soil. Soil phosphates of unknown nature are undoubtedly present, or else their properties are decidedly modified by some characters of the soil. As we shall see, ignition makes soluble all the phosphoric acid in the minerals we tested, but all the phosphoric acid in the soil is not made soluble by the ignition, a quantity being left which is soluble in ammonia, probably in addi- tion to some which is inaccessible to the solvent. EFFECT OF IGNITION ON THE SOLUBILITY OF PHOSPHATES. A method for the estimation of organic phosphoric acid (Illinois . Bulletin 145) has been based upon the effect of ignition on the solu- bility of phosphates. "h portion of the soil is ignited, extracted with cold 12 per cent hydrochloric acid, and the phosphoric acid estimated. From this is subtracted the amount of phosphoric acid extracted from the original soil by the same process, and the result is taken to represent the organic phosphorous. The method is based upon the tacit assumption that the effect of the ignition is to destroy the or- ganic phosphorous compounds and so render the phosphorous solu- ble in acids, without afiecting the solubility of the inorganic phos- phates. It is a well-established fact that aluminum phosphate is rendered more available to plants by roasting, and We considered it desirable to study the effect of ignition upon the solubility of mineral phos- phates. The quantity of phosphate containing 0.1 gram phosphoric acid was weighed into a platinum dish and ignited for ten minutes, at a low red heat. It was transferred, dish and all, to a bottle, 200 cc of 12 per cent hydrochloric acid added, allowed to stand 24 hours, filtered, washed with hot water, and made up to 500 cc. Phosphoric acid was determined in 200 cc. The results are presented in Table 13, Exam- ination of the table shows a marked effect of ignition upon the solu- bility of the phosphates in the acid. Variscite, "dufrenite, and wavel- lite became almost completely soluble. All of the phosphates which we tested, and which were not completely soluble in the acid before ‘ ignition, became almost completely soluble after ignition. It is thus very probable that if the soil contains any inorganic phos- phates which are not completely soluble in cold 12 per cent hydro- chloric acid,‘ ignition of the soil will render them soluble to-a greater extent, and increase the quantity of phosphoric acid extracted by the acid. In other words, the phosphoric acid rendered soluble by ignition may come from inorganic as well as from organic compounds of phosphorous. Increase in the quantity of phosphorous extracted by acid after ignition, cannot be considered as proof of the presence of organic phosphorous compounds, still less can an analytical method be based upon the ignition of the soil. EFFECT OF IGNITION ON SOLUBILITY IN N/5 NITRIC ACID‘. In this work, the mineral was ignited’ at a low red heat for 10 __19__ minutes, transferred, and digested 5 hours at 40 deg. with 500 cc of N /5 nitric acid, filtered, and phosphoric acid estimated as usual. The quantity of mineral taken was equivalent to 0.100 gm phosphoric acid. The results are presented in Table 14, along with estimations on the unignited minerals, taken from Bulletin 126 of this Station. TABLE 14. COMPARATIVE PERCENPAGES OF PHOSPHORIC ACID DISSOLVED BY N/5 NITRIC ACID FROM MINERALS IGNITED AND NOT IGNITED. i l Laboratory i l Not Number i Ignited Ignited 240 ‘Wavellite _______________________________________________________ __': 4.8 80.7 721 lwaveiiite ....................................................... __i 4.5 97,5 726 {Wavellite ________________________________________________________ -3 2.0 53,0 714 ‘Dufrenite _______________________________________________________ __l 4.8 35.5 728 iDufrenite _______________________________________________________ __* 8.0 75,0 1 . 7 100. 716 ‘Variscite ______________________________________________ ___ ________ __‘ 1 Ignition increases the solubility of these minerals in N/5 nitric acid very much indeed. About ten times as much phosphoric acid is dissolved from the ignited mineral, as from the non-ignited. EFFECT OF IGNITION ON OTHER SOIL CONSTITUENTS. In order to ascertain the effect of the ignition on the solubility of other constituents of the soil in 12 % hydrochloric acid, two portions of 10 grams each of soil were weighed out, one portion being ignited, the other, not. Both Were digested for 24 hours, at room temper- ature, with 100 cc 12 per cent hydrochloric acid, filtered, and washed with hot water. The filtrate was evaporated to dryness, heated to render silica insoluble, filtered, and iron and alumina, lime, and magnesia estimated according to the usual methods. No correction was made for the phosphoric acid precipitated with the iron and aluminum oxides. The results of this work are given in Table 15. The chief effect of the ignition is to cause a large quantity of iron and aluminum oxides to go into solution. The lime, magnesia, and silica are affected to some extent, being rendered more soluble in some cases, less soluble in others. The maximum amount of iron and alumina oxides rendered solu- ble by the ignition is 6.83 per cent. It will probably be conceded that this iron is not combined with organic matter. The humus dis- solved by ammonia takes very little iron or alumina with it. If such quantities of iron and alumina are rendered soluble by ignition of the soil, we would have reason to believe that the phosphoric acid associated therewith would also go into solution. IGNITION-SOLUBLE INORGANIC PI-IOSPHORIC ACID IN THE SOIL, Does the soil contain inorganic phosphorous which is rendered solubly by ignition‘! According to the experiments just described, if the extraction with hydrochloric acid leaves any inorganic phos- phoric acid, some of this will be rendered soluble by ignition. __2 ()__ TABLE 15. EFFECT OF IGNITION UPON SOLUBILITY IN 12 PER CENT HYDRO- CHLORIC ACID (PERCENTAGE DISSOLVED). l l l Oxides of iron Silica 1 and alumina 1 Lime Magnesia lr-"'jgk“i"':"x‘fi-—"*"——ffl T_""—JL—"__-\ r——-—4*—"—'-\ Laboratory 1 Ig- Not 1g; _Ig- Not ig- _Ig- 1No_t 1g-1 1g- Not 1g- Number 1_l1it8d nited 1 nited mted nlted nlted 1 nlted mted 1361 Soil 10 Mercedes--. 