By David Burner (USDA-ARS), Larry Campbell (University of Arkansas), & Stephen Meier (Meier HorseShoe Pines)
Silvopasture, the integration of trees, forage plants, and livestock in an intensively-managed system, provides a means of diversifying on-farm income by providing a short-term income from grazing, while trees are grown for longer-term profit. Christmas tree plantations, which are essentially tree rows with vegetated alleys, have the potential to be managed as silvopastures thereby increasing farm diversification, sustainability, production, and profitability. In this article, we summarize the main factors involved in a sheep-based Christmas tree silvopasture system. This management-intensive system requires considerable research and planning before being initiated.
Several successful reports of this system are cited in this article. Larry Campbell also used sheep to manage vegetation in a diverse silvopastoral system in Oregon. Stephen Meier at Meier HorseShoe Pines has grazed sheep for four years on six acres of his choose-and-cut Christmas tree operation in Jackson, MO. We try to draw some general conclusions on the system based on experiences in Oregon and Missouri, realizing that site-specific adjustments may be needed for your particular operation. In this review article we summarize the main factors involved in a sheep-based system, including breed selection, fencing needs, tree growth stage, flock management, and forage systems.
Larger livestock (cattle) have been successfully used for weed suppression in a West Virginia Christmas tree operation (see Kelly, 2000). Cattle, along with some smaller livestock like goats, require additional management inputs by the landowner, including extra fencing to control browsing, trampling, and rubbing damage (English, 1998; Pearson et al., 1990). Depending on experience, formal training in animal husbandry may be needed. In this article we focus on using sheep for Christmas tree silvopastures.
Sheep breed selection
Breeds differ in their gregariousness (clustering) instinct. Black-faced (meat) breeds tend to be preferred because they are less gregarious and their lambs have more rapid growth than white-faced (wool) breeds. Undesirable behavioral habits, e.g., browsing, tend to spread rapidly through gregarious flocks. Thus, Shropshire have been used successfully in Missouri (Compas, 2000; Marceline, 2000), Dorset, Hampshire, Rambouillet, Romney, and Suffolk in Oregon, and Dorset, Leicester, Shropshire, and Suffolk in Europe (Theilby, 1997).
Grazing Initiation - Flock Protection
Predation of the sheep by coyotes and dogs is a major concern. Several methods, used singly or in combination, can be used to protect the flock: perimeter fencing, herding flock into a barn at night, or using guard animals such as dogs, llamas, donkeys, etc. Fencing can be permanent or mobile, barbed wire, plain wire, or electric. Portable electric fencing can be quite effective, economical, mobile, and can be easily removed from the plantation during tree harvesting.
Grazing Initiation - Tree Considerations
Trees as young as one to two years post-planting can be exposed to sheep, but will need to be monitored for browsed terminal leaders and lateral branches (Sharrow et al., 1992). New conifer growth is quite palatable as a main course. Grazing should be delayed about 60 days or until new conifer growth has hardened-off, as browse damage is minimal after that point. Sheep may be introduced after hardening-off until about late-October (Compas, 2000), and again after Christmas prior to new tree growth. Stephen Meier initiates grazing in early spring before bud break, and then beginning in July-August through the fall. Forage availability and browse damage should be monitored daily.
Tree species is important along with growth stage. Stephen Meier has used sheep successfully with Scotch and Virginia pine, but excludes sheep from white pine areas because of browse damage. Various firs, hemlock, Western red cedar, sequoia, and pines have been used in Oregon. It is best to experiment first with small areas of exotic tree species to determine the best species for your operation. For example, we do not know about possible browse damage to Leyland and Arizona cypress, as these species tend to grow more or less continuously.
Flocks are most difficult to manage in spring, when growth of cool-season grasses accelerates and trees are highly susceptible to browse damage. Frequent flock rotation, perhaps every three days or so, may be necessary. Sheep may, through boredom, cause more damage the longer they remain in one pasture. They also will cause more damage as forage becomes limiting. Browsing is a learned behavior, so it is important to get rid of these "lawbreakers" before they teach others their miscreant ways. This advice also applies for "jumpers" who ignore fences.
