Spray volume rate errors in intermittent operation of hydraulic nozzles

TWO air-carrier orchard sprayers, using centrifugal and diaphragm pumps, we re operated at six nozzle selections commonly used to obtain low, medium, o r high volume rates in Florida citrus applications. Nozzle pressure and flo w rate were measured for the one- and two-sided operations. The difference in the pressure or flow rate was related to the application rate error For all nozzle selections, closure of the nozzles on one side of the sprayer in creased the operating pressure and the flow rate on the other (open) side. The sprayer with a diaphragm pump was much more sensitive to the flow restr iction than the sprayer with a centrifugal pump. For the latter the pressur e difference peaked at about mid pressure range and decreased with further increase in pressure of flow rate. However with the positive displacement p ump, the difference generally decreased as operating pressure increased Ove rall, the pressure error of the one-sided versus two-sided spraying was les s than 20% for the centrifugal pump but exceeded 200% for the diaphragm pum p system. The volume rate errors at 470, 2350 and 4700 L/ha nominal rates w ere 1.0, 3.5, and 3.5% (centrifugal) and 6.0, 7.5, and 47.0% (diaphragm), r espectively.