Nitrogen management trade-offs in hybrid rice for agronomy, carbon, and energy efficiency

Efficient use of nitrogen (N) in agro-ecosystems can reduce environmental footprints, prevent degradation of natural resources and support sustainable intensification. The multifarious relationships between N application and performance of hybrid rice concerning productivity, profitability, energetics, and greenhouse gas emissions are rarely studied, particularly in coastal regions. We studied the outcomes of N application rates (0, 40, 80, 120, 160 and 200 kg N ha −1 ) on hybrid rice cultivation for two consecutive years (2017 and 2018) in the coastal region of West Bengal, India. Nitrogen application significantly ( p ≤ 0.05) influenced the grain yield of hybrid rice and 160 kg N ha −1 produced the highest average grain and straw yield of 7.7 and 5.7 t ha −1 , respectively. The relationships between grain yield and N concentrations in stem ( R 2 = 0.98), leaf ( R 2 = 0.91) and grain ( R 2 = 0.99) were significant ( p ≤ 0.05). The net energy gain was highest with 160 kg N ha −1 that declined with reduced N rates. The yield-scaled carbon footprint of hybrid rice cultivation decreased with successive increases in N application rates up to 160 kg N ha −1 . The tested hybrid rice cultivar showed superior economic performance at 160 and 200 kg N ha −1 , giving higher net returns and benefit:cost ratio over the other treatments. Based on regression analysis, the economic optimum N level was derived as 176 kg N ha −1 for hybrid rice cultivation at the coastal soils of West Bengal for higher productivity and profitability while maintaining higher net energy gain and lower carbon footprint. The study’s novelty lies in its focus on assessing N application for rice cultivation with an integrated approach of yield, economics and environmental sustainability.