Getting started with cover crops

Several winter annual cover crops yield harvestable grain and oilseeds that can add economic benefit to farm rotations beyond environmental benefits like reducing wind and water erosion and sequestering nutrients.

Winter camelina is a very hardy, winter annual oilseed that is seeing rapid development as a renewable and carbon-friendly fuel oil source.

Like winter wheat, hybrid winter rye and winter barley are winter annual cereal grains. They have multiple value-added uses including milling, distilling, malting and high-quality animal feed. Research is ongoing at the University of Minnesota Forever Green Initiative to select high-performing varieties, and fine-tune agronomic systems for these crops.

Winter camelina, hybrid rye and winter barley can be sown after harvesting crops like small grains, silage corn, early soybeans, dry beans, canning crops or sunflowers. The seedlings of camelina form rosettes in the autumn, elongate in the spring, and flower in the early summer. They are ready to harvest around mid to late June.

Hybrid rye and winter barley emerge and tiller in the fall and elongate in the spring of the following year, with harvest in late June (barley) to mid-July (hybrid rye).

There is additional research taking place to integrate these winter annual cash crops into a double crop or intercrop system. For example, soybean can be interseeded into established camelina in the spring, and camelina harvested over the top of the soybeans, providing two harvestable oilseed crops in one growing season. Another potential option is to plant very early maturing soybeans after a winter cereal grain like winter barley.

Early maturing varieties of winter barley and winter camelina are being actively developed at the University of Minnesota to better integrate into a double-crop or intercrop system to make the most of our short growing seasons. These crops have the potential to add a second revenue stream to a crop year but currently have limited markets. They provide similar ecosystem benefits to other cover crops, such as reducing soil erosion and nitrogen loss and aiding in water infiltration and retention.

A cover crop that overwinters will provide the best soil protection through the winter and into spring. However, you’ll generally need to terminate it before planting the cash crop in the spring.

• A combination of cereal rye, which will overwinter, and radish, which will winter kill, is an example of a mix where the rye provides added soil protection, while the radish residue decomposes quickly.
• For a quick-growing grain that doesn’t overwinter, seeding barley in the fall is a good option.
• While typically winter-killed, turnips can overwinter if weather conditions are right. 
• If radish is in the mix and there aren’t grazing cattle, then another cover crop that serves the same purpose as radish isn’t needed.

• Brassicas tend to winter-kill and decompose quickly in the spring. It’s believed that nitrogen becomes available earlier in the growing season due to this fast decomposition.
• Grasses aren’t considered to be nitrogen sources. However, as the plant material decomposes, nitrogen is released and some will become available for the cash crop.
• Mixtures of two or more cover crop species will provide more benefits than a single species.

We’ve rated cover crops on how effective they are at providing various benefits, using the following grading system:

• Excellent ****
• Very Good ***
• Good**
• Fair*