Cover Crops May Cause Winter Warming in Snow‐Covered Regions

Planting cover crops is an agricultural management technique in which crops are grown in between cash crop seasons when the soil would otherwise be fallow. Cover crops provide many local benefits to farmers and can increase carbon storage in soils, provide erosion control, and can help maintain soil health. In this study, how planting cover crops in all agricultural regions in North America can change wintertime temperatures. Using model simulations with the Community Atmosphere Model coupled to the Community Land Model (CAM5-CLM4.5), Danica Lombardozzi and NCAR and University collaborators found that cover crops can warm winter temperatures by up to 3 °C in regions with variable winter snowpack, such as central North America. The cause of the warming is vegetation that protrudes above the snow and reduces reflectivity, or albedo, of the surface. Instead of the bright snow reflecting solar heat back into space, crop stems and leaves absorb the heat and warm the atmosphere around them. Planting cover crop varieties that are less leafy or are shorter and get buried under the variable snowpack can help to minimize winter warming. This study suggests that the climate mitigation potential of cover crops may be offset in these regions if cover crop varieties are not carefully selected.

More research is needed to understand the costs and benefits of winter cover crops. A next step would be to look at the total effects of these crops and model a more realistic representation of how cover crops are employed as a land management practice.

Picture of cover crops versus fallow ground
Figure 1: Picture of cover crops versus fallow ground
Simulated winter temperature change associated with planting of tall (50cm, top panel) and short (10cm, bottom panel) cover crops
Figure 2: Simulated winter temperature change associated with planting of tall (50cm, top panel) and short (10cm, bottom panel) cover crops.

Reference

  • Lombardozzi, D.L., G.B. Bonan, W.Wieder, A.S. Grandy, C. Morris, and D.M. Lawrence, 2018. Cover crops may cause winter warming in snow-covered regions. GRL, doi.org/10.1029/2018GL079000