Effect of conservation tillage on natural resources utilization efficiency and sustainability of integrated wheat-maize intercropping system

The integrated production system is effective for crop intensification and also plays an important role in improving biodiversity and grain yield. The reduction of greenhouse gas emissions and crop water consumption are important parameters in developing high-efficient and sustainable agriculture in arid areas. Researches on soil carbon emission, water use and characteristic of the integrated production system will benefit the productivity and sustainability of agricultural practices in this region. The experiment was carried out in 2011 and 2012 at the Oasis Agricultural Scientific Researching and Teaching Station of Gansu Agriculture University and Local Government, China. Wheat-maize intercropping system was used as the object of this study due to its long-term application in Hexi Oasis region. Through integration, different conservation practices, including no-till with stubble standing, no-till with stubble mulching, and reduced tillage with stubble incorporation were applied in wheat-maize intercropping system forming three integrated production systems (named NTS, NTM and RTS, respectively), with conventional intercropping (CTI), conventional monocropped maize (CTM) and wheat (CTW) as the control systems. The study mainly focused on soil carbon emission and water use characteristics of different cropping systems, and further compared the differences in system effectiveness and sustainability. Results showed that the energy yield of integrated wheat-maize intercropping system increased by 113% over monocropping wheat, and by 21% over monocropping maize, and the land equivalent ratios of integrated intercropping systems based on energy yield were greater than 1. The integrated system also significantly reduced soil CO₂ emission, especially for the NTM, of which, the soil CO₂ emission was reduced by 12% than CTM, and by 13% than CTI. Also, its' CO₂ emission efficiency increased by 39% over CTM, and by 31% over CTI. In addition, the integrated system significantly reduced the crop water consumption. Compared to CTI, NTM reduced evaporation, water consumption and carbon emission per unit of water by 11%, 5% and 9%, respectively. Nevertheless, the energy yield per unit of water improved by 19%. Compared to CTI, land (1.78), carbon (1.48) and water (1.22) equivalent ratios improved by 14%, 28% and 20% under NTM respectively. Therefore, the sustainability index was enhanced by 13% over the CTI. Consequently, the integrated wheat-maize production system can be used as a high-efficient and sustainable cropping model in the Hexi Oasis Irrigation Area.