Evaluation of compacted urea fertilizers prepared with acid and non-acid producing chemical additives in three soils varying in pH and cation exchange capacity; II. Yield and N use efficiency by rice

With a view to evaluate the effect of different chemical additives on the efficacy of urea, a green house study was conducted with wet season rice (Oryza sativa L.) as test crop. The results showed that compaction of phosphogypsum (PG), diammonium phosphate (DAP), ZnSO₄, NH₄Cl or KCl with urea increased the rice yield and N use efficiency as compared to that obtained with straight urea. A significant positive correlation between potential N loss (measured by soluble N in floodwater) and NH₃ volatilization (measured by forced air draft system) was observed. The results clearly indicate that N use efficiency can be increased through suitable modification of urea by compacting it with acid and non-acid producing fertilizers such as NH₄Cl, KCl, ZnSO₄ and DAP or industrial byproduct like phosphogypsum.