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Monitoring soil nitrogen (N) dynamics in agroecosystems is foundational to soil health management and is critical for maximizing crop productivity in contrasting management systems. The newly established soil health indicator, autoclaved‐citrate extractable (ACE) protein, measures an organically bound pool of N. However, the relationship between ACE protein and other N‐related soil health indicators is poorly understood. In this study, ACE protein is investigated in relation to other soil N measures at four timepoints across a single growing season along a 33‐year‐old replicated eight‐system management intensity gradient located in southwest Michigan, USA. On average, polyculture perennial systems that promote soil health had two to four times higher (2–12 g kg⁻¹higher) ACE protein concentrations compared to annual cropping and monoculture perennial systems. In addition, ACE protein fluctuated less than total soil N, NH₄⁺‐N, and NO₃⁻‐N across the growing season, which shows the potential for ACE protein to serve as a reliable indicator of soil health and soil organic N status. Furthermore, ACE protein was positively correlated with total soil N and NH₄⁺‐N and negatively correlated with NO₃⁻‐N at individual sampling timepoints across the management intensity gradient. In addition, ACE protein, measured toward the end of the growing season, showed a consistent and positive trend with yield across different systems. This study highlights the potential for ACE protein as an indicator of sustainable management practices, SOM cycling, and soil health and calls for more studies investigating its relationship with crop productivity.

Soil health has received heightened interest because of its association with long‐term agricultural sustainability and ecological benefits, including soil carbon (C) accumulation. We examined the effects of crop diversity and perenniality on soil biological health and assessed impacts on mineralization and C stabilization processes across 10 systems including four no‐till annual row crops, two monoculture perennials, and four polyculture perennials. Crop diversity increased soil biological health in both annual and perennial systems. Rotated annuals with a cover crop increased permanganate oxidizable C (POXC) and soil organic matter relative to continuous corn (Zea maysL.). Perennial polycultures also had 88% and 23% greater mineralizable C relative to the annual and monoculture perennial systems, respectively. All polyculture perennials had significantly greater POXC relative to switchgrass (Panicum virgatumL.) and annual systems, with the exception of restored prairie. Of the systems assessed in this study, incorporating perennial polycultures into rotations is the most effective way to increase soil biological health and enhance C stabilization.