Microbial respiration gives early indication of soil health improvement following cover crops

Farmer participatory research in soil health is important to evaluating soil conservation practices like cover crops on working farms. The Soil Health Partnership (SHP) was a large farmer-led network that conducted a wide-scale assessment of soil health indicators, scores, and crop yields from on-farm research with consistent experimental methods across site-years. The focus of this study was to determine the effect of one to four years of cover crops on 12 soil health indicators, three soil health assessment composite scores, and yields of two crops using data collected from only 35 SHP sites from 2015 to 2019 (total of 45 site-years). Sites applied either single or mixed species winter cover crops in corn (Zea mays L.) and soybean (Glycine max L.) rotations. The strip-level soil health measurements were analyzed using a mixed model analysis of covariance with repeated measures. Observations taken prior to cover crop implementation were used as the covariate. Soil microbial respiration (carbon [C] mineralization) and the composite Comprehensive Assessment of Soil Health score responded to cover crops. Their initial observation values did not influence the impact of cover crops on soil health indicators or scores. These results demonstrate that regardless of initial soil health values, soil respiration might be a helpful indicator to monitor for short-term soil health changes within one to four years following the adoption of conservation practices across the midwestern United States.