麦后免耕直播稻田的生态环境演变与对策

STUDY ON EVOLUTION OF SOIL ECOLOGICAL ENVIRONMENT IN ZERO-TILLAGE RICE FIELDS AFTER WHEAT CROPPING AND COUNTERMEASURES

本研究从土壤基础肥力保持，农田养分转化，植物养分吸收和水稻增产效果的土壤生态观点出发，选择了上海郊区四种不同土壤类型的水稻土作为麦后免耕与浅耕农田生态环境演变研究定位试验的样点。通过土壤理化、生物化学、电化学和水稻植株养分吸收等项分析，3年的结果表明，麦后免耕土壤的基础肥力水平变化趋势同浅耕的基本一致；土壤微生物总量、土壤酶活性、淹水期稻田Eh值免耕的土壤均明显比浅耕的差，水稻植株中N、P、K吸收量及其增产效果浅耕的优于免耕的。由此说明，免耕直播稻田的养分转化与释供环境差于浅耕。鉴此，在本市稻田耕作制中，免耕作为一种补充性或是应变性耕作方式加以合理运用则更为恰当。在水稻栽培管理中，免耕稻田应及时清理沟系，保持农田排灌系统的畅通，以提高土壤内排水能力；淹水期和搁田脱水期间，应通过水分的合理调控，改善免耕稻田的水、气、热环境，同时还应增加有机肥的投入，逐步提高土壤微团聚体营养物质的储量，促进土壤良好团粒结构的形成和土壤肥力增生。

From the point of view of soil ecological environment concerning retention ofsoil basal fertility,conversion of farmland nutrients,absorption of nutrients by rice plants andeffect of increasing rice output,four types of paddy soils in Shanghai suburbs were selected assampling points in orientation tests for investigating the evolution of soil ecologicalenvironment in zero-tillage and shallow-ploughing rice fields after wheat cropping. Throughthe analyses of soil chemical and physical characteristics,microorganism composition,enzymeactivites,oxidizing and reducing materials,Eh value and nutrient absorption by rice plants,the preliminary investigation was completed. The results of 3-year tests showed that thetrend of changes in soil fertility was the same in the shallow-ploughing treatments and zerotillage treatments; the soil total microorganisms, enzyme activity and the Eh value in ricefields during irrigation period were all markedly higher in the shallow-ploughing treatmentsthan in the zero-tillage treatments ;the amounts of N,P,K absorbed by rice plants and theeffect in increasing rice output were also higher in the shallow-ploughing treatments than inthe zero-tillage treatments,which indicated that the shallow ploughing should give a bettereffect on conversion and supply of soil nutrients in rice fields as compared to the zero tillage.Therefore,in rice procudtion in Shanghai the zero tillage should only be taken as a kind ofsupplementary cultivation measure and practiced rationally. In rice cultivation management,the irrigation and drainage system in zero-tillage rice fields should be kept unblocked, inorder to enhance the drainage ability of soil. The environments of water, air and heat intillage layer should be improved by rational water regulation during irrigation and drainingperiods for promoting rice growth,meanwhile it is necessary to increase the application rateof organic manure and improve the soil granular structure in tillage layer.