682 Journal of Agricultural Research voi. xii, no. lo 



SUMMARY 



The investigations reported in this paper include a study of (i) the 

 effects of adding calcium carbonate, tricalcium phosphate, and ammo- 

 nium sulphate on the immediate solubility of calcium and phosphoric 

 acid in a light sandy loam soil; (2) the effects of nitrification of the soil 

 nitrogen, ammonium sulphate, and dried blood on the solubility of the 

 naturally occurring calcium and phosphoric acid; (3) the effects of nitri- 

 fication in soil and sand cultures on the solubility of tricalcium phosphate 

 both with and without the application of calcium carbonate. 



The following results were obtained: 



(i) The addition of calcium carbonate produced no effect on the imme- 

 diate solubility of the soil calcium or that added as tricalcium phosphate. 

 The addition of tricalcium phosphate produced an increase of about 5 

 p. p. m. of soluble calcium and 11.2 p. p. m. of soluble phosphoric acid, 

 while the addition of ammonium sulphate brought about an increase in 

 water-soluble calcium from 27.5 to 90.1 p. p. m. 



(a) Active nitrification of ammonium sulphate and dried blood took 

 place in the soil series, and at the same time notable increases in soluble 

 calcium were produced. 



(3) No increase in the solubility in water of the soil phosphates or of 

 tricalcium phosphate was produced by bacterial action except in the 

 nitrification of ammonium sulphate when added wdthout calcium car- 

 bonate. In this case 0.156 pounds (70.8 gm.) of phosphorous were dis- 

 solved for every pound of nitrogen oxidized, whereas Hopkins and Whit- 

 ing found from solution cultures that 2.033 pounds (922 gm.) were dis- 

 solved for every pound of nitrogen oxidized. 



(4) The addition of calcium carbonate brought about an increase in 

 soluble calcium but tended to lower the solubility of tricalcium phosphate. 



(5) In the absence of calcium carbonate the nitrification of ammonium 

 sulphate in sand cultures was accompanied by the solution of theoretical 

 amounts of tricalcium phosphate. When calcium carbonate was present, 

 however, the solubility of tricalcium phosphate was not increased by 

 nitrification. 



(6) The formation of nitrite from dried blood took place more rapidly 

 in the sand cultures than the formation of nitrate. 



(7) Tricalcium phosphate was not dissolved by the nitrification of dried 

 blood in the sand series. 



(8) It was found that calcium carbonate promoted more active nitri- 

 fication than tricalcium phosphate. 



(9) The experimental results indicate that the nitrification of organic 

 forms of nitrogen does not increase the solubility of rock phosphate under 

 field conditions that are favorable to crop growth. It is possible, how- 

 ever, that the nitrification of ammonium sulphate may result in the solu- 

 tion of small amounts of tricalcium phosphate in soil low in carbonate. 



