What do we know about cover crop efficacy in the North Central United States?

Excerpt

Recent meta-analyses about the efficacy of cover crops predict increased (a) soil organic matter (Poeplau and Don 2015), (b) arbuscular mycorrhizal fungi colonization (Bowles et al. 2017), and (c) nutrient conservation (Quemada et al. 2013; Kladivko et al. 2014; Han et al. 2017), all while improving (with legume cover crops), or at least not reducing (with grass cover crops), main crop yields (Tonitto et al. 2006; Marcillo and Miguez 2017). These analyses broadly support cover crop adoption, and both survey and satellite data suggest that cover crop use in the North Central United States is increasing (Conservation Technology Information Center et al. 2015; Hamilton et al. 2017; Seifert et al. 2018). However, many studies show no benefit of cover crops (Poeplau and Don 2015; Han et al. 2017), and economic analyses show greater expenses and risks with cover crops (Pratt et al. 2014; Roth et al. 2018), so it is critical to clarify what costs and benefits may be expected in varying circumstances. Rather than expecting global benefits to mirror mean effects, we should take into account differences in cropping systems and climate to predict cover crop efficacy and set growers confidently on the lowest-risk path to success (Snapp et…