Abstract:Glyphosate is the most widely used herbicide in the United States; however, concern about increasing residues of glyphosate and its metabolite aminomethylphosphonic acid (AMPA) in soil is escalating. There is a lack of scientific literature examining the response of cover crops to soil residues of glyphosate or AMPA. The objectives of this study were to evaluate the impact of glyphosate or AMPA residues in silty clay loam soil on emergence, growth, and biomass of cover crops, including cereal rye, crimson clov… Show more
“…Indeed, AMPA is phytotoxic even for GR crops and can impact microbial activity thus affecting nutrient bioavailability (Reddy et al., 2004; Samson‐Brais et al., 2020; Smedbol et al., 2019). However, while not considering corn crops nor soybean crops, Ganie and Jhala (2021) did not show negative impact of glyphosate or AMPA contents below 105 mg kg −1 in soil on the tested cover crops species.…”
To avoid yield loss in field crops associated with glyphosate‐resistant weed and changes in their population dynamics, repeated applications of glyphosate‐based herbicides (GBH) and combination with other herbicides are weed management practices (WMP) increasingly used worldwide, and particularly so in southern Quebec (Canada). These practices affect soil biological activity as well as soil functions but could also influence glyphosate and its main degradation product, the aminomethylphosphonic acid (AMPA), persistence. This study was conducted in corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] field crops to evaluate the effects of single vs. repeated GBH applications, with or without the addition of other herbicides, on glyphosate and AMPA persistence in soils throughout a growing season. In corn plots, the highest glyphosate content (0.11 mg kg–1) was observed following two GBH applications combined with other herbicides (i.a. S‐metolachlor and mesotrione). In soybean plots, the highest glyphosate content (0.18 mg kg–1) was also measured following two GBH applications combined with other herbicides (i.a. imazethapyr and chlorimuron). AMPA contents in corn plots soils were similar whatever WMP employed, whereas differences were observed in soybean plots according to the WMP. Soybean plots thus seemed more responsive to variation in weed management practices than corn plots. This study highlights the persistence of glyphosate and AMPA in agricultural soils at least 8 wk after the last GBH application.
“…Indeed, AMPA is phytotoxic even for GR crops and can impact microbial activity thus affecting nutrient bioavailability (Reddy et al., 2004; Samson‐Brais et al., 2020; Smedbol et al., 2019). However, while not considering corn crops nor soybean crops, Ganie and Jhala (2021) did not show negative impact of glyphosate or AMPA contents below 105 mg kg −1 in soil on the tested cover crops species.…”
To avoid yield loss in field crops associated with glyphosate‐resistant weed and changes in their population dynamics, repeated applications of glyphosate‐based herbicides (GBH) and combination with other herbicides are weed management practices (WMP) increasingly used worldwide, and particularly so in southern Quebec (Canada). These practices affect soil biological activity as well as soil functions but could also influence glyphosate and its main degradation product, the aminomethylphosphonic acid (AMPA), persistence. This study was conducted in corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] field crops to evaluate the effects of single vs. repeated GBH applications, with or without the addition of other herbicides, on glyphosate and AMPA persistence in soils throughout a growing season. In corn plots, the highest glyphosate content (0.11 mg kg–1) was observed following two GBH applications combined with other herbicides (i.a. S‐metolachlor and mesotrione). In soybean plots, the highest glyphosate content (0.18 mg kg–1) was also measured following two GBH applications combined with other herbicides (i.a. imazethapyr and chlorimuron). AMPA contents in corn plots soils were similar whatever WMP employed, whereas differences were observed in soybean plots according to the WMP. Soybean plots thus seemed more responsive to variation in weed management practices than corn plots. This study highlights the persistence of glyphosate and AMPA in agricultural soils at least 8 wk after the last GBH application.
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