Evaluation of Rangeland Grass Species Composition in Different Livestock Land use Systems in Marondera Zimbabwe
Abstract
This research work investigated that livestock land use systems influence grass species composition (Density and Biomass), and basal cover. A number of three livestock land use systems; communal livestock land use system, commercial livestock land use system and the resettlement livestock land use system each replicated thrice were assessed using the botanical sampling technique. Grass species density, species biomass and basal cover were measured using 50cm x 50cm quadrats. The collected data was analysed using Minitab version 17 at P≤0.05 significant level. The results revealed that grass species density, biomass and basal cover were lower in the communal livestock land use system than in resettlement and commercial systems. The prevailing grass species were dissimilar where more unpalatable grasses were found dominating in communal areas than in other systems. The invasive and increaser species were found in the communal livestock land use system than in the commercial and resettlement system. Furthermore, the basal cover was lower in the communal grazing lands than in the resettlement and commercial land use systems. Lack of knowledge, high stocking densities as well as poor grazing strategies were ascribed to these results. As a measure against rangeland degradation, there is a need to devise a monitoring scheme or strategy for early recognition of changes as some grass species maybe vanished. The basal cover changes require close attention and monitoring as very low percentages of basal cover might reduce the production potential of the rangeland.
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Introduction
Livestock production is one of the main essential enterprises in Zimbabwe. As of the year 2005 livestock industry contributed 15 to 25% of the total value of agricultural output (Sibanda, 2007). Cattle, goats and sheep are the chief important ruminant species kept, cattle being the most essential while donkeys, pigs and poultry are also reared. Natural grazing remains the principal source of animal feed (Gambiza and Nyama, 2000). Degradation and the unproductiveness of rangelands have been a major problem under this sector. This is relatively accompanied with some drastic losses of vegetation and decline in forage quality, reduced ground cover and aboveground biomass production. The current shortage of forage is to some extend hinged to improper veld management practices and lack of knowledge. The ever increasing need for more cropping and settling land has led to the decrease of land left for grazing. Exceeding carrying capacities increased grazing pressure, grazing severity and overgrazing overall posing a great challenge in the livestock production sector. Veld condition can be defined as the state of the veld in relation to its position in plant succession as modified by some disturbance (Westoby et al., 1989). Measurement and interpretation of parameters like species composition, basal cover, litter cover, bush encroachment, plant vigour, and soil compaction and erosion compound to veld condition assessment (Westoby et al., 1989). Grass species diversity is a good indication of veld condition because different species react differently to grazing pressure. The increaser and decreaser grass species have been used as indicators to appraise veld condition. Categorising these species and monitoring their relative abundance is an essential step for sustainable veld management (Van Rooyen, 2002). The resettlement farming system established through the land reform program by the Zimbabwean government brought some changes to the already existing rangelands (Sibanda, 2007). The program came with the land fragmentation 2 following the handover takeover processes which brought about changes inland management systems. There could be changes in veld species composition due to change in the farming systems from commercial subsectors to the resettlement farming systems. Knowing the changes brought by the difference in management is of essence in making recommendations for monitoring and managing veld condition for maximum production. The farming system influences species richness, species diversity, bush encroachment and biomass yield (Gusha and Mugabe 2013). From the previous research, species richness and diversity were lower in the communal farming system than in the small and large scale commercial farming system (Mugabe and Gusha 2013). According to Mugabe and Gusha (2013), there were notable differences in species composition among farming systems. Invasive, more wiry and weedy grasses were more dominant in the communal farming system than in the large and small scale farming sectors. Poor grazing strategies and high stocking densities were suggested to have attributed to these veld conditions. Considering the great influence of climate and some edaphic factors on the structure and state of vegetation within a veld, there is a need to study relatively similar concepts in a different climate. The veld degradation has been estimated to be 73% in dry land areas of Zimbabwe (Bai et al., 2008). This is, however, an attribute of management which is also a major factor under different farming systems. Quantification of species losses occurring in these rangelands needs to be done to mitigate the losses. Understanding the existing forage resources for stock production is an imperative to know type of supplementation for efficient stock production. This provides the basis for persistent monitoring into species alterations happening in communal, resettlement and commercial farming systems. It is as well important in generating information for government policymakers and formulating regulations helpful in preserving or mitigating veld degradation problems as well as monitoring veld for different farming systems. Through information generation, the research can also be helpful to some researchers for further studies under the same subject. Knowing the species composition within the veld is of great importance in calculating the carrying capacities of different rangelands. It allows the farmer to allocate the animals to grazing areas considering the quality and quantity available to the animal. Thus improving the animal condition as well as lowering the veld deterioration rate. This study therefore aimed at evaluating the effect of different management practices on grass species biomass, density and cover indifferent livestock land use systems.
Conclusion
There was a significant difference in species composition (density and biomass) and cover across all livestock land use systems. Grasses with good forage value (decreasers) were observed to be highly concentrated in the commercial system followed by resettlement and lastly the communal system. The increaser/invasive species were significantly more in the communal set up than in all other systems. In addition, the commercial system had the highest basal cover followed resettlement with the lowest basal cover in communal systems.
VI. RECOMMENDATIONS Rangeland rehabilitation and maintenance takes along and patient process, wherein the mix are annual rainfall and dry spell uncertainties. However, in the face of a degraded rangeland it is important to initially restore the soil fertility. To bare soils with little cover rangeland thatch packing practices can be implemented to aid in water penetration reduce surface runoff; provide shading and aid to detritus build up. This remedial practice must therefore be practiced for several seasons necessary. As a soil remedial practice, it is also important to shape contours channelling water and prevent lateral erosion as well as tilling for aeration and seeding. Bush packing can also be done following the observation of new growth to avoid overutilization of such grasses during their early or establishing stages. To increase grass biomass as well as density, selective bush thinning can be useful as this will give support to grass competition. Decreaser (palatable) grass species losses could be solved by reinforcing the grazing land by planting relatively palatable grasses with some grazing resistance and quick establishment characteristics. Amongst these are Panicum repens and Digitaria diagonalis which under optimum conditions have high prolific rates, density, and biomass and are tolerant to grazing. This will in turn increase the carrying capacities of communal grazing lands. However, the major problem leading to low production potential and level by the communal grazing lands is management related. This is mainly due to lack of knowledge. Therefore, an increase in government extension services and educational campaign enriching people with communal grazing management knowledge can be a long-lasting solution. Government legislation and policies in control and monitoring of rangelands also need to be enforced with increased patrols and assessment. This encompasses the judicious burning legislations, where uncontrolled fires may lead to an accelerated species loss (decrease in biomass and density) as well as basal cover. Indicators and continuous monitoring should be set in place to scrutinize alterations much earlier. To minimize species loss, increasing grass biomass and density, holistic management practices ought to be promoted in the communal livestock land use system. The evaluation of species composition under this study was done over a short period of time. A similar research over an extended period of a season or year might be more relevant in assessing seasonal species composition change.
