长期秸秆还田对稻麦连作制农田杂草种群生态特征的影响

Straw-returning affect weed population occurrence, community composition and weed-crop ecological relationship by altering soil microbial community structure and soil enzyme activity, and releasing allelochemicals. But, there is little research on underlying reasons for effect of long-term straw-returning on weed population ecological characteristics in rice-wheat continuous cropping system. In this project, firstly, we investigate the dynamic of microbial community structure, soil enzyme activities, soil nutrient characteristics, allelochemicals content, weed seed bank and weed community structure in rice and wheat field during straw-returning. After that, we emphasize on the analysis the interaction between microorganism, nutrient and allelochemicals. Further, we elucidate the correlation between soil microbial community structures with weed seed bank and weed composition. Meanwhile, we study the response of main weeds, such as Echinochloa crusgalli (L.) Beauv., Leptochloa chinensis (L.) Nees, Beckmannia syzigachne (Steud.) Fernald and Alopecurus aequalis Sobol., to straw-returning in the aspects of seed germination, photosynthetic performance, water utilization, nutrition metabolism and hormone contents. Then, we discuss the key factors that long-term straw-returning affect weed population ecological characteristics. Finally, we present initially the model for predicting weed population occurrence. The results will provide the scientific evidence for weed population trends, the theoretical basis for weed ecological control, and the technical support for reasonable straw-returning and herbicides scientific application.

秸秆还田通过改变土壤微生物群落结构和土壤酶活性，释放化感物质，影响农田杂草种群发生、群落组成及杂草-作物生态关系，但对长期秸秆还田影响稻麦连作制农田杂草种群生态的内在原因缺乏关注。本项目从秸秆还田下土壤微生物群落结构、土壤酶活性、土壤养分特征、化感物质含量、土壤杂草种子库和杂草群落结构变化动态入手，解析土壤微生物-土壤养分-化感物质互作关系，阐明土壤微生物群落结构与杂草种子库、杂草群落结构的关联；研究稗草、千金子、菵草、看麦娘在种子萌发、光合性能、水分利用、营养代谢、激素含量等生理生态方面对秸秆还田的响应，分析长期秸秆还田对杂草种群生态影响的关键因子，初步建立秸秆还田条件下稻麦田杂草发生预测模型，为把握农田杂草种群变化趋势提供科学依据，为建立杂草生态治理策略提供理论基础，为秸秆合理还田、化学除草剂科学使用提供技术支撑。

秸秆还田是当前稻麦连作地区农业生产中重要的耕作措施，发挥秸秆还田有利的农田生态效应、克服对作物的不利影响有助于利用生态控草推动稻麦田农药减量使用。本项目从秸秆还田下土壤微生物群落结构、土壤酶活性、土壤养分特征、化感物质含量、土壤杂草种子库和杂草群落结构变化动态入手，开展了不同秸秆还田量对稻麦田稗草、千金子、菵草、日本看麦娘等主要杂草在种子萌发、光合性能、水分利用、营养代谢、根系发育、激素含量等生理生态方面的影响，以及对靶标杂草-不同作物品种在光能、水分、营养等方面竞争关系的影响。结果表明作物和杂草竞争条件下，作物在不同生育期的净光合速率、气孔导度、蒸腾速率随着秸秆还田量增加逐渐上升，均高于无秸秆还田条件下相应的光合特性，且不同作物品种之间存在明显差异。同时杂草的净光合速率、气孔导度、蒸腾速率等参数随着秸秆还田量增加而降低。作物产量也有一定程度的增加，但随着秸秆还田时间的延长，与秸秆不还田相比，秸秆还田条件下作物净光合速率、气孔导度等光合参数出现缓慢下降，虽然在较高秸秆还田量下相关参数高于同期较低秸秆还田量处理。因此，短期的秸秆还田可能有利于促进作物对杂草的竞争，有利于杂草的生态控制，但随着秸秆还田时间的延长，秸秆还田可能通过改变土壤C/N、耕作层土壤温度以及化感作用而影响作物生长，本项目初步提出浅旋还田和深翻还田2种方式交替使用的秸秆还田模式，充分发挥生态控草作用，持续推动除草剂减量施用。本研究为后续的秸秆还田下除草剂药效充分表达、稻麦连作制下除草剂无人机飞防研究、机械化规模化种植中稻麦田恶性杂草可持续管理提供了重要的基础性数据。本项目发表论文5篇（另有1篇处于审稿阶段），授权专利1项，科技奖励1项，制定标准2项，培养硕士研究生2名，参加国内外学术会议10余次。