Cover crop response to residual herbicides in peanut-cotton rotation

Abstract

Cover crops can provide many benefits to peanut and cotton crops planted in rotation including suppressing weeds, conserving soil moisture after termination, increasing soil organic matter, and reducing soil erosion. However, herbicide carryover can affect cover crop establishment. The objective of this study was to investigate the responses of 6 cover crops (daikon radish, cereal rye, oat, crimson clover, winter wheat, and common vetch) to 12 soil residual herbicides. A multiyear (2016–2018), multilocation study was conducted in Macon and Henry counties, Alabama. Herbicide treatments included S-metolachlor, acetochlor, pyroxasulfone, diclosulam, imazapic, chlorimuron-ethyl, bentazon plus acifluorfen, pyrithiobac-sodium, trifloxysulfuron-sodium, diuron, prometryn, and flumioxazin, each applied at 10% of the full-labeled rate. At 42 to 52 and 145 to 149 d after planting (DAP), cover crop plant heights and stand counts were evaluated, as was biomass at 145 to 149 DAP. Treatments varied from year to year but not locations. In 2016, significant stand reductions (P ≤ 0.10) of 36% to 43% in rye and 44% to 75% in wheat were observed at 48 to 52 DAP for S-metolachlor, acetochlor, pyroxasulfone, imazapic, and bentazon plus acifluorfen compared with nontreated plants. Vetch had stand reductions ranging from 14% to 80% for all treatments 50 DAP except for plants treated with prometryn. S-metolachlor, pyroxasulfone, and acetochlor reduced stands of rye, wheat, and vetch more than any other herbicides. In 2017, at 147 to 149 DAP, clover stands were reduced by 29% with diclosulam and by 38% with trifloxysulfuron-sodium. Similarly, radish stands were reduced by 64% with diclosulam treatment. No significant biomass reductions were observed for any cover crop species either year. Oat showed the most tolerance with no treatments reducing any growth parameters either year. Although initial injury and stunting may occur, biomass at termination of cover crops were not affected by herbicide residues evaluated in this study.

Evaluation of imazapic and flumioxazin carryover risk for Carinata (Brassica carinata) establishment

“…This type of rotational consideration has been used to ensure the safety of other Brassicaceae species. For example, daikon radish (Raphanus sativus L.) planted as a cover crop was affected by residual herbicides in peanut-cotton rotations, but imazapic reduced plant height more than flumioxazin (Price et al 2020).…”

“…In the southern United States, flumioxazin can be applied relatively late in the spring or early summer in double-crop soybeans (Hay et al 2019), as well as postemergence layby in cotton (Ferrell et al 2007;Ferrell and Vencill 2003b). These late applications might not allow enough time for herbicide degradation, resulting in increased carryover risk for winter crops (Price et al 2020). For instance, plant damage and yield reduction have been reported in cotton due to imazapic carryover after peanut production (York et al 2000).…”

Cereal rye response to eight commonly used wheat herbicides

“…Previous research has demonstrated that pyroxasulfone applied preplant (Price et al 2020) and preemergence (Boutsalis et al 2014;Palhano et al 2018) reduced wheat density, but labels support a delayed PRE application to minimize injury (Anonymous 2017).…”

Persistence of S-metolachlor in the soil as affected by moisture content

“…Thus, there is a concern that S-metolachlor may carryover to sensitive crops, including rice planted in rotation. Herbicide persistence and carryover in soil may be affected by several factors such as physicochemical properties of molecule, soil characteristics, environmental conditions (Price, Price, 2020), association between herbicides (Nunes and Vidal, 2008) or even interactions between these factors. Among soil characteristics, moisture content influences herbicide availability in the soil solution, microbial activity, and other dissipation processes (Gehrke et al, 2021).…”