Cotton population and yield following different cover crops termination practices in an Alabama no-till system

Authors: Kornecki, Ted; Price, Andrew; Balkcom, Kipling

Submitted to: Journal of Cotton Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/14/2015
Publication Date: 11/2/2015
Publication URL: https://handle.nal.usda.gov/10113/5661738
Citation: Kornecki, T.S., Price, A.J., Balkcom, K.S. 2015. Cotton population and yield following different cover crops and termination practices in an Alabama no-till system. Journal of Cotton Science. 19(3):375-386.

Interpretive Summary: In conservation agriculture cover crops are used to improve soil quality, provide weed control and improve soil moisture. A common method to speed-up cover crop termination is to apply synthetic herbicides in addition to mechanical rolling. This study was conducted in central Alabama to evaluate the effects of rolling/crimping and different herbicides (glyphosate and two organic herbicides) applied at different rates on rye and clover for termination. Termination was faster with continuous or reduced applications of glyphosate compared to the roller alone, but not with organic herbicides. Rolling and herbicides did not influence cotton population. Cotton yield following rye was higher than with clover. This was probably due to nitrogen released by clover that promoted vegetative growth over reproductive growth. In general, applying herbicides with rolling did not have an impact on cotton population and yield. In contrast, different weather conditions impacted cotton growth in each of three growing seasons.

Technical Abstract: In Alabama, under optimal weather conditions, a three-week time period is required after rolling down a cover crop to achieve termination rates above 90%, and to eliminate competition for soil moisture between the cover crop and cash crop. A common method to enhance the cover crop termination process and maintain recommended cash crop planting dates is to apply herbicides in addition to rolling. However, synthetic herbicides cannot be used in organic production, thus approved organic herbicides could be used instead. This experiment evaluated the effectiveness of terminating cereal rye (Secale cereale L.) and crimson clover (Trifolium incarnatum L.) using an experimental roller alone or with glyphosate and two organic herbicides (Weed-Zap and vinegar 20% acidity). Herbicides were applied with rolling operation as a continuous spray, every other crimp, and every third crimp to determine the effects of cover crop termination rates on cotton (Gossypium hirsutum L.) population and yield in central Alabama during the 2009, 2010, and 2011 growing seasons. Because of different weather conditions during each growing season, cover crops produced different amounts of biomass which ranged for rye from 3890 kg ha-1 to 9340 kg ha-1, and crimson clover from 3450 kg ha-1 to 8046 kg ha-1 of dry biomass. Cover crop termination rates were assessed one, two, and three weeks after rolling. In the three growing seasons, rye termination rates were between 99% and 100% for all rolling treatments three weeks after rolling. Similar rates were generated for crimson clover three weeks after rolling, but only in 2011. Applying glyphosate with rolling helped to increase rye termination to near 100% two weeks after rolling. Organic herbicides did not increase cover crop termination compared to utilizing a roller alone. Generally, in all growing seasons, average crimson clover termination rates were lower (56%) than for rye (73%). Adding glyphosate to rolling increased clover termination. However, compared with roller alone, applying organic herbicides at any of the spraying rates did not increase clover termination. Herbicide application amounts were reduced by 31% for every other crimp and 42% for every third crimp compared with the continuous rate. In 2009 there was no difference in cotton population following rye and crimson clover, averaging 101056 plants ha-1. In contrast, in 2010, cotton population following clover was higher (105604 plants ha-1) than with cereal rye (78378 plants ha-1). In 2011, cotton population following rye was higher (101311 plants ha-1) compared to 65462 plants ha-1 for crimson clover. In three growing seasons, cotton seed yield following rye was significantly higher compared to crimson clover. In 2009, seed cotton yields were 3446 kg ha-1, and 2780 kg ha-1, following rye and crimson clover, respectively. In 2010, a rainfall deficit and high temperatures negatively impacted cotton yield and substantially reduced yields compared to 2009 (1780 kg ha-1 following rye and 1610 kg ha-1 following crimson clover). In 2011, cotton seed yield due to rye was 2377 kg ha-1 and cotton seed yield was lower for crimson clover (1759 kg ha-1). Overall, rolling treatments, with or without herbicides did not affect cotton population and yield. In contrast, cotton population and yield were affected by different weather conditions during 2009, 2010, and 2011 growing seasons.