Intercropping Wheat with Maize Under Conservation Practices Decreases CO2 Emissions in Dry Areas.

Intercropping a cool- season crop with a warm-season crop in field strips has been reported to increase soil productivity through improved soil water use in arid areas, but it is unknown if the increased productivity is at the expense of large crop input that increased greenhouse gas footprints. A field study was conducted at the Gansu Agricultural University Research Station in Wuwei (37◦96′N, 102◦64′E), northwest China, in 2011-2012. The objective was to determine crop yield, water consumption, and greenhouse gas footprints of wheat-maize intercropping under different tillage and crop residue management options. The results showed that wheat/maize intercropping increased grain yield by 61% in 2011 and 63% in 2012 compared with the corresponding monoculture crops. The intercrops under reduced tillage with crop straw mulching produced yield of 15.8 t ha^-1 which was 8% greater compared to conventional tillage. Measured using soil respiration, the wheat/maize intercropping had a carbon equivalent (eq.) emission of 2400 kg CO₂eq ha^-1 during the growing season, which was about 7% less compared to monoculture maize. Reduced tillage decreased carbon emission over conventional tillage by 6.7, 5.9 and 7.1% for the intercropping, monoculture maize, and monoculture wheat, respectively. Compared to monoculture maize, wheat/maize intercropping used more water, but emitted 3.4 kg CO₂ eq per hectare per mm of water used, which was 23% lower compared to monoculture maize. We concluded that high yield potential can be achieved through intercropping practices without actually increasing water consumption or carbon emissions per unit of input. Wheat/maize intercropping with reduced tillage coupled with crop straw mulching can be used to increase soil productivity and lower greenhouse gas footprint in arid areas.