Integration of wheat-maize intercropping with conservation practices reduces CO2 emissions and enhances water use in dry areas

Crop intensification has been used as a mean to increase crop yield and secure food supplies in developing countries. However, issues about CO2 mitigation, water consumption, and the overall viability associated with the crop intensification have become a concern. The main objective of this study was to investigate how the yield related environmental factors, i.e. soil CO2 emission and crop water use would responsed to wheat-maize intercropping with conservation practices. Here we determined crop yield, plant biomass carbon, soil CO2 emission, and crop water use in various cropping systems. The field experiment was conducted at Wuwei Experimental Station in an arid oasis region (37°57′N, 102°37′E), in 2011 and 2012. Four tillage and crop residue options were applied to wheat-maize intercropping. They were (a) no-till with stubble standing (NTS), (b) no-till with stubble mulching (NTM), (c) reduced tillage with stubble incorporated into the soil (RTS), and (d) conventional tillage without stubble retention (CT). Averaged across two years, wheat-maize intercropping integrated with no-till and stubble mulching yielded 1.6 t ha−1 more grains and 7.1 MJ ha−1 more energy, while emitted 1.2 t ha−1 less soil CO2 than conventional wheat-maize intercropping; at the same time, the system increased plant biomass carbon by 16%, and enhanced CO2 emission efficiency per unit of grain yield by 39%, compared with the conventional system. Also, the integrated system decreased soil evaporation by 11%, increased energy yield per unit of water by 19%, and lowered CO2 emission per unit of water by 9%. Among the wheat-maize intercropping systems evaluated, the treatment with no-till and crop residue mulched on the soil surface had the highest evaluation index at 0.82; this was attributable to the increases of carbon emission efficiency by 48% and water use efficiency by 22%, compared with the conventional system. Wheat-maize intercropping integrated with no-till and stubble retention can be used to increase crop yield efficiently while reducing soil CO2 emission and enhancing crop water use effectively in dry areas.