Cover crop response to residual herbicides in peanut-cotton rotation

Authors: PRICE, KATLYN - Auburn University; LI, STEVE - Auburn University; Price, Andrew

Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2019
Publication Date: 1/13/2020
Citation: Price, K., Li, S., Price, A.J. 2020. Cover crop response to residual herbicides in peanut-cotton rotation. Weed Technology. 34:4 pp.534-539. https://doi.org/10.1017/wet.2020.5.
DOI: https://doi.org/10.1017/wet.2020.5

Interpretive Summary: Cover crops can provide many benefits to a peanut and cotton rotation in terms of suppressing weeds, conserving soil moisture after termination, increasing soil organic matter, and reducing soil erosion. However, residual herbicide used in previous crops can interfere with cover crop establishment. 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. Results revealed no significant biomass reduction for any cover crop species either year. Oats were the most tolerant cover crops species to herbicide residues with no herbicide treatment significantly reducing stands or plant heights for either year. Although initial injury and stunting may occur for most of the cover crops evaluated, final biomass of those cover crops will likely not be affected by herbicide residues evaluated in this study.

Technical Abstract: Cover crops can provide many benefits to a peanut and cotton rotation in terms of suppressing weeds, conserving soil moisture after termination, increasing soil organic matter, and reducing soil erosion. However, residual herbicide used in previous crops can interfere with cover crop establishment. 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 included; S-metolachlor, acetochlor, pyroxasulfone, diclosulam, imazapic, chlorimuron ethyl, bentazon plus acifluorfen, pyrithiobac sodium, trifloxysulfuron sodium, diuron, prometryn, and flumioxazin were applied at 10% of full-labelled rate. At 42-52 and 145-149 days after planting (DAP), plant heights and stand counts were evaluated as well as biomass at 145-149 DAP. Treatments varied from year to year but not locations. In 2016, significant stand reductions (p 0.05) of 30-52% in rye and 22-75% in wheat respectively were observed at 48-52 DAP for S-metolachlor, acetochlor, pyroxasulfone, diclosulam, imazapic, chlorimuron ethyl, and bentazon plus acifluorfen as compared to the non-treated check. Vetch had significant stand reductions for all twelve treatments at 50 DAP ranging from 12.53-80.21%. S-metolachlor, pyroxasulfone and acetochlor had the largest negative impacts on stand counts for rye, wheat and vetch. At 145-149 DAP, all affected cover crops had recovered from herbicide damage. In 2017, wheat had a significant stand reduction of 22% for flumioxazin at 42-45 DAP. At 147-149 DAP, clover had significantly reduced stands of 29-38% for diclosulam and trifloxysulfuron sodium respectively. Radish also had a significantly reduced stand of 64% for diclosulam. No significant biomass loss was observed for any cover crop species either year. Oats showed the most tolerance with no treatments significantly reducing stands or plant heights for either year. Although initial injury and stunting may occur, biomass of those cover crops may not be affected by herbicide residues evaluated in this study.