| Off-target movements of herbicides have been detrimental to crop yields. When new technology is released, it is necessary to understand the potential impact it may have on off-target crops. Field studies were conducted in 2007 and 2008 to evaluate and compare the effects of low rates of glufosinate and glyphosate on rice (Oryza sativa) and wheat (Tritium aestivum) and of glufosinate on non-glufosinate-resistant soybean (Glycine max). Glyphosate (1x rate = 870 g ae/ha) and glufosinate (1x rate = 616 g ai/ha) were applied to rice at 1/2, 1/4, and 1/8x of the recommended usage rate and to wheat at 1/10 and 1/20x rates at the 3- to 4-leaf, panicle initiation, and boot growth stages. Glufosinate was applied to soybean at 1/2, 1/4, and 1/8x of the usage rate at V3, R1, and R5 growth stages. At comparable rates, glufosinate caused substantially greater injury than glyphosate to rice. Rice grain yield was reduced up to 80% with either herbicide. In soybean, glufosinate caused the greatest injury at the V3 stage. Soybean grain yields followed the injury trend closely, with up to 90% yield reduction at the highest evaluated rate. Wheat injury symptoms were minimal for glyphosate compared to glufosinate. However, wheat grain yield reductions were greatest for glyphosate. Because glyphosate is more readily translocated, overall sensitivity of off-target crops may be higher to lower rates or "drift rates" of glyphosate than glufosinate. However, because of a perception that glufosinate damage is "cosmetic" and will not harm off-target crops as much as glyphosate, educational efforts are needed to demonstrate potential negative impacts of glufosinate to off-target crops. |
