New Mexico Chile Task Force

Cover Crop Establishment

You can improve your soil in a few weeks this fall with the time-honored practice of growing a cover crop. These quick crops add tons of nutrient-rich "green manure," priceless organic matter, and crumbly tilth to your soil.
What to plant? Look at what local farmers grow, and check with your county extension office for detailed advice. Legumes are perhaps the best choice because they "fix" nitrogen from the air into the soil. These crops include alfalfa, peas, beans (garden, fava, and soy), clovers, lupines, and vetches. Non-legumes, such as rye grass, oats, buckwheat, winter wheat, and pearl millet, generally grow more quickly than do legumes, however. Even garden plants such as radishes and kale can be used for a quick soil boost.
Typically cover crops are planted in the fall and tilled in a few weeks before spring planting. But if you anticipate a long, wet spring, or a mild winter, go ahead and turn your crop in yet this fall. In general, the younger the plant you dig in, the more quickly it will decompose. The more mature the plant, the more organic matter you'll get, but the nutrient release will be slower.
Remember not to let your cover crop go to seed or you will have weeds galore.

Soil quality improvements--Soil tilth is improved whenever a plant establishes roots and grows into compacted areas. Water infiltration is improved as well. When a field lays fallow for a period of time, the surface tends to seal and water will run off. Cover crops protect the soil surface and reduce sealing. Also, beneficial organisms in the soil, such as earthworms, thrive when fresh plant material is decomposing. Organic matter levels tend to improve with the addition of cover crops.
Erosion control--Cover crops reduce wind and water erosion on all types of soils. By having the soil held in place by cover crops during the fall, winter, and early spring, loss of soil from erosion is greatly reduced.
Fertility improvements--Legumes can add substantial amounts of available nitrogen to the soil. Non-legumes can be used to take up excess nitrogen from previous crops and recycle the nitrogen as well as available phosphorus and potassium to the following crop. This is very important after manure application, because cover crops can reduce leaching of nutrients.
Suppress weeds--A dense stand of winter rye or other cover crop can suppress weeds by soil shading. Allelopathic cover crops suppress the growth of other plants.
Planting cover crops may encourage insect control--beneficial insects, such as lady beetles or ground beetles.