Viable cover cropping opportunities in Minnesota

rows of young rye plants growing in tall corn rows

Cover cropping practices have been gaining popularity and interest as agricultural systems evolve to optimize land and resource management for greater economic and environmental sustainability.

Benefits of cover crops

In other agricultural regions, cover crops are used as an effective tool to sequester nutrients, contribute organic matter and protect soils from erosion during otherwise fallow periods. The high-intensity corn-soybean systems of Minnesota could gain similar benefits from cover cropping, particularly in the spring when soil and nutrients are most vulnerable to offsite movement.

In the upper Midwest, these losses occur through leaching and tile drain discharge, as well as surface runoff. Research conducted in southwestern Minnesota estimates an average of 25 kilograms per hectare (22 pounds per acre) of nitrate-nitrogen is lost through subsurface tile drainage between mid-September and May every year.

Minnesota cover crop research

The primary challenge that successful cover cropping faces in Minnesota is the short growing season. There’s rarely ample time and favorable field conditions to plant and establish a cover crop after the grain harvest and before winter sets in.

University of Minnesota researchers are working to identify and develop viable options for interseeding cover crops into standing corn. They conducted trials at field sites at University of Minnesota Research and Outreach Centers (ROCs) in Waseca (Southern ROC) and Lamberton (Southwestern ROC) in 2014 and 2015.

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Following the 2014 planting in Waseca, all species except NitroMax CC1 overwintered and produced significant biomass in the spring (Figure 4). In Lamberton, only the rye and pennycress successfully overwintered and put on significant spring growth.

bar chart showing biomass based on cover crop type and seeding methods; broadcast, broadcast + incorporated and drilled.
Figure 4: Cover crop spring biomass by species and planting method prior to termination and soybean planting in Waseca (2015).

Lack of snow cover in Lamberton during the winter of 2014-2015 likely resulted in winterkill of the legume cover crops. Cover crops did not affect corn yield at either location in 2014 or 2015 (Figure 5). Soybeans no-tilled into the residues (with no fertilization) all yielded competitively as well (Figure 6).

bar chart showing similar corn yields across locations and type of cover crop
Figure 5: Corn yields by interseeded cover crop. HV=Hairy vetch; N-Max=NitroMax mix; PC=Pennycress; RC=Medium red clover; WR=Winter rye; CHK=No cover crop.
bar chart showing similar soybean yields across locations and type of cover crop
Figure 6: Soybean yields by interseeded cover crop. HV=Hairy vetch; N-Max=NitroMax mix; PC=Pennycress; RC=Medium red clover; WR=Winter rye; CHK=No cover crop.

Other cover crop uses

In addition to ecological benefits, cover crops are being developed and used as added-value crops or cash cover crops that can be grazed or harvested in the spring prior to (or in relay with) the following warm-season crop rotation.

One example is seeding a winter annual forage crop following a corn silage harvest. Taking a silage crop removes more organic matter and leaves soils exposed for an even longer period of vulnerability than grain corn and soybean. You can use this time to give a supplemental winter annual forage crop more time to establish.

Due to the late frost and warm conditions, the fall of 2015 was a prime opportunity for such cover cropping. Figures 7 and 8 illustrate the establishment of a rye cover crop that was no-till planted into corn stubble following a silage harvest near Canby. Under optimum conditions, a stand like this would likely provide spring forage grazing for a couple of months before it’s terminated and planted with short-season soybeans the following spring.

corn field with stubble
Figure 7: Rye planted on Sept. 12, 2015 following corn silage harvest near Canby. Photo taken six days after planting (Sept. 18, 2015).
corn field with stubble, rye cover crop
Figure 8: Rye planted on Sept. 12, 2015 following corn silage harvest. Photo taken one month later on Oct. 31, 2015.

Reagan Noland, graduate student, College of Food, Agricultural and Natural Resource Sciences; Neith Little, former Extension educator and M. Scott Wells, Extension agronomist

Reviewed in 2018

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