Assessment of wetted irrigation patterns for inline and online emitters in different soil textures
Keywords:
Drip irrigation; Wetting bulb; Water distribution in soil; Wetting front in soil.Abstract
Selection of a suitable emitter type is one of the main design parameter which significantly affects the performance of drip irrigation system. Emitters can change wetting pattern under different soils, and may cause water stress if proper emitter spacing is not maintained. The major objective of this study was to investigate the wetting pattern of two generally used emitter types (inline and online) on different soils (loamy sand, sandy loam, silt and clay) of Peshawar valley and compare the observed values with model simulation using Drip Irrigation Water Distribution Pattern Calculator (DIPAC) and Drip-Irriwater models. Experimental trials were conducted of inline and online emitters (n=30) having 60 cm spacing and a discharge of 4 liters per hour. The trials were replicated twice for each soil type. The vertical and lateral infiltration of each emitter and water applied were recorded at 30 minutes and 60 minutes intervals. The wetted depth and width were measured manually by digging and through visual measurements. The results showed an increasing tendency in vertical and lateral infiltration with increasing wetting time for both emitter types, evidenced by 70-80% larger wetted area at one hour wetting time when compared with 30 minutes wetting time. However, the sandy soil showed greater (40-50 %) vertical infiltration when compared to clayey soil. Conversely, the lateral infiltration was identified larger (5-10%) for clay soil than sandy soil. Dripper’s wetting pattern comparison was independent of the emitters type. Drip-Irriwater simulations were in close agreement with the observed values when compared to the empirical model DIPAC. The finding in this study has the potential to improve the decision support system for selecting a suitable emitter type for different soil types. In addition, the results of this study may be effectively utilized to obtain increased application efficiency by using the appropriate emitter type under limited water conditions.
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