Leaching Losses and Use Efficiency of N in Rice as Influenced by Modified Gypsum Urea

In a lysimeter experiment with rice grown on Beni silty clay loam (Aquic Hapludoll), leaching losses of N were 12.27 per cent from urea and 10.43 per cent from gypsum urea at 60 kgN ha⁻¹. The leaching losses occurred mainly in the form of NH₄-N (7–11%) followed by NO_3⁻N (1–3%) and urea (1–2%) of applied N. Increase in N levels increased the N losses significantly. Reduction in leaching loss from gypsum urea was lower than that of same level of urea. The grain and straw yield, nitrogen uptake, agronomic N use efficiency and apparent N recovery also increased.