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Cover crop selection for vegetable growers

There are many ways to incorporate cover crops on a vegetable farm or in a garden. Depending on the crops being grown, there are distinct windows of time when a cover crop can fit into a rotation.

Diagram of cover crop timing options for Minnesota vegetable growers. See page for detailed transcript.
Cover crop timing options for vegetable growers. See below for a detailed transcript.

The timings suggested in the graph are approximate, and planting times will differ slightly depending on where you are located. To find planting dates tailored to your county, use the Midwest Cover Crop Decision Tool. Seeding rates for various cover crops can be found on the cover crop comparisons and planting rates page.

Mixing crops

Though this page highlights one cover crop at a time, it’s often useful to mix multiple crops together. In particular, mixing a legume with a non-legume is a practical way to achieve an optimal blend of ecosystem services.

  • A high biomass grass will boost organic matter in the soil, suppress weeds, control erosion, and scavenge excess soil nitrogen.
  • A legume will fix nitrogen to provide to the following crop.
  • By mixing a grass and a legume, growers can achieve multiple benefits.

Many of the cover crops listed below also provide a food source to pollinators if timed correctly. See the notes on each cover crop for suggestions about mixes.

While mixes with multiple species can offer multiple benefits, pre-made mixes are often not designed with vegetable growers in mind. When deciding on a mix, think about incorporating plants of various families so that the mix can accomplish multiple goals.

Take care to avoid planting a mix that contains cover crops in the same families as your cash crops. Many cover crop mixes contain plants in the Brassica family, which can be hosts for pathogens that infect broccoli, cabbage, cauliflower, many Asian greens, mustard, arugula, turnips and radishes.

Cover crops for early fall that will die over the winter

Cover crops that die over the winter tend to break down quickly in the spring and are a good choice for fields where a grower plans to plant an early spring crop like lettuce or spring Brassicas.

These cover crops need to be planted a bit earlier than overwintering cover crops in order to generate biomass in the fall, and so they are a good fit for vegetables that are harvested in August like cucumbers and sweet corn.

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Cover crops for mid to late fall that will survive the winter

Overwintering cover crops can be planted a bit later into the season, and are a good fit for sowing after late-harvested crops like tomatoes and peppers. They are also well suited to fall manure applications because they can scavenge the nutrients in the soil and hold them in place through winter and spring snowmelt.

These crops need to be terminated in the spring, and growers should allow 3 weeks for the cover crop to break down after terminating. This is especially important for grasses with a high carbon to nitrogen ratio such as winter wheat or rye.

If the next crop is planted too soon before breakdown is complete, the crop may compete for nutrients during cover crop decomposition. Because of this, overwintering cover crops work well when followed by a crop that is planted or transplanted a bit later in the summer such as tomatoes or pumpkins.

Growers can also plan to add nitrogen early in the growing season to make sure the cash crop doesn’t suffer from nutrient competition.

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Cover crops for early spring

For vegetable crops planted later in the season, an early spring cover crop can provide organic matter, scavenge or provide nutrients, and keep the soil free of weeds until planting.

Allow about 3 weeks of breakdown time after terminating and incorporating an early spring cover crop before seeding or transplanting a vegetable crop to prevent resource competition as the residues breakdown.

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Cover crops for midsummer planting

Many vegetable crops are harvested at or before midsummer (broccoli, snap beans, peas, early carrots, etc.). While growers can plant a second crop at this point in the season, some may opt for a cover crop instead to build soil organic matter and provide other ecosystem services.

The non-legume cover crops discussed here are divided by high carbon to nitrogen ratio and moderate carbon to nitrogen ratio. If your goal is to produce as much biomass as possible, the high carbon to nitrogen ratio crops are great choices for adding organic matter to your soil. However, they will take longer to decompose, and so they are best suited for fields where you do not plan to grow a late fall crop, as the breakdown process may tie up nutrients.

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Cover crops for walkways: between row living mulches

Many vegetable growers who use bed systems, either permanent beds or new beds each year, opt for living walkways between rows instead of bare ground or landscape fabric.

Living walkways keep roots in the soil, which helps to prevent erosion, absorb excess water and prevent muddiness in walkways.

Preliminary studies show that living walkways may reduce crop yields compared with bare or landscape fabric-covered walkways, in part due to competition for nutrients. Incorporating a legume and maintaining the cover crop with mowing and hoeing or mechanical cultivation along edges may help to prevent competition.

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More cover crop resources

Authors: Natalie Hoidal, Extension educator, Adria Fernandez and Naomy Candelaria

Reviewed in 2021

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