Effects Of Continuous Grazing Research Articles

The Effect of Continuous Grazing and Rest Rotational Management Systems on Grass Species Composition, Basal Cover and Production on Three Soil Types in the North West Province, South Africa

Rangelands represent the most extensive land cover type on Earth and many people depend on these rangelands for their livelihoods and for the ecosystem services that effect human wellbeing. The impact of grazing on community structure and ecosystem functioning is a key issue for rangeland management in order to maximize livestock production and sustainability of the operations. It is a known fact that soil differences cause differences in the palatability and utilization of grasses. Year-round continuous grazing is the management strategy used in the communal areas of the North West Province of South Africa. In this study the effect of continuous grazing and rest rotation grazing on grass species composition, basal cover and biomass production on different soil types were assessed. From the results it was clear that the effect of continuous grazing was the biggest on the andesitic soils (high clay), then the diabase soils (medium clay), whilst the effect on the quartzite soils was limited to even positive. In the rest rotation system, the effect of soil type on the different variables was negligibly small and the rangeland remained healthy and productive.

Managing agricultural grazing to enhance the carbon sequestration capacity of freshwater wetlands

Freshwater wetlands are important carbon sinks with an estimated ~ 450 gigatons of carbon stored in their sediments. However, when disturbed they can become significant sources of carbon emissions. Understanding carbon dynamics in freshwater wetlands is a research priority to maximise carbon drawdown opportunities through effective management. Grazing can have considerable impacts on the health of freshwater wetland functionality. Fencing to exclude livestock from freshwater wetlands is one approach used to reduce grazer impacts; however, this is not always feasible. Managing grazing intensity is one option that is amenable to most farmers and resource managers; however, to date there have been no studies to evaluate its efficacy. The impacts of seasonal grazing intensity (by sheep) on carbon sequestration by rain-filled freshwater wetlands were investigated in south eastern Australia (Wimmera region). Over a 1-year study duration, this research compared: a) the effects of continuous grazing (sheep present across all seasons); b) crash grazing (sheep present within the spring); and c) exclusion plots (controls; no sheep access) on above-ground plant biomass, soil carbon concentration, and fluxes across seasons. Results suggest that above-ground biomass was 6.4% higher within exclusion plots compared to grazed plots in both continuous and crash grazing regimes. Exclusion plots had 30% higher soil carbon concentration compared to grazed plots. Open-continuously grazed plots had higher fluxes (8.69 ± 10.61 g CO2 m−2 day−1) compared with exclusion plots (6.92 ± 15.86 g CO2-e m−2 day−1). This study shows that exclusion plots had higher soil carbon concentration and lower carbon emissions. Further, excluding grazing from wetlands within the Wimmera region would increase above-ground biomass and soil carbon stock by 545,300 tons of carbon while reducing CO2 emissions by 782,412 tons of CO2 year−1.

The Effect of Continuous Grazing on Herbaceous Species Composition, Basal Cover and Production on Three Soil Types in the North West Province, South Africa

Rangeland health is normally measured by soil condition, grass species composition as well as its acceptability to grazing herbivores. The impact of grazing on community structure and ecosystem functioning is a key issue for rangeland management in order to maximize livestock production and sustainability of the operations. Year-round continuous grazing is the management strategy used in the communal areas of the North West Province of South Africa. In this study the effect continuous grazing on herbaceous species composition, basal cover and production on different soil types was tested. It was clear from the results that the effect of continuous grazing was the biggest on the andesitic soils (high clay), then the diabase soils (medium clay), whilst the effect on the quartzite soils was limited to even positive. The end result was that the different soil types in a continuous grazing system led to serious selective grazing in this study.

