Criteria for Decision Making and Economic Threshold Level for Wild Radish in Wheat Crop

ABSTRACT: Weed competition limits wheat yield by reducing the availability of essential resources for its growth and development. In this sense, this study aimed to estimate the economic threshold level (ETL) of wild radish (Raphanus raphanistrum) in competition with wheat cultivars. Treatments were arranged in a factorial scheme. The factor wheat cultivar consisted of early (BRS 328), medium (BRS 177), and late (BRS Umbu) cycles and the factor wild radish population ranged from 0 to 564 plants m-2 (10 populations) for the cultivar BRS 328, 0 to 472 plants m-2 for the cultivar BRS 177 (11 populations), and 0 to 724 plants m-2 for the cultivar BRS Umbu (10 populations). The early-cycle BRS 328 presented a higher competitive ability when compared to the medium-cycle BRS 177 and late-cycle BRS Umbu. Yield losses of wheat grains due to wild radish interference can be satisfactorily estimated by the rectangular hyperbola model using the variables plant population, shoot dry matter, soil cover, and leaf area of the weed. ETL values varied as a function of the cultivar cycle, being higher for the cultivar BRS 328 (early) > BRS 177 (medium) > BRS Umbu (late). Wild radish is competitive in wheat crop, requiring at least 1.6 plants m-2 for control to be justified.

摘要：杂草竞争通过削减小麦生长发育所需关键资源的可获取性，对小麦产量造成限制。本研究旨在明确与小麦品种形成竞争的野萝卜（Raphanus raphanistrum）的经济阈值（economic threshold level, ETL）。试验采用因子设计方案：其一为小麦品种因子，涵盖早熟品种BRS 328、中熟品种BRS 177与晚熟品种BRS Umbu；其二为野萝卜种群密度因子，其中搭配BRS 328时，野萝卜种群密度范围为0~564株·m⁻²（共10个种群水平）；搭配BRS 177时，种群密度范围为0~472株·m⁻²（共11个种群水平）；搭配BRS Umbu时，种群密度范围为0~724株·m⁻²（共10个种群水平）。相较于中熟品种BRS 177与晚熟品种BRS Umbu，早熟品种BRS 328展现出更强的竞争能力。借助杂草的植株种群密度、地上部干物质、土壤覆盖度及叶面积等变量，通过矩形双曲线模型可较为精准地估测野萝卜竞争干扰导致的小麦籽粒产量损失。ETL值随小麦品种的生育期呈现梯度变化，具体表现为BRS 328（早熟）＞BRS 177（中熟）＞BRS Umbu（晚熟）。野萝卜对小麦具有较强竞争危害，当种群密度达到至少1.6株·m⁻²时，开展防除才具备经济合理性。