Evaluation of Nitrogen Uptake, Growth, and Yield of Rice Affected by Green Manure and Chemical Nitrogen Fertilizer

To investigate the combined effect of green manures (GMs) and chemical nitrogen (N) fertilizer on N uptake, growth, and yield of rice, a pot experiment was conducted at the Department of Agronomy, Yezin Agricultural University (YAU). The experiment was conducted from December to June (the summer season) of 2023. The study used a split-plot design with three replications. Chemical N fertilizer was assigned as the main plot factor and different levels of N0%, N25%, N50%, N75%, and N100% were applied based on the N recommended rate (102 kg ha-1) (1.55 g pot-1) of the Sinn-thu-kha rice variety. GM crops were the subplot factor, including no GM (G0), rice bean (GRB), sunn hemp (GSH), and dahincha (GDC). According to the results, N75 and N100 produced the higher dry matter, N uptake, yield, and yield components of rice. The highest growth characters, N uptake, and yield were found in N100 for N levels, GSH for GM levels, and N100GSH as the combined effect. However, similar values were found in the treatment N75GSH. Statistically, the GSH + chemical N treatment produced higher N uptake and yields than those of GRB or GDC + chemical N treatment. When chemical N fertilizers were applied without the use of GMs, the rice yields were lower in comparison to the treatments GMs + N25 or N50 or N75 or N100. In conclusion, combining GSH with either 75% or 100% chemical N resulted in optimal performance for soil nutrient content, growth, N uptake, and rice yield. Additionally, it was observed that the use of chemical N fertilizers was reduced by 25%, which can help mitigate environmental pollution and improve soil health and rice production in the long run.