Taking a look at cover crops

Tony Nye - OSU Extension

Recently I got a request to take a look at using cover crops in our cropping systems. It is widely used practice that has been slow to be adopted in southwest Ohio but is growing in acceptance each year.

A cover crop is a crop planted primarily to manage soil erosion, soil fertility, soil quality, water, weeds, pests, diseases, biodiversity and wildlife in an agroecosystem.

Cover crops are considered one of the most effective in-field practice farmers can use to reduce nitrogen and phosphorus losses, keeping those nutrients out of streams and lakes.

There are many crops we can utilize as cover crops. No one cover crop is going to accomplish all of the benefits of cover crops. It’s up to farmers to study the situation in their fields and decide what to accomplish because each of the specific potential benefits requires a different seeding program.

Next you need to plan the specific planting time, the specific type of cover crop, and the specific harvest method and time to end the cover crop.” expense and the extra time in the field required.

Farmers need to consider the expenses and extra time that can go into managing a cover crop. Farmers need to weigh carefully both the short term and long term benefits of a cover crop.

Generally cover crops can be grown for several purposes and have three main categories – nitrogen trap crops, sources of cover and residue and sources of nitrogen.

So what are the benefits to cover crops?

Organic matter, soil structure

A major benefit obtained from cover crops is the addition of organic matter to the soil.

During the breakdown of organic matter by microorganisms, compounds are formed that are resistant to decomposition — such as gums, waxes, and resins. These compounds — and the mycelia, mucus, and slime produced by the microorganisms — help bind together soil particles as granules, or aggregates.

A well-aggregated soil tills easily, is well aerated, and has a high water infiltration rate. Increased levels of organic matter also influence soil humus.

Humus — the substance that results as the end product of the decay of plant and animal materials in the soil—provides a wide range of benefits to crop production.

Nitrogen production

Nitrogen production from legumes is a key benefit of growing cover crops and green manures. Nitrogen accumulations can range from 40 to 200 pounds of nitrogen per acre.

The amount of nitrogen available from legumes depends on the species of legume grown, the total biomass produced, and the percentage of nitrogen in the plant tissue. Cultural and environmental conditions that limit legume growth — such as a delayed planting date, poor stand establishment, and drought — will reduce the amount of nitrogen produced.

Conditions that encourage good nitrogen production include getting a good stand, optimum soil nutrient levels and soil pH, good nodulation, and adequate soil moisture.

Soil microbial activity

A rapid increase in soil microorganisms occurs after a young, relatively lush cover crop is incorporated into the soil.

The soil microbes multiply to attack the freshly incorporated plant material. During microbial breakdown, nutrients held within the plant tissues are released and made available to the following crop.

Factors that influence the ability of microorganisms to break down organic matter include soil temperature, soil moisture, and carbon-to-nitrogen (C:N) ratio of the plant material.

Nutrient enhancement

In addition to nitrogen from legumes, cover crops helps recycle other nutrients on the farm. Nitrogen (N), phosphorous (P), potassium (KB), calcium (Ca), magnesium (Mg), sulfur (S), and other nutrients are accumulated by cover crops during a growing season.

Rooting action

The extensive root systems of some cover crops are highly effective in loosening and aerating the soil. When cover crops are planted after a subsoiling treatment, they help extend the soil-loosening effects of the deep tillage treatment.

Weed suppression

Weeds flourish on bare soil. Cover crops take up space and light, thereby shading the soil and reducing the opportunity for weeds to establish themselves.

The soil-loosening effect of deep-rooting cover crops also reduces weed populations that thrive in compacted soils.

The primary purpose of a non-legume cover crop—such as rye, millet, or sudangrass—is to provide weed control, add organic matter, and improve soil tilth. They do not produce nitrogen.

Thus, whenever possible, annual grain or vegetable crops should follow a legume green manure to derive the benefit of farm-produced nitrogen.

Soil, water conservation

The soil conservation benefits provided by a cover crop extend beyond protection of bare soil during non-crop periods. The mulch that results from a chemically or mechanically killed cover crop in no-till plantings increases water infiltration and reduces water evaporation from the soil surface.

Soil cover reduces soil crusting and subsequent surface water runoff during rainy periods. By slowing erosion and runoff, cover crops reduce nonpoint source pollution caused by sediments, nutrients and agricultural chemicals.

Pest management

In addition to the soil-improving benefits, cover crops can also enhance many pest-management programs.

Ecologists tell us that stable natural systems are typically diverse, containing many different types of plants, arthropods, mammals, birds, and microorganisms. Growing cover crops adds diversity to a cropping system.

In stable systems, serious pest outbreaks are rare because natural controls exist to automatically bring populations back into balance.

If you would like more information on how to utilize cover crops in your operation contact me and I can provide more resources as well locate some upcoming field days that could be beneficial.

Tony Nye is the state coordinator for the Ohio State University Extension Small Farm Program and has been an OSU Extension Educator for agriculture and natural resources for 29 years, currently serving Clinton County and the Miami Valley EERA.


Tony Nye

OSU Extension