Global meta-analysis of cotton yield and weed suppression from cover crops

Authors: TOLER, HEATHER - University Of Tennessee; AUGE, ROBERT - University Of Tennessee; BENELLI, VICTORIA - University Of Tennessee; ALLEN, FRED - University Of Tennessee; Ashworth, Amanda

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/29/2019
Publication Date: 3/21/2019
Citation: Toler, H.D., Auge, R.M., Benelli, V., Allen, F.L., Ashworth, A.J. 2019. Global meta-analysis of cotton yield and weed suppression from cover crops. Crop Science. 59:1-13.

Interpretive Summary: In the U.S., the use of cover crops has fluctuated over time; however, the popularity of this practice has increased substantially over the past 10 years. As a provision of the 2014 Farm Bill, the Natural Resource Conservation Service provides financial incentives for farmers to plant cover crops as a means to address various states’ soil and water quality and conservation issues. According to a 2017 national survey of 2,102 producers, 88% reported growing cover crops. Based on the survey, 86% of the respondents cite soil health as a primary reason for using cover crops with yield consistency being listed second. Systematic, quantitative reviews, or “meta analyses” are carried out to ascertain cumulative treatment impacts of a large, multi-study datasets. Such systematic reviews provide a global synthesis of research, and are a promising analytical technique for assessing agronomic performance spatially and temporally. Our meta-analysis identified, on average cottonseed and lint yield increases of 6 and 5%, while decreasing weed biomass by 20% when cover crops are integrated into cotton systems. The impact of cover crops at suppressing weed growth and improving yield varied based on soil type, cover crop species, and cover crop termination (tillage vs. herbicide). Results provided in this study are useful for cotton producers interested in planting cover crops to improve yield and suppress weed pressure.

Technical Abstract: Cover crops can reportedly improve soil fertility, suppress weed growth and pest pressure, and thus improve cotton (Gossypium hirsutum) yield. In order to systematically evaluate cover crop effects on cotton yield and weed suppression, we conducted a random effects meta-analysis investigating 10 moderating variables in 104 articles, yielding 1,117 independent studies over 48 years. Globally, cover crops resulted in average cottonseed and lint yield increases of 6 and 5%, respectively, while decreasing weed biomass by 20%. Overall, leguminous cover crops increased seed cotton yield by as much as 17-43% (Vicia and Pisum genera, respectively). Monocots, non-legume dicots, and legumes were effective at suppressing weed growth (21, 52, and 10%, respectively). Incorporation of cover crops by tillage (rather than chemical burn down) resulted in up to 14% and 42% increases in lint and seed cotton yield. Cover crops increased cotton yields markedly on loamy soils, whereas there were lesser increases for other soil textures (p>0.05). Greater efficacy of cover crops at controlling weeds was proportionate to soil silt content, which was inversely related to sand content. In addition, cover crops were effective at controlling multiple types of weed species; however, weed species with shorter maximum heights were most suppressed by cover crop integration. Meta-analysis results indicate that cover crops have a positive effect on cotton yield and weed suppression. Their effectiveness, however, can vary depending on soil texture, management strategy, and cover crop/weed genera. These results are useful in developing recommendations for suppressing weed growth and improving yield via cover crop integration in cotton cropping systems per geographic region and soil texture.