Seedbed Preparation

Success in establishing pasture and rangeland seedings requires careful planning and timely land preparation. Unlike cereal grains, grass, forb, legume and shrub seeds are generally small and germinate slowly. A seedbed preparation method should be selected that best suits the site, seeded species and available equipment. The selected seedbed preparation should retain the maximum amount of soil moisture.

Two methods of seedbed preparation are recommended.

• Conventional or Clean Tillage – This type of seedbed can be prepared with plows, discs, chisels, tool-bars using sweeps or other types of equipment. After the tillage operation is completed, the land should be smoothed and firmed using equipment such as a roller harrow, cultipacker, spike tooth harrow or other implement to firm the final seedbed. The seed is then planted directly into the prepared seedbed using a disc or furrow-type drill. Tillage is not recommended for saline or sodic soils. It brings salt to the surface, destroys soil structure and residue for soil drainage. Plant residue, even weeds, need to be used for a no-till seeding into saline/sodic soils.
• Standing Stubble – Seed can also be inter-seeded directly into most cereal grain stubble on coarse- to medium-textured soils. Stubble free from weeds and volunteer grain provides a firm seedbed and a favorable micro-climate for seedling establishment. Winter wheat stubble is not recommended for fall dormant plantings due to grassy weeds and volunteer grain that commonly germinate over winter or in early spring. Furthermore, grain straw should be removed from the field or shredded and uniformly scattered. This improves the seed-to-soil contact and reduces chaff toxicity. Harrowing and other chaff spreading operations will disturb the soil and normally cause a flush of volunteer grain. An application of a broad spectrum herbicide such as glyphosate will control this flush. Double disc or deep furrow drills with acra-plantTM openers are recommended for planting into stubble. In addition, if weeds are a problem, spraying the field with appropriate herbicides prior to seeding is recommended. If the weedy competition cannot be controlled using chemicals alone, then conventional tillage and herbicide combinations are recommended.

Some planting sites require only one or two tillage operations to prepare a seedbed. Usually tillage is for the purpose of killing all weeds to eliminate competition. Chemical weed control may be substituted for one or all of the tillage operations when preparing a seedbed. Usually a combination of treatments is best for suppressing cheatgrass infestations.

The seedbed for forage seeds should be weed free, clod-free, smooth, firm and moist. Plowing may not be necessary depending on the soil type. With minimum tillage drills and proper herbicides one may seed directly into cereal crop stubble. Seedbeds prepared by plowing and cultivation usually require packing before seeding.

When a conventional seedbed is prepared, competing vegetation will be controlled and the site will not be subject to erosion. A firm clod-free seedbed ensures seed to soil contact will be provided. A firm seedbed facilitates capillary movement of moisture to the seed and developing seedling. A good rule of thumb is a footprint will be no deeper than 1/8-inch in an ideal seedbed.

The presence of weed populations - especially noxious weeds - will impact seedbed preparations. Each field should be evaluated for weed populations. Seeding on fields with significant weed populations will be delayed until weeds are controlled mechanically or chemically with labeled herbicides. Refer to guidelines in the Field Office Technical Guide (FOTG), Section IV, Practice Standards and Specifications, Pest Management (Code 595), and Montana, Utah, Wyoming Weed Management Handbook. During this period a protective cover crop may need to be planted to control erosion prior to planting.

When planning a seeding, the previous several years of herbicide application must be considered. Any potential carryover problems must be addressed by delaying seeding, establishing a cover crop, and/or changing species to be planted to prevent planting failures.

If a cover crop is necessary, refer to guidelines in the FOTG, Section IV, Practice Standards and Specifications, Cover Crop (Code 340). It is often advisable to grow small grain crops for one to two years prior to the final seeding. Tillage and labeled herbicides used under small grain production economically control weeds and reduce the number of weed seeds in the soil. They also allow high levels of organic matter (root and shoot mass) time to decompose into mineral soil. High organic matter soils, such as perennial sod, make poor seedbeds because they are difficult to firm and they also tend to dry rapidly, resulting in poor seed-to-soil contact for proper seedling germination and establishment conditions. This rotation helps to break disease and insect cycles and is especially important to consider when renovating old pasture or hayland.

Seeding of depleted range and/or pastureland, or cropland fields requires control of existing perennial and annual vegetation. This may be accomplished through chemical or mechanical methods. If tillage is used, a minimum of two years of cultivation and cropping is recommended to control existing vegetation and to store soil moisture. Standing cereal grain stubble provides an excellent seedbed if proper seeding equipment is used.

If chemical methods are used, multiple applications are generally required to achieve satisfactory control of perennial competition. Litter may need to be reduced to allow for proper seed placement and good seed-to-soil contact.

Many landowners want “instant” results and try to inter-seed into existing plant communities. Numerous studies have shown interseeding into existing plant communities almost always fails due to too much competition for water and nutrients from the existing vegetation. In addition, there may be allelopathic effects from living and/or dying and decaying vegetation. Therefore, interseeding is not recommended. Plantings where existing vegetation can be completely destroyed with labeled non-selective herbicides prior to seeding with interseeding-type equipment have been successful when the site is irrigated or receives 15 inches or more mean annual precipitation. Also, interseeding is more successful where the existing species is a monoculture and is vulnerable to herbicides during the same phonologic stage. However, it should be fully understood these plantings are still more risky than conventional land preparation methods.

An exception to this rule is on very wet soil locations where conventional land preparation is not possible. ‘Garrison’ creeping foxtail can be established in an existing stand of less palatable species including Baltic rush (wiregrass) and sedges. The species is very opportunistic and aggressive on wet sites. The seed can be broadcast when the site is frozen or by feeding Garrison hay and allowing livestock trampling to plant seed. With proper irrigation and fertilization, Garrison can establish and eventually crowd out less-desirable species over a 6 to 10 year or longer period.

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Last Modified: 07/05/2007