“Snirt” and How To Minimize It

South Dakota State University Extension

Blowing soils, dust storms, and “snirt” (snow with ‘dirt’ on it that appears black) have been quite evident this winter. High winds combined with dry conditions are certainly a driving force of this issue. The other force is a lack of soil cover and soil resiliency. Keeping soils covered during winter can easily be overlooked when the direct effects of erosion are not clear. However, during a dry, windy winter, erosion becomes quite obvious and even hazardous to drivers when dust storms pop up.

Black snow in the ditch, or snirt, is a clear example of where valuable topsoil is lost to the ditch or neighbor. Topsoil is not only ideal in a healthy soil system, but it contains valuable nutrients, including non-mobile nutrients, Phosphorus (P) and Potassium (K).

Avoiding all soil erosion is nearly impossible. Under extreme conditions (very high wind or record setting rain events), even the best-managed soils can erode. We cannot be certain when erosive events will occur. Having resilient soils that are prepared to take on Mother Nature at their top game should be the ultimate goal. Two of the five principles of soil health (soil cover and limiting soil disturbance) will help keep your soil from eroding and in the field for yourself and the next generation.

Tips for Minimizing Erosion

SOIL COVER

It is very difficult to build soils if you are constantly losing them. Wind erosion can start at speeds as low as 12 to 15 miles per hour. Keeping the previous crop’s residue and/or other living plants on the soil surface helps wind and water become absorbed by the cover, rather than eroding the topsoil. Many view the top layer of residue on a field as “trash,” but do not be fooled. In fact, for every one inch of residue left on a field, there is potential for 4 inches of horizontal erosion prevention (height × 4 = distance of protection).

Crop residues not only protect your soils during dormant periods, but help cycle any nutrients that were left in that residue back to the soil, thereby keeping nutrients on your field rather than in corn stalk bales or straw taken elsewhere. Soil cover in the form of crop residue or cover crops can also help to reduce weed pressure, moderate soil temperatures, retain moisture, reduce compaction and crusting, and provide a home for vital soil biology.

In a rangeland setting, it is all about grazing management. In order to catch as much winter snowfall as possible and protect soils, producers should strive for at least 50 to 60% of organic material cover on the soil surface with at least 4 to 6 inches of residual stubble height for native grasses (if possible) when moving into winter (Kelly, 2021).

LIMIT SOIL DISTURBANCE

The most obvious example of soil disturbance is tillage. Many farmers were taught to till in order to open up the ground, allow air in, and help soils to absorb moisture as well as dry out the surface when needed. As years have passed, research and experience have shown us that tillage actually reduces water infiltration by destroying natural pores and root channels that transport water. Tillage also destroys the natural soil ecosystem, and burns up soil carbon (organic matter) more quickly. In a dry year, keeping as much soil moisture as possible is very important. In fact, soil organic matter can hold up to 20 times its weight in water (Reicosky, 2005). Tillage reduces soil organic matter by exposing it to air, which allows it to be consumed by opportunistic bacteria and lost as carbon dioxide (CO2) to the atmosphere. The very reasons many were originally taught to till the ground have now been proven to be just the opposite. Soils naturally receive all the oxygen and nutrients needed to be healthy by growing a variety of plants, allowing them to build up organic matter and healthy soil microbiology consisting of a balance of fungi and bacteria. Think of a lawn, healthy pasture or alfalfa field—no tillage needed! In fact, one teaspoon of healthy soil can contain between 100 million and 1 billion soil microorganisms! Research and observation tell us that tillage disturbance causes increased wind and water erosion. With no protection (armor) from the elements, fall-tilled soils are especially at risk.

In Summary

Avoid as much erosion as possible while maintaining healthy, resilient soils by excluding tillage and providing soil covering (armor) by leaving crop residues in place on the soil surface. This may look different on every operation, whether you grow row crops, small grains, forages, livestock, etc. In order to work towards a whole systems approach, it is advised to adopt all five of the soil health principles. For information on the remaining three principles (diversity, living roots, and integrating livestock) see the SD Soil Health Coalition website (SDSHC, 2022). Making changes to a farm or ranch operation is not easy, but taking steps towards protecting one of our most important natural resources, soil, is a great way to help your farm or ranch become more resilient and provide a future for the next generations. For information on transitioning to healthy soil systems (especially in eastern South Dakota) see our new extension publication, Transitioning to Soil Health Systems in Eastern South Dakota, or look at resources available at the SD Soil Health Coalition or SD No Till Association webpages.