While there has been a lot of work linking farm management practices with soil health or water quality, few have looked at the connection to both soil and water quality. A new report explores tradeoffs among water quality goals, as well as what we do and don’t know about how soil health practices might change water quality and quantity.
Read the full report
The report was produced by Soil Health Nexus, a university-led team dedicated to increasing access to research-based soil health knowledge, extension and resources. The report helps planners go beyond the simple idea that “soil health is good for water” to a more nuanced understanding of how to manage soil for healthy water. It also provides beautiful diagrams of the nitrogen and water cycles, which are available for educators to download and use. The report is co-authored by Francisco Arriaga (Associate Professor and Extension specialist at the University of Wisconsin-Madison) and Anna Cates (U of M Extension soil health specialist).
A basic assumption of land conservation is that what we do to manage land affects surface and groundwater quality. It does, of course. Rain flows through and over soil on its way to water bodies above and below ground. On the way, the water interacts with everything in the soil (minerals, nutrients, microbes). Depending on how fast the water moves (which is mostly controlled by soil texture, structure and slope), it may pick up nutrients or contaminants. As water pauses in soil pores, organisms can transform contaminants and organic materials into other forms. Land management choices like planting different species, nutrient and manure application practices, and tillage practices, can change water rate and constituents by changing soil structure and nutrient concentrations.
At this general level, the relationship between land and water is intuitive, but then why can’t we predict the water outcomes when we implement a new management practice? Because soil varies at the microscale, across fields, and across watersheds, and because pollutants move differently in the soil, there are often tradeoffs between positive and negative impacts of land management. For example, reducing tillage and increasing living roots boosts soil structure, building large soil aggregates for water and carbon retention, increasing macropores for water infiltration. This helps to reduce runoff, sediment loads, and phosphorus to surface water. However, rapid infiltration can speed movement of nitrate, a water-soluble form of N, to tile lines or groundwater, where it can cause algal blooms or contaminate wells. Whether the runoff reduction benefit outweighs the potential for rapid nitrate delivery to tile lines will depend on local hydrology and water quality goals.
In Minnesota, local watersheds are developing their own goals and strategies via the “One Watershed, One Plan” process and financial support from the state’s Clean Water Fund, both of which support changes meant to improve drinking and surface water quality. From the Red River to the Root River, many communities in Minnesota plan to incentivize planting perennials and cover crops, and reducing tillage, to achieve their goals. At the U of M, the Minnesota Office for Soil Health (MOSH) is working on research and education to make sure these practices are implemented as effectively as possible. We have a lot to learn but the community of Minnesota farmers, local government, and Extension are working together to make progress on these important issues.
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