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

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 surf ace-applied urea fertilizers was measured using a closed dynamic air flow s ystem. 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 occur red on day 4 with all amended urea fertilizers. Total NH3 loss from the una mended 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 recorde d 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. A s compared to urea, all amended urea fertilizers resulted in a significantl y higher dry matter yield, N uptake and apparent N recovery (ANR) efficienc y by sunflower. An increase of 28 and 24% units in ANR over urea could be o btained with U+Py+CuSO4 and U+KCl+CuSO4, respectively. Since the chemical a dditives also have a fertilizer value besides being effective in controllin g NH3 loss from urea and improving N-use efficiency, their use as amendment to urea could be a viable option.