Quality assessment of agricultural water used for fertigation in the Boland district

Abstract

Quality assessment of agricultural water used for fertigation in the Boland district. The study was undertaken to determine the influence of seasonal changes on the water quality (chemical and microbial analyses) of five different rivers in the Boland. The data was collected in the five most important water sources that are used for irrigation purposes in the district, i.e. Berg river, Eerste river, Klapmuts River, Klippies river and Krom river. The samples were collected from all sites once every three weeks for a period of six months. The sampling was carried out during specific periods in summer (December, 2006 to February, 2007) and winter (June to August, 2007). The results of the study showed that Klapmuts river recorded the highest levels of chloride and iron, especially in summer. However, chloride levels were far below the levels set by the Department of Water Affairs and Forestry. Results obtained from this study show the presence of pathogens in some of the rivers assessed which may have resulted from the leaching of these pathogens from nearby agricultural land, livestock watering or informal settlements in the catchment areas.

The bigger rivers recorded low levels of micro-elements and this might have been affected by winter rainfall. In the Berg River, many sources of nitrate pollution seem to be present in the catchment area. The levels of iron in all the rivers assessed were far more than the levels set by the Department of Water Affairs and Forestry in all rivers assessed and these might be due to the pH levels and interaction between the rivers and seasons. Iron and manganese levels should be kept low as this may cause production problems by blocking irrigation drippers.

The water samples tested for bacterial and fungal density showed Klapmuts and Eerste rivers were positive for Phytophthora cinnamomi during winter. Phytophthora citricola and Phytophthora cactorum were detected in the Klapmuts and Klippies rivers in summer. The Berg-, Klapmuts-, Krom- and Eerste rivers tested positive for species of the genera Pythium and Fusarium. Similar organisms were detected in the Eerste river mainly during summer on the fourth sampling date, while Krom river only tested positive for Pythium during summer. The total bacterial and algal density differed significantly between the seasons and was highest in winter. This might be due to high rain water influx and efflux and/or moist and aerobic conditions and air temperature. There is an increased need for farmers to sterilize feeding water (chlorination) due to high microbial count.