Don’t wait to plan for cover crop

Winter can be a tough time for cover crops. Snow, rain, ice and cold temperatures can really push these plants to their limits. Cover crops are the green plants that cover the ground between harvest of a cash crop in the fall, such as corn or soybeans, and planting of a new cash crop during the following spring.

Incorporating more “green” plants into these “brown” periods helps protect soil and water quality, and maintain natural cycles for nutrients now and in the future. Additionally, small grain cover crops can be used for food products, if harvested for grain past the normal cover crop termination period before planting of corn and soybeans.

Key Points

PFI ran cover crop trials this past year with different types of small grains.

Cover crops were planted Oct. 5; fall and spring growth were measured.

Study looked at percent groundcover in fall and spring, and winter survival.

Not so long ago, Iowa farmers commonly used a crop rotation that included these small grains to provide not only additional income streams to make the farm business more stable but also to build the soil and help break pest cycles.

Why think about winter and cover crops during the month of July in Iowa? If you want to have successful cover crop establishment, planning can never begin too early. Depending on the needs of a farm, different varieties of cover crops are selected to obtain the desired maximum benefit.

Some farmers prefer to plant cover crops that do not overwinter, such as oats, while others are looking for cover crops that overwinter well, such as winter wheat.

To learn more about the ability of various winter small grains to overwinter on the Iowa landscape, Practical Farmers of Iowa began exploring which cover crops could be good at both covering the soil through winter and also harvested for food-quality grains. PFI is assessing which winter small-grain varieties, such as winter wheat, rye or barley, could do double-duty.

Cover crops on trial

On Nov. 29, before snowfall, 16 different small-grain varieties and one winter lentil variety’s coverage of the soil was measured. In this trial, cover crops had been planted Oct. 5, following soybean harvest near Boone in central Iowa.

Six different species (soft wheat, hard wheat, rye, triticale, barley and lentil) were tested. Included were four hard red winter wheat, three soft red winter wheat, four winter rye, one winter triticale, four winter barley and one winter lentil varieties.

All cover crops had the same amount of fall growth going into winter. Then in spring the cover crops were measured again after snowmelt on March 2. Arapahoe, a winter wheat variety, actually grew under the snow and was the only variety to have more biomass present following snowmelt.

However, in general, individual varieties were not different but the different species survived winter differently.

Winter rye survived best

Winter rye overwintered best, followed by soft red winter wheat, hard red winter wheat and winter triticale. The graph accompanying this article shows the results. The shorter the blue bars the better the cover crops’ ability to overwinter and keep the ground covered until spring.

These results are in line with a common perception by farmers and others who have grown and studied different cover crops and report that winter rye is the most winterhardy among the different winter small grains. In the spring, winter barley and lentil had very poor growth and stayed small even in May.

Early this fall, PFI will overseed more varieties into standing corn and soybeans near Boone to see how an earlier planting date will affect the ability of different cover crop varieties to overwinter and also be harvested for grain the following summer.

More acres are being planted to cover crops, and more farmers want to harvest these small grain cover crops as an additional cash crop. PFI hopes to be ready with good information for the best recommendations for cover crops that can perform two jobs: improve soil and water quality, while adding another income stream to the farm business.

Carlson is research and policy director and Ogawa is food coordinator with Practical Farmers of Iowa in Ames. Carlson can be reached at 515-232-5661, ext. 305, or sarah@

Ground coverage, overwintering percentage


In comparing cover crops, ground coverage for six different varieties was measured in fall and spring. Ability to overwinter was also rated. Winter rye over-wintered best, followed by soft red winter wheat, hard red winter wheat and winter triticale. Fall growth was similar prior to snowfall; spring growth was different following snowmelt. The shorter the blue bars, the better the cover crop’s ability to overwinter and keep the ground covered until spring.


DOUBLE-DUTY: PFI is studying which winter small-grain varieties, such as wheat, rye or barley, used as a cover crop could be good at both covering soil through winter and harvested for food-quality grain the next summer.

This article published in the July, 2011 edition of WALLACES FARMER.

All rights reserved. Copyright Farm Progress Cos. 2011.