Craig C. Sheaffer, University of Minnesota

The information presented in this fact sheet is not intended to take the place of professional legal advice. In developing any written lease agreement, it is highly recommended that all parties seek professional legal advice.

Summary

• Renovation of CRP fields may be needed for productive forage systems. The type and degree of renovation depend on the intended use of the forage, previous management, and the proportion of legumes, grasses, and weeds.
• A major challenge to renovation is the introduction of legumes. A favorable environment for germination and seedling growth is essential.
• Critical considerations include field preparation, seed quality, planting depth, and time of establishment.

Making the Transition from CRP to Forage

Renovation of Conservation Reserve Program (CRP) fields may be needed to make a transition to productive forage systems. The type and extent of renovation depend on the intended use (pasture or hayland, and type of livestock enterprise), previous management, and botanical composition (proportion of legumes, grasses, and weeds).

A major challenge to renovating CRP land for forage production is the introduction of legumes into existing grass stands. Many CRP fields contain primarily cool season grasses, and some have severe weed infestations (see Persistence of Planted Forages and Weeds and Pocket Gophers in this series). It’s possible to develop such fields into productive pasture or hayland by applying nitrogen fertilizer or manure and removing accumulated dead residue to stimulate regeneration of desired grass species. However, on most land used for grazing or haying, it’s better to have a mixture of legumes and grasses.

Legumes are especially important because they fix nitrogen and have higher feed value than grasses. Because legumes can fix from 50-200 lbs. of nitrogen per acre, fields with adequate legume stands (at least 3 plants per square foot) don’t need any additional nitrogen fertilizer.

Legume selection depends on climate, soil factors, and type of livestock enterprise (Table 1). Alfalfa, red clover, white clover, and birdsfoot trefoil are the most commonly used forage legumes. Alfalfa is the most widely grown perennial forage legume with high yield potential, but it’s intolerant of wet soils and soils with low pH. Characteristics of perennial grasses to plant as companions to legumes are found in Table 2.

The overall time frame for renovation depends on the type of stand the farmer desires (based on intended use) and the degree of inputs he or she is willing to use. A stand that consists primarily of legumes will require more inputs (e.g., moldboard plowing, herbicides, burning) than a mixed grass and legume stand.

Establishment Strategies

Small-seeded legumes and grasses are generally more challenging to establish than large-seeded annual crops such as corn and small grains. Seedlings are fragile and develop slowly. Therefore, a favorable environment for germination and seedling growth must be established.

Conventional tilled seedbed seedings

Seedbed tillage may be necessary to:

• reduce surface vegetation;
• control undesirable species;
• incorporate lime and fertilizer;
• provide a smooth surface for seeding and harvesting.

Tillage operations (plowing, disking, harrowing, etc.) vary with individual farm situations. However, the results should be the same—a firm seedbed, loose surface soil for shallow seed placement, and enough plant residue to protect soil and seedlings from erosion.

Grain drills or cultipacker seeders are used in tilled seedbeds where residue is incorporated. Grain drills should be adjusted for shallow seed placement. Presswheels or a packer should be used to increase the soil-seed contact. If seed is broadcast by mixing with fertilizer, seed should be incorporated by harrowing or packing.

Companion crops often are used with spring seedings on tilled seedbeds. Crops such as oats or barley provide quick ground cover and reduce soil erosion. Companion crops suppress weeds, but often compete with forage seedlings and reduce stands. To reduce this competition, small-grain companion crops should be seeded at one-half the rates used for grain production. Weeds can be controlled using herbicides (see Other Resources #6). In addition, legume and grass stands are greatly improved if small grains are harvested for forage at the boot stage (when grass flower is enclosed in the last leaf) or the soft dough stages (when seeds are developed but spongy).

Minimum tillage strategies

Suppressing existing grasses and weeds before and after seeding is especially important when using minimum till strategies. Grazing or herbicides can be used to control grasses and weeds. New legume and grass seedlings can be established by lightly disking existing vegetation, followed by broadcasting of legumes. Harrowing after seeding provides shallow incorporation. No-till sod-seeding using specialized equipment also can introduce forage legumes and grasses onto CRP lands (see Other Resources #1).

Broadcast frost seeding

Frost seeding is riskier than other establishment strategies. It is successful only for a short period under certain soil and weather conditions. Frost seeding works best when vigorous legume and grass species are used. It’s also more successful if established grass stands are first weakened by heavy grazing or light disking. Seedlings can’t develop if forced to compete with established perennial grasses and weeds.

Seed may be broadcast into established grass stands in late winter following snow melt, before grasses begin to grow. The freezing and thawing of the soil, in addition to rain, provides a shallow seed covering. Seed also may be incorporated by running livestock over the seeded area.

Following seeding, pastures should be grazed when grasses form enough canopy to interfere with the growth of the legume seedlings. Animals should graze fields for a short period at a high stocking rate to avoid excess trampling.

