Response of Aus Rice Cultivars to Different Nitrogen Levels

Abstract

Nitrogen is recognised as the most limiting nutrient element in the soils of Bangladesh, and the application of nitrogenous fertilisers has become indispensable for achieving desirable rice yields. Consequently, nearly all rice farmers rely on relatively costly nitrogen fertilisers to sustain productivity and meet production demands. However, modern high-yielding rice varieties may differ considerably in their capacity to absorb, accumulate, and utilise nitrogen derived from both indigenous soil reserves and applied fertiliser sources. Understanding these varietal differences in nitrogen uptake and utilisation efficiency is essential for optimising fertiliser management strategies, enhancing nitrogen use efficiency, reducing production costs, and improving the sustainability of rice cultivation systems. An experiment is conducted at the Agronomy Field Laboratory of Bangladesh Agricultural University, Mymensingh, from April to September 2022 to evaluate the response of Aus rice cultivars to different nitrogen (N) levels. The study was laid out in a Randomized Complete Block Design (RCBD) with three replications, consisting of five cultivars (Porangi, Mala boro, Binadhan-19, BRRI dhan48, and BRRI dhan83) and four nitrogen levels (0, 40, 80, and 120 kg N ha⁻¹). The results revealed that both cultivars and nitrogen levels significantly influenced grain yield and yield-contributing traits, and their interaction effect was also significant. Among the cultivars, Mala boro produced the tallest plants, while BRRI dhan48 showed superior performance in most yield attributes, including total and effective tillers per hill, panicle length, grains per panicle, 1000-grain weight, grain yield, straw yield, and biological yield. In contrast, Porangi produced the highest number of non-effective tillers and sterile grains, whereas Binadhan-19 recorded the highest harvest index. Nitrogen application had a significant effect on all parameters, with the highest values for most yield components and grain yield observed at 120 kg N ha⁻¹. The interaction results indicated that BRRI dhan48 combined with 120 kg N ha⁻¹ produced the highest grain yield (5.17 t ha⁻¹), straw yield (5.47 t ha⁻¹), and biological yield (10.63 t ha⁻¹), along with the lowest number of sterile grains. Therefore, BRRI dhan48 with 120 kg N ha⁻¹ can be considered a promising combination for maximizing Aus rice production.