Plastic film mulch combined with adding biochar improved soil carbon budget, carbon footprint, and maize yield in a rainfed region

Plastic film mulch is used widely in rainfed areas to increase crop yields, and the addition of biochar to soil has been proposed as an effective measure for reducing greenhouse gas emissions. Comprehensive analysis is required to assess the effects of plastic film mulching combined with adding biochar on the net ecosystem carbon budget (NECB), greenhouse gas emissions, and water use efficiency (WUE) in farmland ecosystems. Therefore, we tested the following six treatments in a three-year (2018-2020) field trial: no mulching or added biochar (NM); biochar applied at 4.5 t ha(-1) without mulching; biochar applied at 9.0 t ha(-1) without mulching; plastic film mulch without biochar application (PM); biochar applied at 4.5 t ha(-1) with plastic film mulching; and biochar applied at 9.0 t ha(-1) with plastic film mulching (PMH). The results showed that plastic film mulching improved the maize yield (20.22%), greenhouse gas emissions (CO2: 22.57%; N2O: 17.58%), NGWP (net global warming potential; 15.19%), and CF (carbon footprint; 13.97%), but the effect on NECB did not differ significantly from that under NM (P > 0.05). Compared with PM, PMH reduced the CO2 (3.24%) and N2O (26.44%) emissions, increased the absorption of CH4 by 65.55%, and significantly increased NECB. Under PMH, the maize yield, WUEg (water use efficiency of grain), and PUEg (precipitation use efficiency of grain), increased by 6.40%, 10.14%, and 6.92%, respectively, whereas the NGWP, GHGI (greenhouse gas intensity), and yield-scaled CF decreased. Therefore, PMH simultaneously improved the productivity, production efficiency (WUE, PUE, and yield-scaled CF) and soil carbon budget in rainfed farmland, as well as reducing greenhouse gas emissions into the atmosphere, and thus it is a possible sustainable management method for farmland in rainfed areas.