Field Preparation

Fertilization and weed control

Planning for renovation of CRP land should begin a year before anticipated seeding dates. Soils should be sampled and existing vegetation evaluated in terms of species present and degree of ground cover. Soils should be tested for pH, phosphorus, and potassium. Soil fertilizers, manures, and lime should be applied if needed, based on soil tests (see Other Resources #7).

Weeds interfere with the renovation of CRP fields for forage production. Many annual weeds can be controlled by timely mowing or grazing. Perennial weeds, however, may need repeated treatment. For renovation that involves reseeding, control of perennial weeds like Canada thistle should be started the year before seeding. Spot treatment may be needed for a dense forage stand. (See Other Resources #6 and Weeds and Pocket Gophers in this series.)

Reducing surface residue

Accumulated mulch from unharvested growth can harm surviving species and new seedlings. It also provides a habitat for pests that eat plant regrowth and new seedlings. There are several options for removing excessive residue. These include burning, grazing, tillage, and baling.

Burning can effectively remove dead residue and kill weed seeds, insects, and rodents. Burning also allows some recycling of nutrients from the old plant material. Properly equipped professionals should conduct the burn for safety and control reasons, as well as to achieve the desired results. Applicable state and local regulations should be followed when burning.

Overgrazing is another effective way to remove residue. Cattle eat residue and trample it into the soil. Their manure and urine improve soil fertility and increase the rate and extent of residue decomposition. Stocking rates and grazing periods should be designed to ensure soil exposure after grazing. Methods include mob-grazing with high stocking densities, overwintering livestock on fields, or using fields for calving.

Firming the seedbed

A firm seedbed (allowing good seed contact with the soil) and shallow seed placement are critical for successful establishment. For tilled seedbeds, the soil should be firm enough that a footprint would sink no deeper than 1 inch. Legumes and grasses vary somewhat in their tolerance of poor seedbeds. Firm seedbeds are more critical for small-seeded species like birdsfoot trefoil and timothy than for the more vigorous legumes and grasses. For most seedbeds, firming with a cultipacker seeder or a press-wheel drill helps establish the stand.

Other Critical Considerations

Seed Quality

To ensure high-quality seed, purchase certified seed of a named variety. Purchased seed should have at least the following information on the tag:

• percent germination and date tested;
• percent inert matter;
• percent other crop seed;
• percent weed seed;
• other crop species.

From this information, pure live seed content (the number of viable seeds available per pound at planting) can be calculated (see Other Resources #3). Recommended pure live seeding rates are shown in Table 3. Many CRP fields with legumes have contained the legumes for only a few (less than 5) years. Seed for these fields should be inoculated with proper Rhizobium bacteria, either as a seed coating or an additive. (The tag will often indicate whether the seed is inoculated.) Rhizobium bacteria reside in nodules on legume roots and fix nitrogen.

Planting depth

Legumes with very small seeds such as white clover, kura clover, and birdsfoot trefoil should be seeded no deeper than 1/4-inch. Most other legumes should be seeded from 1/4- to 1/2-inch deep. Planters should be tested to determine the seeding depth. Seeds sown either on the soil surface or greater than 1/2 inch deep probably won’t develop into seedlings.

Time of establishment

For conventional seedings of cool season species, spring seeding should occur from April 15 (or as soon as soil is fit to work) to June 1 in southern Minnesota and from May 1 to June 15 in northern Minnesota. Early spring seeding takes advantage of good moisture and cool temperatures. In summer, seeding should occur from August 1 to August 15 in the south and from July 15 to August 1 in the north.

Summer seedings generally have less weed competition but also less moisture. For summer seedings, most legume and grass seedlings require at least 3 developed leaves to survive the winter. Seeding beyond recommended August dates may result in winter injury to plants. For information on seeding of warm season species, see Other Resources #2.

Other Resources

The first two resources are available from the Minnesota Department of Agriculture, Sustainable Agriculture Program, 625 Robert St. N, St. Paul, MN 551155-2538 • 651-201-6673.

1. Sod-Seeding Legumes into Grass Pasture (University of Minnesota, 1978).
2. Warm Season Perennial Forage Grasses: Big Bluestem and Switchgrass (USDA-Natural Resources Conservation Service, 1995).

The following publications are available from your local Minnesota Extension Service (MES) office or the MES Distribution Center, University of Minnesota, 20 Coffey Hall, 1420 Eckles Avenue, St. Paul, MN 55108-6069. 612-624-4900 or 1-800-876-8636.

3. Forage Legumes (1993). Item #ES-SB-5963.
4. Alfalfa Management Guide (1994). Item #AG-BU-5798.
5. Varietal Trials of Selected Farm Crops (1995). Item #ES-MR-5615.
6. Cultural and Chemical Weed Control in Field Crops (1995). Item #AG-BU-3157-S.
7. Fertilizer Recommendations for Agronomic Crops in Minnesota (1994). Item #6240-E.

MDA Contact

Barbara Weisman, Conservation Program Specialist
barbara.weisman@state.mn.us
651-201-6631 or 1-800-967-2474
Ag Marketing & Development Division