Effect of Natural Inhibitors on the Transformation of N-Fertilizer and Yield of Rice

A field experiment was conducted at Sher-e-Bangla Agricultural University Farm, Dhaka 1207 during the kharif season of 2008–2009 to study the effect of natural inhibitors on transformation of N-fertilizer and yield of rice. The experimental soil was clay loam in texture having pH of 6.3. The treatments used were 3 levels of urea fertilizer (N) viz. F₁ = low (80 kg N/ha), F₂ = medium (100 kg N ha⁻¹), F₃ = high (120 N kg ha⁻¹) and 5 types of inhibitors viz. I₀ = no inhibitor, I₁ = neem oil, I₂ = neem cake (dust), I₃ = tar, I₄ = DCD (chemical inhibitor). So there were 15 treatment combinations with 3 replications. The results demonstrated that use of neem oil along with urea fertilizer increased grain yield. The maximum significant grain yield was obtained with the treatment combination of F₂I₁ (medium N + neem oil). The use of neem oil and neem cake with medium dose of urea fertilizer increased fertilizer use efficiency. It was also observed that significant amount of available nitrogen (NH₄⁺ + NO₃⁻) was found during the entire growing period due to combined application of neem product and fertilizer. Observation revealed that the amount of NO₃⁻ - N was higher than that of NH₄⁺-N in all the sampling stages.