Grain yield and greenhouse gas emissions from maize and wheat fields under plastic film and straw mulching: A meta-analysis

Understanding the effects of soil mulching on crop yields and greenhouse gas (N2O, CO2 and CH4) emissions is important for developing sustainable agriculture. However, no systematic conclusions have been drawn yet because the environmental factors vary among various studies. A meta-analysis was carried out to evaluate the impact of plastic film mulching (PM) and straw mulching (SM) on grain yields and greenhouse gas emissions from two major cereal crops (maize and wheat) based on data from 61 peer-reviewed publications. The results showed that PM and SM, when averaged across all studies, significantly increased maize yield (13.3 % and 7.3 %, respectively) and wheat yield (12.5 % and 3.5 %, respectively) compared with no-mulching (NM). Generally, PM and SM significantly increased N2O emission by 18.6 % and by 24.7 % compared with NM, respectively. CO2 emission was significantly increased by PM and CH4 uptake was significantly inhibited by PM, while the increase in CO2 emission under SM was not significant but CH4 uptake was significantly promoted. The impact of soil mulching on crop yields and GHG emissions was also affected by temperature, water input amount, cultivation practice and nitrogen (N) application rate. Specifically, ridge-furrow cultivation with plastic film on the ridge was highly recommended for maize production, especially when mean seasonal air temperature was <20℃ and water input was <350 mm. Straw mulching was more suitable for maize production under high temperature (>20℃) and water input (>350 mm). The effect of SM on the increase in wheat yield under low water input (<350 mm) and moderate temperature (>10℃) was not significantly worse than that of PM. N2O and CO2 emissions under SM in the wheat field were not significantly increased compared to NM, while these emissions under PM were significantly increased when water input was <350 mm and temperatue >10℃. However, PM should be given more consideration in wheat production because its greater effect size on wheat yield and lower effect size on N2O emission relative to SM under most classifications, especially under partial mulching. These results have important implications for choosing proper mulching practices to increase crop yields while decreasing the adverse environmental effects in agricultural production.