Characterization of the Weed Flora in Rice Areas under Distinct Cropping Systems and Herbicide Managements

ABSTRACT: The aim of this study was to evaluate the occurrence of weeds in flooded rice areas, as a function of planting system and herbicide programmes in the previous cropping year. The experiment was installed in field conditions, in randomized complete blocks design, arranged in factorial scheme 3 x 2, with eight replications. In factor A, treatments consisted on conventional tillage, minimum tillage and no till cropping systems, coupled to the application (traditional control) or not (semi-ecological system) of herbicides (Factor B). One year after rice cultivation, preceding the planting of the next cropping season, phytosociological evaluations of the weed communities present in the treatments were carried out. We assessed the overall infestation level and weed species composition, which were classified by their respective density, frequency and dominance abilities. We also estimated the diversity coefficients of Simpson and Shannon Weiner, and the sustainability coefficient of Shannon; treatments were also grouped by similarity in weed species composition. Rice growing systems (traditional or semi-ecological) promote remarkable differences in weed occurrence. Herbicide-based crops select specific companion weed species, but crop rotation or winter cover crops are not a sine qua non condition for success since a good herbicide programme is planned. For the Semi ecological system, crop rotation, thick winter soil mulching and association with animal presence and grazing are essential for the short, medium and long-term inhibition of weeds.

摘要：本研究旨在评估淹水水田稻作区的杂草发生情况，分析前茬种植季的种植制度与除草剂施用方案对杂草发生的影响。本试验于大田条件下开展，采用随机完全区组设计（randomized complete blocks design），按3×2因子试验方案设置处理，共设置8次重复。其中因子A的处理涵盖常规耕作、少耕与免耕三种种植制度，因子B则设置两种除草剂施用模式：传统防控体系（施用除草剂）与半生态防控体系（不施用除草剂）。水稻种植一年后、下一茬作物播种前，研究人员对各处理中的杂草群落开展植物社会学调查。本研究评估了杂草总体侵染水平与物种组成，并依据各杂草的密度、频度与优势度对其进行分类；同时估算了辛普森（Simpson）多样性系数、香农-维纳（Shannon Weiner）多样性系数以及香农可持续性系数，并基于杂草物种组成的相似性对各处理进行聚类分组。研究结果表明，水稻种植制度（传统或半生态）对杂草发生情况存在显著影响。以除草剂为核心的种植制度会筛选出特定伴生杂草物种，但只要规划合理的除草剂施用方案，轮作或冬季覆盖作物并非杂草防控成功的必要条件。对于半生态防控体系而言，轮作、厚层冬季土壤覆盖结合畜禽放牧操作，是短期、中期与长期抑制杂草的必要手段。