Effect of continuous grazing on forage quality, quantity and animal performance

Abstract The effects of different grazing intensities of heifers on sward parameters such as sward structure, plant species diversity, herbage growth and forage quality as well as individual live-weight gains and live-weight gains per pasture area were studied in an upland area in the northern part of the Czech Republic over 4 years (1998–2001). The sward was maintained at a target height of 5 and 10 cm under intensive (IG) and extensive (EG) grazing, respectively. The total biomass production was higher under the IG than the EG treatment. In the Czech upland conditions, double peak curves of biomass growth during the grazing season were more typical than curves with one high spring peak. Species that responded positively to both treatments were the predominately short growing Trifolium repens, Taraxacum spp., Veronica arvensis and Agrostis capillaris. Tall species like Senecio ovatus, Alopecurus pratensis, Elytrigia repens and Aegopodium podagraria were associated with unmanaged plots. Total crude protein contents and forage digestibility were higher under IG. The content of crude fibre showed a reverse effect. Seasonal live-weight output per hectare under IG was approximately 1.5 times higher than EG treatment. However, if state subsidies are included, EG can be more profitable under the current Czech conditions than IG and satisfies both farmers and nature conservation objectives.

The effect of continuous grazing on the seed production of Subterranean clover (Trifolium subterraneum).

Three pure swards of subterranean clover were either (a) left ungrazed with a leaf area index (LAI) of 4.6, or (b) continuously grazed leniently to leave 1 600 kg DM/ha herbage mass equivalent to an LAI of 1.0, or (c) hard grazed to leave 1 400 kg DM/ha herbage mass equivalent to an LAI of 0.6 throughout the flowering period. These swards yielded 1 250, 320 and 70 kg/ha of seed, respectively. One intensive sampling during the middle of flowering showed that seed yield was positively correlated with plant weight, leaf area per plant, and area per leaf, specific leaf area and leaf area ratio. Grazing reduced numbers of both inflorescences and burrs and hence seed yield. Whilst reduced leaf area and plant weight may have also been partly responsible, under hard grazing, only 58% of potential reproductive sites were occupied which suggests that grazing animals also reduced seed yield by consuming these. It is recommended that continuous grazing during flowering and seed maturation should be controlled to leave at least 1 600 kg DM/ha of residual herbage mass, equivalent to an LAI of 1.0, if adequate seed is to be produced to be ensure the establishment of a high producing sward in the following growing season. Key words: flowering, grazing, herbage mass, leaf area, seed production, Trifolium subterraneum

Effects of continuous grazing and seasonal closures on the performance and persistence of some sown temperate perennial grasses, North-West Slopes New South Wales

A split-plot experiment was sown at Tamworth in 1992 to examine the effects of continuous sheep grazing and seasonal closures (autumn, spring, spring + autumn, and summer + winter) on the herbage mass, plant frequency and basal cover of 5 perennial grasses, when sown as monocultures or with a perennial (Trifolium repens cv. Haifa) or annual legume (Trifolium subterraneum var. subterraneum cv. Seaton Park). Plant basal area and crown density data were also collected. The perennial grasses were Phalaris aquatica cv. Sirosa, Festuca arundinacea, cv.� Demeter, Lolium perenne cv. Kangaroo Valley, Austrodanthonia richardsonii (syn. Danthonia richardsonii) cv.�Taranna, and A. bipartita (syn. D. linkii) cv. Bunderra. There was no significant effect of legume presence on the herbage mass or persistence of the perennial grasses. The only treatment that had a significant effect (P< 0.05) on either herbage mass, plant frequency or basal cover data was the grazing treatment × perennial grass interaction in each of the years 1993-98, except for herbage mass in December 1993 and basal cover in October 1998. In all of the grazing treatments examined, Kangaroo Valley ryegrass failed to persist after spring 1994; Demeter fescue had failed by spring 1997 and Sirosa phalaris by spring 1998. Six years after sowing the only temperate grass cultivars that were persisting in all grazing treatments were the native perennials, Taranna and Bunderra. Hence, the data represent the entire stand life from sowing to eventual failure for the 3 introduced cultivars. While grazing treatment effects within years for individual species were significant, overall grazing had little effect on the rate of decline in herbage mass and persistence of Kangaroo Valley, Demeter and Sirosa. By 1998, grazing treatment had no significant effect on the herbage mass and basal cover of Taranna and Bunderra, but their plant frequencies were lowest in the spring rest and summer + winter rest treatments.

