Date of Graduation
Master of Science in Crop, Soil & Environmental Sciences (MS)
Crop, Soil & Environmental Sciences
Second Committee Member
Third Committee Member
Fourth Committee Member
Crop Injury, Dicamba, Drift, Offspring, Soybean, Tank Contamination
Introduction of a new dicamba-resistant (Xtend) trait in soybean and cotton will increase dicamba herbicide use. Consequently, concern for injury to sensitive crops from off-target movement and tank contamination will likely increase. For soybean, foliar symptoms associated with dicamba damage do not necessarily reflect yield losses; hence, experiments were conducted to determine the effects of dicamba on soybean growth, yield, and offspring. Low rates of dicamba [1/64X (8.75 g ae ha-1) and 1/256X (2.18 g ae ha-1) of a normal 1X field rate (560 g ae ha-1)] were applied at two vegetative growth stages (V4, V6) and at each reproductive growth stage from R1 to R6. Compared to the nontreated check, dicamba applied during late vegetative and early reproductive growth of soybean caused leaf injury, plant height reduction, and yield loss. Regardless of soybean cultivar, the higher rate of 1/64X resulted in greater yield loss, with R1 being the most sensitive growth stage. Dicamba at 8.75 g ha-1 applied at R1 reduced mature soybean height 35 cm for an indeterminate cultivar and 23 cm for a determinate cultivar. Grain yield was reduced 14% for the indeterminate cultivar and 19% for the determinate cultivar. Injury and height reductions were less apparent when dicamba was applied during later growth stages. Offspring response to dicamba applied to parent plants the previous year was dependent upon application timing and dicamba rate. Negative effects to offspring were observed as reduced seed germination, seedling emergence, plant height, seedling vigor, pod malformation,
and grain yield. Offspring had 17 to 23% injury when parent plants were treated from R4 to R6 with dicamba at 2.18 g ha-1. Seeds from the bottom of the plant were affected more by dicamba than seeds from the top of the plant; however, no relationship existed between grain yield and pod malformation. This research shows that soybean cultivar, growth habit, or planting date may influence soybean recovery from dicamba.
McCown, Mark Spencer, "Dicamba Effects on Soybean (Glycine max) Growth, Yield, and Offspring" (2018). Theses and Dissertations. 2627.