The evolution and widespread distribution of glyphosate-resistant broadleaf weed species catalyzed the introduction of dicamba-resistant crops that allow this herbicide to be applied POST to soybean and cotton. Applications of dicamba that are most cited for off-target movement have occurred in June and July in many states when weeds are often in high densities and at least 10 cm or taller at the time of application. For registration purposes, most field studies examining pesticide emissions are conducted using bare ground or very small plants. Research was conducted in Knoxville, TN, in the summer of 2017, 2018, and 2019 to examine the effect of application surface (tilled soil, dead plants, green plants) on dicamba emissions under field conditions. Dicamba emissions after application were affected by the treated surface in all years, with the order from least to most emissions being dead plants < tilled soil < green plant material. In fact, dicamba emissions were >300% when applied to green plants compared to other surfaces. These findings suggest that dicamba applications made to bare ground will likely underestimate what may occur under normal field use conditions when POST applications are made and the crop canopy or weed groundcover is nearly 100% green material. A potential change to enhance the accuracy of current environmental simulation models would be to increase the theoretical findings to allow for the effect of green plant material on dicamba emissions under field conditions.

中文翻译：

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受地表条件影响的田间条件下的麦草畏排放

抗草甘膦阔叶杂草物种的进化和广泛分布促进了抗麦草畏作物的引入，从而使这种除草剂可以在大豆和棉花后施用。在许多州，最常被引用用于脱靶运动的麦草畏应用发生在 6 月和 7 月，当时杂草通常密度很高，并且在应用时至少 10 厘米或更高。出于登记目的，大多数检查农药排放的实地研究都是使用裸露的地面或非常小的植物进行的。研究于 2017 年、2018 年和 2019 年夏天在田纳西州诺克斯维尔进行，以检查在田间条件下施用表面（耕作土壤、死植物、绿色植物）对麦草畏排放的影响。施用后的麦草畏排放量在所有年份都受到处理过的表面的影响，排放量从最少到最多的顺序是死植物 < 耕作的土壤 < 绿色植物材料。事实上，与其他表面相比，当应用于绿色植物时，麦草畏的排放量 > 300%。这些发现表明，当进行 POST 应用并且作物冠层或杂草地被植物几乎 100% 是绿色材料时，在裸露的地面上施用麦草畏可能会低估在正常田间使用条件下可能发生的情况。提高当前环境模拟模型准确性的潜在变化是增加理论发现，以考虑绿色植物材料对田间条件下麦草畏排放的影响。与其他表面相比，应用于绿色植物时为 300%。这些发现表明，当进行 POST 应用并且作物冠层或杂草地被植物几乎 100% 是绿色材料时，在裸露的地面上施用麦草畏可能会低估在正常田间使用条件下可能发生的情况。提高当前环境模拟模型准确性的潜在变化是增加理论发现，以考虑绿色植物材料对田间条件下麦草畏排放的影响。与其他表面相比，应用于绿色植物时为 300%。这些发现表明，当进行 POST 应用并且作物冠层或杂草地被植物几乎 100% 是绿色材料时，在裸露的地面上施用麦草畏可能会低估在正常田间使用条件下可能发生的情况。提高当前环境模拟模型准确性的潜在变化是增加理论发现，以考虑绿色植物材料对田间条件下麦草畏排放的影响。