Interpretive Summary of the Technical Paper:
“Introducing the North American project to evaluate soil health measurements”
Soils play an essential role in provisioning ecosystem services including food, fiber, and fuel, being an integral part of water and nutrient cycles, mitigating and adapting to climate change, and supporting biodiversity. Ensuring the continued and enhanced delivery of these ecosystem services requires stewardship of our soil resource through the promotion and maintenance of soil health.
The North American Project to Evaluate Soil Health Measurements (NAPESHM) was initiated and led by the Soil Health Institute to identify widely applicable soil health measurements for assessing soil health. To address this objective, we evaluated over 30 soil health indicators at 124 long-term agricultural research sites across North America where conventional systems were compared with regenerative soil health systems. Sites were selected to enable statistical assessment of each soil measurement across a continental range in climates, soils, cropping systems, and management practices. A summary of the study design and approach are below.
Soil health measurements for evaluation were identified via a committee of scientists from public and private sectors, farmers, field conservationists, and soil test laboratories based on the criteria that the measurement could (a) be applied both regionally and continentally; (b) have a clear range of responses based on desired agricultural goals; and (c) be responsive to varying management practices. Based upon these criteria, measures of soil physical, chemical, and biological properties were selected along with three existing soil health evaluation programs.
SHI partnered with over 100 investigators at long-term agricultural field experiments across North America to identify sampling sites under continuous, monitored, replicated management for 10 years or more. Sites were selected to provide a range in soil health due to differences in: (a) physical disturbance (e.g., tillage, erosion, or grazing); (b) cover crops (e.g., grains, legumes, or combinations); (c) crop diversity (e.g., crop rotation or pasture species diversity); (d) nutrient management (e.g., addition of different amendments); (e) water management; and (f) geographical location and diversity.
At each site, plots were selected based on alignment with project criteria, regional relevance, and resource constraints. Avoidance of tillage, fertilization, seeding, or any other plot level disturbance directly before sampling was a priority in collection of all samples which drove timely sample collection between spring thaw and summer planting at northern sites and during the dormant period between crops at southern sites.
The NAPESHM soil archive is comprised of 2029 soil samples from long-term experimental sites which captured a range of climates, management practices, and inherent soil properties. Sampling sites were spread across a large geographic area representing spatially diverse growing conditions with mean annual temperature ranging from 5.8-17.5 °C and mean annual precipitation ranging from 384- 827 mm. This unique dataset has allowed SHI to identify and recommend a minimal suite of soil health measurements that can be widely applied across North America and likely beyond. The peer-reviewed publication summarizing the NAPESHM study design can be found here.