324 EXPERIMENT STATION RECORD. [Vol. 41 



phosphate on a soil poor in phosphates showed that soft I'ock phosphate was 

 not so available to corn as acid phosphate, and in fact showed practiially no 

 availability except in one instance. 



Effect of sulfofication and nitrification on rock phosphate, J. W. Ames and 

 T. E. RicHMOKD {Soil ScL, 6 (lOlS), No. 5, pp. 351-36.^). — Experiments at the 

 Ohio Experiment Station, in which the effect of sulfolicution and nitrilicatiou 

 on the availability of rock phosphate were studied by incorporating^ sulphur, 

 dried blood, and ammonium sulphate in silt loam and black clay soil, ijeat, 

 and quartz sand, are reported. 



In an acid soil the oxidation of sulphur proceeded vigorously, approximately 

 50 per cent being changed to the foi'm of sulphate. While sulfofication was 

 somewhat depressed in an acid soil by the addition of calcium carbonate, in 

 sand mixtures the presence of calcium carbonate was essential. In the absence 

 of other bases the calcium of rock phosphate did not serve as a base for the 

 sulfofying process to any appreciable extent. The proportion of rock phos- 

 phate to soil was such that phosphorus was added at the rate of 1,900 parts 

 per million. Tlie oxidation of sulphur, incorporated with rock phosphate in 

 the absence of calcium carbonate or nitrogen carriers, changed 630 parts of 

 phosphorus into a form soluble in neutral ammonium citrate solution. 



When calcium carbonate was added to the mixture prepared with an acid 

 soil, the oxidation of sulphur had practically no effect on rock phosphate. 

 In a basic soil the acidity resulting from sulfofication was partially neu- 

 tralized by calcium naturally present as carbonate and in other combinations, 

 so that the solvent action on rock phosphate was much less than occurred in 

 the acid soil. 



Ammonium sulphate affected the solubility of rock phosphate very little. 

 Whatever action ammonium sulphate had is attributed to the sulphate ion 

 rather than to biochemical action, since nitrification of ammonia did not occur 

 in a soil deficient in bases unless calcium carbonate was added. Active nitrifi- 

 cation of dried blood and ammonium sulphate occurred in the mixtures when 

 conditions were favorable. 



Nitrification was stimulated by rock phosphate to a very limited extent. 

 This fact, independent of the results for either phosphorus or calcium solu- 

 bility, is considered to be suflicient indication that the process has had no 

 appreciable action on rock phosphate in soil. 



Nitrification of dried blood, so far as the citrate soluble figures furnish evi- 

 dence of availability, was not an active agent for increasing the solubility of 

 rock phosphate mixed with soil. In the absence of rock phosphate or calcium 

 carbonate, the nitrification of dried blood as well as the action of anmionium 

 sulphate, independent of the oxidation of its nitrogen, increased the concentra- 

 tion of water soluble calcium. 



More calcium was taken into solution from the soil than from added rock 

 phosphate. This is considered to be evidence that the calcium of the soil, 

 existing chiefly as silicates and partly in otlier combinations, is almost, if not 

 altogether, as readily attacked as rock phosphate. 



Effect of sulfofication and nitrification on potassium and other soil con- 

 stituents, J. W. Ames and G. E. Boltz {^oil <S'ci., 7 {1919), No. 3, pp. 183-195).— 

 A continuation of experiments at the Ohio Experiment Station on the effect of 

 sulphur on soils and crops is reported (E. S. It., 39, p. S23), the results of which 

 indicated that " nitrification of dried blood and oxidation of sulphur in soil 

 nnxtures increased the water-soluble potassium. The liberation of potassium 

 was brought about by salts formed, rather than by the direct action of acidity 

 on insoluble potassium compounds. 



