SP701-B UTBiofuelsInitiative Using Switchgrass for Forage Gary Bates, Professor, Plant Sciences Pat Keyser, Associate Professor, Forestry, Wildlife and Fisheries Craig Harper, Associate Professor, Forestry, Wildlife and Fisheries John Waller, Associate Professor, Animal Science

witchgrass is a warm-season perennial grass native to much Sof the United States. Over the last few years, switchgrass has re- ceived renewed interest as a renew- able fuel source, since it produces large amounts of cellulose that can be digested and converted to etha- nol. The high yields and environ- mental adaptability of switchgrass make it an excellent choice for biofuel feedstock production. While there has been a great deal of media attention about the merits of switchgrass as a biofuel feedstock, many are less familiar with the potential of switchgrass as a forage crop. Switchgrass, like a number of other native warm-sea- son grasses (NWSG), can actually produce high-quality forage. Yields switchgrass is planted primar- switchgrass as a species is of 2-5 tons per acre can be expect- ily for biofuels production, better than tall fescue, but be- ed, depending on rainfall and soil there is potential to harvest cause hay-making conditions type, as well as other environmental the early growth through hay- are better during the switch- conditions. The nutrient content of ing or grazing, then managing grass growing season and this forage can be as high as 16-17 the remainder of the season’s because rain and cool temper- percent crude protein, if harvested growth for the biofuels feed- atures often delay cutting tall correctly. stock market. fescue. A delayed tall fescue • Summer hay production – harvest results in decreased Characteristics that make Since switchgrass is a warm- protein and energy. switchgrass attractive as a season grass, it is adapted • Summer grazing – The sum- forage crop to hot, summer conditions. mer growth of switchgrass • High yields – Switchgrass As peak growth occurs from also makes switchgrass an grown for forage can produce May through September, it excellent forage for grazing. up to twice as much as tall is easy to produce hay be- Since most cattle operations fescue on an acre of land. cause of better drying condi- in the Mid-South use tall fes- Research in Tennessee has tions. It is not unusual to find cue as their primary pasture shown that, if grown exclu- switchgrass hay that is better grass, there is limited forage sively for hay, 4-5 tons per quality than the average tall production during summer. acre are not uncommon. If fescue hay. This is not because This limited production UTBiofuelsInitiative 2

reduces the performance of because of drop in forage quality in Caution about Horses and grazing cattle, and may lead the maturing stand. Switchgrass Hay: While switch- to overgrazing and weakened These early-forage harvests grass hay has excellent value for stands of tall fescue. Switch- (haying or grazing) should leave a beef and/or dairy cattle, as well as grass can provide good-quality minimum 8-inch residual height other livestock, there is evidence forage for grazing animals and to ensure rapid regrowth and an that horses fed switchgrass hay may provide the opportunity to rest adequate final biomass harvest. have a phototoxic reaction. In short, tall fescue pastures during a Producers must realize that leav- horses may lose some hair and stressful time of the year. ing high residual heights is very suffer sunburns. Although it is not important to quick recovery of the common, horse owners should be Research has shown switch- plant, due to the elevated grow- aware of this problem. At this time, grass can be grown successfully as ing point on switchgrass (often > switchgrass is not recommended both a biofuel feedstock and forage 5 inches above the soil surface) for horse hay. crop. There is no need, however, and the minimal leaf surface area to grow it as only one or the other. present below 8–10 inches. Remov- Grazing Switchgrass There is the possibility of having ing the growing point and all leaves Because early-season switch- switchgrass as a “dual-purpose” will result in delayed regrowth that grass has good nutritive value crop. The early growth of the for- will substantially reduce final yields for cattle, the material could be age, which is generally the highest and, in the long run, stand vigor. removed through controlled graz- quality, can be hayed or grazed. The Because biorefineries will re- ing rather than haying. Grazing, of later growth can be allowed to ma- quire switchgrass on a year-round course, requires adequate fencing, ture and harvested after frost as a basis, producers would have the access to water and shade. Where biomass crop. Biomass production opportunity to later sell switchgrass this infrastructure is lacking, the will be lower under this scenario, harvested for hay as biofuel feed- investment may not be cost-effec- but, depending on the objectives stock if they find they do not need as tive. This is due to the relatively and needs of the producer, this may much as hay. While dormant-season short grazing season available in be a useful strategy. harvested material is considered an integrated system where a good better quality for biofuel produc- deal of switchgrass growth will be Keys to using switchgrass as a tion as a result of reduced mineral reserved for biofuels. On the other hay crop concentrations, there is no reason hand, temporary fencing and leav- Early-season production (late to believe mid-summer “hay” crops ing gates open to water on other April–late May for switchgrass) pro- will not be acceptable for processing pastures could be effective. This duces the highest-quality forage and switchgrass into biofuel. Following strategy will be even more effective can be easily utilized for hay. Crude guidelines for proper hay storage later in the spring when the quality protein levels may range from 14-20 will help ensure the material will and production difference between percent at this time of year. How- be available for future hay needs or cool-season grasses and switchgrass ever, forage yields will be relatively biofuel production. is more pronounced. low (e.g., two tons per acre, depend- ing on the timing of harvest). As Figure 1. Crude protein changes with maturity in two with any hay crop, waiting a few switchgrass cultivars. weeks will increase forage yield and decrease forage quality (Figure 1). % CP 16 In addition, the later the forage is Cave in Rock SG harvested, the greater the reduction Alamo SG in the final biofuel feedstock harvest 12 for that season. Most biomass ac- cumulation in switchgrass occurs in 8 the first half of the growing season. For example, in one Southeastern 4 study, 56 percent of annual biomass accumulation was obtained by late 0 June each year. Obviously, delay- 6-May 10-Jun 14-Jul 19-Aug 23-Sep 28-Oct ing the forage harvest too late (past late-boot stage) would also be coun- Source: Sladden and co-workers.1994. American Forage and Grassland Council terproductive for forage production, Conference Proceedings p. 242 UTBiofuelsInitiative 3

