#Irrigationmanagement #waterconservation #energyefficiency #distributionuniformity #overheadirrigation #dripsystems #pumppressure #nozzleselection #systemmaintenance
As a farmer, agronomist, agricultural engineer, or farm owner, you know the importance of efficient irrigation practices for crop growth and yield. One essential aspect of irrigation management is achieving application uniformity, which refers to the evenness of water distribution across the field or growing area. Poor uniformity can lead to over or underwatering, which can negatively impact plant growth and increase water and energy use.
Overhead irrigation systems are particularly challenging to achieve uniformity, but even drip systems need to be checked. Boom systems, troughs, ebb & flood benches, and floors have become increasingly popular because they provide the greatest uniformity. Uniformity is affected by several factors such as nozzle selection, spacing and height, water pressure, pipe size, and system maintenance.
One way to measure irrigation application uniformity is through Distribution Uniformity (DU), which is expressed as a percentage. The DU test provides a visual picture of how water is being applied and can help identify areas where improvements can be made.
For overhead systems, the DU test involves placing 16 or more straight-sided catchment cans evenly spaced throughout a representative section of the crop. After running the system until there is at least an inch of water in the cans, the water from each cup is poured into a graduated cylinder or beaker, and the amount is recorded. The DU is calculated by dividing the average of the lowest cans by the average of all the cans and multiplying by 100. A DU rating greater than 90% is excellent, 80-90% is good, 70-80% is fair, and less than 70% is poor.
For drip systems, the DU test involves sampling the output from a number of emitters. Depending on the application and manufacturer, emitters can have outputs from ½ to 16 gallons/hour. Three or four sampling locations should be chosen for each lateral line in the zone, one near each end, and one or two evenly spaced in the center. After running the system for one minute, the output from each emitter is recorded, and the DU is calculated by dividing the output for the lowest 25% of emitters by the average rate for all the emitters and multiplying by 100.
If the DU rating is fair or poor, it is essential to clean and check filters/screens, nozzles or emitters that have the lowest output. Checking pump pressure with in-line gauges against the pressure at the beginning and end of lateral lines can also help identify leaks, too small supply pipes, or too many nozzles/emitters.
Improving irrigation application uniformity can result in more efficient water and energy use, as well as more uniform crop growth and yield. By regularly testing and maintaining your irrigation system, you can identify areas for improvement and make adjustments to optimize your irrigation practices.
