Management practices and soil health: Insights from dairy farms in the United States

Improving soil health in dairy forage systems is crucial to making dairy more sustainable. This study evaluated four key soil health indicators from commercial dairy farms under a range of management practices across dairy-producing regions of the U.S., including New York, Wisconsin, Texas, New Mexico, and Idaho. The selected soil health indicators included soil organic carbon (SOC), aggregate stability, carbon (C) mineralization potential (Cmin), and available water-holding capacity (AWHC). To account for environmental variability when assessing management effects, we used an ANCOVA to incorporate climatic, topographic, and edaphic covariates. Dairy forage soils in humid continental climates, particularly in New York and Wisconsin Driftless region, had higher SOC concentrations (20.4–35.8 g C kg⁻¹) compared to drier regions of northwestern Texas and northeastern New Mexico (SOC 7.3–12.6 g C kg⁻¹) and southcentral Idaho (SOC 15.8–18.8 g C kg⁻¹). Similarly, aggregate stability and Cmin were generally higher in humid continental climates. Soils under grazed and hayed pastures consistently had higher soil health indicators than those under row crop systems in the surface 15 cm. In semi-arid regions, irrigated systems had higher SOC concentrations, Cmin, and AWHC than dryland systems in Texas and New Mexico. The effects of reduced tillage on soil health were inconclusive in New York and Wisconsin, perhaps because of differences in tillage implements and soil compaction from heavy manure and harvesting equipment. Our results help establish soil health conditions in dairy forage soils and highlight the importance of considering environmental covariates when assessing management effects. These findings provide a foundation for tracking soil health trends in dairy systems and informing the calibration of biophysical models to enhance their accuracy in predicting soil dynamics in dairy forage systems.