3.12 0.18 l 6-50 1-25 ------ --i ------ --i -------------- -- 2196 Heavy black ricel 1 ' ‘ Sgi] ___________ __. 0.14 0.10 1 3.22 1.39 ______________________________ -- 2834 Sherman clay 0-8_~ 2.67 0.09 l 8-24 2-50 ------ --. ------ --f ------ --‘1 ------ -- 2946 Hougtonblackclayf 0.95 0.16 1 5.60 2.00 ______ -_1 ______________ -_1 ______ __ 3357 “Second bottom,”1 1 * ' Bcnbrook _-_..___i 1.93 0.16 ‘ 4.86 .1-17 -------------- --1 ------ -_1 ------ _- 3371 “Made lan ,”1 ' 1 ‘ Donna -------- --1 3-1; 3-15 1 1g; 13g ------ -------------- ------ -- 741 Minnesota soil ___. . . 1 . . ...... __‘ ---------------------- -_ 832 Orangeburg clay__j 0.10 0.09 1 3.81 3.20 ______ _-, -------------- __. ------ _- 992 Orangeburg fine1 1 1 1' 4.73 4.63 ______ __1 ______________________ __ sandy 10am ___-f 0.05 0.08 an e r01 ___ . . 1 . . 4 ______________________ -1 ...... -_ 3612 Slibsiiil gtsaltldyi 1 73 0 13 1 s 33 1 50 l 3613 Soil s’o1mito_-_--l 0.75 0.12 4.37 . 3.01 ______ -_; .............. --1 ...... -- 3347 Sandy soil, mod-1 ’ ‘ 1 erate, Denton __1 0.41 0.21 1' 3.10 f 0.38 2.10 1 2% 0.38 1 0.31 3392 S. S. t0 3391,1 1 ~ 1 1 143140113611 ________ _-1 0.63 0.27 1 3.62 i 095 236 2.25 043 1 039 336s s. s. to 3367.1 1 1 . . 1 Buffalo ________ __l 0.12 0.125 ' 8.48 1 2.63 0.86 1 0.16 1 10st .06 3376 s. s. to 3375.1 1 1 ; 1 1 Ouero __________ 013 0.122 4.43 1 112 0303; 0.49 0.19 1 10 3377 Surface soil, Ste- i phenville _____ _- 0.12 0.0971 1.13 1 0.60 .051; 0.09 .0731 06 3382 S. S. to 3381, “post 1 1 1 ‘ 1 oak,” Lingleville 0.12 .1531 3.21 1 1.37 .171‘ .19 1 14 .07 3385 S0116, Como ____ 0.03 .1391 0.13 1 .075 .037 .07 06 .04 3391 Soil 12, Asherton. 0.10 .164 3.32 1.17 .13 .16 16 .03 3173 Soil 6, 0113133143- .11 .11 1 2.32 1 1.13 .27 05s 14 . .00 3174 s. s. to 3173, ; . 1 12-18,0na1aska__ .10 .13 1 2.01 1 1.91 .24 .53 16 06 3341 Yazoo clay, Waco .22 .16 l 2.78 1 1.65 ______________________________ __ 3331 Surface, 7, Lin- 1 1 gleville _________ __ .09 - .12 1 1.03 . 0 46 - .10 .10 11 O4 3383 Surface, 10, l 1 Frankston ______ -_ .09 .09 0.71 1 021 1 .03 .07 1 03 02 3302 s. s. to 3391, 1 1 . 22, Ashert0n_____ .53 .14 3.7s 1 1.25 1 We have evidence that inorganic phosphates are left. First, ex- traction a second time with acid dissolves a further quantity of phosphoric acid, That is, the first extraction is not complete. Second, ignited soils extracted with 12 per cent acid contain am- monia-soluble phosphoric acid. That is, even after the ignition has increased the solubility of the inorganic phosphates, the extraction with acid is not complete. Still less complete ought to be the extrac- tion before ignition. Table 16 shows the results of an experiment to ascertain the phos- phoric acid removed from soils by several successive extractions with cold 12 per cent hydrochloric acid. Fifty grams soil were ‘digested 24 hours with the solvent at room temperature, filtered, washed with cold water, made up to 1000 cc, and 200 cc taken for the estimation of phosphoric acid. The soil residue was washed from the filter with 500 cc ‘of 12 per cent hydrochloric acid, digested 24 hours, filtered, washed, and the entire filtrate taken for the estimation. Six succes- sive extractions were made. " +21- TABLE 1e. PHOSPHORIO ACID REMOVED BY SUCOESSIVE DIGESTIONS wrrn 12 PER GENT HYDROOHLORIO ACID IN PARTS PER MILLION. W_Wl l l 1 1 ' is? l I l 3 ;Bv§3 l . Parts per million of phosphoric acid ‘ i fgffé Laboratory 1 ; Extraction Number , q m g q, f, w” m, Number 5 ‘r Q a “'5 --"‘ lwczv-E 1 l ‘ ; ‘ 1 * ‘. '—1fl ‘UOQ of Soil l l 1 V 2 3 l 4 ' 5 3 e ‘ ~25 513 l§95§§ i: \ ‘ ; 1 Em HE Gum 992 l--______-___§ 446 1 214 ‘ 243 : 202 y 169 172 l, 1000 594 i 168 1331 i .......... -1, 1195 lost 42 ; 4s 1 19 . 32 i 131* 530 1 34 219s ’ ___________ 00 - 37 i 19 1 15 g 11 15 97 525 19 2334 i __________ _-“ 250 . 76 1 47 j 30 g 31 47 1 231 - 515 45 3371 ........... _. 1130 . 97 42 1 23 ; 1s 21 I 201 075 1 3o 3013 y .......... "l 2370 1 s9 30 - 19 ; 17 , 2o g 131 3 475 g 3s ‘Estimated 40 for second extraction. Cold hydrochloric acid does not extract all the inorganic phosphates in one extraction. This is very striking in the case of soil N0. 992. The successive extractions dissolve phosphoric acid from the other soils also. We can compare the quantities of phosphoric acid so extracted with the total ignition-soluble phosphoric acid, taken from succeed- _ing tables. These figures are presented in the tables. We find that successive extraction with acid takes more phosphoric acid from soil No. 992, than is dissolved from it by ammonia, or rendered soluble by ignitionj We also find- that from 19 to 45 per cent of the ignition- soluble phosphoric acid is contained in the five acid extracts which succeed the first one. This by no means represents the entire quan- tity of inorganic phosphoric acid present, since, as we have pointed out, the phosphates which are made soluble by ignition are but slightly soluble in acid. IGNITION-SOLUBLE AND AMMONIA-SOLUBLE PHOSPHORIC ACID. The ammonia-soluble phosphoric acid of a soil consists of am- monia-soluble organic phosphorous compounds, and of phosphoric acid dissolved from inorganic phosphates by ammonia. The ignition-soluble phosphoric acid (a term which We will use to designate the phosphoric acid rendered soluble in 12 per cent hydro- chloric acid by ignition) consists of organic phosphorous compounds destroyed by ignition, and of inorganic phosphates