The efficacy and safety of bromacil based herbicide for the control of the invasive bush species in South African rangelands

The use of bromacil based herbicides in agriculture and environmental management is a growing practice with economic importance. Bromacil possesses broad toxicity to many plant species, although, different formulations exist that are used for different purposes in farming systems. There is increasing concern about its use for the control of invasive woody species on South African rangelands; especially its effects on non-target grasses, broad leaved plants and other bioticcomponents of the rangeland ecosystem. This review outlines the importance of bromacil use, its nature and activities as an ingredient in herbicide formulation and the effects of its use on biotic andnon-biotic components of rangeland ecosystems. The current use of bromacil based herbicides for the control of bush encroachment seems necessary to derive good productivity from encroachedrangelands and reduce cost and drudgery associated with other methods of bush control. Bromacil is absorbed through the plant’s root system and translocated upwards via the xylem vessels to theleaves, where it interferes with light harvesting complexes and disrupt the photosynthetic pathways of the plant. This kills the plant slowly; sometimes, it spans over two years. Bromacil could be persistentin the environment for the same length of time, depending on the application method, the target species and the soil properties at the application site. Bromacil has a very low mammalian toxicity, but isconsidered to be slightly toxic to fishes and amphibians. The effect of Bromacil on soil microbial population depends on the exact formulation, concentration and microbial species in question. Yet, bromacil is degraded by microorganisms in the soil and water, portions that escape into open water bodies are also degraded by photo-oxidation reaction. While bromacil provides for sustained weed control, its persistence in the environment and low degradation rates, is a cause for concern

Fodder Production and Conservation: AGP 321

Fodder Production and Conservation: AGP 321, degree examination Novemebr 2010

Herbaceous biomass, species composition and soil properties of key grazing patches in coastal forest thornveld and two grassland types of the Eastern Cape province, South Africa

In spite of predictions of communal rangeland collapse due to continuous grazing and increased livestock populations, this grazing system remains prevalent in communal areas, suggesting animals utilise heterogeneity found in these areas. A study was conducted to compare biomass and herbaceous species composition in patches frequently grazed by cattle to randomly selected control sites in three communal areas located in Lesotho Highland Basalt Grassland (Magwiji), Bhisho Thornveld (Mnyameni) and Tsomo Grassland (Cala). The relationship of vegetation parameters in frequently selected patches to the corresponding soil properties, topography and human impact was also examined. Biomass of frequently selected patches was significantly (p < 0.05) higher in the dry season (June) at Magwiji (528 kg ha-1) than in less frequently selected patches (130 kg ha-1). There was an association between sites selected in winter and soil organic carbon, and these sites were dominated by Cynodon dactylon and Pennisetum clandestinum. The floristic patterns observed in Magwiji were associated with soil organic carbon content. Low-lying swampy patches had high soil pH in Cala, while mountain top soils in Magwiji had low electrical conductivity and these areas selected in winter were associated with grass species such as Eragrostis superba and Heteropogon contortus.Keywords: cattle; graze; key resource areas; livestockAfrican Journal of Range & Forage Science 2010, 27(3): 151–16

Physicochemical characteristics of communal rangeland soils along two defined toposequences in the Eastern Cape, South Africa

To proffer a sustainable solution to rangeland degradation, an understanding of the innate soil properties is vital. This study investigated the relative association of surface (0–20 cm) soil physicochemical properties, viz. electrical conductivity, cation exchange capacity (CEC), soil organic carbon, available phosphorus, particle size composition, soil aggregate stability and microbial respiration, along a toposequence in two vegetation types. The study sites and vegetation types were Magwiji (Lesotho Highland Basalt Grassland) and Upper Mnxe (Tsomo Grassland). In each site, we identified three experimental units along toposequence delineation, classified as crest, midslope and valley bottom. Vegetation type significantly (p < 0.05) affected sand fraction, aggregate stability under fast wetting, and mechanical disaggregation and CEC. Toposequence delineation significantly (p < 0.05) affected fast wetting, slow wetting, mechanical disaggregation, microbial respiration and CEC. There was significant variation and relationship between vegetation types, toposequence delineation and soil properties. The results suggest that toposequence delineation more than vegetation type influences soil property rangelands; therefore, in determining site-specific management techniques for communal rangelands it is important to consider the direction and magnitude of these relationships.African Journal of Range & Forage Science 2010, 27(2): 89–9

Communal area grazing strategies: institutions and traditional practices

Grazing strategies found in communal areas are a result of interactions between social, ecological and institutional factors. To understand the processes in operation, and help in improving management, the perceptions of communal people on institutional structures, utilisation patterns and possible intervention for improving their grazing lands were studied. A more comprehensive understanding of communal rangeland grazing strategies is important as the mere transplanting of large-scale commercial farming management strategies would be met with viability and acceptability constraints. In addition to participatory rural appraisals, a questionnaire-based survey was conducted among a sample of 553 households in Amathole, Chris Hani and Ukhahlamba districts of the Eastern Cape province, South Africa. Although the need for fences and paddocks was highlighted as the best intervention to improve range management in communal areas, lack of strong local-level institutions, little or no knowledge of veld management, absence of rules and lack of seasonal restrictions on rangeland resource use are additional constraints that would minimise the impact of fencing. It is concluded that communal range management remains complex and there is a need to consider socioeconomic and ecological factors, as well as institutional factors, in any planned grazing management intervention. Strengthening of local-level institutions and helping in ways to effectively utilise stockposts and abandoned fields will improve the management of communal rangelands. Keywords: communal grazing management; institutions; rules; traditional practicesAfrican Journal of Range & Forage Science 2008, 25(2): 47–5

Bush Encroachment Mapping for Africa: Multi-Scale Analysis with Remote Sensing and GIS

Bush encroachment (BE) describes a global problem severely affecting savanna ecosystems in Africa. Invasive species and woody vegetation spread out in areas where they are not naturally occurring and suppress endemic vegetation, mainly grasses. Livestock is directly affected by decreasing grasslands and inedible invasive species which are a result of the process of BE. For many small scale farmers in developing countries livestock represents a type of insurance particular in times of crop failure and droughts. Among that, BE is also becoming an increasing problem for crop production. Studies on the mapping of BE have so far only focused on smaller regions using high-resolution data and aerial photography. But they rarely provide information that goes beyond the local or national level. In our project, we aimed at a continental-wide assessment of BE. For this, we developed a process chain using a multi-scale approach to detect woody vegetation for the African continent. The resulted map was calibrated with field data provided by field surveys and experts in Southern and Eastern Africa. Supervised classification linked field data of woody vegetation, known as BE, to the respective pixel of multi-scale remote sensing data. The regression technique was based on random forests, a machine learning classification and regression approach programmed in R. Hotpots of woody vegetation were further overlaid with significant increasing Normalized Difference Vegetation Index (NDVI) trends which can refer to BE. Secondly, the probability of BE occurrence based on possible identified causes such as fire occurrence, mean annual precipitation rates, soil moisture, cattle density and CO2 emissions was analyzed. By this, possible areas for BE occurrence based on their pre-conditions and risk factors were identified. This approach includes multiple datasets derived from earth observation data to detect BE – a severe and ongoing global problem – at the continental level. Within the study´s duration of seven months, a method to upscale field data to a larger level could be developed. Nevertheless, improvement is needed to provide a reliable continental map on BE. Especially the integration of more field data will be needed which is currently under consideration. The identification of woody vegetation and the probability of its occurrence can help to prevent further ecosystem degradation. Moreover, sustainable land management strategies in these areas can be focused to support pastoralists and their livelihoods in rural areas