Assessing the effect of in-field rainwater harvesting on soil physico-chemical properties and crop yield in comparison with the traditional farmers’ practice.

Abstract

Most communal farmers in South Africa rely on rain-fed agriculture. However, the country is experiencing rainfall variability as well as low soil fertility. These are major limiting factors to food production especially since South Africa is dominated by a semi-arid climate. It is for this reason that rural communities must optimally utilise their limited water reserves. Rainwater harvesting (RWH) technologies are amongst possible alternatives to maximise agricultural crop production. The aim of this study was to assess the effect of in-field rainwater harvesting on selected soil physico-chemical properties and maize crop yield in comparison with the traditional farmer practice. The study was conducted in homestead gardens in Kwa-Zulu Natal (KZN) province, under Msinga local municipality and in Eastern Cape Province (EC), under Tsolo local municipality. The study was set up at five homestead gardens namely Madosini, Beya, Mjali, Quvile and Sokhombe in the Eastern Cape and three field trials in Kwa-Zulu Natal (Mntungane, Xoshimpi and Mxheleni). It was designed as randomised complete block design, that compared in-field rainwater harvesting (contour ridges) with the traditional farmer practice (control) over two seasons (2013/14 and 2014/2015). Data was collected for soil chemical and physical properties as well as for crop grain and dry matter yields. Soil samples were collected at 0 - 10, 10 - 20 and 20 - 30 cm depths for analysis of soil pH, exchangeable bases, micronutrients and aggregate stability, and for analysis of bulk density at 0 -10 cm. These samples were collected at planting (2013) and at harvesting (2015). Gravimetric soil moisture content was periodically monitored at different stages of maize growth (planting, vegetative growth, tasselling and harvesting) in 2015. Biomass and grain yield were determined at harvest. Results showed that rainwater harvesting improved soil moisture content, aggregate stability, grain and dry matter yields. No clear trend was observed on the effect of rainwater harvesting on exchangeable bases, soil pH and micronutrients across all study sites in Kwa-Zulu Natal and Eastern Cape. It was therefore recommended that rainwater harvesting be used by resource constrained rural farmers who are experiencing unfavorable precipitations to improve crop yields and soil productivity.