Management practices to improve economic benefit and decrease greenhouse gas intensity in a green onion-winter wheat relay intercropping system in the North China Plain

Abstract

The simultaneous effects of N fertilizer management and straw returning on net economic benefit (NEB) and greenhouse gas intensity (GHGI) in a green onion-winter wheat relay intercropping system in the North China Plain are not well understood. A two-year field experiment was conducted to evaluate the effects of N fertilizer management and straw returning on yield, NEB, and GHGI, i.e. yield-scaled net global warming potential (NGWP) and NEB-scaled NGWP, over two seasons of green onion-winter wheat relay intercropping system. The five treatments included in the field experiment were no fertilization (CK), farmer's practice (FP), optimized fertilization (OPT), optimized fertilization with 25% nitrogen input (OPT-N), and optimized fertilization + straw returning (CN). We found that compared with CK, the treatments FP, OPT, OPT-N and CN increased the total yield of wheat and green onion by 18.3%, 35.3%, 26.7% and 48.0%, respectively, and NEB by 13.8%, 41.7%, 31.1% and 53.4%, while decreasing the yield-scaled NGWP by 47.9%, 63.4%, 56.3% and 97.2%, and the NEB-NGWP by 46.7%, 66.7%, 56.7% and 96.7%, respectively. When compared to FP, treatments with lower N rates (OPT, OPT-N and CN) resulted in higher yield and NEB, and lower yield-scaled NGWP and NEB-scaled NGWP. This suggests that a reasonable reduction of N fertilizer rate could reduce GHGI without compromising yield or NEB. In practice, we recommend optimized fertilization combined with straw returning be a promising practice for achieving agronomically and economically sustainable green onion-winter wheat production in the North China Plain.