SIMPLE MICROIRRIGATION TECHNIQUES FOR IMPROVING IRRIGATION EFFICIENCYON VEGETABLE GARDENS

Microirrigation techniques can be used to improve irrigation efficienc y on vegetable gardens by reducing soil evaporation and drainage losse s and by creating and maintaining soil moisture conditions that are fa vourable to crop growth. Water balance experiments in Zimbabwe showed that over 50% of the water applied as surface irrigation on traditiona l irrigated gardens can be lost as soil evaporation. This result gives an indication of the potential improvement in irrigation efficiency t hat can be achieved by adopting irrigation methods that reduce soil ev aporation at the same time as minimising losses due to drainage and ca nopy interception. During the period 1985 to 1995, irrigation trials a nd experiments were carried out in south-east Zimbabwe and northern Sr i Lanka with the main aim of comparing and quantifying the benefits of using simple microirrigation techniques on traditional vegetable gard ens. This paper reviews the results of these trials and experiments. M icroirrigation techniques that were evaluated included low-head drip i rrigation, pitcher irrigation and subsurface irrigation using clay pip es, Of these methods, subsurface irrigation using clay pipes was found to be particularly effective in improving yields, crop quality and wa ter use efficiency as well as being cheap, simple and easy to use. The comparative advantages of subsurface irrigation were maintained for a range of crops grown under different climatic conditions. Good result s were also obtained with subsurface irrigation when irrigation was ca rried out using with poor quality irrigation water.