Rice-Rape Rotation Benefits to Improve Radiation and Heat Use Efficiencies and Mitigate Global Warming Potential of Paddy Cropping Systems in Central China

摘要

Replacing bare fallow by rotation with winter cereal crops such as winter wheat and oil rape have been used to improve annual productivity in paddy cropping system in central China. However, the effects of rotation on light and heat resources utilization and greenhouse gases have yet to be measured. A two-year field experiment was conducted to compare solar radiation and heat use efficiencies, methane (CH4) and nitrous oxide (N2O) emissions and global warming potential (GWP) of two winter rotations: rice-wheat and rice-rape taking rice-fallow as a check. The results of this study showed that rice-wheat had the highest annual grain yield (two-year means were 16.2 t ha-1 ) and annual above ground biomass (32.9 t ha-1 ) followed by ricerape and by rice-fallow. No significant effect was observed for winter rotation on the performance of rice grain yield and growth, in spite of a large quantity of straw returning by winter crops. Solar radiation and heat resources utilization and their production efficiency were improved in the winter season by rotation with winter crops. Rice-wheat and rice-rape also increased light and heat resources utilization efficiency from the annual perspective. Compared with rice-fallow, CH4 flux in the rice season among the two studying years was increased by 42.0% by rice-wheat but was decreased by 35.6% by rice-rape. For the annual level, CH4 flux was promoted by 40.9% by rice-wheat and declined by 35.5% by rice-rape. For the rice season the N2O seasonal flux was increased by 54.2 and by 8.3% in rice-wheat and rice-rape plots, respectively. The values for GWP and for yield-scaled GWP were highest in rice-wheat and lowest in rice-rape system. In conclusion, rice-rape system could be a better choice to increase solar radiation and heat resources utilization and mitigate greenhouse gases emission.