Bates, Gary

Harper, Craig

Keyser, Pat

Waller, John

English

University of Tennessee, Knoxville: Trace

University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Biofuels UT Extension Publications 3-31-2011 SP701-B Using Switchgrass for Forage Gary Bates Pat Keyser Craig Harper John Waller Follow this and additional works at: https://trace.tennessee.edu/utk_agexbiof  Part of the Agricultural Science Commons, Animal Sciences Commons, and the Biotechnology Commons Recommended Citation "SP701-B Using Switchgrass for Forage," Gary Bates, Pat Keyser, Craig Harper, and John Waller, SP701-B , https://trace.tennessee.edu/utk_agexbiof/16 The publications in this collection represent the historical publishing record of the UT Agricultural Experiment Station and do not necessarily reflect current scientific knowledge or recommendations. Current information about UT Ag Research can be found at the UT Ag Research website. This Article is brought to you for free and open access by the UT Extension Publications at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Biofuels by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact trace@utk.edu. SP701-BUsing Switchgrass for ForageGary Bates, Professor, Plant SciencesPat Keyser, Associate Professor, Forestry, Wildlife and FisheriesCraig Harper, Associate Professor, Forestry, Wildlife and FisheriesJohn Waller, Associate Professor, Animal ScienceSwitchgrass is a warm-season perennial grass native to much of 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 of 2-5 tons per acre can be expect-ed, depending on rainfall and soil type, as well as other environmental conditions. The nutrient content of this forage can be as high as 16-17 percent crude protein, if harvested correctly. Characteristics that make switchgrass attractive as a forage crop•	 High yields – Switchgrass grown for forage can produce up to twice as much as tall fescue on an acre of land. Research in Tennessee has shown that, if grown exclu-sively for hay, 4-5 tons per acre are not uncommon. If switchgrass is planted primar-ily for biofuels production, there is potential to harvest the early growth through hay-ing or grazing, then managing the remainder of the season’s growth for the biofuels feed-stock market.•	 Summer hay production – Since switchgrass is a warm-season grass, it is adapted to hot, summer conditions. As peak growth occurs from May through September, it is easy to produce hay be-cause of better drying condi-tions. It is not unusual to find switchgrass hay that is better quality than the average tall fescue hay. This is not because switchgrass as a species is better than tall fescue, but be-cause hay-making conditions are better during the switch-grass growing season and because rain and cool temper-atures often delay cutting tall fescue. A delayed tall fescue harvest results in decreased protein and energy.•	 Summer grazing – The sum-mer growth of switchgrass also makes switchgrass an excellent forage for grazing. Since most cattle operations in the Mid-South use tall fes-cue as their primary pasture grass, there is limited forage production during summer. This limited production UTBiofuelsInitiativereduces the performance of grazing cattle, and may lead to overgrazing and weakened stands of tall fescue. Switch-grass can provide good-quality forage for grazing animals and provide the opportunity to rest tall fescue pastures during a stressful time of the year. Research has shown switch-grass can be grown successfully as both a biofuel feedstock and forage crop. There is no need, however, to grow it as only one or the other. There is the possibility of having switchgrass as a “dual-purpose” crop. The early growth of the for-age, which is generally the highest quality, can be hayed or grazed. The later growth can be allowed to ma-ture and harvested after frost as a biomass crop. Biomass production will be lower under this scenario, but, depending on the objectives and needs of the producer, this may be a useful strategy.Keys to using switchgrass as a hay cropEarly-season production (late April–late May for switchgrass) pro-duces the highest-quality forage and can be easily utilized for hay. Crude protein levels may range from 14-20 percent at this time of year. How-ever, forage yields will be relatively low (e.g., two tons per acre, depend-ing on the timing of harvest). As with any hay crop, waiting a few weeks will increase forage yield and decrease forage quality (Figure 1). In addition, the later the forage is harvested, the greater the reduction in the final biofuel feedstock harvest for that season. Most biomass ac-cumulation in switchgrass occurs in the first half of the growing season. For example, in one Southeastern study, 56 percent of annual biomass accumulation was obtained by late June each year. Obviously, delay-ing the forage harvest too late (past late-boot stage) would also be coun-terproductive for forage production, because of drop in forage quality in the maturing stand. These early-forage harvests (haying or grazing) should leave a minimum 8-inch residual height to ensure rapid regrowth and an adequate final biomass harvest. Producers must realize that leav-ing high residual heights is very important to quick recovery of the plant, due to the elevated grow-ing point on switchgrass (often > 5 inches above the soil surface) and the minimal leaf surface area present below 8–10 inches. Remov-ing the growing point and all leaves will result in delayed regrowth that will substantially reduce final yields and, in the long run, stand vigor.Because biorefineries will re-quire switchgrass on a year-round basis, producers would have the opportunity to later sell switchgrass harvested for