Development and assessment of an updated tool for the design of soil and water conservation structures in the sugar industry of South Africa.

Abstract

Sugarcane in South Africa is grown on wide-ranging soils, sometimes in non-ideal climates and on steep topographies where soils are vulnerable to erosion. Sugarcane fields are protected against erosion through, inter alia, the use of engineered waterways, contour banks and spill-over roads. A comparison of design norms in the National Soil Conservation Manual and norms used in the sugar industry of South Africa clearly shows discrepancies that need to be investigated. Furthermore, the sugar industry design nomograph was developed based on an unsustainable soil loss limit, does not include any regional variations of climate and the impact on soil erosion and runoff and does not include vulnerability during break cropping. The aim of this research was to develop and assess updated design norms for soil and water conservation structures in the sugar industry of South Africa. The Agricultural Catchments Research Unit (ACRU) model estimates event-based erosion and the ACRU was used to conduct simulations for the different practices in the sugar industry and the outcome used to build the updated tool for the design of soil and water conservation structures in the sugar industry of South Africa, using MS Access with a graphical user interface. The updated tool is robust, based on sustainable soil loss limits, includes regional variations of climate and their impact on soil erosion and runoff and also includes vulnerability during break cropping. It is more representative of conditions in the sugar industry of South Africa and therefore recommended for use in place of the current sugar industry design norms. Keywords: Agricultural Catchments Research Unit, design norm, soil and water conservation, soil loss, sugarcane, South Africa