Hill-Pasture Renovation Using Phosphate Rock and Stocking with Sheep and Goats

Abstract

The introduction of legumes to hill-pasture may be complicated by plant competition and soil chemical and physical limitations. The existing undesirable plant community must be modified before enhanced productivity can be realized. In many cases, soil phosphorus is limiting to legume growth. A study was conducted to determine the effect of phosphate rock, over-seeding birdsfoot trefoil (Lotus corniculatus L.) and stocking with goats (Capra hircus hircus) and sheep (Ovis spp.) upon the floristic composition and productivity of hill-pasture. Treatments included: stocked only, stocking with overseeding with 0, 45, 90, or 180 lb P as phosphate rocklacre, and an untreated (not stocked or fertilized with phosphate rock) control. Treatments were replicated three times in a randomized block design on a steep (30% slope) site with a Dekalb series soil (loamy-skeletal, mixed, mesic Typic Dystrochrept). Goats and sheep were effective in controlling most tall-growing forbs and brush on abandoned hill-pasture. The presence of yellow crownbeard (Verbesina Occidentalis L.), a toxic weed species, increased since neither goats nor sheep consumed the plant. Control of this weed is essential if hill-pasture improvement is to succeed. Birdsfoot trefoil alone improved dry matter production by 34% and, in combination with phosphate rock, improved production by 78% over stocked controls. Phosphate rock application increased surface strata plant-available P and the presence and dry matter yield of birdsfoot trefoil in oversown plots. Birdsfoot trefoil and phosphate rock significantly improved the productivity of hill-pastureand appear to be a viable low-input option for hill-land pasture improvement. Research Question Phosphate rock was used in the past in row crop production situations with limited success. Phosphate rock may be more appropriate for use in perennial plant production situations since P release is a function of solubility and is dependent upon acid soil environments for enhanced solubility. Our objective was to determine if stocking with goats (used to control weeds), phosphate rock application, and overseeding birds-foot trefoil could bring about a change in the floristic composition of hill-pasture with acidic soil, leading to improved productivity. Literature Summary Unmanaged hill-pastures abound in the Appalachian Region of the eastern USA. The floristic community becomes dominated by non-pastoral species of low productivity or quality. The plant community must be improved before enhanced production efficiency can be realized. In many cases, topographic or economic constraints limit mechanized or chemical renovation options. Livestock such as goats can be effective brush and weed control agents. Once the canopy competition is reduced, desirable plants, including legumes, can flourish. Legumes can then theoretically supply the N which limits hill-pasture productivity. Furthermore, successful production of legumes in Appalachian soils depends upon an adequate supply of phosphorus. Study Description The experiment was conducted from 1989 through 1992 in southern West Virginia (2800 ft elevation). Replicated (3) plots were established on a northeast facing slope (30%) on Dekalb soil (eroded, loamy skeletal, mixed, mesic Typic Dystrochrept). A wide range of plants including grasses, forbs, and brush occurred across the site. Four rates of phosphate rock (0, 45, 90, and 180 lb/acre) were applied to plots oversown with birdsfoot trefoil. Controls received no phosphate rock and were: a) excluded from stocking, b) stocked only, or c) stocked and oversown. No other chemical fertilizer or herbicides were used. Applied Question Can stocking with goats and sheep, application of phosphate rock and overseeding birdsfoot trefoil be used as a hill-pasture renovation technique in the Appalachian region? Goats effectively controlled tall-growing weeds allowing light to reach the base of the canopy. Grasses became the primary component of the flora making the pasture suitable for sheep and cattle grazing. Animals refused to consume a known toxic weed, yellow crownbeard, and enabled it to flourish. Effective methods must be developed to control yellow crownbeard if pasture renovation in the region is to succeed. Application to phosphate rock contributed to increased herbage productivity and supported an increased legume component in the sward. Surface application of less than 180 lb/acre phosphate rock is unlikely to have a significant influence on soil P availability. Birdsfoot trefoil over-seeding resulted in a 34% increase in herbage dry matter yield, and overseeding in combination with phosphate rock resulted in a 78% increase in yield over controls. Regular defoliation (through grazing) is required to maintain a desirable floristic composition.