The Effects Of Straw Incorporation On Crop Yield And Greenhouse Gas Emissions Under Rice-Wheat Cropping Systems

In order to assess the effects of straw incorporation on net ecosystem economic budget?NEEB?,this study analyzed changes in reducing substance,functional microbial gene abundance,greenhouse gas?GHG?emissions and crop yield under different straw retuning treatments.The treatments were arranged with a split-plot design of a randomized complete block.The main plots was straw returning level including no straw application?CK?,1/3 preceding crop straws?1CS?,2/3 preceding crop straw?2CS?,and all preceding crop straw?TCS?incorporated into the soil.Our results are shown as follows.?1?Concentrations of reducing substances and active reducing substances increased with increasing amount of straw incorporation.Compared with CK,1CS,2CS and TCS treatments significantly increased concentrations of reducing substances by 43%,17%and 23%,and active reducing substances 48%,49%and 18%respectively.But reduced redox potential?Eh?under straw incorporation treatments was observed.?2?Straw incorporation remarkably affected on functional gene abundances.1CS,2CS and TCS treatments increased mcrA abundances by 27%,29%,and 15%compared with CK.Straw incorporation did not affect pmoA abundance.Straw incorporation significantly reduced nitrous oxide genes.Compared with CK,1CS and 2CS treatments,TCS treatment reduced the abundance of AOA by 8%,15%and 5%,abundance of AOB by 18%,11%and 4%,abundance of nirS by 13%,12%and 7%,abundance of nirK by20%,5%and 6%,and abundance of AOB by 20%,5%and 5%,respectively.?3?CH₄ mainly emitted in summer and two peaks were observed at the tillering and booting stage.In comparison with CK,cumulative CH₄ emissions under 1CS,2CS and TCS treatments were significantly increased by 60%,21%,and 26%,respectively.Peaks of N₂O emissions were found immediately after each N fertilization.Application of straw incorporation significantly reduced N₂O emissions.In comparison with CK,1CS,2CS and TCS treatments significantly reduced cumulative CH₄ emissions by 18%,39%,and38%,respectively.?5?Straw incorporation significantly affected crop yield.Compared with straw incorporation treatments,CK significantly decreased crop yield by 6.7%-9.4%.?6?Straw incorporation significantly influenced NEED;the NEED followed the order of CK?TCS?1CS and 2CS.1CS and 2CS treatnebts resulted in 12.5%and 3.5%of increases in NEED compared with TCS treatment,respectively.In conclusion,1/3 preceding crop straw incorporation into the soils not only increased crop yield and reduced GHG emissions,but also led to the highest NEEB.Therefore,this measure is a better way to deal with crop straws for increasing farmer incomes,reducing the phenomenon of straw burning,rolling back the spectre of a warming planet,improving soil fertility and protecting agricultural soil microbial diversity.