canopy. During the second year of the stand, there will be produc- tion, but it will likely be only 50–70 percent of the stand’s potential. It is important to not overgraze the stand this second year to enable the root system to fully develop. Such a system will ensure full production levels in future years and promote considerable stand longevity typical of switchgrass (> 15 years). Fertilization of Switchgrass for Forage Production Even though switchgrass is adapted to poor soil fertility, pro- ducing large amounts of high-qual- ity forage requires adequate levels of potash, phosphate and nitrogen. Research has shown that pH has limited effect on switchgrass yield. Because of the reasons listed 2–4 week period, freeing up the re- Current recommendations are that under haying guidelines, it is im- mainder of the growing season for pH should be maintained at 5.0 or portant not to graze switchgrass accumulation of switchgrass feed- higher. There is no need to lime to too closely. Leaving a residual stand stock for biofuels. Experience will keep pH at levels needed for most height of at least 8 inches, and dictate how to adjust these stocking other forage crops. Nitrogen should preferably as high as 12 inches, will rates to achieve desired results. be only be applied to native grasses result in more rapid regrowth and Keep in mind, during the establish- if soil moisture is not limiting, and greater yields of biomass for biofu- ment year, no grazing should be if extra forage production is desired els at the end of the season. While planned unless it is a brief period (Table 1). most producers managing switch- of high stocking to remove a weed grass strictly as a forage crop will practice rotational grazing to ac- commodate this growth, it is unnec- Table 1. essary when attempting to integrate Nitrogen fertilization recommendations grazing and biomass production. for switchgrass used for forage. That is because a single rotation of only 2–4 weeks of grazing should be planned. Switchgrass could be Early summer Mid-summer Use grazed later into the season, but as ------lb actual N per acre ------with haying, increased consump- tion as a forage crop will reduce Hay1 45-60 45-60 final biomass yields. Grazing2 45-60 up to 60 lb N Initial livestock entry into switchgrass in the spring should oc- 1Mid-summer application should be eliminated if soil moisture is limited cur once the stand is 18–24 inches 2Apply N only if extra forage growth is needed. tall, typically mid-May. Stocking at lower rates or creep-grazing calves will make it possible to begin soon- Summary er. Stocking rates of three to five Even though many people are yields and good-quality forage can steers per acre will probably be best currently focused on switchgrass be produced during summer, if it is under normal circumstances. This as a biofuel feedstock, it should be managed correctly. If switchgrass should allow enough animals to re- kept in mind that switchgrass can is cut while it is young and leafy, move the available forage within a also be used as a forage crop. High the nutrient content will be equal UTBiofuelsInitiative 4 to other grasses. If switchgrass is sirable for biofuel production. can be used for biomass. Haying allowed to mature and become It should also be kept in mind early may reduce biomass produc- fibrous, forage quality will suf- that this crop does not have to be tion, but the ability to use some of fer drastically. This is noteworthy; used only for forage or only for bio- the growth for cattle production given the tendency of switchgrass mass. It can be harvested as a dual- will add flexibility to a producer’s to produce high amounts of fiber purpose crop, so early growth can operation and provide the opportu- when mature is what makes it de- be used for forage, and later growth nity to increase profitability.

What about Other Native Grass Species? Selection of grasses other than switchgrass can enhance the stand as forage and wildlife habitat. Grasses such as big bluestem, little bluestem and indiangrass have been planted along with switchgrass to form a mixed-grass stand. Each of these grasses has a slightly different maturity date, which spreads out the potential timing of quality forage harvest. These mixtures also contribute to a different sward structure, which can provide better wildlife habitat than a single grass species. There is also the possibility to use legumes to improve forage quality and to replace nitrogen fertilizer. Research is still needed to identify the proper legume species and management techniques for successful use of legumes in the stands. Therefore, each producer must consider his or her individual goals and the potential trade-offs between switchgrass yields, forage potential and wildlife habitat enhancement.

Biofuels Initiative

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SP701B-5M-3/08(Rep) R12-4110-070-012-08 08-0166 Programs in agriculture and natural resources, 4-H youth development, family and consumer sciences, and resource development. University of Tennessee Institute of Agriculture, U.S. Department of Agriculture and county governments cooperating. UT Extension provides equal opportunities in programs and employment.