One‐time N fertilization reduces greenhouse emissions and N leaching while maintaining high yields in a rape–rice rotation system

Abstract

AbstractIn China, the rice (Oryza sativa L.)–rapeseed (Brassica napus L.) rotation system is facing great challenges, including constantly growing demand, on‐going labor shortages, and increasing environmental burdens. Thus, producing more food and higher benefits while minimizing environmental costs is required for future development. A 2‐yr field experiment comparing three nitrogen (N) fertilization treatments (non‐N treatment as control [CK], conventional urea application [CU], one‐time application of controlled‐release urea [CRU]) was performed. Results showed that the rice season dominated annual CH4 emissions (>95%) and on average contributed more than 50% of the annual N2O emissions. Additionally, the main forms of mineral N leaching were different for rape and rice. Nitrate (NO3–)–N was the major component of leaching in rape season, while for rice season NO3––N and NH4+–N were equal. Relative to CU, CRU significantly increased the rapeseed yield by 10.7∼13.9% and maintained the rice productivity, reduced mineral N leaching losses by 19.6∼20.8% for the rice season, and resulted in less total methane (CH4) and nitrous oxide (N2O) emissions (TGHGs) by 12.1% across the two rotations. Furthermore, a net economic benefit (NEB) considering yields, fertilizer input, labor, and other input costs indicated CRU increased the economic return by 58.3%. However, CRU did not improve partial factor productivity of nitrogen fertilizer (PFPN) and decreased the NEB by 3.1% without considering the labor cost. It indicated a one‐time application of the CRU for rice–rapeseed rotation system was an environmentally and economically profitable technology. This paper provided a promising solution for farmers to enhance rice–rapeseed productivity and increase income while minimizing the environmental footprint.