秸秆还田对再生稻田土壤有机碳组分的影响

  【目的】  在再生稻系统下，探讨秸秆还田对再生稻田土壤有机质组分及其养分含量的影响。  【方法】  试验设置秸秆不还田(CK)、水稻秸秆半量还田(SH)、水稻秸秆全量还田(SW)和水稻秸秆全量还田配施腐熟剂(SWF)共4个处理，分析各处理土壤有机碳及其组分和土壤速效养分含量。  【结果】  与秸秆不还田相比，秸秆还田能提高土壤有机碳及其组分含量。与CK处理相比，在头季和再生季水稻收获期，秸秆还田处理(SH、SW、SWF)土壤中水溶性有机碳含量分别增加了19.62%～22.63%、20.99%～41.48%；土壤中颗粒有机碳含量分别增加了8.47%～20.62%、24.71%～30.90%；三个施秸秆的处理间土壤总有机碳、胡敏酸和富里酸含量无明显差异。秸秆还田可以改变水溶性有机质结构，使其结构趋于简单。秸秆还田下土壤碱解氮、有效磷、速效钾和铵态氮含量均呈增加趋势；在头季水稻收获期，SWF处理的碱解氮、有效磷和速效钾含量显著高于CK处理。在再生季水稻收获期，与头季稻收获期相比，CK处理土壤速效养分含量呈下降趋势，而秸秆还田下各处理速效养分含量均呈增高趋势。  【结论】  秸秆还田可以提高再生稻田土壤有机碳、颗粒有机碳、水溶性有机碳以及腐殖酸组分的含量，促进水溶性有机质结构的变化，从而有效改善土壤养分的供给能力。

Effects of straw returning on soil organic carbon components in ratoon rice field

  【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.