Maintaining uniform distribution of irrigation water is critical for optimizing irrigation efficiency and scheduling. High distribution uniformity (DU) ratings indicate even water supply across the orchard, critical to ensuring all trees receive similar quantities of water.
Low DU results in simultaneous over- and under-irrigation across the orchard block, higher water use to meet the demands of every tree, and unnecessarily long pump run times. Elements that contribute to high DU are balanced pressures, matching sprinkler types and nozzle sizes, and system maintenance.
Poor maintenance is one of the leading causes of low DU. Greater than 80% of the systems evaluated by the Tehama County Mobile Irrigation Lab between 2002-2013 with below- average DU had pressure and/or maintenance problems (See chart).
Of the systems with above-average DU, nearly half still had maintenance issues that could be corrected to further improve their DU. System maintenance is an essential component of an efficient irrigation system that is easy to overlook amid the numerous demands required to run an effective growing operation.
All types of irrigation systems can benefit from maintenance, although the intensity and amount of time required varies pointedly by irrigation system type. While micro and drip systems tend to be the most uniform in application if well maintained, the amount of attention they require to run at optimal levels is substantially higher than other systems. Regardless of the system, routine maintenance is critical.
• Clean primary filters (at the pump) and any secondary filters (often located in the field). Backwash to remove organic or particulate matter. If using a sand media filter, check that sand is not caking and replace what is lost in backwash cycles. Be sure you have installed the correct type of filter for the type of debris in your water source.
• Pressure gauges should be installed before and after filters. If there is a 5 to 7 psi difference between the two gauges, check for filtration plugging. Replace gauges (about $15) approximately every 3 three to 5 five years because reliability decreases in aging gauges.
• Ensure that pressure-regulating valves are accurately providing the desired pressure by checking against a quality new pressure gauge.