Effect of amitrole and 2,4‐D applied preplant and pre‐emergence in soybean (Glycine max)

Abstract

There is limited information on the effect of amitrole and 2,4‐D ester applied preplant and pre‐emergence in soybean (Glycine max L.) in Ontario, Canada. Six field trials were conducted over a 2 year period (2004 to 2005) at three Ontario locations to evaluate the response of soybean to amitrole or 2,4‐D ester applied at 14 days preplant (DPP), 7 DPP, 1 day after planting (DAP), and 7 DAP. The application of amitrole resulted in as much as 5.8, 3.9, 1.7, and 1% visible crop injury in soybean at 7, 14, 28, and 56 days after emergence (DAE), respectively. There was no visible injury in soybean with any amitrole treatment at 56 DAE, except for amitrole applied at 7 DAP, which caused 1% visible injury in soybean at 2310 g ha−1. The application of the 2,4‐D ester caused ≤8.3, 9.7, 4.6, and 1.3% visible injury in soybean at 7, 14, 28, and 56 DAE, respectively. The visible injury decreased over time. There was no visible injury in soybean with any of the 2,4‐D ester treatments at 56 DAE, except for the 2,4‐D ester treatment applied at 7 DAP, which caused 1% visible injury at 1155 g ha−1 and 1.3% visible injury at 2310 g ha−1. Soybean generally responded similarly to amitrole and 2,4‐D ester when applied at 14 and 7 DPP; however, soybean was more tolerant to amitrole compared to 2,4‐D ester when applied at 1 or 7 DAP. The application of amitrole and 2,4‐D ester resulted in no biomass or yield reduction in soybean compared to the weed‐free, untreated control at all doses and application timings evaluated. Soybean is tolerant to the preplant and pre‐emergence application of amitrole or 2,4‐D ester at the doses evaluated.