Production Requirements
Soil Types: Switchgrass is suited to most soil types. Yields are lower on extremely heavy or light soils
Soil pH: 6.0–6.8
Recommended Rotational Crops: Switchgrass is a long-term perennial crop and rotation crops do not apply. Cereal crops may serve as nurse crops during establishment
Minimum Soil Temperature: 10°C
Optimum Air Temperature: 24°C–29°C
Earliest Planting Date: Late April to May
Required Growing Season: Perennial crop 10+ years
Switchgrass is a relatively new perennial crop for Ontario that has industrial and agricultural uses for fibre, biocomposites, paper, bioenergy (liquid and solid), livestock and poultry bedding, and ginseng bedding. It is also known by other names such as tall panic grass, tall prairiegrass and thatchgrass.
Rotation
Switchgrass is a long-term perennial crop used for fibre, biocomposites, paper, bioenergy, animal feed and bedding. It has an extensive root system that gives the crop relatively good drought tolerance. Once established it is not rotated to other crops for many years. Switchgrass production is highest on fertile soils but is also well suited to marginal lands where other annual crops are less productive.
Tillage and Seedbed Preparation
Switchgrass seed is very small, and therefore requires a seedbed that ensures good seed to soil contact. Establishment has been most successful on welldrained, medium-textured soils that warm quickly and where weed competition is low. A light packing prior to planting will improve uniform seeding depth and again following seeding will improve the seed to soil contact.
Seeding switchgrass following soybeans in the rotation has provided a low-residue, firm seed-bed well adapted for no-till seeding.
Planting
Planting generally occurs mid-spring but can also occur in the fall. The optimum seeding rate is 9 kg/ha (8 lb/acre) or less of pure live seed with a seed weight of 570,000 seeds/kg (260,000 seeds/lb). Switchgrass seed has strong dormancy. Pure live seed is a measure of the number of live seed in a bulk seed lot. The seed is very small which requires a good seedbed to ensure good seed to soil contact. Seed is typically planted in 18 cm (7–7.5 in.) row widths at a depth of 1–1.5 cm (0.25–0.5 in.). Soil moisture is required for good emergence. Weed control is absolutely critical to establishment and production success, therefore, a nurse crop of spring wheat may promote better stand establishment, reduce weed pressure and provide income during the first year. Spring wheat is preferred over oats or barley as spring wheat tillers less and causes less shading of the switchgrass seedlings. Seed spring wheat at full seeding rates. A nurse crop can aid in establishment success but may limit chemical weed control options.
Fertility Management
Limited fertility guidelines exist for switchgrass. Current Ontario research indicates economical yield response to nitrogen rates of 50–80 kg/ha (45–70 lb/acre) depending on price of switchgrass and the expected yield potential. Nitrogen fertilizer should not be applied during the seeding year because it encourages weed competition.
In most cases, the only operation required following harvest is the application of nitrogen (N) fertilizer. For a spring harvest regime, 60–70 kg of N/ha (50–60 lb/acre) is sufficient to sustain production for an 8–10 t/ha yield target. A general rule of thumb is to apply 6 kg N/t (12 lb/ton) of biomass removed from the field.
Over-fertilization with nitrogen usually results in crop lodging, yield reductions and harvesting difficulties. Fertilization is commonly done in mid-to-late May, when the crop is about 15–25 cm (6 – 10 in.) high and when switchgrass has resumed its growth. This timing helps to minimize N losses where urea is used. Earlier N applications tend to help support grass weed growth, especially annual grass weeds and quackgrass. Switchgrass tends to have its peak N demand in year three. This is because considerable N is required to fully develop the large root system of the plant.
The amount of phosphorus and potassium required will depend on the harvest method used. Switchgrass harvested in late fall or from spring baled windrows will have lower requirement for phosphorous and potassium due to leaching of these nutrients out of the biomass and the loss of leaves that often hold a high amount of the nutrients. Harvest in the summer or early fall will remove more of these nutrients with the harvested biomass.
Most producers in Ontario mow the crop in late fall, allow it to winter in the fields in a swath and bale early the following spring. Producers in Ontario have found there is little decomposition of switchgrass over winter when using this system. The grass stays largely in a frozen state and rests on the 10 cm (4 in.) high stubble, keeping the swath separated from contact with the soil. By adopting a spring biomass harvesting regime, phosphorus and potassium fertilizers are usually not required on soils with medium-to-high fertility. Approximately 90%–95% of the potassium in switchgrass is leached back into the soil when the crop is left in the field over-winter. The annual potassium demand is very low when managed as an over-wintered crop since dry switchgrass contains only about 0.1% potassium. A 10 t/ha (4 ton/acre) switchgrass biomass crop will only remove 10 kg/ha (9 lbs/acre) of potassium from the field. Producers can soil sample for P and K periodically to monitor their levels.
Phosphorus and potassium fertility should be at target soil test levels (12–18 P and 100–130 K). If soil phosphorous and potassium levels are below target ranges, incorporate these nutrients into the soil ahead of planting, at rates that meet crop removal rate plus an amount that will build up the soil test over time.
Harvest and Storage
Harvest
Harvest management depends on intended end-use. Harvesting switchgrass twice in the same year, or before natural senescence has occurred, could lead to stand degradation. Switchgrass can be harvested in the summer if market conditions warrant, but this should not occur in the first year of growth, or on a yearly basis.
Standard field-crop equipment including sickle/disc mowers, haybines, and round or large square balers and forage harvesters can be used.
If switchgrass is being used for livestock bedding, pasture or roughage in the diet it can be grazed during the growing season or cut for hay in July or August with the possibility of two harvests. If used for cellulosic ethanol, switchgrass is often fall harvested since yield is highest, but moisture levels may be too high for long-term storage. If used as a biofuel for combustion, one-cut with windrowing in late fall and harvest in the spring provides the highest quality product for this market. Spring harvest will result in 15%–25% lower yields, but the grass will be of higher quality for combustion.
Switchgrass is usually left unharvested in the establishment year until the following spring to improve winter hardiness. Expected yield in the establishment year is about one-third of full stand potential and the year after establish is about twothirds of full production potential. Once established and properly maintained, a switchgrass stand will remain productive for an indefinite period and can produce 8–12 t/ha of dry fall harvest material.
Storage
Market demands will determine what type of storage is required. Switchgrass has been tested for storage in Ag-bags or under cover as well as outside, with and without tarps. Results have been mixed but it is important to note that this crop stands up to the elements better than cereal straw.
The crop may need to be ground and densifed or pelleted for ease of transport and/or end use. Research is ongoing to examine other methods of treatment (e.g., torrefaction) that will increase the density and storability of the crop.
Insects and Disease
Specific pests observed on this crop in Ontario are based on limited experience. To date rust (Puccinia spp.), has been the most significant issue in Ontario. Other diseases and insect pests of switchgrass include: head smut (Tilletia maclagani), viruses (barley yellow dwarf virus, panicum mosaic virus), grasshoppers, leafhoppers, aphids, stem borers and wireworms.
Weed Control
Weed control prior to establishment and during the first 1–2 years is critical for achieving an adequate stand, since weeds will compete with establishing plants. There are no registered herbicides for switchgrass which makes weed identification, pre-plant herbicide and tillage options for control more important.
For further production information, refer to:
- Ontario Biomass Producers’ Association at www.ontariobiomass.com
- Switchgrass Production in Ontario at www.reap-canada.com
- ontario.ca/crops
Other Biomass Crops
Other potential biomass crops in Ontario include perennial grasses (big bluestem, prairie cordgrass, indian grass) and annual grasses (pearl millet, sorghum, sudangrass).