Short-term influence of straw return on the contents of soil organic carbon fractions,enzyme activities and crop yields in rice-wheat rotation farmland

【Objectives】Straw return is an effective way to recycle straw resources,improve soil fertility and increase crop yields. The amount of straw return affects the soil labile organic carbon pool,soil enzyme activity and crop yields in different extent,so it is meaningful to study the suitable straw returning amount for best yield and soil fertility efficiencies. 【Methods】A field trail with a random block design was carried out in rice- wheat rotation farmland with three replicates. There were totally seven treatments in the trail: non- straw return in both rice and wheat season( CK),25%,50%,75% and 100% of total straw from previous crop returned in rice or wheat season,and 100% of straw returned only in rice or wheat season. Both the rice and wheat yields were investigated and the soil labile organic carbon pool and enzyme activity were measured. 【Results】1) Compared to the CK,straw return could improve the contents of soil labile organic carbon fractions and soil enzyme activities,and increase both yields and their components of rice and wheat. 2) The highest soil total organic carbon( TOC) andmicrobial biomass carbon( MBC) contents are turned out with the straw return proportion of 50% in both rice and wheat seasons,and the highest soil dissolved organic carbon( DOC),labile organic carbon( LOC) and carbon pool management index( CPMI) are in proportion of consecutive 25%. 3) The consecutive 25% of total rice and wheat straw return induces the most significantly soil urease,catalase and sucrase activities. 4) Both the yields of rice and wheat in the treatments of consecutive 25% and 50% of rice and wheat straw return are significantly higher than in CK,with the increases of 9. 0% and 11. 45%,respectively. 5) The correlations among soil carbon pool,soil enzyme activities and the crop yields are significant. 【Conclusions】Under the condition of this experiment,the consecutive returning of 25% and 50% of the rice and wheat straw could significantly increase soil carbon sink capacity,and improve the crop yields in short term.