Cover crop response to residual herbicides in peanut-cotton rotation

Authors: Price, Andrew

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/6/2019
Publication Date: 2/6/2019
Citation: Price, A.J. 2019. Cover crop response to residual herbicides in peanut-cotton rotation [abstract]. Southern Weed Science Society Annual Meeting. p. 29.

Interpretive Summary:

Technical Abstract: Cover crops can provide many benefits to peanut and cotton rotation in terms of suppressing weeds, conserving soil moisture for planting, increasing soil organic matter, and reducing soil erosion. However, in fields where residual herbicides were used during the growing season, establishment of cover crops can be negatively affected by the herbicide residues. The objective of this study was to investigate the responses of six cover crops (daikon radish, cereal rye, cocker oats, crimson clover, winter wheat, and common vetch) to twelve common soil herbicides used in peanut and cotton. A multi-year (2016-2018), multi-location study was conducted in Macon and Henry County in Alabama. Herbicide treatments were applied at 10% of full labelled rate for cotton or peanut at cover crop planting. At 50 and 150 days after planting (DAP), plant heights and stand counts were evaluated as well as wet biomass at 150 DAP. Treatments included S-metolachlor, acetochlor, pyroxasulfone, diclosulam, imazapic, chlorimuron ethyl, bentazon plus acifluorfen, pyrithiobac sodium, trifloxysulfuron sodium, diuron, prometryn, flumioxazin, and a non-treated check (NTC). In 2016, significant stand reductions (p 0.05) of 30-52% in rye and 22-75% in wheat respectively were observed at 50 DAP for S-metolachlor, acetochlor, pyroxasulfone, diclosulam, imazapic, chlorimuron ethyl, and bentazon plus acifluorfen over both locations. Vetch had significant stand reductions for all twelve treatments at 50 DAP ranging from 12-80% over both locations. S-metolachlor, pyroxasulfone and acetochlor had the largest negative impacts on stand counts for rye, wheat and vetch. Daikon radish had significant height reductions of 9, 15, and 31% at 50 DAP for diuron, chlorimuron ethyl, and imazapic, respectively, in Macon County. At 145-149 DAP, all affected cover crops had recovered from herbicide damage and did not show any significant treatment differences in any of the growth parameters evaluated in 2016. In 2017, wheat had a significant stand reduction of 22% for flumioxazin at 42-45 DAP over both locations. At 147-149 DAP, clover had a significantly reduced stands of 29-38% for diclosulam and trifloxysulfuron sodium respectively, over both locations. Radish also had a significantly reduce stand of 64% for diclosulam. Oats, rye and vetch did not have any significant stand reductions at either timing in 2017/2018. Oats showed the most tolerance with no treatments significantly reducing stands or plant heights for either year. Overall, the type of cover crop planted should be based on the residual herbicides applied to row crops the previous season as well as the biomass goal and nutrient needs of the field. Although initial injury and stunting may occur, biomass of those cover crops may not be affected by herbicide residues evaluated in this study.