Weed interference period and economic threshold level of ryegrass in wheat

ABSTRACT The study of weed interference periods and the economic threshold level (ETL) of weeds on crops allows the adoption of management methods and the rationalized use of herbicides. The objective of this study was to determine the periods of interference and to test mathematical models to determine the economic threshold level of ryegrass in the wheat crop. Two experiments were carried out in a randomized block design with four replications. The first experiment was conducted in the 2014/2015 agricultural season. The periods of interference and control of ryegrass were studied in wheat. The periods of interference and/or control were: 0, 10, 20, 30, 40, 50 and 120 days after emergence (DAE). The second experiment was conducted in the 2016/2017 agricultural season. The ETLs were studied, being the treatments composed of wheat cultivars and 12 populations of ryegrass, in competition with the respective cultivars. The results allowed concluding that the management methods of weed ryegrass must be adopted in the period between 11 and 21 days after crop emergence, which is described as a critical period of control of this weed. The wheat grain yield loss competing with ryegrass reached 59% when grown with ryegrass. For ETL, the linear regression model of the rectangular hyperbola adequately estimates grain yield losses in the presence of ryegrass. The cultivar presenting the lowest values of ETL, that is, less capacity to live with the weed, was TBIO Alvorada. The other cultivars presented similar ETL values.

摘要 针对作物杂草干扰期与杂草经济阈值（Economic Threshold Level，ETL）的研究，可为杂草防控方案的制定与除草剂的合理施用提供科学依据。本研究旨在明确黑麦草对小麦的干扰周期，并通过数学模型测算小麦田中黑麦草的经济阈值。本研究设置两项试验，均采用随机区组设计，设置4次重复。第一项试验于2014/2015农业季开展，以小麦与黑麦草的干扰及防控周期为研究对象，设置的干扰/防控时长分别为出苗后0、10、20、30、40、50及120天（Days After Emergence，DAE）。第二项试验于2016/2017农业季开展，聚焦经济阈值研究，处理组由小麦品种与12个黑麦草种群构成，各处理均为小麦品种与对应黑麦草种群的竞争组合。研究结果表明，杂草黑麦草的防控应在作物出苗后11~21天内开展，该时段即为该杂草的关键防控期。当小麦与黑麦草共生时，籽粒产量损失可达59%。针对经济阈值，矩形双曲线线性回归模型可较好地估算黑麦草存在下的小麦籽粒产量损失。供试品种中，TBIO Alvorada的经济阈值最低，即其与杂草共存的能力最弱，其余供试品种的经济阈值无显著差异。