Global Meta-Analysis of Cotton Yield and Weed Suppression from Cover Crops

Cover crops can reportedly improve soil fertility, suppress weed growth and pest pressure, and contribute to cotton (Gossypium hirsutum L.) yield improvements. 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 1117 independent studies over 48 yr. Globally, cover crops increased cottonseed and lint yield by 6 and 5%, respectively, while decreasing weed biomass by 20%. Overall, leguminous cover crops increased seed cotton yield by 17 to 43% (Vicia spp. and Pisum spp., respectively). Monocots, nonlegume 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 lint (14%) and seed (42%) yield increases. Cover crops increased cotton yields markedly on loamy soils, whereas there were lesser increases for other 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 crops. Overall, cover crops had a positive effect on cotton yield and weed suppression. Their effectiveness, however, can vary depending on soil texture, management strategy, and cover crop or 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.