Agriculture

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http://196.216.167.205/handle/10628/945

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Browsing Agriculture by Author "Joubert, David F."

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    Case study of adaptive rangeland management by an innovative Kalahari farmer.
    (2008) Zimmermann, Ibo; Joubert, David F.; Smit, G.N.
    Scientists can learn a great deal from innovative farmers who apply adaptive management principles based on experience gained over decades. This paper records 31 observations that a farmer, Jan Labuschagne, made on his farm to the south of Gobabis. The observations relate to aspects such as animal behaviour and performance, animal trampling, and applications of grazing and fire. They are tabulated together with their possible explanations and their management applications. The conceptual model the farmer has built to aid his understanding and decision making is also shown as a diagram and explained. Of critical importance is the strategic timing of management interventions on different parts of the farm in relation to rainfall events, texture and organic content of the soil and maturity of the vegetation. Data are presented to support some of the observations
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    A crude quantification of wood that is and can be harvested from bush thickening species in Namibia.
    (Namibia, Ministry of Environment and Tourism, 2002) Zimmermann, Ibo; Joubert, David F.
    The increasing rate at which thickening bushes are being harvested in Namibia requires better information on the availability and sustainability of the resource, in order to improve management. Two sources of data from the literature were combined to give a rough approximation of the standing biomass of wood of appropriate size for charcoal production, in each of nine bush-thickened zones. The overall estimate came to roughly 135 million tons of dry wood in about 260 000 square kilometres of Namibia, or an average of just over 5 t/ha. The legal commercial harvest for the 1999/2000 financial year came to the equivalent of just under 0.2 million tons of dry wood. Interviews with ten charcoal producers, and field data gathered at one site, suggest that harvesting could take place at intervals of roughly 20 years, provided that harvesting is selective and leaves sufficient bushes of different size classes for regeneration. However, it is likely that subsequent harvests would be lower and more difficult to obtain. Previously chopped bushes could then only be re-harvested on every third or fourth cycle, preferably after being pruned to maintain a more appropriate growth form, which is easier to harvest and more conducive to grass growth.
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    A problem tree to diagnose problem bush.
    (2008) Zimmermann, Ibo; Joubert, David F.; Smit, G.N.
    The term “problem tree” refers to a conceptual model used as a diagnostic tool to analyse a sequence of events that leads to a problem (such as bush encroachment in rangelands). A problem tree is useful because the consequences of different interventions can be visualised and understood more easily in diagrammatic form, thereby guiding management decisions regarding the problem. A problem tree was constructed to show multiple causes of bush encroachment. It was generalised by considering many possible causes, and not only those applying to particular areas of encroachment or specific species of bush. If the problem tree is to be useful in decision-making, one needs to determine which of the multiple pathways are of greater significance in any particular situation. Management decisions are bound to be more effective in the long run if they address causes higher up in the tree and closer to the root causes, than the proximate causes or symptoms at the bottom of the tree.