Balancing grain yield and environmental performance by optimizing planting patterns of rice-wheat cropping systems

To alleviate the adverse consequences of conventional planting of the rice-wheat cropping system and achieve long-term sustainability, a 3-cycle experiment (2019-2022) was conducted to investigate the effects of six planting patterns (PPs) on the grain yield and environmental performance. PP1 entailed annual rotary tillage (RT) without straw returning but without fertilization for rice and wheat seasons. PP2 was the same as PP1 but involved fertilization. PP3 was the same as PP2 but included straw return. PP4 entailed rice planting the same as in PP3, but with innovative zero-tillage (ZT) seeding technology for wheat planting. PP5 entailed wheat planting the same as in PP4, but with rice planting involving direct paddy seeding under RT. PP6 entailed wheat planting the same as in PP4, but rice planting followed dry direct seeding under ZT. The results showed that the average total yield under PP2, PP3, PP4, PP5, and PP6 was 64 %, 54 %, 69 %, 51 %, and 54 % higher than that under PP1, respectively. The highest methane and nitrous oxide emissions occurred under PP4 and PP6, respectively. When soil organic carbon changes were included in the calculations, the carbon footprint per unit area (CF_A) was sharply reduced under PP4 and PP6, and the highest CF_A was achieved under PP1, followed by PP2. Implementing annual RT promoted soil mineral nitrogen accumulation under PP2 and PP3 after wheat harvest, increasing the risk of mineral nitrogen leaching and the nitrogen footprint per unit area than that under the other PPs. PP4 exhibited the highest ammonia volatilization, which was offset by reduced mineral nitrogen leaching. Overall, PP4 exhibited a yearly increase in the comprehensive scores obtained via Z-score analysis and yielded the highest score in the last year due to the highest annual grain yield, steady SOC increase, and lower nitrogen loss.