Alabama: Cover Crop Responses to Residual Herbicides in Peanut-Cotton Rotation

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, reducing soil erosion, etc. 

However, in fields where residual herbicides were used during the growing season, establishment of cover crops could be negatively affected by the herbicide residues. Therefore, 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. 

Herbicide Resistance Info

This study was conducted at Wiregrass Research Extension Center in Headland, AL and E.V. Smith Research and Extension Center in Tallassee, AL, from Oct 2016 to April 2017.  Growth parameters such as plant height, stand count, and percentage of crop cover were evaluated at 50 and 145 days after planting (DAP), as well as a wet weight biomass at project termination at 145 DAP. 

Herbicide treatments sprayed at the day of planting included Dual Magnum, Warrant, Zidua, Strongarm, Cadre, Classic, Storm, Staple LX, Envoke, Direx, Caparol, Valor, and a non-treated check (NTC). Each herbicide was sprayed at 10% of label rate.

Analysis showed significant (p<0.05) growth reductions of 29.95%-51.58% for stand counts in rye and 28.06% – 75.2% in wheat 50 DAP for Dual Magnum, Warrant, Zidua, Strongarm, Cadre, Classic, and Storm treatments. 

Vetch showed significant stand count reductions for all twelve treatments at 50 DAP ranging from 12.53% to 80.21%. Dual Magnum, Zidua and Warrant had the largest impacts on stand counts for all three cover crops mentioned above. 

Daikon radish showed significant reduction of 9.25%-30.52% in plant heights 50 DAP, at the E.V. Smith location for Direx, Cadre, and Classic.

At 145-149 DAP, all of the cover crops recovered from herbicide damage and did not show any significant treatment differences in any of the growth parameters collected at the end of the trial. 

Oats showed the most tolerance with no herbicides affected any growth parameter evaluated (p<0.05) throughout this study.  

Based on experiment data, we recommend producers utilize oats as a cover crop when there is a concern for residual herbicide injury. 

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