Low head drip irrigation kits and treadle pumps for smallholder farmers in Zimbabwe: a technical evaluation based on laboratory tests

Abstract

Most smallholder farmers in Southern Africa rely on rainfed agriculture and frequently face dry spells and droughts that affect agricultural productivity. Low head–low cost drip irrigation may be a viable alternative for smallholder farmers, who often lack sufficient water and energy resources to enable irrigation with more conventional irrigation technologies, as these require more water (lower efficiencies) and/or more energy inputs (e.g. sprinkler irrigation). This paper reports results from laboratory tests of four treadle pumps and eight drip kits currently available in Zimbabwe. The results show that it is viable to irrigate drip irrigation gardens up to a size of 1000 m 2, if the treadle pump and drip kit are well chosen. Such a garden will not only ensure food security of the farmers, but may also generate significant income. It is concluded that farmers can opt to invest in two distinctly different types of low-head drip systems; (i) systems with in-line emitters generating low emitter flow rates (<0.3 l/h at low heads) and (ii) systems with micro-tubes generating high emitter flow rates (in this test generally exceeding 1 l/h). Well designed micro-tube systems with high flow rates such as the Forster system generate high uniformity, even at extremely low head (0.1 m), and present lower clogging problems and higher placement flexibility than the low flowing systems. Even though this may indicate that micro-tube systems are more appropriate for smallholder farmers, this study did not assess impacts on crop growth of different emitter rates and the relationship between emitter discharge and non-productive soil evaporation.