Effect of operating pressures on microirrigation uniformity

Abstract

The e ect of operating pressure heads on water application uniformity in microirrigation submain units was evaluated. Research results show that water application uniformity either increases or slightly decreases as operating pressure head increases in a range when the emission exponent x £ 0.5 in most cases. The water application uniformity decreases as operating pressure head increases in a range when the emission exponent x > 0.5. The relationship between operating pressure head and average emitter discharge in submain units can be considered as approximately linear for operating pressure heads in a small range (usually between the allowable minimum and maximum operating pressures of the submain units). These results help to estimate the average emitter discharge rate easily in a submain unit for an increased or decreased operating pressure head when one is attempting to manage emitter discharge dynamically according to the requirements of crop root growth for di erent periods. Generally, a microirrigation system designed to meet the desired uniformity of water application according to the allowable minimum operating pressure head would be better when x £ 0.5 because water application uniformity increases as operating pressure increases if emitter discharges are being managed dynamically. However, a microirrigation system designed to meet the required water application uniformity according to the allowable maximum operating pressure head would be better when x > 0.5 because, in general, water application uniformity increases as operating pressure decreases.

Effect of Different Types of Irrigation Systems on Soybean Production Under Clayey Soil Conditions

“…Vertical component of the wetting front is deeper for the smaller than for the higher discharge rate. This agrees with Kang (2000) and Elmaloglou and Diamantopoulos (2007). While the horizontal component of wetting front is wider than for the higher discharge rate, in the duration of off cycle, wetted soil volume was vertically moved by gravitational effect, but it was insignificantly changed in horizontal directions.…”

“…However, root length density was significantly affected by irrigation treatment at the 0 to 0.15 m depth with the more frequent irrigation treatment. Kang (2000) evaluated the effect of operating pressure heads on water application uniformity in micro irrigation sub main unit. Results showed that water application uniformity either increases or slightly decreases as operating pressure head increases in a range when the emission exponent x≤0.5 in most cases.…”

Graphical method for determining lateral and manifold pipe diameters in drip irrigation

“…The exponent x is nearly 0.5 for orifice drippers, varies between 0.6 and 1.0 (especially between 0.6 and 0.8) for microtube or longpath drippers, and is less than 0.2 for pressure compensating drippers (Howell and Hiler, 1974;Keller and Karmeli, 1974;James, 1993). Kang (2000) shows that water application uniformity decreases as operating pressure head increases in a range when the exponent x is higher than 0.5 in microirrigation. (2) can be used for determining the relationship between discharge and inlet pressure for the ith lateral on a manifold line with an assumption the exponent x equals 0.5.…”

Hydraulic characterization of porous pipes

“…However, studies have shown that the permeability of these pipes varies over time, negatively affecting their use in irrigation (Teeluck & Sutton 1998;Kanda et al 2018). Considering the variation in permeability over time, the performance of a surface application system may be negatively impacted since the amount of water applied is inconstant (Fang et al 2000;Kang 2000;Shu et al 2007;Ren et al 2017).…”