Effect of cover cropping on soil greenhouse gas emissions during summer fallow under manipulated rainfall

doi:10.11686/cyxb2017263

Abstract

Abstract: Cover cropping during the summer fallow period has various ecological benefits in dryland farming systems. However, its effect on greenhouse gas (CO₂, N₂O and CH₄) emissions is not well known. A rainfall-manipulated winter wheat pot experiment was carried out to investigate the effects of cover cropping on soil greenhouse gas emissions during summer fallow under different rainfall patterns. Two rainfall treatments (ambient and 50% ambient) and different cover crops (ryegrass 21.4 kg·ha^-1, Changwu soybean at a rate of 82.5 kg·ha^-1, ryegrass 10.7 kg·ha^-1 plus Changwu soybean 41.25 kg·ha^-1 and a no crop control) were compared in a completely randomized design. Soil CO₂, N₂O and CH₄ fluxes were measured using a static chamber gas chromatograph. Both CO₂ and N₂O were emitted but the soil acted as a weak sink for CH₄.The effects of both rainfall pattern and cover cropping were significant for soil greenhouse gas emissions during the summer fallow period. Compared with ambient rainfall, 50% rainfall decreased daily mean CO₂ and N₂O flux by 33% and 17.9% respectively, but had no effect on CH₄ flux when averaged across all cover crops. Compared with the control, ryegrass, Changwu soybean and the ryegrass/soybean mixed increased the daily mean CO₂ flux by 140.8%, 135.6% and 137.7%, and decreased the daily mean N₂O flux by 8.0%, 21.8% and 27.4%, respectively. There was no significant difference among different cover crops in CO₂ flux, the differences in N₂O flux between ryegrass with other two cover cropping treatments were significant. The daily mean CH₄ uptake in Changwu soybean was lower by 65.8%, 63.7% and 68.9% compared with those in the fallow control, ryegrass and mixed, respectively. Averaged across cover crops, the average global warming potential was 26.1% lower while greenhouse gas intensity was 47.2% higher under 50% compared to ambient rainfall. Averaged across rainfall patterns, the global warming potential was 67.9%, 65.5% and 67.8% higher in ryegrass, Changwu soybean and the ryegrass/soybean mixed respectively than the fallow control. Compared with ryegrass and the ryegrass/soybean mixed, Changwu soybean had a higher shoot biomass and a lower green house gas intensity, indicating that Changwu soybean is more suitable for cover cropping during the summer fallow period in the dryland areas of the Loess Plateau.

Key words: rainfall manipulation, cover crop, greenhouse gas emission, global warming potential

GE Xiao-rong, WANG Jun, ZHANG Qi, FU Xin, LI Zhi-peng. Effect of cover cropping on soil greenhouse gas emissions during summer fallow under manipulated rainfall[J]. Acta Prataculturae Sinica, 2018, 27(5): 27-38.

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