Design and development of tensio-emitter

Abstract

Timely application of precise amounts of irrigation water increases crop yield due to the decreased moisture stress to plants. Automatic application of irrigation water ensures timely and precise water application, reduces labour cost and prevents water loss and nutrient leaching. Automatic irrigation usually involves sophisticated and expensive instrumentation requiring external power. An irrigation control system that utilizes only the moisture tension to directly control the water application, without using any external power source is desirable for its simplicity and usability in remote areas. In this study, an attempt was made to develop a simple and cost effective irrigation controller working on the basis of soil moisture tension without any external power source. A Tensio-Emitter was developed after evaluating several designs suitable for the same. The developed Tensio-Emitter consists of a porous cup fixed on a stem and an emitter cum valve assembly. The porous cup acts as a sensor which equilibrates the tension inside the stem to that of the surrounding soil. The emitter cum valve assembly consists of a bottom part to be fixed on the stem containing the porous cup, a flexible diaphragm, a conical part to be attached to the diaphragm and a top part which has as the water inlet and outlet. The dimensions of the emitter cum valve assembly was determined based on the size of the available porous cup, the soil moisture tension available at MAD and the deflection of the diaphragm at the tension corresponding to MAD. The Tensio-Emitter is calibrated by adjusting the conical part such that water flow through the emitter starts when the soil becomes dry and stops when the soil reaches field capacity moisture content. Tensio-Emitter – a simple and cost effective irrigation controller cum emitter which is activated by soil moisture tension - was successfully developed, fabricated and calibrated for use in potted plants. The ability of the developed Tensio-Emitter to automatically control the irrigation according to the soil moisture level was evaluated to be good.