Cover crops

Cover crops are grown outside of the cash crop growing season, usually seeded in the fall and killed before spring planting.

Keeping living roots in the ground year-round can improve water management, soil protection and nutrient scavenging, but they need to be given the same attention as a cash crop to ensure success.

Try cover crops on a small scale first, and look into cost-share from state and local governments. 

Some of the best opportunities are with early-harvested cash crops like corn silage, small grains, and canning crops like beans and peas, as you’ll get more vigorous fall growth if you plant in late summer and early fall.

In fields where wheat was just harvested, simply allowing it to reseed itself without tilling the land would work as a cover crop. But cover crops can work with standard corn-soybean rotations as well.

Benefits of cover crops

Erosion control

Cover crops reduce erosion in a few different ways.

• Aboveground, living cover crops protect the soil from rainfall impact and reduce the effect of wind. Runoff is reduced along the way. 
• Belowground, roots hold soil in place during active erosion events and build structure. Better soil structure means the soil is less likely to erode even if left bare later in the season, such as between harvest and cover crop planting.
• Runoff sediment also contains soil phosphorus, so reducing runoff is an important strategy for reducing P loading in surface water. 

Infiltration and water management

Cover crop root systems create large channels through the soil to allow increased infiltration. This effect is especially significant for species with large taproots, but other cover crops also increase infiltration.

• Increased infiltration means fields are less likely to stay saturated during Minnesota’s rainy springs.
• Many farmers report dry field conditions more quickly after a rain event when they use cover crops.

Cover crops can also help soil store water by building soil structure and creating a network of large and small pores.

• Once water enters the soil through infiltration, this pore network retains water for plants to take up as necessary.
• This increase in soil water holding capacity can be especially beneficial in dry years.

Nitrate reduction

Soil nitrate reduction is well-established in Minnesota for a variety of cover crops.

• Nitrate is often left in the soil after fall harvest of corn.
• A winter cover crop takes up soil nitrogen, so less nitrogen is leached. This is an important benefit for reducing groundwater nitrate contamination.
• Farmers should expect some nitrate drawdown by cover crops and plan the subsequent season’s fertility accordingly.
• Soil testing before applying N to cash crops can help with field-specific recommendations.

Minnesota cover crop recipes

For a quick way to get started, Minnesota cover crop recipes provide step-by-step guidance to some of the lowest-risk starting points for cover crops. These recipes don’t cover all possibilities, but they can help beginners incorporate cover crops into a farm operation.

• Post corn, going into soybean: Use cereal rye
• Post soybean, going to corn: Use oats
• Post corn silage, going to corn: Use cereal rye
• Post corn silage, going to soybean: Use cereal rye

Learn more about reducing tillage and incorporating cover crops: