A soilscape survey to evaluate land for in-field rainwater harvesting in the Free State Province, South Africa
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Date
2004-09
Authors
Tekle, Semere Alazar
Journal Title
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Publisher
University of the Free State
Abstract
Land evaluation is currently important in South Africa. Soilscape surveys can make a contribution in this connection by bridging the gap between land type surveys and detail surveys. Land Type Dc17 (area = 237 651 ha) east of Bloemfontein include the densely populated areas near Botshabelo and Thaba Nchu. The objective of this study was to subdivide Land Type Dc17 into smaller more homogeneous land units, to estimate the area of each unit suitable for maize and sunflower production using the In-field Rainwater Harvesting technique (IRWH), and to estimate attainable yields of these crops on the available areas. The soilscape survey technique was developed to serve this goal. Soilscape is defined for this specific study as a mapping unit consisting of a portion of land mappable at a scale of 1:50 000 in such a way that it facilitates the identification of potentially arable land. Earlier Northcote (1978) described soil landscapes as areas of land that have recognizable and specifiable topographies and soils, that are capable of presentation on maps, and can be described by concise statements The delineation of 66 soilscapes was done on 1:50 000 maps. Detailed pedological investigations were made on selected pedoseque nces of some soilscapes using 1:10 000 maps, soil pits, auger holes and depth probe observations. Nine soilscapes with a total area of 82 222 ha were found non-arable. For the remaining 57 soilscapes, covering an area of 155 429 ha, the improved knowledge gained during the detail studies was extrapolated to estimate the area of each one suitable for IRWH. The result was 56 875 ha, or 24 % of the total area of Dc17. The results of previous field experiments on relevant ecotopes predict the following maize yields in tons/ha/yr: conventional tillage = 82 000; simplest type of IRWH = 127 000. It is therefore estimated that this land type can provide the staple maize diet for about 600 000 people using IRWH. The soilscape survey technique proved successful within this land type, but should be refined for application to other land types and other feasibility studies.
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Keywords
Dissertation (M.Sc.Agric. (Soil, Crop and Climate Sciences))--University of the Free State, 2004, Soil surveys -- South Africa -- Free State, Land use -- South Africa -- Free State, Water harvesting -- South Africa -- Free State