Iowa State Research Reveals Rapid Soil Health Gains from Prairie Strips

Research conducted by scientists at Iowa State University in collaboration with the Soil Health Institute has demonstrated that prairie strips can enhance soil health measures more quickly than previously anticipated. These prairie strips, which consist of 30-100 ft strips of herbaceous, perennial plants within crop fields, aim to restore the ecological benefits of Iowa’s native prairies while minimally impacting crop yield.

Previous studies have established that dedicating roughly 10% of a field to prairie strips significantly boosts biodiversity, supports pollinator habitats, reduces soil erosion, and improves water quality. However, the influence of these strips on soil health has not been thoroughly explored until now.

Key Findings on Soil Health Improvement

The recent findings, published in the Journal of Soil and Water Conservation, reveal that prairie strips have enhanced various soil health metrics within a timeframe of 10-12 years. Specifically, these perennial strips showed significant improvements in eight out of twelve soil health indicators, with notable gains in the following areas:

– Soil aggregate stability improved by up to 80%, indicating a greater capacity for soil to resist erosion.
– Microbial biomass increased by up to 54%, highlighting a rise in the microscopic organisms essential for nutrient cycling and carbon sequestration.
– Soil organic matter saw an increase of up to 23%, a critical component for maintaining healthy soil.
– Maximum water-holding capacity improved by up to 7%, enhancing the soil’s ability to retain moisture.

Marshall McDaniel, an associate professor of agronomy at Iowa State who coordinated the study, expressed his excitement about the findings, stating, “It was an exciting surprise to see the degree of these changes over just a decade or so. It has been thought that it would take much longer to see some of these levels of change, especially soil organic matter and maximum water-holding capacity.”

While aggregate stability and maximum water-holding capacity continued to improve throughout the study, some measures, such as microbial biomass and soil organic matter, plateaued towards the end of the observation period.

Research Methodology and Broader Implications

The study utilized a “paired chronoscope” methodology, which involved comparing 15 paired control and treatment sites with prairie strips aged between 2 and 13 years. These sites represented four of Iowa’s seven major landforms. Each pair consisted of a prairie strip treatment and a traditional cropland control managed under a conventional corn-soybean rotation, with most sites located on private farmland.

Six key aspects of soil health were assessed in the top six inches of soil, while a comprehensive evaluation was conducted at the Neal Smith National Wildlife Refuge near Prairie City, led by Elizabeth Riecke, a scientist with the Soil Health Institute.

Additional research led by Cole Dutter, who earned his doctorate in sustainable agriculture and soil science during this project, indicated that changes in microbial communities extended beyond the prairie strips into adjacent cropland soils. These shifts included increased enzyme levels associated with enhanced nutrient and carbon cycling, which could improve nutrient availability for crops and boost carbon storage.

The effects of prairie strips on soil moisture and plant-available nutrients reached up to 3 feet (approximately 1 meter) beyond the strips, with minimal adverse effects on crop yields.

Dutter noted, “Our related projects show that prairie strips are a relatively quick way to build soil health in the top of the soil profile. We think there is a lot of potential to expand these benefits throughout fields and even improve yields.”

Research collaborators are now exploring the prospect of rotating prairie strips after a decade to distribute benefits more evenly across fields. Lisa Schulte Moore, director of ISU’s Bioeconomy Institute, stated, “Some farmers we have worked with are interested in rotating their prairie strips after 10 years to spread the benefits across their fields.”

The study’s findings also emphasize that the techniques used to measure aggregate stability and water-holding capacity are accessible and cost-effective. McDaniel highlighted the usefulness of DIY tests that landowners can employ to evaluate soil health on their own properties after implementing management changes like prairie strips.

With funding primarily from the Foundation for Food and Agriculture Research and the USDA Farm Service Agency, alongside support from the National Science Foundation and USDA Hatch funds, this research underscores the significant potential of prairie strips in enhancing soil health within agricultural landscapes.