Companion Grazing Using Goats and Cattle to Control Leafy Spurge (continued)

Abstract

Keywords

Introduction

Methodology
and Design

Results and
Discussion

Conclusion/
Implications

References

Project
Background

Leafy spurge is a long-lived plant native to Europe and Asia. It was introduced to North America in 1827 and first reported in North Dakota in 1909 (Messersmith and Lym 1983). It spreads rapidly by seeds and rhizomes and forms colonies primarily in untilled agricultural land.

Leafy spurge has become a troublesome weed in the Northern Great Plains region of North America where it grows largely devoid of insect and disease pests (Messersmith et al. 1985). This weed, which is extremely persistent and competitive, has contributed significantly to economic losses to livestock producers.

Leafy spurge continues to be a serious problem in North Dakota, infesting over 1,000,000 acres (ac) of land, predominately rangeland (North Dakota Department. of Agriculture 1996). Chemicals are the primary method for control and eradication attempts. However, biological control methods with insects show great potential (Lacey et al. 1984, Lym and Carlson 1994, Spencer 1994). Sheep grazing has been a control method since the 1930s but has been utilized sparingly (Bartz et al. 1985; Helgeson and Longwell 1942; Helgeson and Thompson 1939). Goat grazing studies investigating the potential to control leafy spurge are limited but have shown potential as a control technique (Lym et al.1997; Sedivec et al. 1994; Hanson 1994).

Study objectives were to determine 1) the effect of goat grazing on leafy spurge stem density and associated herbaceous production, and 2) differences between multi-species grazing and single species grazing of leafy spurge-infested rangeland in regard to herbaceous species utilization patterns. The study hypothesis was graminoid degree of use on the CG treatment should be significantly greater than the other two treatments.

Some knowledge of range, weather, animals, and season of the year is essential when determining the most desirable mix of grazing animals in any given situation. Great potential exists for use of multi-species grazing of livestock to maintain forage production and species diversity. Land managers should recognize the value of multi-species grazing and be encouraged to apply this concept on public and private lands.

Study Area

The study area comprised 211.3 ha located in Sections 12 and 13, T149N, R63W in southeast Eddy County, North Dakota. Research was conducted on mixed-grass prairie of Camp Grafton South (CGS), a facility of the North Dakota National Guard. Camp Grafton South is comprised of 10,000 ac found approximately 20.0 miles east of New Rockford, North Dakota. The area is predominately rangeland that has been exposed to many decades of cattle grazing.

The 30-year annual average precipitation at the McHenry weather station in Eddy County is 18.6 in. annually (NOAA, NCDC 1996). In 1993, more than 80 % of total precipitation occurred from May to August. During this time period nearly 12.2 in. of precipitation was above the expected average for this period. This high rainfall precipitation pattern continued in 1994 with 18.9 in. above average rainfall received.

The study area vegetation was primarily mixed-grass prairie (Whitman and Wali 1975, Barker and Whitman 1989). Küchler (1964) classified the potential natural vegetation of this northern transition grass prairie as a moderately dense, short to medium tall wheatgrass-bluestem-needlegrass (Agropyron-Andropogon-Stipa) association. Dominant grasses found on CGS included western wheatgrass (Agropyron smithii Rydb.), blue grama (Bouteloua gracilis H.B.K.), Kentucky bluegrass (Poa pratensis L.), smooth brome (Bromus inermis Leyss.), needle-and-thread (Stipa comata Trin. & Rupr.), green needlegrass (Stipa viridula Trin.), quackgrass (Agropyron repens L.), little bluestem (Schizachryium scoparium Michx.), and various upland sedges (Carex spp.) (Barker and Whitman 1989). Forb species included leafy spurge (Euphorbia esula L.), fringed sage (Artemisia frigida Willd.), white sage (Artemisia ludoviciana Nutt. ), silver-leaf scurf pea (Psoralea argophylla Pursh.), white aster (Aster ericoides L.), dotted gayfeather (Liatris punctata Hook.), prairie coneflower (Ratibida columnifera Nutt.), and stiff sunflower (Helianthus rigidus Pers.). The dominant shrub species were western snowberry (Symphoricarpos occidentalis Moench) and prairie rose (Rosa arkansana Porter)(Barker and Whitman 1989).

