Article

Cover Crops and Extreme Weather in the United States Corn Belt

Written by: Tyler Williams, ForGround by Bayer Sustainable Systems Agronomist

Extreme weather is, has, and always will be a challenge for agricultural producers. Depending on your scenario, cover crops can be a tool to help mitigate some of that risk. The climate varies across the United States; however, at some point during the year many areas experience extreme heat, heavy rainfall events, flooding, drought, and other agronomic and environmental events. Since 2000, about $64 billion in indemnity payments (losses paid to insured) were paid for corn, soybean, and wheat losses from excessive rainfall, flooding, heat, or drought. (1) Many of those losses are out of the farmers control, but in some cases, cover crops can serve as a tool to help mitigate crop failure and non-direct crop losses, such as loss of soil or nutrients.

Extreme Rainfall

One benefit regarding extreme weather is the value cover crops can have in heavy rainfall events. Even an average rainfall event or season can have a negative impact on exposed or highly erodible soil. Normal rainfall in the spring ranges from just a few inches near the Rockies to over 10 inches near Iowa (Figure 1). Cropland during winter and early spring is typically bare in a corn-soybean rotation and is at high risk to soil loss from excessive precipitation.

Cover crops can be a key tool to protect soil by decreasing runoff loss by up to 80% and sediment loss from 40 to 96%; however, that is a function of biomass, timing, slope, etc. (2) The value of losing topsoil can be high for crop productivity and farm economics because topsoil contains the majority of the soil’s organic matter and plant available phosphorus and potassium. (3) It has been shown that each ton of lost soil includes over two pounds of nitrogen and one pound of phosphorus. (4) The nutrient loss alone is costly, plus the expense of field, ditch, or culvert repair.

Cover crops can also help maintain water infiltration by protecting the soil from the impact of raindrops which can dislodge soil particles and clog surface pores. (5) Reducing the amount and speed of runoff with cover crops can also help increase infiltration and retain soil moisture for the cover crop or cash crop.

Spring MAM Figure 1. Normal precipitation for Spring (March, April, and May) from 1991-2020. Map from the NOAA National Weather Service. (6)

Tips for Managing Conditions from Extreme Rainfall:

Cover the ground with a cover crop when cash crops are not - seed right after harvest (or before) and terminate near planting to help optimize growth (if limited by growing season).
Utilize no-till in combination with cover crops to prevent the risk of erosion after tillage of cover crops.
If gullies or drainage areas need worked in the fall, plant a winter-hardy cover in those drainage areas and use a spring burndown to terminate the cover crops.

If fields have been flooded for an extended period, cover crops can help bring the soil back to life. When the water subsides, growers should move quickly to minimize the risk of wind erosion and control weeds. A fast growing, high biomass cover crop for the appropriate time of the year should be considered.

Drought and Extreme Heat

Using cover crops to help mitigate the risk of drought is highly dependent on location, cover crop type, timing, and other variables. In short, cover crops can help build water holding capacity, improve infiltration, and reduce runoff loss. (7) These actions can provide additional moisture for plants that may otherwise be lost. The added residue can also reduce surface evaporative losses and soil surface temperature during extreme heat events. These are positive aspects when a drought hits; however, cover crops also need moisture to grow; therefore, cover crop type and scenario may need to be altered to match local conditions. Extreme drought conditions during seeding can cause germination failure and reduced growth. It can also be a risk if grown in a water-limited region and the cover crop utilizes moisture that the cash crop may need.

Tips for Managing Conditions from Drought and Extreme Heat:

Consider using cover crops now to build soil organic matter and water-holding capacity to better withstand future drought conditions.
Consider drilling cover crops in the fall to help increase establishment; or start planning early to broadcast in front of the infrequent rain events.
If corn crop performance is reduced due to drought, consider the use of grass cover crops in the fall to utilize leftover nitrogen.
Watch current conditions and forecasts in the spring for early termination (if needed) to help reduce cover crop water use before cash crop planting.

Other extreme events such as hail, tornadoes, or thunderstorm events can devastate crops leaving behind exposed soil. Cover crops are often used to protect the soil, prevent loss of nutrients, and help prevent weed growth after the event; however, don't forget to check with your insurance company and review herbicide labels for any replant or rotation restrictions.

Ultimately, when used effectively, cover crops can be a tool to help reduce losses associated with extreme events. Some of the risk management advantages require a long-term investment with cover crops or they can be used immediately ahead or after the event to garner the benefit.

Sources: 1 Reyes, J.J. and Elias, E. 2019. Spatio-temporal variation of crop loss in the United States from 2001 to 2016. Environmental Research Letters, 14(074017). https://iopscience.iop.org/article/10.1088/1748-9326/ab1ac9/.

2 Blanco-Canqui, H., Shaver, T.M., Lindquist, J.L., Shapiro, C.A., Elmore, R.W., Francis, C.A., and Hergert, G.W. 2015. Cover crops and ecosystem services: Insights from studies in temperate soils. Agronomy Journal, 107(6), 2449. doi:10.2134/agronj15.0086. https://acsess.onlinelibrary.wiley.com/doi/full/10.2134/agronj15.0086/.

3 Kaisi, M., Hanna, M., Miller, G., and Tidman, M. 2002. Soil erosion: Effect on soil productivity. Integrated Crop Management. Iowa State Universityhttps://crops.extension.iastate.edu/encyclopedia/soil-erosion-effect-soil-productivity/.

4 Duffy, M.D. 2012. Value of soil erosion to the land owner. AG Decision Maker. Iowa State University Extension and Outreach. https://www.extension.iastate.edu/agdm/crops/html/a1-75.html/.

5 Hoorman, J.J. and Sundermeier, A. Using cover crops to improve soil and water quality. 2017. Ohioline. The Ohio State University Extension. https://ohioline.osu.edu/factsheet/anr-57#:~:text=Cover%20crops%20protect%20soil%20aggregates,reduce%20wind%20and%20water%20erosion/.

6 Climate normal 1991-2020. National Weather Service. National Oceanic and Atmospheric Administration. https://www.weather.gov/rah/ClimateNormals1991-2020#Spring/.

7 2018. Cover crops – Keeping soil in place while providing other benefits. Lafayette County For Land’s Sake. United States Department of Agriculture. Natural Resources Conservation Service. https://www.lafayettecountywi.org/sites/default/files/fileattachments/land_conservation_planning_and_zoning/page/34801/for_lands_sake_-_september_2018.pdf.

Websites verified 4/18/23.

Legal Statements

ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. Performance may vary, from location to location and from year to year, as local growing, soil and weather conditions may vary. Growers should evaluate data from multiple locations and years whenever possible and should consider the impacts of these conditions on the grower’s fields.