On-farm progress toward soil health potential in Southern US row crops

Abstract

There is growing interest in managing agroecosystems to not only produce crops but also reduce erosion, increase soil organic carbon (C) storage, enhance microbial activity, and generally improve ecosystem functioning. Farmers are modifying their management systems (e.g., reducing tillage and planting cover crops) to address these soil health objectives and reap economic benefits. The nature of soil health–promoting practice changes varies regionally, as do climate and soils’ inherent capacities to sustain ecosystem functioning. Hence, using soil health measurements to understand how farmers’ practice changes have affected ecosystem functions requires interpreting data in a regional and soil-specific context. To operationalize context-aware soil health assessment at scale (e.g., across multiple states), we surveyed soil health and organic C stocks (0 to 30 cm) in seven regions with contrasting cropping systems, practice changes, inherent soil properties, and climates across the Southern United States. The sampled regions represent 2.5 million ha of cotton (Gossypium hirsutum L.) production, from the Texas Southern High Plains to the Georgia Southern Coastal Plain. Compared to soils under the predominant crop production systems in each region, soils under soil health management systems had greater soil organic C, aggregate stability, and/or C mineralization potential, with the magnitude of management effects varying by indicator and region. Relative differences in soil health indicators and organic C stocks between crop production systems with and without practice changes ranged from 11% to 22% and were statistically significant. These regional scale differences are comparable to the mean effects of reduced tillage and cover cropping reported in meta-analyses of agricultural experiments. The soil health improvements achieved by farmers represent 11% to 39% of the total potential improvement in soil health indicators as constrained by inherent soil properties and climate. While the specific practice changes that improved soil health varied by region (e.g., multiyear bedding in the Southern Mississippi River Alluvium and strip/no-till with cover crops in Georgia), in all cases, these practices are currently used on less than half of the regions’ cropland. Increasing practice adoption via farmer-led experimentation and knowledge exchange presents a major opportunity to unlock the benefits of healthy soils at scale.

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