Food security has become a global issue, seriously threatening developing countries owing to fast-growing human populations and declining availability of land for agriculture. Increasing crop yields could be achieved by intensive systems, but these usually need higher energy and emit more carbon (C). Here, we studied crop productivity, energy yields, and C emissions of intercropping versus sole cropping. We tested maize-wheat, maize-rape, maize-pea, and soybean-wheat intercropping, and sole crops as controls in field experiments at Wuwei experimental station in from 2009 to 2011 in a randomized block design with three replicates. We used an evaluation index integrating yield and environmental factors. Results showed a yield increase of 27 % for maize-wheat, 41 % for maize-rape, and 42 % for maize-pea versus sole crops. Water use efficiency increased by 25 % for maize-wheat intercropping over sole wheat, 152 % for maize-rape over sole rape, and 95 % for maizepea over sole pea. The three maize-crop intercrops produced 68, 308, and 256 % more energy yield than did the sole wheat, sole rape, and sole pea crops, respectively. They emitted 42, 52, and 45 % less C per unit of water in 2009, 2010, and 2011, respectively, compared with the sole maize crop. The maize-based intercropping received a the highest evaluation index (0.82 out of 1.0) among the systems evaluated, clearly showing that the maize-based intercropping is the most effective and sustainable cropping system for arid irrigation areas.
