Short-term response of farmland carbon emission to straw return, two-year plastic film mulching and intercropping

In conventional crop production, high yield has always meant high carbon emissions. It has therefore become urgent to develop theoretical and practical strategies for high yield with low carbon emissions in modern agriculture. In this study, a field experiment was conducted in a typical oasis irrigation region to determine the integrated response of carbon emission in wheat-maize intercropping systems under different straw-return (straw standing, straw mulching and no-mulching), plastic film mulching (mulching for one year and two years), cropping (wheat-maize intercropping, monoculture of wheat and maize) and tillage (no-tillage, conventional tillage) patterns. The results showed that intercropping significantly decreased soil carbon emissions in farmlands. Compared with monoculture wheat and maize under conventional tillage management, the averaged total soil CO₂ emissions in wheat-maize intercropping systems reduced by a range of 279–876 kg·hm^-2, the equivalent of 5.1%–16.0%. No tillage with straw-return and plastic film mulching for 2-year reduced soil carbon emissions in the next year. No-tillage in combination with straw-return to soil decreased total soil CO₂ emissions by 648–966 kg·hm^-2, the equivalent of 21.3%31.8%, than conventional tillage without straw-return to soil in mono-cropped wheat field. Plastic film mulching for two years reduced total soil CO₂ emissions by 632 kg·hm^-2 compared with that of conventional tillage in mono-cropped maize. In particular, wheat-maize intercropping in combination with straw-return to soil and 2-year plastic film mulching further reduced the carbon emissions. Compared with conventional intercropping with plastic film mulching for 1-year and conventional tillage (CTI₁), wheat-maize intercropping with 25–30 cm of standing straw, 2-year plastic film mulching and no-tillage (NTSSI₂) and wheat-maize intercropping with 25–30 cm straw mulching on the soil and 2-year plastic film mulching and no-tillage (NTSI₂) reduced total soil CO₂ emissions by 471 kg·hm^-2 and 518 kg·hm^-2, the equivalent of 9.2% and 10.1%, respectively. The carbon sequestration potential (ratio of total plant carbon fixation to total soil carbon emission, i.e., NPPC/Ras) were 13.7 and 14.0, respectively, in NTSSI2 and NTSI₂ treatments, they were higher by 19.1% and 21.5% than that of CTI₁, respectively. This indicated that NTSI₂ had a more prominent potential for reducing carbon emissions and enhancing carbon sequestration. Thus, NTSI₂ was recommended as the best farming pattern due to its high-efficiency of carbon emission reduction and carbon sequestration in irrigated arid oasis regions.