Mower County and southeast Minnesota have a new tool to show how different farming practices affect soil erosion and the way rainfall infiltrates the land.

Area soil-health specialists now have a rainfall simulator that can be transported around the state. Acquired earlier this year for demonstrating soil-health properties, the simulator was made possible by the Minnesota Board of Water & Soil Resources (BWSR) and the Legislative-Citizen Commission on Minnesota Resources (LCCMR).

In August, the Mower Soil & Water Conservation District hosted a demo with the rainfall simulator at the Mower County Fair, with its resource specialist Steve Lawler leading the event with Dean Thomas of the Fillmore SWCD. Lawler and Thomas also work with ag producer-led Mower-Fillmore Soil Health Team formed in 2015.

The simulator has been used throughout this year at various soil-health events and field days. Most recently, Lawler and Thomas conducted a rainfall simulation Aug. 23 for U.S. Rep. Tim Walz at a Minnesota Land Trust event on a farm near La Crescent to show the effect of agronomic practices on soil samples taken from Mower County farm land.

Using soil samples collected from different land uses, the device works by sprinkling water on trays filled with undisturbed soil, simulating a rainfall event. Soil in each tray represents a particular cropping method or land use, such as no-till cropping, conventional tillage, cover cropping, urban lawn, and managed or unmanaged pasture.

Glass bottles under each tray collect water that runs off and/or infiltrates the soil. Results are determined by examining each bottle’s volume of water and sediment levels. Soils that inherently resist the forces of erosion will have less water runoff and more water infiltration. Soils with compaction and/or poor physical/biological properties will yield high volumes of runoff water and sediment with little infiltrative water.

The bottle results are influenced by a variety of soil health attributes. Soils under land-use practices that promote low soil disturbance, high biological diversity and net carbon accumulations generally will have less runoff and sediment loss. Soils under practices involving tillage, monocultures and/or compacting activities that thwart natural, structural development and biological diversity typically will have less infiltration and greater volumes of runoff and sediment loss.

Results from analyzing the bottles also can give a picture of how soil-health attributes can influence watershed hydrology, erosion and sedimentation. Soils in watersheds that have good infiltrative properties might reduce stormwater volume and/or velocities.

Soils that resist erosion might help to reduce total suspended solids and nutrient concentrations in surface water. Soils that maintain good structural integrity might be more resistant to the effects of extreme weather events.