rendered soluble -in acid by ignition. In order to secure further information in regard to the phos- phoric acid of soils, We have estimated the phosphoric acid in various forms. ' Method of Work. Ten grams soil Were digested with 100 cc of 12 per cent hydrochloric acid (made up by titration) for 24 hours at room temperature. It was then filtered and Washed. The filtrate was evaporated, etc., and phosphoric acid estimated as in soils. The soil residue was washed from the paper with about 450 cc ammonia, let stand 36 hours, made up to 500 cc, let settle four or five hours, and about 400 cc was poured off. Two grams ammonium sulphate were added, and the solution filtered as soon as the clay had coagu- -22_ n lated. Three hundred cubic centimeters of the filtrate Were evapo- rated t0 dryness. In the case of ignited soils, the residue was taken up With acid, evaporated, filtered, and phosphoric acid estimated. With soils not previously ignited, 2-3 cc magnesium nitrate were added, the residue ignited t0 destroy organic matter, taken up in acid and Water, evaporated to remove silica, and phosphoric acid esti- mated. Results. The results of this Work on 27 soils are presented in Table 17. ' ~ ___23__ 8888088080 3on8 8%. H0 83205.... W 88. .............. ................. 1% @8285. W W .5 55. W 885. :88. . 8.8. W 8s. 85. W . .. W 3 888. W 3.8. 55. W S5. W £5. W E8. 83. ............ --...:bm2:85 .5558 55:3 5.5 85w m; 8 5.88. WW 838. W 8.88. W 8H5. 88. W 885. 8x8. ..... 33E .803 2G 838.38: 85 3 88. W 83. _ 88. W E3. . E3. . 8.8. 8E8. W ......................... .. 88088003 30.5. =08 m.» 38 888. W 38. W 388. 8N8. W 88. 85. 838. W111111-1--1~-~-11680~ >808 800 033A 3w 3 88. 838. W 8888. 888. W 888. W 88 88. .................. 1 1 3.02 880mm 808 wysnwwafifioW 5w 3 838 W 833. W 888. $3. W $83. W 838. 88. W ...................... --.1~883- .55 >35 088.23; 88w 8 38. . 83. W 88. 33. W 33. W 38. 88. WW-111.-..1..1... ...............1......1- .1 - 88.5 3a 0838i 3.8 03 838. W 83.8. W 8888. 38. W P888. W 3.88. 8008. W I 1 . . I 1 1 E83 838w 3E 8588888588 38. 8N :8 W. 83. W 85. 853. . 8888. W 88. 88.5. W111mWdWmmwlmmmmmmfiwwfi.188088.80w wénwwnfioW 8c 88 88. W 38. _ 838. 888. W 838. W 88. . 888. W . . . . . . . . . -1 “WW3. 888 38 088.23. 3w 8 38. WW 83. 838. 33. W 83. 88. 883. W11111111-1111 H11 88.03 35 08853 E3 E 838. W 83. _W 838. 883.. W 85.3. W 88. W 33. W ......................... - - 8.3 >30 005580 . $3 88 .35. 58. W S5. w“... W 8%. W 8W8. mo“... W ................... -552 83%.“... mmmmwmmwwmW 8 38. W 38. W 88. W 8 8. 88 . W E. 8. 3 8. W ............................ 1 . . E W 888. E8. W 88. W 88. W 38. W 838 38. WW .......................... 13.8 .38»: £5 0888i 5w 83 88. 838. 88. W 838. 838. W 88. 8.38. W .................. 1053 8.28M. 8 m E03 808W 83 88 888. 38. 38. W 38. W 88. W 88. 838. W1. .................. J .... 13.8 008 2E 503078. 833 8 388. 8.8. 88. W 888. W 88. 838. 888. . .............. 13.8 383 883mm 808 38080882 3m m.» 83o. W mmmo. $08. 888. W 338. 88. 0088. ........................... 18.0 0388.838 53.02,; 88 s. W . W 8 W 8 WW... ............................. --..-............W..WWM 888...... 3 838. 88. 88. W w. . . 8. ........................... 1 -8 . 5 W 38. $3. _ $8. _ 803. 883. W 838. 883. .......................... lwémwhwuufi. 808 053.3 88 8 838. 38. 888. W 88. W 88. W 838. 88. ............................ 1 3-8 Si: 0505.. 88 8.8 888. 88. 38. . 38. W 88. W 838. 38. WW ........................ 18.8.3 8.882800 E03 88w 83 83 888 888. 838. . 838. W ~38. _ $8. W 888. W ...................... 18.3 :85 0585 808263 85 8 838. 38. 88. W 38. W 88S. 838. W 8808. W ................. 188.3 .682 8808.808 c503 88 w“. 888. 38. 88. W 838. W E8. >38. W 888. W ..................................... 18 8S8 85380.3 8w _ . W W W W W . W . W .111‘. I 830305 W W W on 8.33 0053mm 230E W 8830338 E08 W 130B W 8800338 W E88 .6255! 823B 8E >0. 85 W >8. .3 W 358 .50 358 .50 . . 8.6830083 .3088? .30.». 388 fl <| W w hfl mm k8 W W .0330 H0 E 8m88H8QHW 8:08 ©8303 WW, i=1 LW W 88300380 W W 08823 80c 820m W . 353852 .W W #320234 Q73. A504 NM 0.1.3.3085 G304 0333833 3O 3645230333 .5 3338i. _g4_ Ammonia-soluble phosphoric acid is present both before and after the ignition. The quantity present after ignition is much less than before. This is what We would expect were the ammonia-soluble phosphoric acid either organic or inorganic in nature, for as we have seen, the inorganic phosphates are rendered almost completely solu- ble by ignition, and the organic phosphates are destroyed, The ammonia-soluble phosphoric acid after ignition is on an aver- age, 51 per cent of that before ignition (the percentages being averaged) with a maximum of 100 and a minimum of 12.“ If we assume that the ammonia-soluble after ignition Was also ammonia- soluble before ignition, then at least 12 to 100 per cent of the am- monia-soluble phosphoric acid in these soils must be inorganic, and in addition to this percentage, would be the iron and aluminum phosphates made soluble by ignition. We are, to a great extent, jus- tified in assuming that the ammonia-soluble after ignition represents ammonia-soluble before ignition, for our experiments show that igni- tion makes the iron and aluminum phosphates more soluble rather than less so. Hence the above assumption is justified. But there is of course, the possibility that if very little phosphates of iron or aluminum are present, the ignition might cause some of the phos- phoric acid of the organic matter set free by the ignition, to unite with iron and alumina and convert it into ammonia-soluble. In order to test whether or not ammonia-soluble phosphoric acid might be formed from soluble phosphates during ignition, we added 1O cc water containing 2O mg. phosphoric acid to 1O grams soil, ignited, extracted with acid and then with