Putting weaned lambs by themselves in with trees should be avoided. Lambs challenge and butt into trees, and investigate by browsing more than ewes. The frequency of flock rotation should be adjusted to minimize tree damage. Lambs by themselves take much more time and management for use in silvopastures; however, they tend to follow the example of older sheep in a pasturing routine. Dry ewes are best for this system, but ewe-lamb pairs may be used if necessary.
Sheep will seek shade during the heat of the day and if none is provided, they will lie under larger trees (Figure 1), possibly damaging lower branches and ruining otherwise merchantable trees. So, artificial shade may be needed to minimize effects of summer temperature stress. A portable shed large enough to accommodate the entire flock can be constructed. This can be done preferably on high ground on south side of hill land, without walls for optimum air flow. By placing a water source near the shed, the sheep will naturally rest there after watering. Depending on rainfall, sheep may receive adequate water from forage in spring, but in summer an adequate supply of fresh water is critical. It is also important to control external parasites, as they can stimulate a rubbing response, and to provide adequate feed and minerals as may be needed.
Sheep are sensitive to copper toxicity, so this may affect use of copper sulfate (Bordeaux). Exposure of sheep to some pesticides may prevent you from being able to sell the meat. Pesticide labels will need to be checked with regard to sheep exclusion during spraying, and reentry times after spraying.
Sheep have diverse diets, preferring forage legumes and broad-leaf vegetation to pure grass pasture. Sheep browse difficult-to-control weeds like red alder (Sharrow et al., 1992), honeysuckle, and multiflora rose. They also nibble the lichen off tree bark with no apparent ill effect on the trees. In mixed pastures in Oregon, sheep preferred Kentucky bluegrass, white clover, and orchardgrass, but avoided tall fescue and bentgrass. Taller grasses like orchardgrass and tall fescue also are undesirable because they can shade newly-planted Christmas tree seedlings. To optimize tree and sheep management, one suggestion is to use a pure stand of white clover, or a bluegrass-clover mixture. Silvopasturing is not a "silver bullet" for weed control, although it can be a realistic alternative to traditional weed control methods for the small producer (Theilby, 1997).
Sheep-Christmas tree silvopastures are not for everyone. Your management skills will be tested to make both industries work. It is crucial that trees, pasture, and sheep be checked twice per day. If you have negligible forage growth in your tree fields, this will not work, period! However if you have abundant, diverse forage (a grass-legume mix or broad-leaf weeds), you could benefit from this system. The best sellers of the technology are those producers who make it work. Take the Missouri producer who was amazed at the thoroughness with which sheep ‘mowed' the grass, the summertime labor and cost savings, plus the modest income from sheep sales (Stephen Meier sells market lambs, 120 to 130 lb, in October-November). Like Stephen Meier, you also can enhance the choose-and cut experience by housing lambs or ewes in the retail area as a mini-petting zoo (Compas, 2000; Marcelina, 2000).
Compas, L. 2000. Small farms, big ideas, News for Missouri sustainable agriculture. http:// agebb.missouri.edu/sustain/smfarm/white.htm. Accessed 4/3/03.
English, J. 1998. Growing Christmas trees organically. Maine organic farmers and growers association. http://www.mofga.org/mofctrees.htm. Accessed 4/3/03.
Kelly, E.B. 2000. Regional news, the southern view, West Virginia. Christmas Trees 27(4):32.
Marcelina, E. 2000. Sheep and Christmas trees: a good combination. Inside Agroforestry. National Agroforestry Center. Fall/winter 1999-2000, p 3.
Pearson, H.A., T.E. Prince, Jr., and C.M. Todd, Jr. 1990. Virginia pines and cattle grazing - an agroforestry opportunity. Southern Journal of Applied Forestry 14:55-59.
Sharrow, S.H., W.C. Leininger, and K.A. Osman. 1992. Sheep grazing effects on coastal Douglas fir forest growth: a ten-year perspective. Forest Ecology and Management 50:75-84.
Theilby, F. 1997. Weed control by sheep grazing in Christmas tree plantations. http://www. mst.dk/udgiv/publications/2002/87-7944-984-0/html/kap08_eng.htm. Accessed 4/3/03.
This article originally appeared in the July 2003 issue of the Temperate Agroforester.