Agronomy

Site Selection

Switchgrass can be grown in a wide range of soil types and climatic conditions. According to the NRCS, best production areas for switchgrass are on soils that are well to moderately drained, have a pH of 5.5 to 6.5, measure medium to high fertility and are moderately fine-textured. Switchgrass is also noted for its ability to produce acceptable yields on marginal land if proper management and inputs are used. Fields that should be avoided include excessively wet areas, steep terrain or areas that have perennial weed infestations. Switchgrass can grow on fields with eroded soils, and it has been shown to rejuvenate those depleted soils.

Establishment

The switchgrass planting date is typically in late April to mid-June. Initial field preparation may include fertilizer and lime, if indicated by a soil test, and herbicide application. Planting can be done with most seed drills or a broadcast spreader. For forage use, switchgrass can be seeded as a pure stand or mixed with other native grasses or legumes. According to the NRCS, seeding rates should be close to 5 pounds to 6.5 pounds of pure live seed per acre. Seeds should also be planted no more than a quarter to half inch deep. Miscanthus can be planted in a tilled seedbed or a no-tilled field. In fields with heavy residues, producers may need to reduce those residues before they plant switchgrass. Residue reduction methods may include grazing the area or shredding or baling the residue material. Alternatively, tillage can help to manage surface residues. For tilled planting sites, the area needs to be firm before planting. The field should be packed enough that just a slight footprint would be noticeable after walking over the planting site. Liming material can be applied and incorporated to adjust the pH balance. Phosphorus and potassium can be applied if recommended by a soil test before or after the seeding time. Nitrogen should not be used at seeding time due to stimulating weed growth. A portion of the switchgrass crop may need to be replanted in year two where the grass did not initially establish.

Bioenergy Management

Fertilizer application will be needed after the establishment year based on nutrient removal rates. If the land is being grazed, many nutrients will be recycled back into the soil. According to the University of Tennessee, switchgrass fertilizer practices for maintenance years in energy crop production would include 60 pounds per acre of nitrogen, 40 pounds per acre of phosphate and 80 pounds per acre of potash. These amounts may differ if deemed low by soil test recommendations. Also, switchgrass has shown some response to more nitrogen, so increasing from 60 pounds to 90 pounds per acre will result in increased yield.

Grazing Management

Management is important for switchgrass to maintain forage quality on a grazing operation. According to the University of Tennessee, grazing can begin when the forage has reached a height of 18 inches to 24 inches. After grazing, a minimum residual of 8 inches should remain, and switchgrass should have an adequate rest period before the next grazing period. Early-season production is the best forage quality – up to 17 percent crude protein – both for grazing and hay production. Generally, grazing switchgrass in the establishment year is not recommended. Studies in Missouri have shown that switchgrass should be used as either a bioenergy crop or forage crop but not both.

Weeds, Pests and Diseases

Switchgrass is very susceptible to weed competition in the first and second years. Herbicide should be applied in those years to control weeds. In the establishment year, the switchgrass crop will not be fully developed and will most likely require a mowing operation to reset the crop for the next growing season. Switchgrass is currently resistant to many insects and disease issues, but new issues could arise in the future.

Harvest and Storage

For switchgrass as an energy crop, the optimal harvest time in Missouri is approximately one month after the first killing frost, typically toward the end of November or beginning of December. This harvest time allows the plant to become dormant and enables nutrients to translocate back into the root system. Cutting height should be at least 6 inches high to ensure stand survival and optimize yield potential for subsequent years. According to the NRCS, typical moisture content for baling switchgrass is around 13 percent to 15 percent. High moisture content should be avoided due to its effect on feedstock quality and production needs from a conversion facility.

Conventional hay or silage harvesting equipment can be used to harvest switchgrass in Missouri. However, baling equipment specifically designed for biomass production may handle switchgrass feedstock better and have a longer life expectancy than traditional hay balers. Custom operators could be contracted to provide this service, or farmers could potentially purchase or use existing equipment.

The transportation equipment used will vary depending on the end destination. High-speed tractors and bale wagons can move bales to the field edge or nearby storage locations. Trucks with flatbed trailers can transport bales from field edge to further storage locations or end-users.

Storage systems must minimize dry matter loss and protect the quality of the switchgrass before transporting to the end-user. Storage losses will vary by storage system (inside or outside), time in storage and weather conditions for bales stored outside. Inside storage is the best method for reducing storage loss, but constructing storage structures, improving land surfaces in storage areas or using tarps to cover bales increases storage costs. Acceptable storage losses, storage costs and end-user product needs will determine the appropriate storage system.

Sources

Bates, Gary, Pat Keyser, Craig Harper, and John Waller. 2011. Using Switchgrass for Forage. UT Biofuels Initiative. University of Tennessee Extension. SP701-B.

Dolginow, Joseph and Ray Massey. 2013. Switchgrass and Miscanthus: Economics of Perennial Grasses Grown for Bioenergy. Publication G4980. Columbia: University of Missouri Extension.

Garland, Clark. 2011. Growing and Harvesting Switchgrass for Ethanol Production in Tennessee. UT Biofuels Initiative. University of Tennessee Extension. SP701-A.

Mitchell, Rob, Ken Vogel and Marty Schmer. 2013. Switchgrass (Panicum virgatum) for Biofuel Production. eXtension.

USDA-Natural Resources Conservation Service. 2009. Planting and Managing Switchgrass as a Biomass Energy Crop. Plant Materials Program, Technical Note 3.