Abstract
With the goal of determining optimal emitter spacing in drip irrigation, experiments were performed to examine the effects of emitter discharge on the wetted perimeter and spacing of emitters. Four types of soils were investigated using emitter discharge of 1.0, 2.0, 3.0 and 4.0 l h −1 . Wetting diameter was measured at six equal time intervals of water application. An equal volume of water was applied. After 1 h of supply of water, wetted soil was cut to observe the maximum wetted width and depth. Wet soil samples were taken from every patch of 10 × 10 cm to find the percentage of moisture by the gravimetric method. Empirical equations were developed for wetted depth and radius. Additional experiments with emitter discharge of 1–18 l h −1 were performed in sandy loam to obtain more data for accurate estimation of the coefficients of the empirical equations. Two computer programs based on trial and error and the generalized reduced‐gradient non‐linear‐optimized technique were used to find values of the coefficients. Root mean square error between the measured and simulated wetted radius and depth was minimized in optimization. Optimal emitter spacing for each type of soil was determined from the recorded data, which was found to be 35, 40, 40 and 45 cm in sandy loam, loam, clayey loam and clay respectively. © 2018 John Wiley & Sons, Ltd.