Optimal spatial and temporal utilization of grassland resources for extensive livestock production.
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Date
2018
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Abstract
South Africa naturally experiences variation in rainfall patterns with distinct seasonal
distribution. The anticipated disruptive effects of climate change, in this region, on vegetation
dynamics is likely to accentuate the impact of seasonal forage nutrient fluctuations on livestock
production. Although there are several grazing philosophies that have been adopted to mitigate
these constraints (continuous and variations of rotational grazing systems), debates on
superiority between these systems continue to be of interest to researchers and livestock
producers. Nonetheless, continuous grazing systems have largely been condemned due to the
detrimental effects of extensive selective grazing on vegetation composition and soil
conservation. Poor implementation of these systems has resulted in extensive veld degradation,
significantly reducing sustainability of livestock production. This is more pronounced in
communal rangelands where production capital is limited. Moreover, erratic rainfall and
extreme temperatures have resulted in the abandonment of large areas of croplands, and thus
further impacting negatively on livestock production dynamics.
Therefore, it is necessary to quantify utilization regimes of the abandoned crop lands,
continuously and rotationally grazed veld and examine their effects on ecosystem health and
livestock production. To examine these effects, a study was conducted in Mzongwana,
Matatiele (old lands and continuously grazed veld) and in Wakefield Research Farm, Fort
Nottingham (rotationally grazed veld). In each site, six 100m line-transects were laid and a 0.5
by 0.5m quadrat were placed in 2m intervals along each transect. In each quadrat, sampling for
species composition, biomass accumulation, and bulk forage quality were sampled. Along each
transect, soil samples were collected at 0-15cm depth at 25m intervals and analysed for soil
fertility. To examine the influence of forage utilisation intensities, as affected by the previous
management, seasonal nutrient dynamics, data were collected during summer (November,
January, and April) and during winter (June and August).
The results revealed that species composition and biomass accumulation had a direct influence
on forage quality, while grazing systems mostly affected soil fertility. Additionally, the results
confirmed that previous cultivation has a negative effect on soil organic carbon (C) and
nitrogen (N) concentrations, and revealed a significantly high mineral variation between
seasons. These variations were also evident in the nutrient accumulation in the forage, with
distinctively high crude protein (CP) and low acid detergent fibre (ADF) and neutral detergent
fibre (NDF) in early summer. Therefore, to effectively utilize the old lands towards improved
livestock production, grazing should be during early to mid-summer. On the other hand, despite
soil nitrogen in the continuously grazed site being lower than the rotationally grazed site, CP
was significantly higher and steadily declined over the season. Therefore, suggesting that
biomass accumulation has a negative influence on forage quality. Moreover, lower forage
quality in the rotationally grazed veld was largely attributed to extended rest periods which
allowed grass to mature, thus reducing the overall quality.
Based on these findings, it can therefore, be recommended that the old lands be grazed during
the early to mid-summer and rested during late-summer. This will improve nutrient
availability for livestock and will allow for seeding rest to improve succession rate.
Moreover, the continuously grazed veld is recommended to be grazed interchangeably with
the old land, that is, in winter. As a result of slow crude protein decline in the continuously
grazed veld, grazing in winter will improve livestock morbidity and mortality resulting from
low forage availability. Finally, in the rotationally grazed veld high intensity grazing should
be incorporated in the grazing systems employed to reduce biomass carryover and keep
forage low and nutritious, as this veld in a high rainfall area.
Description
Master of Science in Grassland and Rangeland Science. University of KwaZulu-Natal, Pietermaritzburg, 2018.
Keywords
Theses - Grassland and Rangeland Science., Rotational grazing - South Africa., Grazing - Management - South Africa., Livestock productivity - South Africa.