Herbicide carryover to various fall-planted cover crop species

Abstract

Residual herbicides applied to summer cash crops have the potential to injure subsequent winter annual cover crops, yet little information is available to guide growers’ choices. Field studies were conducted in 2016 and 2017 in Blacksburg and Suffolk, Virginia, to determine carryover of 30 herbicides commonly used in corn, soybean, or cotton on wheat, barley, cereal rye, oats, annual ryegrass, forage radish, Austrian winter pea, crimson clover, hairy vetch, and rapeseed cover crops. Herbicides were applied to bare ground either 14 wk before cover crop planting for a PRE timing or 10 wk for a POST timing. Visible injury was recorded 3 and 6 wk after planting (WAP), and cover crop biomass was collected 6 WAP. There were no differences observed in cover crop biomass among herbicide treatments, despite visible injury that suggested some residual herbicides have the potential to effect cover crop establishment. Visible injury on grass cover crop species did not exceed 20% from any herbicide. Fomesafen resulted in the greatest injury recorded on forage radish, with greater than 50% injury in 1 site-year. Trifloxysulfuron and atrazine resulted in greater than 20% visible injury on forage radish. Trifloxysulfuron resulted in the greatest injury (30%) observed on crimson clover in 1 site-year. Prosulfuron and isoxaflutole significantly injured rapeseed (17% to 21%). Results indicate that commonly used residual herbicides applied in the previous cash crop growing season result in little injury on grass cover crop species, and only a few residual herbicides could potentially affect the establishment of a forage radish, crimson clover, or rapeseed cover crop.

Response of broadleaf and grass cover crop species to soil residues of glyphosate and aminomethylphosphonic acid (AMPA)

“…Husnot)], legumes (Austrian winter pea, crimson clover, and hairy vetch), and brassica [forage radish (Raphanus sativus L.) and rapeseed (Brassica napus L.)]. Results from this study indicated no impact of herbicide carryover on cover crop biomass, though it recorded injury of ≤20% in grass cover crops, 20% to 50% in brassica species, and ≤30% in legumes (Rector et al 2020). On the contrary, Palhano et al (2018) reported reduction in the emergence of leguminous (Austrian winter pea, crimson clover, and hairy vetch) and cruciferous cover crops (rapeseed) following the application of atrazine, diuron, fluridone, fomesafen, metribuzin, pyrithiobac, and sulfentrazone.…”

“…cropping systems in the Midwestern United States are predominantly based on herbicides; therefore, the impact of herbicide carryover is critical for establishing cover crops (Cornelius and Bradley 2017;Palhano et al 2018;Rector et al 2020). For instance, Rector et al (2020) evaluated 30 preemergence and postemergence herbicides, including inhibitors of acetolactate synthase, 4-hydroxyphenylpyruvate dioxygenase, very-long-chain fatty acids, protoporphyrinogen oxidase, and photosystem II commonly used in corn, soybean, and cotton (Gossypium hirsutum L.) for potential impact on grass [winter wheat, winter barley, cereal rye, winter oats, annual ryegrass (Lolium multiflorum (Lam.) Husnot)], legumes (Austrian winter pea, crimson clover, and hairy vetch), and brassica [forage radish (Raphanus sativus L.) and rapeseed (Brassica napus L.)].…”

Atrazine, mesosulfuron‐methyl, and topramezone persistence in North Carolina soils

“…Mesosulfuron‐methyl half‐life ranges observed in this study at 7 and 23 °C agree with the published range, with half‐life increasing with decrease in temperature and increase in soil pH (Lewis et al., 2016). Degradation rate of sulfonylurea herbicides slows as soil pH increases because nonmicrobial processes, such as hydrolysis and cleavage of the methyl ester at the phenyl ring or ether demethylation at the pyrimidine ring of mesosulfuron‐methyl, are more rapid at lower pH (ECHA, 2015; Rector et al., 2020; Sarmah & Sabadie, 2002). Correlation between soil pH and OM content and the association between soil pH and the buffering capacity attributed to OM may have influenced mesosulfuron‐methyl persistence (Table 6) (McCauley et al., 2017).…”

“…The half‐life of topramezone is reported to be 85 to 495 d under aerobic laboratory conditions and 10.8 to 69.3 d under field conditions (Lewis et al., 2016). Topramezone has moderate to slight risk for carryover potential, and the susceptibility of some rotational crop and aquatic plant species to topramezone residue in soil and irrigation water has been investigated (Hartzler & Owen, 2013; Rahman et al., 2014; Rector et al., 2020; Torre et al., 2018). However, specific soil properties that influence persistence and carryover of these herbicides have not been elucidated in soils relevant to North Carolina.…”

Cover crops to improve soil health in the North American Great Plains

“…Another potential cause of smaller CC biomass production is injury from residual herbicides. Some herbicides have long carryover periods that may limit CC establishment or compromise their safety as livestock feed (Rector et al, 2019). In dryland cropping systems, residual herbicides are frequently used to control weeds when growing grain crops as well as dur-ing fallow.…”