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A field of no-till tobacco in Clark County.
Cover crop has been left as dead mulch between the rows.

Have you ever driven past a farmer's field in late fall or early spring and seen a beautiful carpet of green "grass" growing in it? This "grass" is actually a cover crop, and in Clark County that is oftentimes wheat.

Cover crops are grasses, legumes or small grains grown between the regular crop production periods. They do just what their name states - they cover the soil in order to protect or improve it while it is not in production. A cover crop may, or may not, be harvested. It can be tilled into the soil as a "green manure" or used as a living or dead mulch on the soil surface.

Most farmers plant cover crops in the fall and then till them under or kill them in the spring before planting their main crop. They can also be used in rotation with short season summer vegetables or before planting a fall crop.

Are cover crops beneficial?

Yes! Cover crops have many benefits:

Cover crops increase the organic matter in soil. Organic matter is the part of the soil that is composed of anything that once lived. It is very beneficial to the soil and the subsequent crop. Organic matter improves the condition of the soil by:

improving soil tilth - the physical condition of the soil as it relates to ease of tillage, seedbed quality, ease of seedling emergence, and deep root penetration. improving the stability of soil aggregates. Soil aggregates are groups of soil particles that bind to each other more strongly than to adjacent particles. Aggregate stability is the ability of soil aggregates to resist disturbance from outside forces (usually water).improving the rate of water infiltration. Infiltration is the process of water entering the soil. Soil that is in good condition has a stable structure and continuous pores to the surface. This allows water from rainfall to flow unobstructed through the soil during a rainfall event.reducing soil crusting. Crusts are continuous layers of the soil surface that often restrict water movement, air entry, and seedling emergence from the soil. Generally, the soil beneath a crust is loose.
increasing the populations of soil microbes and earthworms, which contribute to efficient nutrient cycling and improvements in soil structure.

Cover crops reduce soil erosion. They hold the soil in place preventing it from being blown away by winds or carried away in rainwater flow. This is important in Indiana as over 40 percent of our 13.5 million cropland acres have sufficient slope to be seriously damaged by water erosion, and at least a 1,000,000 acres are subject to serious wind erosion if not protected.

Fertility of the soil can be increased with cover crops. Legumes can add substantial amounts of available nitrogen to the soil, while non-legumes can take up excess levels of nitrogen from previous crops and recycle it to the following crop. Cover crops can also reduce leaching of nutrients.

A cover crop can suppress weeds by through competition and shading. They continue to do so by blocking out light after they are killed and left on the surface as mulch. Some cover crops can also suppress weeds chemically by releasing chemicals which prevent the germination or growth of other plants.

Cover crops can increase the number of beneficial insects present by providing them pollen, nectar and a physical location to live while feeding on pest insects.

Types of Cover Crops

There are two basic categories of cover crops: legumes and non-legumes. Legumes fix atmospheric nitrogen into a form plants and microorganisms can use. Non-legumes recycle existing soil nitrogen and other nutrients and help prevent leaching losses. The following table lists some common cover crops.

Hairy Vetch	Legumes	Non-Legumes	Wheat
	Clovers	Rye
	Hairy Vetch	Oats
	Field Peas	Wheat
	Annual Medic	Forage Turnips
	Alfalfa	Oilseed Radish
	Soybean	Sudangrass
		Buckwheat

How does a farmer decide which cover crop to use?

A farmer looks at what his main cash crop(s) will be for the coming year and then determines when a cover crop(s) can be used. Actual selection of a cover crop species will depend on when it can be planted and the goal for its use. In Indiana, cereal crops like rye or wheat are popular because they are easy to establish, fast growing, and seed is readily available and relatively inexpensive.

Are there disadvantages to using a cover crop?

I wouldn't really call them disadvantages, but there are things that the farmer needs to be aware of in planting a cover crop:

If a cover crop does not naturally winter-kill, then the farmer should have a method for killing the crop (mechanically or with herbicides) so that it does not compete with the next cash crop. Cover crops can act as weeds if not controlled.Timing is important when killing a spring growing cover crop. For maximum nutritional benefits and weed suppression, cover crops should be left on as long as possible. However, if left too long, they can use up soil moisture and hurt the following cash crop if dry conditions exist.Ample moisture is needed to establish a cover crop. In Clark County, water supply is critical during the months of July and August which could lead to failure of the cover crop.A failing crop may also result from late establishment.
Cover crops sometimes harbor armyworms, grubs or cutworms that can attack the cash crop.

All in all, the advantages of cover crops far outweigh the disadvantages. Too much of Indiana's cropland is being lost to soil erosion to maintain its future productivy. It behooves us to promote the use of cover crops in order to adequately protect our soil resources.