Meta‐analysis of soybean yield response to cover cropping in the Mississippi Portal

Abstract

Despite well‐documented environmental benefits, cover crop adoption in the Mississippi Portal region of the United States remains low. This study evaluated whether cover crops exert region‐specific effects on soybean [Glycine max (L.) Merr.] grain yield and whether responses vary by cover crop functional group or duration of use. A meta‐analysis of published US studies was conducted to quantify yield responses across United States Department of Agriculture, Economic Research Service Farm Resource Regions, cover crop functional groups (grass, legume, and mixtures), and duration in cover crop systems. In the Mississippi Portal, soybean yield declined by up to 7.2% following monoculture grass or legume cover crops compared to winter fallow controls, whereas mixed seeding of functional groups had no effect. In contrast, grass, legume, and mixed cover crops increased yield by 8.6%–14.5% in the Southern Seaboard. Significant yield effects were not observed in other US regions. Duration of cover cropping did not influence soybean yield as a covariate effect nor through interactions with region or functional group. Interpretation of results was constrained by unbalanced representation of factor levels and co‐varying management and edaphic variables (e.g., tillage practices and soil texture classes) among studies. Nonetheless, consistent regional patterns emerged. In the Mississippi Portal, monoculture grass and legume cover crops may reduce subsequent soybean yield and increase economic risk, whereas mixtures appear to mitigate yield penalties. These findings highlight the importance of regionally tailored cover crop recommendations and suggest that mixed‐species systems may provide a more resilient agronomic and economic strategy for soybean producers in the Mississippi Portal.