ammonia, and then de- termined the phosphoric acid in the ammonia solution. The methods were as previously described. Results are in Table 18. TABLE 18. PERCFNTAGE OF AMMONIA-SOLUBLE PHOSPHORIC ACID WITH AND WITHOUT ADDITION OF PHOSPHORIO ACID TO THE SOIL BEFORE IGNITION. l Laboratory i Phosphoric No y Number ! ,acid added addition Increase 880 ' iAustin fine sandy loam, 12-36 _______________ "i .0066 .0%8 l .0008 310 ‘Orangeburg fine sandy 10am __________________ __, .0242 1i .0092 ~ .0150 876 Houston black clay, 1036 ____________________ __ .0192 1 .0100 1 .0092 913 Susquehana fine sandy 10am __________________ __' .0100 ’ .0030 .0070 1956 Sand, E. J. Ky1e’s farm ____________________ __- .0050 . .0033 ‘ .0017 829 Houston loam _________________________________ _- .0092 _ .0050 p .0042 Water-soluble phosphoric acid was thus converted into ammonia- soluble, tho only to a small extent except with one soil. However, We had the same thing to take place without ignition; that is, the phosphoric acid absorbed by the soil is not completely extracted by acid, and what remains is partly ammonia-soluble. (See page 10.) Further, the soil phosphates do not come into such intimate contact with the fixing particles, as does phosphoric acid in solution, hence a less possibility of production of ammonia-soluble phosphoric acid during ignition. We appear justified in concluding that the ammonia-soluble phos- phoric acid after ignition of the soil should be, as a rule, less than the ammonia-soluble phosphoric acid in iron and aluminum phos- phates present before ignition. __25__ Applying this result to the 27 soils we subjected to analysis, we find that on an average more than 51 per cent of the ammonia-soluble phosphoric acid is probably of inorganic origin. The results do not _ show us how much of the ammonia-soluble phosphoric acid is inor- ganic, but lead us to believe that more than from 12 to 100 per cent is in such forms. The sum of the acid-soluble and ammonia-soluble after ignition is, on an average, more than their sum before ignition. This result Qould be expected. The inorganic phosphates we tested were changed to a greater extent by the ignition, than they were dissolved by the ammonia. Ammonia did not extract all the phosphoric acid from them, while ignition rendered practically all their phosphoric acid soluble, - The same thing Would occur if organic phosphorus compounds were present which were not soluble in ammonia. RELATION OF IGNITION-SOLUBLE TO AMMONIA-SOLUBLE PHOSPHORIC ACID. There is no definite relation between the ‘ammonia-soluble phos- phoric acid and the ignition-soluble phosphoric acid. Theignition- soluble phosphoric acid may be one-half as much as the ammonia- soluble, or it may be twice as much. There is less difference when * larger quantities of both are present. The ignition-soluble and ammonia-soluble phosphoric acid do not represent exactly the same thing. Part of their content is the same, but not all. We see this when we note that while the average am- monia-soluble and the average ignition-soluble are nearly the same, yet, after the ignition-soluble has been extracted, there remains, in the soil, ammonia-soluble equivalent, on an average, of nearly 4.0 per cent of the ignition-soluble, and to nearly 37 per cent of the ammonia- soluble. Hence the ignition-soluble phosphoric acid and the am- monia-soluble phosphoric acid do not represent the same thing in the soil. » . ' We have not decided-as to the explanation of the ammonia-solu- ble phosphoric acid remaining after ignition. It may be due to am- monia-soluble phosphates of iron and aluminum which are not com- pletely made soluble in acid by ignition. It may be due to the fix- ing powers of the soil. . IGNITION-SOLUBLE “PHOSPHORIC ACID IN TEXAS‘ SOILS. The ignition-soluble phosphoric acid represents, we believe, organic Yphosphorus compounds, and also inorganic phosphates. The or- ganic phosphorus compounds should not, as a rule, exceed the igni- tion-soluble phophoric acid, but must be less, and may be very much less. While the estimation of the ignition-soluble phosphoric acid thus ‘does not show.the quantity of organic phosphorus bodies which are present, it shows us the maximum amount which may be pres- ent, and this information is of some service. We have determined the ignition-soluble phosphoric acid in a number of Texas soils, selecting, for the most part, those compara- tively high in nitrogen or phosphoric acid. The results are pre- ‘sented in Tables 19 and 20. ._26__ TABLE 19. PERCENTAGE OF IGNITION SOLUBLE PHOSPHORIO ACID, ETO., IN TEXAS SOILS. I Nitrogen y Ignition 3 Alumina ‘ to 1 of Laboratory .Phosphoric . i and oxide jPhosphoric _ Number j acid Nitrogen § of iron i acid 1 1 Group 1. Less than .01 per cent‘ ‘ ignition-soluble phosphoric acid. . 817 Lufkin fine sandy loam __________ __<. .0095 ‘ .07 4.62 7 813 Wabash fine sandy loam ________ __‘ .0045 1 .07 4.31 15 1316 Wabash clay _____________________ __. 0075 ‘ .18 17.02 24 3007 Wabash silty loam _______________ __} .0075 ‘ .21 8.87 29 893 Lufkin clay ______________________ __ .0080 .098 6.32 12 876 Houston black clay _______________ _. .0050 .10 18.88 20 1809 Soil from College farm __________ __ .0090 .11 6.56 12 1592 Lufkin sand _______________________ _. .0()25 p .016 .52 6 310 Orangeburg fine sandy loam--- -1 .0010 .028 8.54 28 1134 Norfolk fine sand S. S _________ __ -1 .0085 ‘ .027 1.76 3 1456 Sand from E. J. Ky1e’s farrn______i .0005 .033 1.01 66 827 Laredo silt loam __________________ -4 .0092 ' .05 5.57 5 1111 Laredo silt loam __________________ -_. 