The Soil Beneath Your Lawn
Are you curious about what is happening in the soil beneath your lawn? Have you seen neighbors replacing parts of their lawn with tall prairie grasses and wildflowers and wondered why? Are you curious how your lawn could be impacting the streams and lakes near your home? If so, then sign up to have the District assess your soils!
Staff are entering their third year of conducting soil assessments across the District. This year we are heavily focusing on assessing residential lawns. We would love to come out and assess your soils to see how they are functioning. Not only will this provide valuable data on how lawns affect soil functions and hydrology in our watersheds, but it allows us to give you information on the health of your soils. With this data, we can also provide you with information on how to improve your soil health and water infiltration.
Learn more about the District's Soil Health Study.
But why are lawns so imporant to assess? Lawns comprise approximately 40 percent of the District. They have an altered hydrology compared to native forests, prairies, or savannas. Because they are usually established in conjunction with construction projects, their soil is typically compacted by heavy equipment. Lawns shed much more runoff than native plant communities because of shallow root systems and compacted soil. Due to their altered hydrology and compromised plant communities, they have a negative impact on the ecosystem and consume significant natural resources through their maintenance (irrigation, fertilizer, pesticides, and fuel for mowing). All our small individual lawns add up to a lot of turf and can yield more than five times the amount of runoff compared to the natural woodlands once present in the landscape. All this runoff carries excess nutrients and pollutants downstream to our natural waterbodies, further degrading those resources.
Sign up for a soil assessment.
What to expect from your soil assessment
District soil assessments of your lawn can be completed within a workday, are minimally invasive, and done entirely by staff. After you sign up, we will reach out to make sure your yard is a suitable candidate for assessment. At this point, you can discuss limitations to where we can sample, and we can provide you with a proposed map of sample points. From there we can set up a time to come visit your property.
District soil assessments consist of two main components: infiltration testing and soil sampling.
Infiltration testing
Infiltration testing is conducted using a Modified Philip Dunne (MPD) infiltrometer which automatically measures and records infiltration rates and hydraulic conductivity of the soil. At each sample point, three small patches of sod are neatly removed and a 4 inch diameter cylinders are pounded into the soil several inches at each patch. We may dig deeper down below the surface, but we work to keep the hole just big enough so that everything can be replaced back to the state it was previously in. From here, the cylinders are filled with water and they are turned on, beginning testing and automatic measurements. Once the cylinders are completely drained, they are removed, data is saved, and staff replace the soil and sod.
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Hydraulic conductivity is the infiltration rate of the water once the soil has reached 100% saturation and the infiltration rate has become constant. This data helps identify areas which may have more capacity for capturing and storing stormwater and potentially reducing runoff.
Soil sampling
Soil sampling consists of collecting several 6" x 2" subsamples from below the surface (anywhere from 0 - 12 inches depending on the point) across a site, mixing them together, and removing a composite sample to be analyzed for a series of soil health indicators.
Soil sample data helps identify how sites in different land uses measure up to one another in terms of soil health. This includes measuring and comparing their biological, chemical and physical properties. These measurements show us how well the soil is functioning. Greater soil function leads to better infiltration and stormwater capture, as well as healthier microbial and vegetative communities.
For more information about District soil monitoring, read the report:
2023 Soil Health Program ReportCheck out the District's basic guide to soil health:
Soil Pamphlet (digital view).pdf
FAQs
The methods we use for data collection create minimal disturbance. For the soil samples, we will dig holes 12” deep using a tile spade. Our method of removal is to remove the soil as one “plug” so that when we are done with data collection, we can put the plug back where we got it from. For infiltration we may dig holes 12" deep and remove soil as that same “plug” and place it back in the ground after data collection.
Nope! This is free to participants.
No. Staff is only focusing on collecting data from residential lawn sites for this part of the study. These sites are defined as single or multi-unit family homes that have cultivated turf.
Staff will reach out to you via email within a week from when you filled out the form.
In the interest form, there will be a question asking if there is anywhere on your property staff should not collect data from. You can describe where you'd like staff to avoid and, when creating our sampling maps, staff will avoid placing any points in those areas. You do not need to provide a reason for why you don't want sampling done there.
Cornell has a more robust sample analysis and tests for properties related to water resources that the UMN doesn’t test for. Cornell tests for properties such as available water capacity and soil respiration, both of which are important to understanding how the soil can affect the hydrology of a landscape.
No. We remove the soil as a "plug" so we cause as little disturbance as possible.
