By Stephanie McLain
Did we have an extreme winter? According to the Midwest Regional Climate Center, about 90% of Indiana is within 10% of mean snowfall accumulations. That’s based on a mean of 28 inches for northern Indiana and 10 inches for southern Indiana. The mean period is 1981 to 2010.
Parts of northwestern Indiana are at 20% to 30% greater mean accumulated snowfall. The Accumulated Winter Season Severity Index indicates all of Indiana had a severe winter. Evaluate what effect winter had on your fields.
Check physical conditions. Are there gullies or large washed areas where crop residues moved off-site? Soil erosion like this occurs even on frozen soils, especially with tillage or if residue was removed.
Less visible is sheet erosion. Estimates from David Montgomery’s book “Dirt” are that 0.1 of an inch of soil is eroded every year under normal non-erosive conditions. After 100 years, that’s almost 1 foot of topsoil!
Erosion takes topsoil
Erosion doesn’t steal less-productive subsoil. It takes the most-productive topsoil. If erosion due to heavy rains or wet harvest compaction has occurred, deal with it head on. Sometimes fixing erosion problems takes a backseat to everything else. The degraded soil resource becomes the norm, and we become complacent with a failing system.
Tillage will not fix erosion. Neither will ignoring it. No-till and strip-till management and cover crops help stabilize soil and keep it in place. Targeted practices such as filter strips and field borders help prevent soil from leaving fields. Engineering practices such as grassed waterways and terraces stop in-field erosion.
Not as easily surveyed is loss of nutrients. The severe winter would indicate that less leaching and overland flow of nutrients occurred due to continuously frozen conditions. However, leaching and runoff of nutrients occur every year, regardless of winter weather. Why not plan to keep nutrients in place?
I attended the Indiana certified crop adviser conference and listened to two researchers discuss studies on nitrate loads in subsurface drainage. Both researchers looked at aspects of nitrate loading in tile lines, and how nitrogen application timing and cover crops affected these loads.
Here are their research findings:
Fall nitrogen applications stand out. Compared to all other application treatments, fall applications delivered much higher nitrate loads in tile lines.
Cover crops have an effect. Significant reduction of nitrate loading occurred with cover crops. In plots with spring-applied nitrogen and a cover crop mix of cereal rye and radish, there was a 50% reduction in nitrate loading when compared to no covers.
Cover crops not only interact with applied fertilizer nitrogen, but with all forms of nitrogen in the soil profile. This nitrogen is stored in the biomass of cover crops and released for the next crop. Currently, there’s field-scale research looking at cover crop nitrogen release.
Save commercial fertilizers. Purchased fertilizers are a large investment. Cover crops and nutrient management practices help keep this investment in the field.
Cover crops offer many benefits. Different varieties of cover crops work better for certain operations, soils and after specific crops. Contact your local Natural Resources Conservation Service district conservationist to find out more about what varieties and mixes would work best for you.
McLain is an NRCS state soil health specialist. The Indiana Conservation Partnership provides contributors for the Salute Soil Health column.