Submitted to: Experiment Station Bulletins
Publication Type: Experiment Station
Publication Acceptance Date: 10/20/2008
Publication Date: N/A
Interpretive Summary: Switchgrass (Panicum Virgatum L.) is a perennial, native warm-season (C4) grass indigenous to the continental US. It is a bunch-type grass found in all parts of the country, except the extreme northwestern states, and will persist well in North Carolina and the Mid-Atlantic Region. Persistence is dependent, however, on properly managed defoliation frequency and degree of defoliation. Due to its very erect growth habit, utilization of switchgrass in grazing systems requires control of herbage mass through defoliation intensity. Canopies maintained below 18 inches will generally remain vegetative. This reduces maximum dry matter production, but provides forage of greater nutritive value (especially crude protein concentration and digestibility) for the grazing animal and subsequently supports desirable daily animal performance. Because grazing results in a reduction in dry matter yield, but retains forage of greater nutritive value, indicates that switchgrass maybe best utilized as a special purpose pasture. In a grazing system consisting of tall fescue and bermudagrass, the brood cow can. be retained on the base pasture and young growing stock can be creep grazed onto switchgrass pasture to enhance daily gains. Also, fattening stock can be rotationally grazed on switchgrass pasture that has sufficient nitrogen and properly grazed during the summer period to improve their daily performance compared with bermudagrass. Switchgrass can also be harvested as hay but the quality of the hay can be an issue as digestibility and dry matter intake declines rapidly as stems elongate above 4 feet in the initial growth or as the regrowth approaches the boot stage. Switchgrass can also be ensiled and preserved as silage but requires care in excluding air during the ensiling process. The soluble carbohydrate concentrations in switchgrass are border line to sustain anaerobic fermentation sufficiently long to decrease the pH enough to insure a stable bunk-life silage. Consequently, once a silo is opened, the silage needs to be fed daily to prevent spoilage due to exposure to air. The use of switchgrass for biomass requires the least challenging management, once established, for both the producer and for the switchgrass plant, as it will thrive under a one or two cut system, being very competitive with other grasses (Johnson grass is an exception). The major results from 25 studies reported in this bulletin are presented below. The reader is encouraged to turn to the study designated after each summary point for further detail and information. Although many of the herbicides and insecticides evaluated in this bulletin are not registered for use on switchgrass, it is important to not that most have been cleared for use on one agronomic crop or another. Consequently, sufficient interest in growing switchgrass should provide the impetus for the collection of the necessary data to acquire approval for their use on switchgrass. Switchgrass grown for biomass purposes would be expected to have fewer restraints than switchgrass grown for animal feed.
Technical Abstract: This document reports results from 26 studies addressing the establishment, cell wall content, cultivar improvement, defoliation management, nutritive value and utilization of switchgrass (Panicum virgatum L.) as pasture, or its conservation as hay or silage or harvested as biomass. Both lowland and upland commercial cultivars and lowland germplasms were evaluated and in some experiments compared for yield, nutritive value and quality characteristics. Comparisons were also made with other warm-season grasses. Switchgrass is a very flexible forage species having potential as a pasture, stored forage or a biomass crop. Cytotypes, also referred to as ecotypes, and cultivar selections within cytotypes are important considerations when growing switchgrass in the Mid-Atlantic Region being dependent on its use and geographic location.