Native warm-season grasses: Drought proof or drought tolerant?

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An article in a recent agriculture magazine had a quote claiming that native warm-season grass pastures are drought proof, and producers are excited at that possibility. Native warm-season grasses (for forage) in this case are defined as switchgrass, big bluestem, little bluestem and indiangrass.

Drought proof and drought tolerant are not the same thing. Many warm-season forages are drought tolerant. No forage is drought proof. Drought tolerance implies that a forage can tolerate effects of drought and survive. It doesn’t mean that the grass will thrive during drought. All forages need water and an optimum temperature range to grow well. Drought proof means the grass suffers no ill effect of drought and keeps on growing as if weather conditions were normal. Native grasses can be part of a forage program and can be cost effective, BUT they must be managed differently and they are NOT drought proof.

The University of Tennessee has done work recently with native warm-season grasses through their biofuels program. Dr. Gary Bates leads the forage management effort. Gary provided several points at the recent Forage and Legume Management Conference in Harrison. (To see the presentation, go to http://vimeo.com/61109401). He pointed out that native grasses require less fertilizer for good hay yield than bermudagrass. Hay quality is moderate and can be very poor if allowed to get mature before harvest. Yield can be 4-6 tons per acre with fertilization and proper harvest. Under grazing, these grasses can be stocked at a high rate during the first 6 weeks of the growing season, but the stocking rate must be reduced later in summer to avoid stand damage. Stocker calf gains can be quite good, exceeding 2 lbs/hd/day, under good management.

Two big factors that must be accounted for in managing these grasses is that they should never be cut or grazed shorter that 8-12" and the grazing or hay season is about 100 days at most. Native grasses should not be harvested or grazed past mid-August at all. Any late-season growth must be left to allow the plants to store root reserves for winter. Grazing too late, grazing during winter and grazing too early in spring will damage stands. Winter annuals like wheat or ryegrass should not be overseeded into native grasses or the competition and grazing can damage stands. Under hay management, these grasses should not be cut more than twice in a year. To avoid weakening stands, hay should only be cut once the year following a two-harvest year.

Establishment is slow and requires patience. Native grasses are notorious for poor seedling vigor. Very little topgrowth is produced the seeding year. Most growth is directed toward root growth. That means weed control is critical during the seeding year. With good weed control, native grass yield the second year will be about half to two-thirds of a fully established stand with top yields not occurring until the third year after planting.

Herbicide options are available but differ for the different species. Seeding rates are generally 5-6 pounds of Pure Live Seed ((PLS) per acre as pure stands. This rate can be adjusted in mixtures so the total seeding rate of mixtures is 10 pounds PLS/acre. The PLS of many natives may only be 30 percent, so it may take 3 pounds bulk seed to get 1 pound PLS.

Switchgrass is usually planted alone because it can dominate in mixtures. Big bluestem is a good choice for hay or grazing and has good wildlife benefit under deferred forage harvest management. Big bluestem and indiangrass mixtures are commonly recommended, although big bluestem alone is easier to manage and maintain stands. Natives are promoted heavily for their benefit to wildlife, especially quail and rabbits. However, optimizing forage production from native grasses will not optimize wildlife habitat. Hay harvest or grazing must be deferred until forage is poor quality to protect the major quail nesting period of mid-summer.

These grasses can be effective additions to a forage program but in no way are replacements for all other forages. Planting these grasses without realistic expectations will lead to disappointment and stand failures. Native grasses have been around since before settlers. Overgrazing took them out before. Good management must be part of a program to make them work now.

Source: John Jennings, Professor


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