Abstract:
Timely application of irrigation water in precise amounts increases crop yield due to
decreased moisture stress to plants and decreases loss of water through percolation and
subsequent nutrient leaching. Many times, automatic scheduling of irrigation is desired as it
ensures timely and precise application and reduces labor cost. Automatic scheduling of irrigation
usually involves sophisticated instrumentation which is expensive and requires external power.
Irrigation can be scheduled by measuring the moisture tension in the soil which indicates the
amount of water available to the crop. A system which utilizes the sensed moisture tension to
directly control the water applied without using an external power source is desired. The
tesiometer controlled irrigation control valve developed earlier could achieve this but the
fabrication of the valve assembly was quite sophisticated. In this study an attempt is made to
develop and fabricate a soil moisture tension controlled irrigation emitter which is simple to
fabricate and doesn’t involve the use of any external power sources.
The developed tension-emitter consists of a porous cup and a watering head assembly.
The porous cup has the same function as that in a tensiometer where it acts as a sensor which
equilibrates the tension inside the tensiometer to that of the surrounding soil. The watering head
consists of a diaphragm, an adjustable screw and two triangular heads. The micro tube supplying
water to the plant passes between the triangular heads. One of the triangular heads is attached to
the diaphragm which moves according to change in the soil moisture and the other to the
adjustable screw head so that it can be moved up and down by turning the screw. The tensio-
emitter is calibrated by adjusting the screw so that water flows through the micro tube only when
the soil becomes dry and closes the micro tube when the soil receives enough water.
Tensio-emitter was successfully developed, fabricated and calibrated for use in potted plants.
