Grazing Projects
Capitalizing On The Sheep’s Ability To Be Used As A Tool To Manipulate The Landscape While Maintaining A Profitable Production System
It has long been assumed that infestation of non-native invasive weeds was basically an agriculture problem, but, given their impact on landscape diversity, wildlife habitat and recreational value of wildlands it can be concluded that the spread of noxious is a societal issue. Non-native invasive plants are the primary environmental threat to western wildlands. These plants quadrupled their areas of infestation in the last 10 years. If they continue to spread at their current rate, they will, at some point in the future, be the dominant plants on the western landscape. Over 17 million acres of "public land" in the west are infested with noxious weeds with an additional 5,000 acres becoming infested each day. In Montana, it is estimated that about 8 million acres are seriously infested with noxious weeds. In many cases the cost of traditional weed control methods (primarily herbicides) actually exceeds the original cost of the land. Previous research conducted at MSU indicates that sheep and/or goat grazing offer an additional, non-traditional, tool in a weed management. Sheep grazing can provide land managers an alternate control method in their fight against these invasive plants that is more economically feasible and environmentally sensitive.
Any type of weed management strategy is a long term commitment. A minimum of 5 and more likely a 10 year period of management may be necessary. The primary focus of this project is to build on existing weed management and sheep research and experience. The Montana Sheep Institute is developing grazing strategies that facilitates the use of sheep as a tool to manage large infestations of invasive plants. These grazing strategies will maintain a production system which is profitable to the sheep owner. This project is currently in the third field season and is showing significant impacts. In addition, this project is receiving support from many associated individuals in the weed control field (including county weed supervisors, weed boards and county commissioners, local ranchers and citizens boards) throughout the state of Montana.
Sheep Institute weed projects involve:
- 22 Projects
- 35 Monitoring Sites
- 31 Sheep Producers
- 30,000 Ewes & Lambs
- 1,000 Landowners
- 100,000 Weed infested acres
Results from leafy spurge monitoring sites are summarized in figures 1 and 2. Figure 1 reinforces what happens if we allow these non-native weeds to continue to invade and dominate the landscape. The first and most critical issue is that as these weeds invade the landscape our research demonstrates that the forb component is eliminated from the landscape. Forbs are a critical component of a healthy wildlife habitat. Secondly, the noxious weed component gradually replaces the grass component until landscape diversity is compromised. The landscape trend is to a monoculture of the non-native invasive plant. Many sites investigated in this project have been altered because of high weed infestation levels. Most traditional weed control methods (i.e. herbicides) would be economically prohibitive under the current infestation conditions. For instance, it has been estimated that to control the weed problem in Missoula county alone with herbicides it would cost about 12 million dollars per year for 5 years. Figure 2 demonstrates that under a controlled grazing régime, sheep will selectively graze leafy spurge. In our studies, we were to achieve 60 to 70% utilization of the leafy spurge and limit the utilization of the grass to 30 to 40 percent. Over time this type of grazing should favor the re-establishment of grass and forb component of the landscape. Knapweed plot grazing results are summarized in figures 3 and 4. In general, these results followed similar trends to those observed in the leafy spurge sites. It appears that with spotted knapweed, there seems to be a more prevalent or distinct trend to a monoculture as infestation becomes more severe (figure 3).
Key areas that were representative of the site that prescriptive sheep grazing was to be used to manipulate the forage resource were identified and permanent monitoring sites established. A permanent photo plot (3 ft x 3 ft square) was staked and identified by GPS coordinates. In the spring, prior to grazing and at about the same time of the month, the plots were evaluated. Each photo plot was set up so that the 4 sides were running north, south, east and west. Photos were taken of the 3 ft x 3 ft plot square and of the landscape in all four directions originating from the photo plot (south, east, north and west).
In addition, a transect was run from the photo plot and five 50 x 50 cm quadrants located and clipped. In order to avoid sampling areas that had been previously clipped, the transect was run in a different direction from the photo plot each year. The direction of the transect, however, was consistent at every plot within each year.
The quadrants were located along the transect beginning 2 paces from the photo plot corner and then 2 paces apart. Within each quadrant only current year’s growth was clipped and vegetation separated by life form; perennial grass, annual grass, forbs, shrubs and target weed (leafy spurge, knapweed). Forages were dried and relative dry matter production of each life form calculated. In some instances, it was not possible to sample the permanent monitoring plot at about the same calendar time and prior to grazing. In these instances data from that particular site that year was not collected.
A preliminary comparison from project sites that had a minimum of two consecutive years of grazing (three sites with three consecutive years of grazing and 5 sites with 2 consecutive years of grazing) are summarized in Figure 3. As a general rule, leafy spurge composition decreased about 9% per year of grazing while the grass component of the landscape increased by 10%. Composition of leafy spurge decreased and grass increased at all monitoring sites except one.
