Effectiveness of Phosphoroamides for Retardation of Urea Hydrolysis in Soils

The effectiveness of two phosphorodiamides (phosphorodiamidic acid, phenylphosphorodiamidate) and 10 phosphorotriamides [( N ‐phenylphosphoric triamide, N ‐(4‐nitrophenyl)phosphoric triamide, N ‐(diaminophosphinyl)benzamide, 4‐cyano‐ N ‐(diaminophosphinyl)benzamide, N ‐(3‐trifluoromethylphenyl)phosphoric triamide, N ‐(diaminophosphinyl)‐3‐pyridinecarboxamide, 4‐chloro‐ N ‐(diaminophosphinyl)benzamide, 4‐fluoro‐ N ‐(diaminophosphinyl)benzamide, N ‐(diaminophosphinyl)benzeneacetamide, and phosphoric triamide] for retardation of urea hydrolysis in soils was studied by determining the effects of 10 µg g −1 soil of each compound on the amounts of urea hydrolyzed when soils treated with urea were incubated at 20°C for 3, 7, and 14 d. The soils used were selected to obtain a wide range in properties, and the effects of the 12 phosphoroamides studied were compared with those of five compounds known to be among the most effective of the compounds thus far proposed for retardation of urea hydrolysis in soils (hydroquinone, catechol, 1,4‐benzoquinone, 2,5 dichloro‐1,4‐benzoquinone, and phenylmercuric acetate). The data obtained showed that most of the phosphoroamides studied were as effective as the compounds used in this comparison and that phenylphosphorodiamidate was considerably more effective than all other compounds studied.