耕作措施与秸秆还田方式对土壤活性有机碳库及水稻产量的影响

Effects of Tillage Practices and Wheat-straw Returned to the Field on Topsoil Labile Organic Carbon Fractions and Rice Yield

[目的]探明耕作措施和秸秆还田方式对耕层土壤(0～20 cm)活性有机碳和水稻产量的影响。[方法]于2012年在湖北省大法寺镇稻麦复种系统试验基地,设置了免耕(NT)和翻耕(PT) 2种耕作方式以及5 250(SR3)、3 500(SR2)、1750(SR1)、0 kg/hm^2(SR0) 4种秸秆还田量。[结果]与翻耕相比,免耕显著降低10～20 cm土层土壤总有机碳(TOC) 5%～21%、易氧化态碳(EOC) 7%～43%、微生物生物量碳(MBC) 10%～46%、碳库管理指数(CPMI) 6%～44%,显著降低5～10 cm土层土壤水溶性有机碳(DOC) 23%～36%。与秸秆不还田相比,处理SR3和SR2增加5～10 cm土层土壤DOC 29%～38%。处理SR3能显著降低水稻产量9%～24%。相关分析结果表明,产量与EOC呈极显著正相关,与DOC则呈显著负相关,表明EOC、DOC对于短期内稻田耕作方式与秸秆还田量的改变响应最为敏感,与作物生长密切相关。[结论]相较于传统耕作方式,短期免耕与秸秆还田不是适合砂壤土质增碳增产的技术模式。

[Objective]To study the effects of tillage practices combined with wheat-straw returned to the field on top soil(0-20 cm)liable organic carbon(LOC)and rice yield at the Dafasi in Hubei Province of China.[Method]Treatments were established following a split-plot design of a randomized complete block with tillage practices[plough tillage(PT)and no-tillage(NT)]as the main plot and wheat straw returning level[5 250(SR 3),3 500(SR 2),1 750(SR 1)and 0 kg/hm(SR 0)]as the sub-plot treatment.[Result]In 10-20 cm soil layer,compared with PT,NT significantly decreased the content of soil total organic carbon(TOC)by 5%-21%,easily oxidizable carbon(EOC)by 7%-43%,microbial biomass carbon(MBC)by 10%-46%,carbon pool management index(CPMI)by 6%-44%,decreased the water-soluble organic carbon(DOC)by 23%-36%in the 5-10 cm soil layer.Compared with SR 0,the SR 3 and SR 2 significantly increased the DOC contents by 29%-38%in the 5-10 cm soil layer.The treatment SR 3 significantly increased rice grain yield by 9%-24%.Correlation analysis showed that rice grain yield had a significant positive correlation with EOC,significant negative correlation with DOC,revaled that EOC and DOC is active organic carbon that more sensitive to the changes of tillage practices and straw returned,closely associated with crop growth.[Conclusion]Compared with traditional farming modes,short-term tillage practices and wheat-straw returned to the field is not an effectively way to increase organic carbon content and grain yield under the sandy soil.