Assessment of the pressure and discharge rate variations along the perforated lateral pipes of novel subsurface irrigation system

Optimizing the use of water resources is inevitable due to water shortages in agricultural areas.  Pistachio gardening has been an attractive agricultural activity for several decades in Iran. Given the limited water resources, areas under pistachio cultivation in arid regions are not economical due to low production. There has been a continuous trend towards application of efficient irrigation systems such as pressurized subsurface drip irrigation methods, but their complexity and high initial investment, make them less suitable for small scale and scattered owners. This research describes the field performance of a very low-pressure subsurface irrigation method which has been introduced before (Dastorani et al., 2010). In this subsurface porous pipe irrigation system, water is delivered directly to the pistachio tree’s roots via perforated PVC pipes covered by plastic textile sleeves. The feasibility of this system has been demonstrated for irrigating pistachio orchards. They compared the effect of traditional (surface) irrigation and such subsurface irrigation method on crop yield and annual growth traits. Their results showed that subsurface irrigation method had relatively higher performance than the surface method. To accurately design such a system, it is necessary to assess the time variations of irrigation parameters including lateral infiltration q (leakage flow rate per unit length), local water pressure along laterals Px in terms of input water flow rate If , and pipe orifice density n, as it is the subject of this research.