Abstract:

In order to study the effects of straw returning on soil active organic carbon components and carbon cycle related enzyme activities in rice-rape rotation farmland of Chengdu Plain,we carried out 3-year straw returning field experiment(2017—2020),including no straw(CK),chemical fertilizer alone(NPK),50% straw returning and chemical fertilizer(SR1),100% straw returning and chemical fertilizer(SR2),200% straw returning and chemical fertilizer(SR3).We measured soil physical-chemical properties,soil organic carbon content(SOC),soil labile organic C fractions,carbon cycle related enzymes,and their correlations.The results showed that straw returning could effectively improve soil physical-chemical properties,soil available nitrogen,phosphorus and potassium contents.Compared with CK treatment,straw returning treatments significantly increased SOC,ROC,DOC,and MBC contents by 5.05%—8.55%,18.40%—36.80%,35.76%—66.93% and 27.20%—52.10%,respectively.In general,higher returning dosage resulted in higher C content.On the other side,compared with CK and NPK,straw returning treatments significantly increased soil cellulase,β-glucosidase,catalase,polyphenol oxidase.The activities of soil cellulase,β-glucosidase,and polyphenol oxidase under SR2 treatment were the highest,which were significantly higher than SR1 treatment by 16.25%,8.49%,and 14.69%,respectively.The catalase activity of SR3 treatment was the highest,which was significantly higher than that of SR1 treatment by 25.10%(P<0.05).There were significant positive linear correlations among soil SOC,labile SOC fractions,and carbon cycle related enzyme activities.Consequently,full straw returning has been proved of the most efficient way of improving active organic carbon components,carbon cycle related enzyme activities,and promoting the improvement of soil quality in rice-rape rotation farmland of Chengdu Plain.

Key words: Rice-rape rotation, Straw returning, Soil active organic carbon components, Enzyme activity