Cover cropping terms to know
Cover cropping terms to know
Cover crop means a crop that is grown to build soil and benefit the farming system, rather than for harvest. Sometimes cover crops are referred to as “green manures.”
Seeding rate is the amount of seed planted per land area.
Broadcast seeding means scattering the seed over the surface of the soil, as opposed to using a planter that buries the seed.
Nitrogen fixation is the process of capturing nitrogen from the atmosphere and converting it into a form that plants can use. Nitrogen fixation is carried out by a partnership between plants in the legume family and special soil bacteria called rhizobia.
Biomass is another word for plant material, including stems, leaves, and roots.
Termination is the process of killing a cover crop. Some cover crops can be terminated by cutting or mowing; others must be tilled.
Incorporation means mixing into the soil. It often refers to tilling cover crop biomass into the soil as part of the termination process.
Nutrient immobilization happens when microbes take up nitrogen and other soil nutrients as they decompose plant material with high carbon content. This can lead to nutrients being temporarily unavailable for crop growth.
Cover crop options
| Crop | Note | Nitrogen-fixing legume |
|---|---|---|
| Oats | Often planted in mixture with peas or clover | |
| Peas | Breaks down quickly in spring to allow for earlier crop planting. Austrian winter peas are hardier but usually will not survive the winter in MN. | X |
| Berseem clover | Excellent N fixer, breaks down quickly in spring. | X |
| Tillage radish | Breaks up compact soils. Very little surface residue remains in spring |
| Crop | Notes | Nitrogen-fixing legume |
|---|---|---|
| Winter wheat | Terminate when flowering begins | |
| Winter rye | Can be difficult to terminate without tillage. Some growers mow rye and leave it on the field as a mulch. | |
| Vetch | If planted too late, it will not survive the winter | X |
| Red clover | Excellent N fixer. Terminate when flowering begins, not before. | X |
| Crop | Notes | Nitrogen-fixing legume |
|---|---|---|
| Oats | Can be terminated at any point - do not need to wait until flowering | |
| Spring barley or wheat | Good for preventing erosion. High C:N ratio unless planted with a legume | |
| Annual ryegrass | Quick establishment, easy to incorporate | |
| Red clover | Excellent N fixer and strong competitor with weeds. Can be frost seeded | X |
| Crimson clover | If mixing with grass, plant clover first so the grass doesn’t overtake it | X |
| Peas | Can use yellow (white flowers) or speckled (pink flowers) field peas | X |
| Crop | Notes | Nitrogen-fixing legume |
|---|---|---|
| Buckwheat | Quick growing, flowers quickly and attracts beneficial insects. Works well for short windows if you plan to plant a second crop afterwards | |
| Sorghum-sudangrass | Should be mowed when it reaches 3-4' to encourage deep root growth. Likely to outcompete legumes if using a mix | |
| Cowpea | Establishes well in hot weather. Choose a variety bred for leafy green vegetation vs. seed | X |
| Phacelia | Good weed suppression. Flowers support honeybees and native pollinators |
| Crop | Notes | Nitrogen-fixing legume |
|---|---|---|
| White clover | Hoe or cultivate bed edges regularly to prevent clover from entering rows. Not winter hardy in northern Minnesota | X |
| Oats | Good companion plant with white clover. Mow when flowering begins | |
| Annual ryegrass | Good companion plant with white clover. Mow when flowering begins | |
| Fescues (mix of tall and fine) | Stands up well to traffic |