hay as biofuel feed-stock if they find they do not need as much as hay. While dormant-season harvested material is considered better quality for biofuel produc-tion as a result of reduced mineral concentrations, there is no reason to believe mid-summer “hay” crops will not be acceptable for processing switchgrass into biofuel. Following guidelines for proper hay storage will help ensure the material will be available for future hay needs or biofuel production.Caution about Horses and Switchgrass Hay: While switch-grass hay has excellent value for beef and/or dairy cattle, as well as other livestock, there is evidence that horses fed switchgrass hay may have a phototoxic reaction. In short, horses may lose some hair and suffer sunburns. Although it is not common, horse owners should be aware of this problem. At this time, switchgrass is not recommended for horse hay.Grazing Switchgrass Because early-season switch-grass has good nutritive value for cattle, the material could be removed through controlled graz-ing rather than haying. Grazing, of course, requires adequate fencing, access to water and shade. Where this infrastructure is lacking, the investment may not be cost-effec-tive. This is due to the relatively short grazing season available in an integrated system where a good deal of switchgrass growth will be reserved for biofuels. On the other hand, temporary fencing and leav-ing gates open to water on other pastures could be effective. This strategy will be even more effective later in the spring when the quality and production difference between cool-season grasses and switchgrass is more pronounced. 04812166-May 10-Jun 14-Jul 19-Aug 23-Sep 28-Oct% CPCave in Rock SGAlamo SGFigure 1. Crude protein changes with maturity in two switchgrass cultivars. Source: Sladden and co-workers.1994. American Forage and Grassland Council Conference Proceedings p. 242UTBiofuelsInitiative 2Because of the reasons listed under haying guidelines, it is im-portant not to graze switchgrass too closely. Leaving a residual stand height of at least 8 inches, and preferably as high as 12 inches, will result in more rapid regrowth and greater yields of biomass for biofu-els at the end of the season. While most producers managing switch-grass strictly as a forage crop will practice rotational grazing to ac-commodate this growth, it is unnec-essary when attempting to integrate grazing and biomass production. That is because a single rotation of only 2–4 weeks of grazing should be planned. Switchgrass could be grazed later into the season, but as with haying, increased consump-tion as a forage crop will reduce final biomass yields. Initial livestock entry into switchgrass in the spring should oc-cur once the stand is 18–24 inches tall, typically mid-May. Stocking at lower rates or creep-grazing calves will make it possible to begin soon-er. Stocking rates of three to five steers per acre will probably be best under normal circumstances. This should allow enough animals to re-move the available forage within a 2–4 week period, freeing up the re-mainder of the growing season for accumulation of switchgrass feed-stock for biofuels. Experience will dictate how to adjust these stocking rates to achieve desired results. Keep in mind, during the establish-ment year, no grazing should be planned unless it is a brief period of high stocking to remove a weed 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 ProductionEven 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. Current recommendations are that pH should be maintained at 5.0 or higher. There is no need to lime to keep pH at levels needed for most other forage crops. Nitrogen should be only be applied to native grasses if soil moisture is not limiting, and if extra forage production is desired (Table 1).SummaryEven though many people are currently focused on switchgrass as a biofuel feedstock, it should be kept in mind that switchgrass can also be used as a forage crop. High Table 1. Nitrogen fertilization recommendations for switchgrass used for forage.UseEarly summer Mid-summer------------- lb actual N per acre -------------Hay1 45-60 45-60Grazing2 45-60 up to 60 lb N  1Mid-summer application should be eliminated if soil moisture is limited 2Apply N only if extra forage growth is needed.yields and good-quality forage can be produced during summer, if it is managed correctly. If switchgrass is cut while it is young and leafy, the nutrient content will be equal UTBiofuelsInitiative 3Programs 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.SP701B-5M-3/08(Rep)    R12-4110-070-012-08  08-0166to other grasses. If switchgrass is allowed to mature and become fibrous, forage quality will suf-fer drastically. This is noteworthy; given the tendency of switchgrass to produce high amounts of fiber when mature is what makes it de-sirable for biofuel production.It should also be kept in mind that this crop does not have to be used only for forage or only for bio-mass. It can be harvested as a dual-purpose crop, so early growth can be used for forage, and later growth can be used for biomass. Haying early may reduce biomass produc-tion, but the ability to use some of the growth for cattle production will add flexibility to a producer’s operation and provide the opportu-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.UTBiofuelsInitiative 4For more information about the UT Biofuels Initiative, please visithttp://www.UTbioenergy.orgVisit the UT Extension Web site athttp://www.utextension.utk.edu/Biofuels Initiative

SP701-B Using Switchgrass for Forage

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SP701-B Using Switchgrass for Forage

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