0045 .. .07 6.69 15 Average for soils less than .01‘ l 5 per cent (13) ____________________ u! .0059 .082 1 6.97 18.61 Group 2. .01—.02 per cent. - - 1131 Wabash clay, surface soil ______ __§ .0145 .11 16.15 8 1933 Sharkey clay, surface soil _______ -1 .0140 .12 13.82 9 2313 Victoria black clay, surface soil__i .0200 . .15 11.32 8 880 Austin fine sandy loam ____________ -1 .0155 .04 4.58 3 829 Austin loam ____________________ __ _‘ .0160 .13 11.54 8 877 fLarcdo silt loam _________________ __; .0160 ' .05 5.49 3 828 jNorfolk fine sand _________________ __; .0110 .02 1.03 2 344 IOrangeburg fine sandy loam ____ -_l 0110 . .05 13 74 5 1347 |Ca1neron clay, surface soil ______ --l .0100 a .061 14.54 6 913 Susquehana fine sandy loarn ____ __; .0150 .04 2.37 3 869 Laredo silty clay _________________ __j .0190 .08 10.66 4 1337 Rice soil __________________________ __' .0170 j .16 ' 9.54 9 l Average for soils .01—.02 per cent (12) ______________________________ __ 0149 .084 9 56 5.6 Group 3. .02—.03 per cent. 1929 Yazoo clay, surface ______________ -_. .0260 - .19 11-43 8 1935 Houston black clay, surface ____ __ .0245 3 .22 11.14 0 2471 Amarillo clay loam, surface ____ __ .0215 .15 10.23 7 3006 Wabash silt loam, surface _______ __ .0280 ‘ .23 12.73 8 3173 Surface soil, 0-6, Onalaska ______ __ .0280 v .22 11.82 8 3269 Surface soil, 0-12, black waxy_-__ .0260 .15 16.60 6 938 Austin fine sandy 1oam____ ______ __ .0210 .089 2.69 4 872 Laredo fine sand __________________ __ .0300 ; .065 8.63 2 831 Laredo silty clay ________________ __ .0210 '1 .09 10-18 4 834 Orangeburg fine sandy loam _____ __ .0205 - i .09 a 9.40 3 334 Houston loam ___________________ __ .0250 i .18 6-23 7 845 Wabash clay loam ________________ __ .0290 } .18 i 11.07 6 ‘Average for soils .02-.03 per cent (12) ______________________________ __ 0255 .154 9 26 6 Group 4. .03—.05 per cent. . 2430 Cottonwood loam _______________ -_ .0385 .20 7.39 5 3357 “Second bottom,” 0-10 ___________ _- .0475 .155 10.91 a 3 3612 Sandy upland subsoil, 10-20 ______ _- .0420 .1511 ---------- -- .3613 Truck land, 0.3 ___________________ __ .0475 .275 __________ -- 6 832 Orangeburg clay _________________ __ .0415 - = .07 13-81 2 992 Orangeburg fine sandy loam ____ -_ .0450 g .04 16.09 1 1925 Yazoo sandy loam ________________ __ .0420 i .16 7-23 4 1930 Yazoo clay, subsoil _______________ -- .0440 = -24 8.50 6 1312 Franklin clay ____________________ _- .0470 - .24 13-24 5 Average for soils .03——.05 per cent 0 0 17 11 02 4 _______________________________ __ 44 . Group over .% per cent. 1 . 1361 Surface s01], Mgfcedes ____________ __ ,O53O ‘ .17 ‘ 11.24 3 2196 Heavy black rice soil, Port Arthur .0525 I .15 13.80 3 2834 Sherman clay. surface ____________ -- 0515 J8 15-84 4 - 2946 Houston black clay, surface _____ __ .0555 i .25 15.12 5 3371 “Made mud," 0.6 _________________ __ .0675 . .18 12.07 3 741 Soil from Minnesota ______________ -- 0535 i -32 ‘ ----------- -~ 6 744 Soil from Kiltson county, lvlinnesota .0870 ~42 ----------- -i 5 331 Crawford stony clay _____________ -- 0755 ~28 i 15-60 3 1075 Soil _______________________________ -- .0970 .20 I 13-55 2 1936 Houston black clay ______________ __ .0515 23 ; 13-49 i 5 Average for soils over .06 per cent_ .0645 4 .238 l 13.84 i 3.9 __g7_ It is possible to group these soils according to their content of ignition-soluble phosphoric acid, or their content of nitrogen, Both groupings have been tried. Table 19 contains the details of the analyses, arranged according to the ignition-soluble phosphoric acid. The first group contains soils having less than .01 per cent ignition- soluble phosphoric acid. The other analyses are quite variable, the nitrogen ranging from .016 to 0.18, and the iron and alumina oxide from 0.52 to 18.88. The ratio of nitrogen to 1 of phosphoric acid ranges from 3 to 66. The ratio is, however, high for most of the soils, only four having lower ratios than 9, which is the highest ratio found in group 2 or any of the other groups. A low content of ignition-soluble phosphoric acid is thus associated with a variable amount of nitrogen, but with a small amount of such phosphoric acid in proportion to the nitrogen present. Group two contains, on an average, three times as much ignition-- soluble phosphoric acid as group 1, but practically the same average amount of nitrogen. The ratio of nitrogen to phosphoric acid is much lower. . Group 3 averages nearly twice as much ignition-soluble phosphoric acid as group 2, with nearly twice as much nitrogen, and almost the same ratio. Group 4 has a somewhat lower ratio than group 3. Group 5, which contains all the soils having over 0.05 per cent igni- tion-soluble phosphoric acid, also has a higher average nitrogen con- tent, and a lower ratio of nitrogen to phosphoric acid than the other groups. All the soils in Group 5 contain over 0.15 per cent of nitro- gen and over 11 per cent of oxides of iron and alumina. A high con- tent of ignition-soluble phosphoric acid is thus associated with a high content of nitrogen, and of oxides of iron and alumina. A high con- tent of nitrogen is not, however, necessarily associated with a high content of ignition-soluble phosphoric acid, since we have soils high in nitrogen in the lower groups. TABLE 20. AVERAGE’ COMPOSITION OF SOILS GROUPED ACCORDING TO CONTENT OF IGNITION SOLUBLE PHOSPHORIO ACID AND OF NITROGEN. , . i i _ Nitrogen l Per cent . Number Phosphoric to 1 of iron oxide a 0i aci Nitrogen Dhosllhoric and soils per cent per cent acid ‘ alumina, Arranged according to phosphoric Mild ____________________________ .._ 1 Less than .01 per cent ____________ -_ 13 l .0059 1; .082 14,0 6_g7 .0101—.02 per cent ________________ __ 12 i .0149 i .084 5,6 g_55 .02—.03 per cent ____________________ _- 12 .0255 l .154 61) 926 .O3-——.05 p61‘ cent ____________________ __ 9 .0440 1 .17 4,0 rpm Over .05 per cent-_____-____-_______ 10 .0645 ; .238 3,5 i 1334 Arranged according to nitrogen. ‘ , Less than .05 per cent ____________ __ 11 - .0123 . .035 l 2_9 ‘ ____ __ .05—.10 per cent __________________ __ 12 .0167 , .079 1 4,7 ______:"" .10—.20 per cent __________________ -_ 21 - .0341 ; .16 ; 4_7 ________:"' Over .20 per cent-__--------_-____-- 12 .0410 ; .245 l, 5,3 ;_________:: Table 20 summarizes the averages for the groups just given, and also summarizes the averages from the arrangement of the soils in groups according to their nitrogen content. ' We see from the table that when the soils are grouped according __g3__ to their content of ignition-soluble phosphoric acid, their average nitrogen content increases with the average phosphoric acid content, but not regularly—-not at all, indeed, with the first two groups. The ratio of nitrogen to 1 of phosphoric acid decreases from 14.0 with the soils lowest in ignition-soluble phosphoric acid, to 3.5 with those highest, the decrease being greatest between the first and second groups. The average percentage of iron and aluminum oxides in- creases as the percentage of ignition-soluble phosphoric acid in- creases, though not in the same proportion. This fact is of import- ance, to take into consideration in connection with the fact that igni- tion increases the solubility of the iron and alumina oxides at the same time that it increases the solubility of the phosphoric acid of _the soil. When the soils are grouped according to their content of nitrogen, we find that the average ignition-soluble phosphoric acid increases with the average nitrogen-content, but not regularly. The ratio of nitrogen to phosphoric acid increases with the quantity of nitrogen, reversing the order found in the previous grouping. The differences, however, are not so marked, indicating that the tendency of this method of arrangement is to average off the differences in the indi- vidual soils, while the other method places them more closely to- gether. » On considering both methods of grouping, we find that a low quan- tity of ignition-soluble phosphoric acid is not necessarily associated with a low quantity of nitrogen. As the quantity of ignition-soluble phosphoric acid increases, the quantity of nitrogen may increase, but the increase is by no means regular. There is more phosphoric acid in proportion to nitrogen as the quantity of ignition-soluble phos- phoric acid increases. A low quantity of nitrogen is usually associated with fairly low quantities of ignition-soluble phosphoric acid, but a high quantity of nitrogen is not necessarily associated with high quantities of ignition- soluble phosphoric acid. The ignition-soluble phosphoric acid on an average increases in proportion to the quantity of nitrogen present, but not regularly, and there is less average phosphoric acid in pro- portion to the nitrogen as the quantity of nitrogen increases. PROPOSED METHODS FOR ESTIMATING ORGANIC PHOSPHORIC ACID. Method 0f Calculation. This method is proposed by Hopkins and Pettit, (Illinois Experiment Station, Bulletin 123) and emphasized by Stewart (Illinois Experiment Station Bulletin 145), Where the surface soil and subsoil contain the same percentage of potash, they assume that these have uniform mineral composition. They then sub- tract the “phosphorus” in the subsoil from the “phosphorus” in the surface soil, and assume that the result represents organic phos- ~ phorus. They then calculate the ratio of carbon to “phosphorus” and of nitrogen to “phosphorus” and calculate the organic phos- phorus in other similar soils by multiplying their nitrogen content by this ratio, although the factor given by Stewart (Table 14 p. 110) is for carbon. _29__ ;~ This “method” is based upon assumptions which must be substan- ¢_;-= before it can be considered as worthy of further consideration. f1 first assumption, that the identity of potassium content of soil id subsoil is suflicient proof of identity of mineral content, is open ;_ serious objection, and requires further evidence. The second as- ZuPtlOII, that the “phosphorous” present in the surface soil in ex- s of that in the subsoil, is in organic combination, also requires ' ect experimental proof. The fact that a larger quantity of nitrogen ssociated with this larger quantity of phosphoric acid, is not suf- ent proof that the phosphoric acid is organically combined. This indicates association, but is not proof of combination. Until dence is furnished to justify the assumptions upon Which i1; is ‘d, the “method of calculation” must be considered as purely ulative. In making this statement, we are fully aware that wart (Illinois Bulletin 145) examined one soil and drew the fol- ‘g conclusion :' “Thecalculation method for "determining organic phorus is very conservative in character and can be relied upon ‘ drawing broad general conclusions.” mmoiiia-Solitble Phosphoric Acid. The phosphoric acid dissolved h monia from a soil, after extraction with acid, comes from both phoric acid in the ammonia extract does not show the quantity rganic phosphoric acid in the soil. _ iiitio/ri-Soliible Phosphoric Acid. The phosphoric acid rendered le by ignition may originate from organic or inorganic com- I ds of phosphorus. It does not show how much phosphoric acid I esent in organic forms. We believe it to show the maximum {A t which may be present. y toclaoe-Digestioii Method, Stewart also estimated the “or- e” phosphoric acid by heating the soil with acidulated water '2 hours at a temperature of 140 deg.