Assessing the use of wetting front detectors in water management at Dzindi Small Small Scale Irrigation Scheme in Limpopo Province

Abstract

Irrigation uses the largest amount of water, estimating to 60 % of the total consumption in South Africa. For this reason, the efficient and reasonable use of water by irrigators is of paramount importance. Thus, this study was carried out to assess the suitability of Wetting Front Detectors (WFDs) in improving water management. The study involved an on-farm survey; field installations; testing of WFD technology on selected plots within the scheme; identification of the crops grown; documentation of the current water supply and documentation of the challenges faced by farmers in relation to irrigation. These were carried out to identify the ideal situations in the scheme. Irrigation scheduling helps farmers to know when to irrigate and amount of water required supplying for crop need. The study presented WFD, as a means of improving irrigation efficiency. The WFD is a simple tool that helps farmers to identify what is occurring around the root zone. Four plots with a representative farmer in each of the plot were identified in four Blocks (Block 1 farmer 1, Block 1 farmer 2; Block 2 farmer 1; Block 3 farmer 1 and Block 4 farmer 1). On-farm experiment of the WFD was carried out. However, with Block 4 farmer 1, insufficient data was collected due to absence of LongStop equipment. This also involved field installation, observation and measurements of the LongStops (LSs) and FullStops (FSs) WFDs at placement depth of 30 cm, 45 cm and 60 cm. The efficiency of an irrigation system depends on different performance indicators including Irrigation Efficiency (IE), Conveyance Efficiency (CE), Application Efficiency (AE), Storage Efficiency (SE), Distribution Uniformity (DU) and Coefficient uniformity (CU). In this study, attention was focused only on DU; CU and SE, as represented by water moisture availability. All the DU for all plots in blocks were below the standard DU of furrow, which is 65%. Farmer 2, in Block 1, had a higher DU and CU, which were 60% and 68%, respectively- considered closer to the standard DU value. For the other farmers, their DU and CU prior to irrigation were very low, which indicated that there was uneven distribution of water in these plots. The poor DU in Block 1 farmer 1, indicated by the uneven infiltrated water, resulted in excessive watering. Analysing the WFD showed that farmers were performed well in all the Blocks, except for farmer 1 in Block 1. Average soil moisture content result indicated high water loss through deep percolation. The highest volumes of water recorded before and after irrigation were 131 ml and 159 ml, respectively, for LS90 placed at a depth of 90 cm in Block 2 farmer 1. High volumes of water were collected in Block 1 farmer 2, Block 2 farmer 1 and Block 3 farmer 1 before and after irrigation. The result showed that, the more placement depth down the soil profile, the more accumulation of water in the LSs. Therefore, it was recommended that farmers continue to use the WFD as a tool for irrigation efficiency. However, there is need for improvement and capacity building in using the tool.