Working Ranch Magazine January/February 2025

regulators are not used, the pressure in the sprinkler lateral at the designated location must be determined.” Nozzle diameter influences dis charge. Using a formula, it’s verifi able that doubling the nozzle diame ter will result in four times as much discharge. Pressure has less effect on discharge than nozzle diameter. Sprinkler pressure is affected by pressure at the pivot inlet, the change in elevation of the pivot location rel ative to the elevation of the pivot inlet, and the loss of pressure along the pivot lateral due to friction. Using a single pipe size will also affect the practical flow rate. “Investment costs could be reduced by using 8-inch pipe for the initial por tion of the lateral and the 6 5/8 inch pipe for the remainder of the pipe line,” the publication notes. “It is com mon to install larger pipe on the first couple of spans of the lateral and then

Most producers are aware of these values with “reasonable accuracy.” Determining capacity for a specific site involves soil texture and evapo transpiration rates (ET). Soil texture affects the amount of water soil can provide to crops during periods of high ET demand. System capacity must be higher when less water is stored in the soil to buffer against water use during periods of high demand. “Discharge required from a sprin kler depends on the system capacity, the distance of the sprinkler from the pivot inlet, and the spacing between the sprinklers at that location along the lateral (as illustrated),” the UNL publication says. “Required nozzle size can be determined after computing sprinkler discharge. Pressure available to the sprinkler must be determined to select nozzle size. If pressure regulators are used, available pressure is usually the pressure rating of the regulator. If

smaller pipe for the rest of the lateral. The majority of the pressure loss along a pivot lateral occurs over the initial portion of the pipeline. Half of the total pressure loss along the pipeline occurs over the first 28%, and 80% occurs over the first half of the pipeline. The outer portion of the pivot will experience about the same pressure in the pipe line since most of the pressure loss has already occurred. Thus, if one mea sures the pressure in the outer portion of the pivot lateral, the measurement is accurate for the outer spans.” Center pivots can be equipped with an end gun to increase the portion of a field that is irrigated. An end gun is a large sprinkler mounted on the end of the pivot lateral, which throws water a long distance, increasing the amount of irrigated land. A valve attached to the end gun opens when the pivot rotates to field corners, opening when the pivot lateral reaches a preset rotation

We’ll see you in San Antonio, TEXAS, in February! Stop by booth #2010 for a visit! – Tim and the WR Crew

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