Studies on Reaction products of Tetraammonium Pyrophosphate Formed in Soils

Application of saturated solution of tetraammonium pyrophosphate (TAPP) to six soils resulted in five solid phase reaction products, namely, calcium diammonium pyrophosphate monohydrate in Oxisol, Haplaquent, Haplaquoll and Pellustert; magnesium diammonium pyrophosphate tetrahydrate (monoclinic) in Oxisol, Haplaquent and Pellustert; ferrous dihydrogen pyrophosphate in Haplaquent and Pellustert and both magnesium hexaammonium pyrophosphate hexahydrate and ferrous hexaammonium pyrophosphate hexahydrate in Pellustert. Calcium diammonium pyrophosphate monohydrate and magnesium diammonium pyrophosphate tetrahydrate (monoclinic), however, were obtained in abundance in most soils. Significant hydrolytic degradation of TAPP reaction products to orthophosphate was not observed. When TAPP was point-placed in soil, the reaction products formed were predominantly calcium diammonium pyrophosphate monohydrate, magnesium diammonium pyrophosphate tetrahydrate (monoclinic) and ferrous dihydrogen pyrophosphate.