Abstract
Abstract
Laboratory experiments were carried out to investigate the effect of operating pressure on wetting pattern in layered soil for subsurface point water source. This study helps to determine a suitable operating pressure and appropriate spacing between emitters and drip lateral pipes . The layered soil profiles were prepared using two types of soil (clay and loam) in two combinations (clay over loam and loam over clay) . Three operation pressures (4.99, 9.99 and 16.14, m) with a nominal dripper discharge rate (2 l/hr) were used . The experimental results showed that positive back pressure around dripper outlet develops, when the water application rate is larger than the soil infiltration capacity , and the actual dripper discharges were less than the rated dripper discharges by about (10%-28%) due to back pressure effect . Furthermore, it has been observed that water start rising up to the soil surface (Chimney Effect) when the operating pressure is (16.14m) for the loam over clay soil profile, which occurs when water application rate exceeds the soil capability to spread the water. It is found that the total wetted area for both layers was not affected by the operation pressure for the same volume of applied water . In the relationship of the wetting advance (a tb) , it is found that , the constant (b) is not effected by operation pressure while the constant (a) increased with increased operation pressure .
