Chloris virgata is a problematic weed around the world. Prediction of weed germination rates could be a useful strategy to optimise timing of weed control actions. We studied the germination and emergence of C. virgata collected seeds under different after‐ripening treatments and different exhumation dates after seed dispersal, to estimate seed dormancy level and predict weed emergence dynamics under field conditions. Three experiments were conducted under controlled conditions to determine base, optimum and maximum germination temperatures (T_b, T_o and T_m respectively) and comprised: (a) exposure of seeds to gradually increasing and decreasing temperatures between 5 and 35°C; (b) exposure of seeds to different constant temperatures; and (c) exposure of seeds to different light quality conditions (red – far red ratio) and temperature regimes (constant and alternating temperatures). To explore genuine environmental conditions, a field experiment was performed to determine weed emergence under different shading levels. Finally, with the data obtained, a thermal time model for dormancy release was used to predict C. virgata seedling emergence in the Argentine Pampas region. Seeds after‐ripened in cold and wet conditions and constant 25°C showed the highest germination percentages. The values of T_b (7°C), T_o (28°C) and T_m (40°C) remained constant at all exhumation dates. Neither light quality nor thermal regime modified the final germination percentages. However, shading delayed seedling emergence under field conditions, even when it was adjusted by thermal time. These results may allow predicting C. virgata emergence in temperate regions and help to improve weed control in integrated weed management strategies.

中文翻译：

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模拟在不同温度和光照条件下虎尾草的萌发和出苗

虎尾草是世界各地有问题的杂草。杂草萌发率的预测可能是优化杂草控制措施时机的有用策略。我们研究了在不同的后熟处理和种子散布后的不同掘尸日期下，虎尾草种子的萌发和出苗，以估计种子的休眠水平并预测田间条件下的杂草出苗动态。在受控条件下进行了三个实验，以确定基础发芽温度，最佳发芽温度和最大发芽温度（T _b，T _o和T _m分别包括以下内容：（a）将种子暴露于5至35°C的逐渐升高和降低的温度下；（b）将种子暴露于不同的恒温中；（c）将种子暴露于不同的光质量条件（红色至远红色比率）和温度范围（恒定和交替温度）下。为了探索真正的环境条件，进行了野外试验，以确定在不同遮阴水平下的杂草出苗。最后，利用获得的数据，将休眠释放的热时间模型用于预测阿根廷南美大草原地区C. virgata苗的出现。在寒冷和潮湿的条件下以及在25°C恒定的温度下再熟的种子发芽率最高。的值Ť _b（7℃），Ť在所有掘尸日，_o（28°C）和T _m（40°C）保持恒定。光照质量和热状况均未改变最终发芽率。但是，即使在受热时间调节的情况下，遮荫也会在田间条件下延迟幼苗出苗。这些结果可能有助于预测温带地区的C. virgata出现，并有助于改善杂草综合治理策略中的杂草控制。