A MODIFIED UREA BASED NP FERTILIZER - UREA-TSP-MAP COMBINATIONS

Applying urea with acidic phosphate fertlizer increases urea fertilize r efficiency by reducing ammonia volatilization and toxicity to crop f rom urea hydrolysis. However, urea and triple superphosphate (TSP) are not recommended to be cogranulated because blends might become wet an d sticky. Monoammonium phosphate (MAP) is a less acidic P source than TSP, but is compatible with urea. The objective of this study was to e valuate compound NP fertilizer products made from MAP and TSP combinat ions as P sources with urea. Fertilizer mixtures were pelletized from commercial urea, TSP and MAP with different N:P2O5 ratios and MAP/TSP combinations. Moisture changes during storage, pH of fertilizer soluti ons, and ammonia volatilization from surface applied fertilizer pellet s were measured. Using MAP with TSP in urea-P mixtures reduced moistur e increases during storage. Increasing MAP in urea-TSP-MAP combination s increased fertilizer solution pH by over 1 unit as the MAP/TSP-P2O5 ratio increased from 0/100 to 100/0. Adding MAP as 50% of P in urea-MA P-TSP mixtures at 3:1 and 1.5: (N:P2O5) ratios reduced ammonia loss fr om urea 50% to 60% compared to urea alone; and ammonia loss was simila r to that of urea-TSP combinations. A urea-TSP-MAP fertilizer combinat ion could make efficient use of urea-N by crops by reducing ammonia lo ss from urea hydrolysis.