Soil health update!

Soil health update!

UW Discovery Farms is continuing to evaluate the factors that have the greatest influence on soil health. Between 2015 and 2018, field staff collected soil samples from over 300 farm fields across Wisconsin and southern Minnesota. From these fields, information was gathered about management practices, including details on tillage, crop rotation, manure applications and cover crops. Information about each field’s soil properties was also gathered, like soil texture, drainage class and pH. All of this information was analyzed to identify the effects of each factor on soil health indicators such as soil organic matter (SOM), potentially mineralizable carbon (PMC) and potentially mineralizable nitrogen (PMN).

Our analysis has led to some interesting results. While many studies have shown that cover crops, manure applications and reduced tillage improve soil quality, one of the most important aspects of what we’ve found is that place-based factors are just as important. In particular, our data highlight the following:

Soil texture has a significant impact on total soil organic matter, carbon and nitrogen levels. In particular, soils with greater clay content tend to retain more organic matter through physical and chemical protection of the material from decomposition.

Drainage class is important to organic matter accumulation. Soils that drain more slowly tend to build organic matter over time. While fields containing tile drainage have oxidized much of the readily decomposable organic matter, they still tend to maintain higher overall levels of organic matter than well-drained soils. This is likely correlated with soil texture as sandier soils tend to drain more quickly.

The region where the field is located and the associated soil forming factors at the site (e.g. parent material, native vegetation, micro-climates) contribute to whether the field is likely to have higher or lower organic matter. Crop rotations with higher biomass (e.g. corn and alfalfa) tend to contribute more residue to the soil and accumulate more organic matter, particularly in labile forms that cycle more quickly through the soil.

Most of these factors are beyond a farmer’s control, except perhaps crop rotations. So what is a grower supposed to do? The good news is that numerous studies have shown that it’s still possible to increase soil health through the use of cover crops, manure and reduced tillage. The results presented here provide the clear message that goals should be set according to the conditions you’re working with. If you want to compare your soil health to others’, connect with peers in your area who farm in the same region and with similar soil types. Comparing your soils to those farmed in New England or the Great Plains will not be useful.

What’s next? UW Discovery Farms will continue conducting soil health research with participating farmers to help advance the resilience of our soils. Key locations will be tested using a broader range of measurements, including infiltration, bulk density, water retention and other measures of biological activity. To view more comprehensive results from this soil health study, visit www.waterwaynetwork.org and watch a recent webinar recording titled “Digging deeper into soil health." §