LEPA FOR CENTER PIVOTS

Low Energy Precision Application

LEPA is a pivot irrigation concept developed at Lubbock-Halfway Texas Agricultural Experiment Station by Dr. Bill Lyle and James Bordovsky. Dr. Leon New of the Texas Agricultural Extension Service at Amarillo helped refinement and application of the concept. The LEPA concept diverges from conventional pivot sprinkler packages. With LEPA (Low Energy Precision Application) the plant canopy remains dry and water is applied directly to the furrow — typically every other furrow. Delivering water directly to every other furrow requires some special management and tillage practices. 

 

To be classified as LEPA the system should:
•     Make use of a pivot or linear system utilizing close outlet spacings (i.e. LEPA spaced pipe configurations of 30” (76 cm), 40” (102 cm), 60” (152 cm), and 80” (204 cm) outlet spacings are available).
•     Utilize emission devices that deliver water precisely into a single crop furrow. 
•     Discharge water very near to or on the soil surface at low pressure, with little energy in order to have very low evaporation in the air.
•     Use reservoir tillage storage basins to hold applied water. Furrow diking provides the storage basin for the high application rates of LEPA. Other recommended tillage practices include: Deep Chiseling to improve infiltration and incorporating crop residue to improve surface storage capacity.
•     Utilize circle planting of the crops under center pivot systems to provide uniform application and to prevent runoff so that each plant has uniform access to the moisture. 

 

The D3000 Sprayhead can be used in LEPA applications by incorporating the Hose Drag Adapter or Bubbler Clip. LEPA can also be adapted to the A3000 Accelerator with the sprinkler converter. It's important to use LEPA where it fits. While offering the advantages of low pressure operation and minimal water loss due to canopy evaporation and wind drift, LEPA is limited to its areas of application. Limitations include: • Soils — Without careful management and tillage practices, LEPA is limited to soils with good infiltration rates due to the high application rates. The speed of operation of a pivot or linear may also need to be adjusted to prevent runoff. • Slope — LEPA is limited to a field slope of less than 2%, or 1 % or less in high-intensity rainfall areas. • Inner Spans — Due to nozzle size limitations and susceptibility to nozzle plugging, other 3000 Series products may be substituted for LEPA devices in the first spans. Due to the very low pressure used, it is necessary to manage the system pressure and monitor it closely. Very little pressure or elevation change can be tolerated. Pressure regulators are generally a necessity for good uniformity of LEPA nozzle discharge. Some level fields are irrigated without the use of pressure regulators. Areas where the water table in wells changes during the season can benefit from following the pump output rather than locking on to a regulator preset pressure. This decision must be made for each site. Here are several hints regarding using the HD3000 Hose Drag & Bubbler Clip: • The maximum flow which can be held in the surface storage basins is the limiting factor of the nozzle flow for the hose drag. The largest flow per each unit is generally about 6 gpm. • Caution! if rigid drop pipes are used. Drag force may cause damage to the rigid pipe. Normal application is on flexible hose drops. • The hose drag adapter must be tightened adequately to avoid untwisting of the thread and loss of the adapter and nozzle.