Changes in characteristics of pastures in the coastal subtropics when grazed by cattle during years of low rainfall

Summary. The effect of continuous grazing on pasture composition and quality was assessed on 2 pasture types in a subtropical environment. The pastures were native stocked at 1 cow/2.5 ha, and previously improved stocked at 1 cow/1.6 ha. In August 1990, carpet grass (Axonopus affinus) was the major species in both the native (49.8%) and improved (61.3%) pastures. However, the proportion of carpet grass decreased during the study to 33% in the native pasture and 30% in the improved pasture in February 1994. In the native pasture, blady grass (Imperata cylindrica) increased at the expense of carpet grass, whereas in the improved pasture higher quality grasses, and to a lesser extent Giant Parramatta grass (Sporobolus indicus), increased at the expense of carpet grass. Overall, dry matter on offer and green dry matter depended on rainfall and these peaked in late summer. Dry matter on offer differed between non-drought and drought periods in both pastures and was ≤3500 kg/ha in drought months in the native pasture and ≥3500 kg/ha in comparable months in the improved pasture. Green dry matter was higher in pastures towards the end of the summer growing season (83%, March 1992) and lower during many of the drought months (12%, May 1991). Grazing pressure (liveweight 0.75/t green dry matter) was highest in August, the crucial period for weed incursion. Organic matter digestibility was highest following rain in late spring (November 1990; 69%, improved pasture) but lowest in the absence of rain (November 1993; 38%, native pasture). The proportion of green dry matter in the native pasture was not related to organic matter digestibility nor to the nitrogen content of plucked pasture samples. However, in the improved pasture the proportion of green dry matter was related to organic matter digestibility on 3 occasions but not to nitrogen content.

Effects of Continuous Grazing on Habitat and Density of Ground-Foraging Birds in South Texas

We analyzed the response of the key habitat features and ground-foraging birds to 2 intensities of continuous grazing on sandy loam and clay soils in the Texas Coastal Bend during 1984-1985. Heavy continuous grazing increased the disperion but not necessarily the availability of bare ground in comparison with moderate continuous grazing. Responses of habitat features (structure of ground cover, key food plants) depended on soil type. Seasonal densities of eastern meadowlarks (Sturnella magna) were higher on clay than on sandy loam soils and higher under moderate than under heavy grazing. Mourning doves (Zenaida macrowua) were more abundant on sandy loams than on clays and more abundant under heavy than under moderate grazing. Northern bobwhite (Colinus viglnla=) abundance was uniformly low, regardless of grazing intensity and soil type.

Effect of continuous grazing in the dohne sourveld on species composition and basal cover

Abstract In a grazing trial conducted at the Dohne Agricultural Research Station, natural grassland was grazed continuously for 36 years with cattle. In a second investigation conducted on similar grassland, paddocks were grazed or rested, in all combinations of the four seasons of the year, over a ten year period. Changes in botanical composition and cover of the sward were monitored at regular intervals. The results of these investigations indicate that under a regime of non‐selective grazing the composition of Dohne Sourveld is remarkably stable. After 36 years of continuous grazing the species composition of the sward was largely maintained. Floristically Dohne Sourveld is dominated by a small number of grass species of which Andropogon appendiculatus, Elionurus muticus, Heteropogon contortus, Sporobolus africanus, Themeda triandra and Tristachya leucothrix are the most important. These species react differently to under‐utilization or increasingly severe defoliation, enabling them to be classified into decreaser or increaser categories. Severe defoliation resulted in a marked decrease in basal cover but only small changes in relative species composition. As the intensity of defoliation increases, decrease in grass cover is associated with an increase of forbs, such as Senecio retrorsus.

Effect of Continuous Grazing on the Diet of Steers

Effect of Continuous Grazing on the Diet of Steers

2. A comparison between the effects of continuous grazing by angora goats and merino sheep on veld in the central lower karoo

Abstract The long term effects of continuous grazing by Merino sheep and Angora goats and complete protection on short Karoo shrubveld of the Central Lower Karoo were investigated. Botanical surveys were done by means of the wheel point method. For statistical analysis the vegetation was grouped into ephemerals, grasses, Karoo shrubs and succulent shrubs each with sub‐classes of palatable and unpalatable. The results showed that continuous grazing by goats at a realistic stocking rate was less harmful to the palatable perennial component of the vegetation than was continuous grazing by sheep. Complete protection over a period of 11 years resulted in a sustained improvement in the perennial palatable component, thus demonstrating the advantages of a long rest for Karooveld.