406 NATURE AND PROPERTIES OF SOILS 



224. The sulfur compost. — It has been noted by a num- 

 ber of experimenters that the presence of sulfur compounds 

 in the soil and especially elemental sulfur tends to develop 

 considerable acidity. The cause of this acidity has already 

 been explained. In 1916, Lipman * and his co-workers sug- 

 gested that a practical use be made of sulfofication in ren- 

 dering certain mineral nutrients, such as potash and phos- 

 phoric acid, available. Lipman devised a compost of sulfur 

 and raw rock phosphate. His results seem to indicate that 

 sufficient acid might be formed by biological oxidation ap- 

 preciably to influence the solubility of the rock phosphate. 



Brown and Warner 2 later used a compost of sulfur, farm 

 manure and raw rock phosphate. Remarkable increases in the 

 solubility of phosphoric acid, measured by extraction with 

 a solution of ammonium citrate, were recorded. The results 

 of Lipman, Brown, and Warner have been corroborated by 

 Ames and Richmond, 3 and Shedd. 4 Ames and Boltz 5 in 

 1919 found that sulfur composted with feldspar appreciably 

 influenced the solubility of potash. Such results as those 

 recorded above indicate the importance of sulfofication in 

 the soil under ordinary circumstances, as well as a possible 

 value in a more intensified procedure. 



The practicability of using sulfur composts on the farm 



1 Lipman, J. G., et al., Sulfur Oxidation in the Soil and Its Effects on 

 the Availability of Mineral Phosphates; Soil Sci., Vol. II. No. 6. 

 pp. 499-538, 1916. 



2 Brown, P. E., and Warner, H. W., Production of Available Phos- 

 phorus from Boclc-Phosphate by Composting with Sulfur and Manure; 

 Soil Sci., Vol. IV, No. 4, pp. 269-282, 1917. 



3 Ames, J. W., and Eichmond, T. E., Effect of Sulfofication and 

 Nitrification on Bock Phosphate; Soil Sci., Vol. VI, No. 4, pp. 351-364, 

 1918. ' ^ ** 



4 Shedd, O. M., Effect of Oxidation of Sulfur in Soils on the Solu- 

 bility of Bock-Phosphate and on Nitrification; Jour. Aer. Ees., Vol. 

 XVIII, No. 6, pvp. 329-345, 1919. 



5 Ames, J. W., and Boltz, G. E., Effect of Sulfofication and Nitrifica- 

 tion on Potassium and Other Soil Constituents; Soil Sci., Vol. VII, 

 No. 3, pp. 183-195, 1919. See also, Tottingham, W. E., and Hart, E. B., 

 Sulfur and Sulfur Composts in Belation to Plant Nutrition: Soil Sci., 

 Vol. XI, No. 1, pp. 49-65, 1921. 