-145 deg. We intended to this method, but after finding that all phosphoric acid of the uble iron and aluminum phosphates became soluble on ignition, gjelt satisfied that they would also be dissolved on treatment with dulated” water l2 hours at 140-145 deg. If any inorganic phos- es are present, they certainly stand a good chance of being dis- d. We therefore did not consider it necessary to purchase an . lave which would stand such pressure, for the purpose of testing proposed method. Before this method can be considered seriously, ‘nce must be furnished that the treatment does not dissolve the anic phosphates which may be present in the soil. ‘sphoric Acid Precipitated iuith Hitmic Acid. The phosphoric [precipitated with the humic acid from ammonia does not _repre. hecessarily all the organic phosphorus, and this is not a method _he estimation of organic phosphorus. We now are not alto- i, satisfied that the phosphoric ac1d with this precipitate is all '0. It is possible that some of it may be merely absorbed. 5 eral Conclusions. We have at present no method for the esti- en of organic phosphoric acid. _All the proposed methods are I to serious objections. The ignition method, we believe, shows aximum amount of organic phosphoric acid which may be pres- _}| it does not show how much is present. in and inorganic compounds of phosphorus. The quantity of A A “It is probably derived from the iron and aluminum phosphates”. _3 ()_ CONCLUSIONS OF STEWART. Bulletin 145, Illinois Agricultural Experiment Station has following conclusions: _ l ' I “8. The contention ‘of Fraps that “There is no evidence that n‘: phosphoric acid in the filtrate is in organic combination” and ff entirely untenable.” The full statement from which these sentences were selected, ; as follows: .,; “The Fvlltrate. It appears probable that most of the phospho acid in the filtrate from the precipitation of humus with acid is ' inorganic forms, altho a small percentage of it may be in organic co ~51. bination, since the organic precipitate is soluble in water, We shown that the inorganic phosphoric acid absorbed by the soil” i_ soluble in ammonia, and therefore some of the ammonia solub phosphoric acid must be of inorganic origin. There is no eviden that the phosphoric acid in the filtrate is in organic combination. *3: is probably derived from iron and aluminum phosphates.” (A"' Chem. J. 1908, page 385.) i In the summary and conclusions of the same article appears the fol lowing statement: “6. The phosphoric acid with the clay is not in solution. if in the filtrate is probably for the most part of inorganic origin, =i rived from iron and aluminium phosphates.” We state clearly in the article that there may be organic phof phoric acid in the filtrate, although we believe this phosphoric aci to be for the most part of inorganic origin. We could find no evi ‘dence that the phosphoric acid in the filtrate is in organic combi, nation at the time the article was written, and so stated. If th author of Illinois Bulletin No. 145 thinks that he has furnished evi- dence that this phosphoric acid is in organic combination, this do j< not make our statement “untenable.” None of the references giveng in his article supply the desired proof. _ Our opinion in regard to this matter is correctly stated in thq summary and conclusions of the article referred to. “That (phos-i phoric acid) in the filtrate is probably, for the most part, of. inor- ganic, derived from iron and aluminum phosphates.” It is quite possible that there are soils in which the bulk of the ammonia-soluble phosphoric acid is in organic combination. It is quite possible that there are soils in which a large portion of phos- phoric acid in the filtrate may be in organic combination. We do not state that such can not or does not occur. The fact that the fil- trate‘ contains organic matter shows that it may contain phosphoric acid in organic combination, and we stated this in the article quoted. It allows the possibility, but does not prove this to be a fact. One soil or two soils, in which the ammonia-soluble phosphoric acid- is in or- ganic combination, would not prove that all soils or the majority of soils so contain it. The author of Illinois Bulletin No. 145 draws very sweeping conclusions from the analyses of one soil. The object of our article was to show that the ammonia-soluble phosphoric acid is not necessarily organic, and that the determina~ __3 ]___ n of the ammonia-soluble phosphoric acid is not the determination organic phosphoric acid. {IThere is no discussion of my work in Illinois Bulletin 145 which _ds to conclusion eight, quoted above, and so we can not give ex- y the line of thought followed, but only what we suppose it to be "I f» the body of said Bulletin, and this may not beexactly correct. iglf we are correct, the argument is as follows: The soil which has extracted a second time with cold 12 per cent hydrochloric acid 95 pounds phosphorous in two million pounds of soil. The W soil yielded "to ammonia, after extraction with acid, 555 pounds phosphorus. It would seem very unreasonable, he says, to sup- 71:‘ that dilute ammonia has as great a solvent power for organic phorous as does 12 per cent hydrochloric acid, but assuming, for , sake of argument, that it does, then the organic phosphorus is , less 95, that is, 460 pounds. By ignition he finds 543 pounds, '4» by heating in an autoclave, 607 pounds of-organic phosphorus, orming to the previous figure. We do not see where the 504 “n for ammonia-soluble organic phosphorus in Table 26 comes i» f the 555 pounds of total phosphorus in the ammonia extract, pounds is precipitated by acid, leaving 406 pounds in solution, fwhich he grants only 95 pounds to be inorganic. Hence, most of piphosphoric acid in the filtrate must be organic. - is appears to us to be the line of reasoning followed. pone of the methods used in Illinois Bulletin 145 show the quan- s; of organic phosphorus in the soil. have shown (Table 13) that 12 per cent hydrochloric acid dis- , es some phosphates almost completely. Those not dissolved bles 12-13) are much more easily soluble in ammonia than they __ in a second treatment with the acid. Hence, the extraction of a ‘with 12 per cent hydrochloric acid would be likely to leave be- ". inorganic