Assessing water and nitrogen footprints of alternative cropping systems across the precipitation gradient of the North China Plain

Alternative cropping systems can sustain productivity and reduce impacts (e.g., excessive groundwater exploitation, nitrogen losses), but microclimate impacts in diversified systems are mostly unexplored. The aim of this study was to explore innovative cropping systems to reduce water use and nitrogen losses across different precipitation gradients. The well–calibrated Agricultural Production Systems sIMulator (APSIM) model and life cycle assessment were combined to analyze the water and nitrogen footprints of five alternative cropping systems, namely, spring maize–winter fallow (sM–F), winter wheat–summer fallow (WW–F), winter wheat–summer maize–winter fallow–spring maize (WW–M–sM), ryegrass–spring maize (R–sM) and winter wheat–summer maize (WW–M) in the North China Plain from 1980 to 2020. Our findings indicate the total water footprint (m³/10³ MJ) followed the order: WW–F (70) > WW–M (43) = sM–F (43) > R–sM (42) > WW–M–sM (41), while the total nitrogen footprint (g N–eq/10³ MJ) followed a different order: WW–F (423) > WW–M (335) > R–sM (246) > WW–M–sM (212) > sM–F (96). Green and blue water footprints were the primary contributors to the total water footprint for all cropping systems, but the proportion of grey water footprint increased across the precipitation gradient due to higher nitrate leaching. Ammonia volatilization and nitrate leaching were the primary factors contributing to nitrogen losses for all cropping systems, depending on drainage and N application. The most promising alternative cropping systems for sustaining groundwater use and mitigating nitrogen losses shift from sM–F and WW–M–F at dry sites to R–sM at wet sites. These findings highlight the importance of diversifying cropping system to the local climate, offering a scientific basis for green agriculture development across diverse regions in China.