Technical Note: A Low-Cost Pressure Regulator for Improving the Water Distribution Uniformity of a Microtube-Type Drip Irrigation System

Abstract

<abstract><title><italic>Abstract.</italic></title> Irrigation application using a low-cost microtube-type drip irrigation system tends to be relatively non-uniform especially under steep slopes and low operating pressure heads. This study was conducted to evaluate the effect of using a simple and inexpensive adjustable valve (AV) pressure regulator on water distribution uniformity of the low-cost microtube-type drip system under sloping conditions at various operating pressure heads. A 100 m² microtube-type drip kit developed by the International Development Enterprises (IDE) was tested for water distribution uniformity with and without AVs under average operating pressure heads of 0.5, 1.0, and 1.5 m, submain slopes of 10%, 20%, and 30%, and lateral slope of 0%. Based on volumetric measurement of emitter discharge, the average Christiansen’s coefficient of uniformity (CU) and Merriam and Keller’s distribution uniformity (DU) values improved to a range of 76% to 94% and 64% to 91%, respectively, with AV adjustment. For all pressure heads and submain slope of 30%, CU and DU were increased by an average of 25% and 82%, respectively, with AV adjustment. Pair-wise t-test comparison (α=5%) of average CU and DU values for each setting showed significant improvement of water distribution uniformity except for a combination of a high pressure head of 1.5 m and steep slopes of 20% and 30%. These exceptional results suggest that at relatively steep slopes, the microtube-type drip system may be operated at relatively low pressure heads with proper AV adjustment to increase the water distribution uniformity. Results indicated that the use of AVs can significantly improve water distribution uniformity of the low-cost microtube-type drip irrigation system at low pressure heads even at slopes as steep as 30%, and offers the potential for maximizing crop yield in steep upland areas.