phosphates much more easily soluble in ammonia than he acid. Hence it is not only not “unreasonable” to suppose that jonia has a greater solvent power than 12 per cent hydro- iric acid for the inorganic phosphates remaining in the soil after revious extraction with acid, but it is “unreasonable” to suppose I it the acid has a greater solvent power than the ammonia. Thus the lysis giving the inorganic phosphoric acid as 95 pounds, above ted, may or may not show the inorganic phosphoric acid, but at any proves nothing. If he had made several more extractions with d, as we did (Table 16), the 95 would have been doubled or bled. As we have already shown, the method of ignition is a method for estimating organic phosphoric acid, and we will’ consider the method of heating in an autoclave to be a method til it is proved that it is. Therefore, all the results of Illinois Bulletin 145, quoted above, open to serious question, and the conclusions derived from them fi the ground. Que other “method” remains to be considered. When their soil _l=: extracted with ammonia direct, the extract contained 238 pounds sphorus per two million pounds soil, while when the soil was pre- _%-32__ “fir... viously extracted With acid, the ammonia dissolved 516 pounds. p difference, 278 pounds, they say, is unquestionably phosphorus g rived from organic sources. Why it should be unquestionably sue We can not see, because there are no unquestionable things in‘ s ence. But We have proved that an ignited soil, Which contains l} organic matter, Would contain organic phosphorous if this reasoni is correct (see Table 11), so this process of reasoning falls to th ground; i ACKNOWLEDGMENT. The analytical Work presented in this bulletin Was done, for th most part, by Assistants E. C. Carlyle, T. L. Ogier. S. E. Asbury and N. C. Hamner. A SUMMARY AND CONCLUSIONS. (l) as phosphates of lime, and as phosphates of iron and aluminia, (2) The ammonia-soluble phosphoric acid is partly inorganic and partly organic. <3) . . of iron and aluminia. (4) _ Some soils may fix phosphoric acid from ammonia solution. (5) The concentration of the phosphoric acid in ammonia or Phosphoric acid is present in the soil as organic phosphates,‘ Ammonia dissolves phosphoric acid chiefly from phosphatesj i a N/5 nitric acid increased With the quantity of soil present, but the i parts per million of phosphoric acid extracted from the soil de- creased as the quantity of soil Was increased. This behavior of the soil phosphates towards ammonia is not in accord With the theory that the ammonia merely combines With organic compounds con- taining phosphorus. (5) solved by the ammonia Were small. _ (7) Phosphoric acid fixed by the soil Was partly extracted by acid, partly extracted by ammonia, and a portion remained in the soil. - (8) Organic matter added to the soil increases the ammonia- soluble phosphoric acid. As the organic matter decays, the ammonia- soluble phosphoric acid usually decreases, though sometimes it in- creases. r (9) An increase in ammonia-soluble phosphoric acid during decay does not necessarily mean an increase in organic phosphoric acid. ' (10) Phosphoric acid is dissolved by ammonia from ignited soils. This is evidence that the ammonia-soluble phosphoric acid is partl.y of inorganic origin. _ (11) More phosphoric acid Was ‘dissolved from ignited soils by am- monia, after extraction With acid, than from the same soils before ex- traction. The increase in ammonia-soluble phosphoric acid brought about by the action of acid on the soil is thus not necessarily entirely due to the liberation of organic compounds containing phosphoric acid, Which are dissolved by ammonia. The quantities of iron and alumina, lime and magnesia dis- _33._ (12) Ammonia has a greater solvent action upon some mineral _ phosphates (wavellite) than has 1 per cent hydrochloric acid. r (13) Twelve per cent hydrocholoric acid Goes not extract all the phosphoric acid of wavellite, variscite or dufrenite. (14) Ammonia extracts more phosphoric acid from wavellite ._ than does 12 per cent hydrochloric acid. (15) An extraction with ammonia following an extraction of the : soil with 12 per cent hydrochloric acid may dissolve more inorganic phosphoric acid than a second extraction with 12 per cent acid. ' (16) ‘Ignition has a marked effect on the solubility of phosphates n acids. Wavellite, dufrenite and variscite become almost com- ,...-_»~».-..~1..~n.qi i i‘ a; (17) About ten times as much phosphoric acid was dissolved by __.N/5 nitric acid from the ignited minerals tested, as from the non- ignited. " (18) Ignition increases the solubility in 12 per cent hydrochloric acid of the iron oxide and aluminia in the soil, sometimes to a very | organic combination. (20) The method of ignition and solution can not be used as a ' (21) From 12 to 100 per cent of the ammonia-soluble phosphoric id of the soil (average 51 per cent) was present in the ignited (ils. § (22) I There was no definite relation between ammonia-soluble and i1 ition-soluble phosphoric acid in the soils tested. » g. d do not represent the same thing. f (23) A high content of ignition-soluble phosphoric acid was as- A iated with a relatively high content of nitrogen and of oxides of 1 n and aluminia in the soils examined. A high content of nitrogen as not, however, always accompanied with a high content of igni- Ion-soluble phosphoric acid. i (24) When the soils were grouped according to their content of ition-soluble phosphoric acid, the average nitrogen content in- i) eased with the average ignition-soluble phosphoric acid, though W regularly. The average content of iron oxide and aluminia also creased. (25) We have at present no method for estimating the organic osphoric acid of the soil, (22) The ignition-soluble and the ammonia-soluble phosphoric)