Effect of Carrier Volume on Corn (Zea mays) and Soybean (Glycine max) Response to Simulated Drift of Glyphosate and Glufosinate¹

Abstract

In traditional simulated herbicide drift research, dose response is evaluated using a constant carrier volume. The influence of carrier volume was evaluated in field experiments with drift rates representing 12.5 and 6.3% of the use rates of 1,120 g ai/ha glyphosate (140 and 70 g/ha, respectively) and 420 g ai/ha glufosinate (53 and 26 g/ha, respectively). Corn and soybean were exposed to herbicide rates applied in constant carrier volume of 234 L/ha and in proportional carrier volumes of 30 L/ha for the 12.5% rate and 15 L/ha for the 6.3% rate. Averaged across herbicides, corn height reduction 14 d after treatment (DAT) was greater for the 12.5% rate when applied in proportional 30 L/ha carrier volume (45%) compared with constant 234 L/ha carrier volume (28%). The 6.3% rate reduced corn height 38% when applied in proportional 15 L/ha carrier volume but not when applied in 234 L/ha carrier volume. When carrier volume was changed from constant to proportional, corn injury 14 DAT increased from 33 to 51% for the 12.5% rate and 18 to 38% for the 6.3% rate. Compared with constant spray volume, corn yield reduction was 1.5 times greater for the 12.5% rate but 4 times greater for the 6.3% rate when spray volume was varied proportionally to the herbicide rates. Differential response due to carrier volume was not observed when herbicides were applied to soybean. Soybean was injured more by glyphosate than by glufosinate, but recovery was rapid and yield was not negatively affected. Results suggest that drift research using constant spray volume may underestimate the yield reduction expected for sensitive crops exposed to glyphosate or glufosinate.

Effect of Carrier Volume on Grain Sorghum Response to Simulated Drift of Nicosulfuron

“…In 2010, grain sorghum yield was reduced 73% when applied in the constant carrier volume of 224 L ha À1 compared to a yield reduction of 55% when applied in the proportional carrier volume averaged across 56, 28, and 14 L ha À1 . These data are in contrast to those previously reported for 2,4-D on cotton (Gossypium hirsutum L.) and for glyphosate on sweet corn (Zea mays L.) (Banks and Schroeder 2002) and for glyphosate on corn (Ellis et al 2002) and for glyphosate on wheat (Triticum aestivum L.) (Roider et al 2008). A possible explanation for this is the number of droplets deposited on the grain sorghum leaves.…”

“…These results showing greater yield reduction in 2012 are likely attributable to reduced rainfall during the growing season (Table 1), perhaps due to decreased herbicide metabolism as the plants adjusted to drier conditions. The increased yield reduction from the proportional carrier volumes agree with results reported for glyphosate (Banks and Schroeder 2002;Ellis et al 2002;Roider et al 2008) but disagrees with 2010 results. A possible explanation could be increased epicuticular wax loads on grain sorghum plants in 2012.…”

“…However, many grain sorghum production areas in Texas will likely experience conventional and herbicide-resistant grain sorghum varieties growing in close proximity. Previous research on simulated drift of herbicides has shown differences in injury and yield because of changes in carrier volumes (Ellis et al 2002;Roider et al 2008). Previous research has been conducted to evaluate simulated herbicide drift to grain sorghum from glufosinate, glyphosate, imazethapyr, and sethoxydim (Al-Khatib et al 2003).…”

Simulated mesotrione drift followed by glyphosate, imazethapyr, bentazon or glyphosate plus chlorimuron in soybean

“…Herbicide drift occurs when spray droplets are displaced from their intended flight path (Ellis et al 2002). Drift from unshielded sprayers can range from 1 to 16% of the applied herbicide rate (Maybank et al 1978;Wolf et al 1992).…”

Qualidade de sementes de algodão provenientes de plantas tratadas com doses reduzidas de glyphosate

“…O glyphosate é um dos ingredientes ativos mais usados na dessecação da cobertura vegetal nesse sistema (Rodrigues & Almeida, 1998;Puríssimo, 1999;Kruse et al, 2000;Magalhães et al, 2001), e sua deriva se torna sério problema para culturas sensíveis (Banks & Schroeder, 2002;Ellis et al, 2002;L yon et al, 2003), como o algodoeiro, quando cultivadas próximo dessas áreas.…”