Reduced Dose and Delayed Application of Nitrogen Influence Growth, Yield and Nitrogen Use Efficiency of Transplanted Aman Rice Variety BRRI dhan87

Abstract

The yield potential of rice mostly depends on judicious management and the appropriate combination of applied nutrients. A pot experiment was conducted at the Professor Purnendu Gain Field Laboratory of the Agrotechnology Discipline, Khulna University, Khulna, during the monsoon season of 2022. The experiment was conducted to study the influence of reduced doses and delayed application of nitrogen on the growth, yield, and nitrogen use efficiency of transplanted Aman rice variety BRRI dhan87 and to determine the proper nitrogen management schedule for the Aman season. The experiment was conducted in a completely randomized design consisting of three nitrogen doses: D₁ = 180 kg urea ha⁻¹ (recommended dose), D₂ = 162 kg urea ha⁻¹ (10% less), and D₃ = 153 kg urea ha⁻¹ (15% less), and three nitrogen application timings: T₁ = three split applications at 7, 25, and 40 DAT (recommended), T₂ = three split applications at 7, 35, and 50 DAT, and T₃ = three split applications at 7, 40, and 60 DAT, with three replications. The growth characteristics, such as plant height, tiller number, leaf number, and SPAD value, mostly showed a significant response to nitrogen dose rather than nitrogen application timing. However, the growth characteristics mostly exhibited a non-significant response to the combined effect of different rates and timings of nitrogen application. The performance of the yield parameters (1,000-grain weight, grain yield, biological yield, and harvest index) was found to be the best when treated with 180 kg urea ha⁻¹ (D₁) along with application timings T₁ (three split applications at 7, 25, and 40 DAT) and T₂ (three split applications at 7, 35, and 50 DAT). A 10% reduction in the urea dose from 180 kg urea ha⁻¹ to 162 kg urea ha⁻¹ did not significantly reduce grain yield. Nitrogen use efficiency (NUE) was highest with 162 kg urea ha⁻¹ applied at 7, 35, and 50 DAT (T₂D₂), while the performance of 180 kg urea ha⁻¹ and 162 kg urea ha⁻¹ applied at 7, 25, and 40 DAT (T₁) or 7, 35, and 50 DAT (T₂) was almost similar. Major yield parameters showed a positive correlation with grain yield.