Gypsiferous mine water use in irrigation on rehabilitated open-cast mine land: Crop production, soil water and salt balance

Abstract

The use of gypsiferous mine water for irrigation of agricultural crops is a promising technology, which could alleviate a shortage of irrigation water and address the problem of disposal of mine effluent. A field trial was established at Kleinkopje Colliery in Witbank (Mpumalanga Province, South Africa) during the 1997-1998 season. Sugar beans and wheat were irrigated with three center pivots, on both virgin and rehabilitated land. The objectives were to determine crop response to irrigation with two types of mine water, to determine the impact of irrigation with inferior quality water on virgin and rehabilitated soil, and to collect atmospheric, crop and soil data for detailed validation of the soil water balance (SWB) computer model. Crop yields were generally satisfactory. Yield of sugar beans on rehabilitated land was low compared with virgin land, probably due to the late planting date, hail damage and soil compaction. SWB simulations were compared with field measurements of weather, crop growth, water and salt balance parameters. Both field measurements and model simulations indicated an increase in soil salinity, with limited drainage and salt leaching. Long-term simulations of the water and salt balance were carried out with SWB to predict the long-term sustainability of irrigating with gypsiferous water.