Commercial production of crops irrigated with gypsiferous mine water

Abstract

The use of gypsiferous mine water for irrigation of agricultural crops is a promising technology that could add value through agricultural production and utilise mine effluent. Crop response to irrigation with gypsiferous mine water, as well as the impact on soil and groundwater resources were investigated in a three-year field trial set up at Kleinkopje Colliery (Witbank, Mpumalanga Province, South Africa). Sugar-beans, maize and wheat were irrigated with four centre pivots on virgin and rehabilitated land, under three irrigation management regimes using two qualities of mine water. Good crop yields were obtained compared to dry-land cropping. Waterlogging in certain areas of the fields indicated that especially rehabilitated land should be properly prepared and, where necessary, waterways built to prevent yield reduction. Soil salinity increased over the duration of the trial due to high concentrations of Ca2+, SO42- and Mg2+ in the irrigation water, but this never reached levels critical to yields of most crops. Exchangeable Ca2+ and Mg2+ in the soil increased with time, whilst K+ decreased. Plant analyses indicated possible nutrient deficiencies, which should be easily managed through corrective fertilisation. The groundwater impact was limited based on borehole measurements, indicating the presence of a buffer zone between the cropped soil profile and groundwater, but this should be monitored over a longer period. Commercial production of crops under irrigation with gypsiferous mine water is feasible and the resulting environmental impact is limited, but further research is required to confirm these findings over a longer period.


WaterSA Vol.28(4) 2002: 413-422