紫云英还田配施氮肥对稻田土壤碳库的影响

Effects of combined application of Chinese milk vetch(Astragalus sinicus L.) and nitrogen fertilizer on paddy soil carbon pool

紫云英是南方稻田重要的绿肥作物,研究紫云英还田配施氮肥对土壤有机碳及其活性的影响,有助于优化稻田施肥管理和培肥土壤,为南方稻田农业可持续发展提供理论依据。本研究采用紫云英-水稻周年轮作田间试验,设置冬闲+不施氮(CK)、单种紫云英返田、紫云英+减量施氮、紫云英+常规施氮、紫云英+高量施氮等5个处理,分析紫云英还田配施不等量氮肥对土壤有机碳、土壤微生物量碳、土壤活性有机碳、碳库管理指数等指标的影响。结果表明:与冬闲+不施氮相比,单种紫云英处理的土壤总有机碳含量增加了14%,活性有机碳含量22%;紫云英还田各处理下土壤微生物量碳平均增加了70%,土壤微生物熵平均增幅为58%,土壤碳库管理指数平均增幅为8%;紫云英配施氮肥各处理下土壤总有机碳平均增加了8%,活性有机碳含量平均增加了15%,土壤微生物熵平均增幅为72%。综上所述,与冬闲+不施氮处理相比,单种紫云英能够显著增加土壤总有机碳和活性有机碳含量;紫云英还田后配施氮肥可以显著增加土壤微生物量碳,提高微生物熵值和土壤碳库管理指数,以紫云英还田条件下减施氮和常规施氮两个处理的提升效果较好。

Chinese milk vetch (Astragalus sinicus L.) is an important green manure crop of paddy fields in southern China. Understanding the effects of planting Chinese milk vetch in combination with nitrogen fertilizer application on soil organic carbon is crucial for the optimization of fertilizer application and soil fertility management, which could provide a theoretical basis for the sustainable development of agriculture in paddy fields. There were five treatments, including no Chinese milk vetch planting in winter + no nitrogen application ( CK) , planting Chinese milk vetch without nitrogen application, planting Chinese milk vetch with nitrogereducing applica? tion, planting Chinese milk vetch with conventional -level nitrogen application , and planting Chinese milk vetch with high-level nitrogen application. The results showed that, compared with CK, soil total organic carbon and active organic carbon under the treatment of planting Chinese milk vetch alone increased by 14% and 22% respectively. For the four treatments of planting Chinese milk vetch, soil microbial biomass carb on, soil microbial entropy and carbon pool management index increased by 70%, 58% , and 8% , respectively. For the three treatments of planting Chinese milk vetch with varied nitrogen application levels, total organic carbon , active organic carbon ,and soil microbial entropy increased by 8% , 15% , and 72% , respectively. In summary, as compared with fallow in winter without nitrogen application, single application of Chinese milk vetch could significantly increase soil total organic carl)on and active organic carbon content.Planting Chinese milk vetch in combi nation with nitrogen fertilizer applications could significantly increase soil microbial biomass, microbial entropy, and soil carbon pool management index. Among all the treatments, planting Chinese milk vetch in combination with nitrogereducing application and conventional-level nitrogen application had better performance.