

Cover crops
Figure 1. Research has shown that cover crops (left) tend to use less water than what is lost to evaporation from bare soil (right) and they provide valuable organic matter as they break down in the soil.  


Benefits of Cover Crops

Cover crops can be used for a variety of purposes including protecting the soil, improving soil structure, fixing nitrogen, feeding the soil biological life, and managing soil moisture. A key soil health concept is that there should be something green and growing during as much of the year as possible. This is important to protect and feed the soil system, especially arbuscular mychorrhizae fungi.




Cover Crop Seed Mixtures


Cover crop cocktails should be used as much as possible. The diversity in the mixture builds microbial and physical soil function and reduces the risk of failure.


As an example, a mixture of a cool season grass (oats), a winter annual grass (cereal rye), a winter annual legume (hairy vetch), and a brassica (winter canola) would provide some quick cover in the fall, some nutrient scavenging, some nitrogen fixation, and more cover in the spring, while helping the soil system. Cover crop cocktails should be used as much as possible to accomplish multiple objectives.

Cover Crop Type and Time of Seeding

Cover crops are usually classified as cool season, warm season, winter annual, biennial, or perennial and as grass, legume, brassica, or other. Often times, cocktail mixes of the various types are used to ensure success or to achieve a variety of goals as the diversity of the mix adds to the benefits. Selecting a single cover crop, the seeding rate, or the amount of any type in a mix would depend on the goals and the time of seeding. (See Table 1 for some suggestions.) Most cover crops need at least 30 days of growth to start being effective and many should have 60 days of growth or more for the full benefits.

Most cover crops need at least 30 days of growth to start being effective and many should have 60 days or more days to provide full benefits.



While most brassicas are cool season annuals, they are most effective if they have 45 to 60 days before a killing frost to allow the tap root to penetrate deeper into the soil. They shouldn’t be used as a single species cover crop because the residue breaks down rapidly, they don’t fix nitrogen, and they aren’t very mycorrhizae friendly. Many producers include them in cover crop cocktails as the seeding rate is fairly low and the benefits of the large tap root are great, if the killing frost comes later in the fall. However, after mid-September, the odds of getting much growth aren’t very good.

If unable to seed any cover crops in the fall, a cover crop seeded in the early spring would still provide benefits. For a spring seeding, consider cool season grasses and legumes, like oats and forage peas, to help build the soil and manage soil moisture. Often these spring cover crops are seeded as soon as the soil conditions allow, before the spring rains really start. Brassicas, mustards, and other cool season broadleafs can be used in the spring, but they won’t develop the large tap roots as if they were seeded in the early fall.

Check with your local USDA FSA Office and your crop insurance provider regarding the use of cover crops with your farm programs.

Frost seeding of oats, mustards, vetches, or clovers may also be an option, once the temperature drops and the soil firms up. These cool season cover crops will then germinate and grow in the spring, providing some cover and feeding the soil system. However, they may start growing early and be killed by a frost later because of the lack of residue to help protect them from temperature fluctuations.


Table 1. Cover crops and seeding suggestions following corn or soybean harvest.
Cover Crop Type* Full Seeding
Planting Date Seeding Depth

 Oats   CG  40-75 Early fall or early spring  0.5-1.5
 Cereal Rye  CG  50-100  Fall  1-2
 Winter Wheat   CG   50-100  Fall  1-2
 Winter Triticale   CG   50-100  Fall  0.75-1.5
 Winter Barley  CG   50-100  Fall  1-2
 Spring/Forage Peas  CL   50-100  Early fall or early spring  1.5-3
 Lentils  CL  20-40  Early spring  1-1.5
 Chickling Vetch  CL  50-90  Early spring  0.75-1.5
 Hairy Vetch  CL  15-20  Fall  0.5-1.5
 Winter Peas  CL   50-100  Fall  2-3
 Mustard  B  4-6  Early fall or early spring  0.25-0.75
 Rape/Canola/Turnips  B  4-6  Early spring  0.25-0.75
 Oilseed Radish B  8-12  Early spring  0.25-0.75
 Oats/Forage Pea Mix    30/30  Early spring  1-2
 Cereal Rye/Hairy Vetch Mix    40/20  Fall  1-2
 Cereal Rye/Winter Pea Mix    40/40  Fall  1.5-2.5

* B = brassica, C = cool season, G = grass, L = legume, W = warm season
** Use the higher rates when broadcasting seed. When used in a cocktail, divide the full seeding rate by the number of species in the cocktail.