The LEPA applicators provided more water to the plants. This could be attributed to the reduced energy of the water making it more resistant to wind drift and evaporation. Low pressure operation provided additional savings in the form of reduced energy required to pump the water. In addition, the close spacing of the LEPA sprinkler heads greatly diminished burrowing varmint damage to fields by creating an undesirable habitat. Triple D Ranch is located in Dyer, Nevada USA (Longitude: 118.01, Latitude: 37.615) in Esmeralda County. Elevation is 1492.9 meters and the climate is windy with little to no rainfall and very low humidity. The primary soil type is heavy silt clay loam. The ranch encompasses 1861.5 overall hectares with 52 center pivots over alfalfa. Thirty-seven center pivots irrigate with LEPA applicators excluding two test machines. Area water table levels are declining in this area, which led farm managers to investigating ways to reduce water use and still retain successful yield levels. Exposure to Close Spacing LEPA irrigation practices at the World Ag Expo led farm managers to additional independent research. This included information about the success of LEPA in Texas dating back to the 80's and renewed interest in the practice, as well as recent university studies. The managers of Triple D Ranch investigated different product options recommended by the Texas Senninger Irrigation District Manager, secured product samples and tested several combinations. After this investigation, they settled on the Senninger LDN with a single pad equipped with the CM1 insert and Shroud at 10 psi (0.69 bar). They converted two machines in 2015 to 30 inch (76 cm) spacing between hose drops and 18 inch (45.7 cm) applicator height. The results were water and energy savings.
Background - LEPA close spacing
Close Spacing is a water-efficient irrigation practice that combines the low-pressure bubbler heads made for LEPA (Low Energy Precision Application) with conservation tillage practices. LEPA bubblers operate at low pressures ranging from 6 to 20 psi (0.41 to 1.4 bar). They use less energy than conventional low-pressure sprinklers, and operate using fewer gallons per minute than conventional spray nozzles. Pivots equipped with LEPA systems deliver water 8 to 18 inches (20.3 to 45.7 cm) above the ground in an effort to combat wind-drift and prevent evaporation loss. When LEPA was initially conceived, sprinklers were placed 152.4 to 203.2 cm apart to irrigate every other furrow. In contrast, Close Spacing method distributes water over most of the soil surface with 101.6 cm or less between heads. Conservation tillage practices further help prevent evaporation loss, and run-off.
In depth testing
In order to learn what was actually contributing to the improved results, Triple D Ranch partnered with Senninger on a new test beginning July 2016. This would include a span to span direct comparison measuring the following: Yield, Water Penetration, Salinity, Soil temperature, Total Water applied, ET. This allowed for a more direct comparison of moving deflector sprinklers with LDN LEPA applicators within the same field reducing the variability of different soil types and plant ages.
The test was set-up with three spans of moving deflector sprinklers and four spans of LDNs with LEPA pads (C33/CM1) and Shrouds.
. Sprinklers were at 3 meters spacing, 91.4 cm height, with 10 psi (0.69 bar) pressure regulators.
. LEPA applicators were at close spacing of 76 to 101.6 cm, 45.7 cm height, with 10 psi (0.69 bar) pressure regulators.
. Balanced flow rates consistent with their pivot span location.
. Two soil moisture probes employed per pivot - one under span with moving deflector sprinklers and one under span with LEPA LDNs.
. Pivots tested had similar characteristics. There were slight variations in the soil but the crop was the same seed variety and the field inputs were the same.