Objectives Under the ratoon rice system, the effects of straw returning on the soil organic carbon components and nutrient contents were investigated through field plot trials.
Methods In a ratoon rice system experiment, four rice straw treatments were designed, including no rice straw returning (CK), straw return of 7500 kg/hm2 (SH), straw return of 15000 kg/hm2 (SW) and organic matter-decomposing inoculant application plus straw of return 15000 kg/hm2 (SWF). The soil organic carbon and its components and soil nutrient contents were analyzed.
Results Compared with the control, straw returning could improve the contents of soil organic C and its components in ratoon rice fields. Compared with CK treatments at the harvesting stage of the main rice and ratoon rice, the contents of dissolved organic C in the straw returning treatments (SH, SW, SWF) were increased significantly by 19.62%–22.63% and 20.99%–41.48%, respectively. The content of particulate organic C was increased significantly by 8.47%–20.62% and 24.71%–30.90%, respectively. The difference of soil organic C, humic acid and fulvic acid among the three straw treatments was not obvious. The straw returning could change the structures of dissolved organic matter, making them tend to simple. The contents of alkaline N, available P, readily available K and NH4+-N all showed an increasing trend under straw returning. At the main rice harvest, the alkaline N, available P and readily available K in SWF treatment were significantly higher than those in CK. At the ratoon rice harvest, compared with main rice harvest, soil available nutrient content of CK treatment decreased, while those of straw treatments increased.
Conclusions Straw returning can increase the content of soil organic carbon, particulate organic carbon, dissolved organic carbon and humic acid components in ratoon rice field, the soil dissolved organic matter structure tended to change, and the supply capacity of soil nutrients is improved.
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