Design, Development and Evaluation of an Automated Drip Irrigation System

Abstract

The present study was conducted to design, develop and evaluate an automated drip irrigation system working on the basis of soil moisture deficit and to establish the relationship between soil moisture content, electrical conductivity. The study involved fabrication of a soil moisture deficit based automation system and testing of the system under laboratory and field conditions. The system was tested and calibrated for automatic irrigation scheduling. As the soil started drying up, water content decreased and the conductivity reading in the data logger decreased. When the sensor readings reach the preset threshold level, the system gets automatically switched on. The irrigation setup was operated until the moisture reached the preset level of field capacity. Conversely, an increase the soil water content increased the conductivity. In this way, automation system continuously recorded fluctuations in soil moisture content under varying field conditions. Laboratory tests were conducted to evaluate the performance of the drip automation system in salt solution, sandy loam and laterite soils to develop the calibration curves. It was observed that there existed a significant correlation between the soil moisture content and electrical conductivity of sensors. Soil moisture sensors were evaluated with respect to the moisture content of sandy loam and laterite soils. In sandy loam soil, the values of maximum and minimum sensor output values were 17.5 to 3.3 mS/m and for laterite soil it was 15.1 to 2.4 mS/m. In the field evaluation using amaranths crop, the moisture distribution was more or less uniform near the soil surface soon after irrigation. The developed electrical conductivity based soil moisture sensors performed well in the laboratory study using sandy loam and laterite soils, but during field evaluation in sandy loam soil its performance was not satisfactory. In case of capacitor type soil moisture sensor, the performance was satisfactory in both conditions. Capacitor type soil moisture sensor performed well in sandy loam soil in the field evaluation. From the results of this study it can be concluded that capacitor type soil moisture sensor can perform better than electrical conductivity based soil moisture sensor for field use. The drip automation125 system developed was simple, precise, sensitive, light weight, cost effective in construction and fast responding. The speed of measurement, cheapness and portability are the key advantages and the system is easily adaptable for use with automatic logging equipment. There is scope for further studies on optimization of the electrode geometry and evaluation of electrical conductivity based soil moisture sensors with different fertilizer and chemical application.