Grazing treatments

The study area consisted of three tracts of land, each equally infested with 30 to 40% leafy spurge. Study area No. 1 was a 92.2 ac plot grazed by cattle only (CO). Study area No.2 was 102.3 ac and grazed by cattle and goats (CG) together. Study area No.3 was grazed by goats only (GO) and included 21.5 ac.

The CO was stocked with 21 cow/calf (angus/hereford cross) pairs in 1993, 1994 and 1995. Grazing dates were 15 June to 1 November (140 days) and a stocking rate of 0.98 ac/Animal Unit Month (AUM). The GO was grazed by 30 angora goat nannies from 27 May through 1 September (96 days) and a stocking rate of 0.98 ac/AUM. The CG was grazed by 21 cow/calf pairs from 15 June through 1 November (140 days) at a stocking rate of 0.98 ac/AUM and by 156 angora goat nannies from 27 May through 1 September (96 days)at a stocking rate of 0.62 ac/AUM. Overall stocking rate on the CG treatment was 0.74 ac/AUM. The CG grazing treatment was stocked 56 % higher than either single species grazing treatment, with the added stocking rate the addition of goats. Cattle stocking rates remained the same between CO and CG treatments. Goats were added to the CG treatment without adjusting cattle numbers due to the attempt to mimic what livestock producers would do in a real situation.

Methodology and Design
The paired-plot clipping technique was used to determine forage production and disappearance for leafy spurge, graminoids, shrubs, and other forbs (Milner and Hughes 1968). Plant species nomenclature follows The Great Plains Flora (Great Plains Flora Association 1986).

Peak herbage mass was calculated yearly for all treatments from two, 0.82 ft² (0.91 ft x 0.91 ft) quadrats within each of 32 exclosures (8.2 ft x 16.4 ft) in 1993 through 1995. Two quadrats were clipped inside and two outside each exclosure. The goats only, cattle only, and cattle and goat treatments had 14, 6, and 12 exclosures, respectively. Exclosures were randomly located on sandy and overflow range sites for each treatment. Paired grazed and ungrazed plots were clipped in early August when herbage mass was near maximum (Whitman et al. 1952) and again immediately following the grazing season to determine degree of disappearance. Herbage was hand clipped to ground level in each quadrat. Samples were oven dried at 140^o F for 48 hours. Vegetation samples were hand separated into leafy spurge, graminoids, shrubs, forbs, and litter during removal process.

Utilization or herbage disappearance was estimated by the difference between peak herbage mass inside and outside exclosures at the end of the grazing season. Disappearance of forage from paired grazed plots was used to estimate utilization.

Leafy spurge communities were mapped for each treatment using aerial photos. Twelve 75 m permanent transects were randomly dispersed to collect leafy spurge stem counts, 4 on the CO, 4 on the GO, and 4 on the CG. There were 15 permanent quadrats distributed evenly throughout the transect. Leafy spurge stem counts were conducted before angora goat grazing on 25 and 26 May, 1993, to achieve initial stand counts.

Leafy spurge stems counts were conducted in late May 1994 through 1996 to compare yearly differences on the same transects initiated in 1993 using the same methodology. Stems were counted using 1.0 ft² (1.0 ft x 1.0 ft) frame on 10 line transects in the spring of the year before grazing. Fifteen systematically placed 1.0 ft² quadrats per transect were used to determine forb and shrub composition per stand. Species were identified and densities recorded. Relative frequency and relative density were computed and summed to produce importance values. Density data represented individual plants.

Statistical Analyses

Statistical analysis for leafy spurge stem densities and degree of use for graminoids, leafy spurge, and western snowberry were attained using the multi-response permutation procedure (Biondini et al. 1988) at the 95 % confidence level. Multi-response permutation procedure allowed evaluation of nonnormality and absolute differences which were resistant to outliers. A modified t-test (Zar 1984) was used to evaluate percentage change in grass, leafy spurge, and western snowberry production at a confidence level of 95 %.

BACK | NEXT
Table of Contents – Winter 1997