SOIL UREASE INHIBITION BY THERMAL POLYMERS OF THIOPOSPHORYL TRIAMIDE AND PHOSPHORYL TRIAMIDE

Ammonia volatilization losses from urea applications are particularly high when urea is not mixed well into soils. These losses have been shown to be reduced by use of urease inhibitors, but as yet there has been no commercial development of these materials. The effectiveness of urease inhibitors formed by the thermal polymerization of phosphoryl triamide (PTA) and thiophosphoryl triamide (TPTA) was investigated under carefully controlled experimental conditions. The PTA-derived thermal polymers showed less apparent urease inhibitory activity than phenyl phosphorodiamidate (PPDA) but were nearly equal or slightly better than PTA itself. The TPTA-derived polymers were significantly better urease inhibitors than their PTA-derived counterparts. Several of the PTA-derived products had greater persistence than PPDA. The urease inhibition in soils indicated that the optimum chain length for these polymeric inhibitors may be from two to four.