Soil health management practices and crop productivity

Authors: MINER, GRACE - Colorado State University; Delgado, Jorge; IPPOLITO, JIM - Colorado State University; Stewart, Catherine

Submitted to: Agricultural and Environmental Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2020
Publication Date: 7/14/2020
Publication URL: https://handle.nal.usda.gov/10113/7071268
Citation: Miner, G., Delgado, J.A., Ippolito, J., Stewart, C.E. 2020. Soil health management practices and crop productivity. Agricultural and Environmental Letters. https://doi.org/10.1002/ael2.20023.
DOI: https://doi.org/10.1002/ael2.20023

Interpretive Summary: While soil health management practices such as no-till and cover crops can have multifaceted ecological and economic benefits, improvements in crop yield and crop nutrition are not inevitable outcomes of managing for soil health, and soil health initiatives must credibly delineate yield and quality outcomes. In this commentary, we underscore that management and soil health impacts on crop nutrient density are poorly quantified. While there is undoubtedly need for additional research on how soil health impacts crop nutrient density, we caution against language that broadly connects improvements in soil health to improvements in crop nutritional quality without substantive and quantitative support. Farmers, conservation groups, and industry groups, and policymakers need timely, accurate, and regionally-specific summarization of potential yield outcomes of implementing soil health practices — where is optimism surrounding yield and yield stability improvements warranted, what benefits may be only realized in the mid- to long-term, and where may yield declines persistently occur? Long-term data from conservation agriculture experiments indicates that yield impacts of no-till are regionally specific, with benefits in water-scare regions in large part due to increases in water use efficiency. Similarly, cover crop yields effects are also regionally specific, with benefits more consistently realized in water-rich regions. Overarchingly, there is a need for synthesis and analysis of regional-scale yield impacts of soil health practices, with accompanying mechanistic probing of the factors underlying positive or negative yield outcomes.

Technical Abstract: The global food system faces multiple challenges, including minimizing the environmental impacts of agricultural production, maintaining economic viability for growers, adapting to a changing climate, increasing crop yields, and maintaining or increasing crop nutritional quality — action is needed on all fronts. Management techniques that focus on maximizing soil health (SH) are undoubtedly promising solutions to mitigating some environmental impacts of agriculture and may increase economic returns in some systems. However, claims that increases in SH will concurrently increase crop quality (e.g., nutrient density) and productivity merit careful examination. The questions surrounding how SH management impacts crop quality are fraught with complexity, as there are multiple processes and factors beyond SH that determine nutrient uptake and nutrient densities in harvested crop components. Yield outcomes of SH management practices are of particular import, as there are concerns that current yield increases are insufficient to meet future global food demands. While SH indicators and assessment frameworks are comparatively recent initiatives, there are thousands of published studies focused on comparison of yield outcomes under conservation agriculture practices (e.g., no-till, crop rotations, cover crops). This existing body of literature underscores that SH practices can influence both biotic and abiotic yield components, with negative or neutral yield impacts reported in many systems. Only in select regions and systems have consistent yield increases been realized with SH practices, highlighting the need for careful clarification of language, as well as coordinated efforts to improve mechanistic understanding of yield impacts at a regional scale. The leadership efforts of environmental, research, and industry groups to protect, responsibly manage, and restore agricultural soils must include presenting evidence-based information on near-term, mid-term, and long-term yield and quality outcomes.