Effect of amending urea fertilizer with chemical additives on ammonia volatilization loss and nitrogen-use efficiency

Abstract

 Effects of amending urea with pyrite (Py) or potassium chloride (KCl) alone and in combination with copper sulphate (CuSO₄) on NH₃ volatilization and N-use efficiency in an Alfisol were evaluated. NH₃ volatilization from surface-applied urea fertilizers was measured using a closed dynamic air flow system. Kinetics of NH₃ volatilization over a 10-day period showed that the peak rate of NH₃ loss was on day 3 with the unamended urea, whilst it occurred on day 4 with all amended urea fertilizers. Total NH₃ loss from the unamended urea was 48% of the applied N, which was reduced to 38 and 40% with U+Py and U+KCl, respectively. A further reduction in N loss was recorded with U+Py+CuSO₄ (34%) and U+KCl+CuSO₄ (36%). The inhibition of NH₃ with U+Py+CuSO₄ and U+KCl+CuSO₄ was markedly high, at 30 and 25%, respectively. As compared to urea, all amended urea fertilizers resulted in a significantly higher dry matter yield, N uptake and apparent N recovery (ANR) efficiency by sunflower. An increase of 28 and 24% units in ANR over urea could be obtained with U+Py+CuSO₄ and U+KCl+CuSO₄, respectively. Since the chemical additives also have a fertilizer value besides being effective in controlling NH₃ loss from urea and improving N-use efficiency, their use as amendment to urea could be a viable option.