Effects of coating agents on nitrogen dynamics and yield of wheat (Triticum aestivum L.) under irrigated and rainfed conditions

Nitrogenous (N) fertilizers are widely applied in agriculture for improving crop yield. However, significant quantity of chemically-applied N is lost leading to low nitrogen use efficiency (NUE). Therefore, two laboratory incubation studies were designed to evaluate the effects of different coating agents [no coating, neem (Azadrichta indica) oil coating and potassium ammonium phosphate (PAP) coating) on urea hydrolysis and nitrification under varying temperatures (25, 35 and 40 °C) and moisture regimes (30, 60 and 90% of field capacity). Results revealed that the NH₄⁺ and NO₃^- concentrations increased both with temperature and moisture levels. Using the organic-coated neem oil coated urea (NOCU) significantly reduced the release of NH₄⁺ and NO₃^-. Thereafter, a field experiment was conducted to explore the best coating agent [N₀, 100% conventional urea, 75, 50 and 25% of recommended neem oil coated urea (NOCU)] using irrigated (Akbar-2019) and rainfed (Barani-2017) wheat cultivars. Even the reduced rates (50%) of the recommended NOCU performed at par to 100% recommended uncoated urea fertilizers. Application of 1% NOCU @ 75% of the recommended urea resulted in maximum grain yield (3.65 Mg ha^{- 1}), N in roots (0.87%), N in straw (0.85%) and N in grains (1.07%) in irrigated wheat variety (Akbar-2019). Thus, using 1% neem oil coated urea @ 75% of the recommended uncoated urea has the potential to enhance the growth, yield, N uptake and NUE in wheat effectively under both rain fed and irrigated conditions.