Fixed Spray Irrigation

LEPA/LESA: Advantages, drawbacks and areas of application

A vital part of designing a center pivot system is choosing the right irrigation spray heads. This involves a number of important decisions – including the choice between rotating and fixed spray irrigation sprinklers. The factors that should be taken into account include the type of crop you intend to irrigate, the climatic conditions within your region, the depth, consistency and composition of the soil, and the topography of the respective field. While every scenario will present its own requirements and challenges, there are some guiding principles that can be applied on a relatively universal basis.

Broadly speaking, freely rotating spray irrigation sprinklers (or distribution devices) are designed to cover a more expansive area over longer periods of time. Due to their lower application rate, the water emitted by rotating sprinklers has more time to infiltrate the soil (which is why freely rotating spray irrigation with distribution devices is generally the better choice for sloping terrains). Freely rotating sprinklers also offer a better, more continuous ground coverage with less risk of streaking, compared to sprinklers with a fixed spray pattern.

There are, however, settings in which fixed irrigation devices are the more practicable option. LESA (Low Energy Spray Application) irrigation, for example, is based on fixed spray irrigation devices whose narrow, vertical stream delivers water straight into the furrows between the crop rows. The aim of LESA irrigation is to enable a very localized, low-pressure irrigation. LESA sprinklers are usually suspended no more than 3 feet (1 meter) above the soil surface, and spaced at around 30 inches to create an overlap between their sprinkler head spray patterns. Similarly, in LEPA (Low Energy Precision Application) irrigation systems, bubblers are positioned on or just above the soil surface, directly targeting the root zone of the crop.

The main advantages of LEPA / LESA sprinkler irrigation include low water usage and pumping costs, along with a minimized risk of water losses caused by wind drift and evaporation. For this reason, LEPA / LESA irrigation can be particularly useful in regions that are prone to high temperatures and severe winds, as well as areas affected by pronounced water scarcity. LEPA / LESA spray irrigation is also beneficial for crops that are susceptible to foliar diseases, as the plant canopy itself tends to remain dry. In addition, LEPA and LESA irrigation can reduce overall wear and tear on the entire center pivot system, as the soil profile is filled more quickly – so that fewer passes are required.

It is important to note that only very specific soils, climates and topographies are suited to LEPA / LESA sprinkler irrigation. Due to the relatively high instantaneous application rate (which allows less time for the water to infiltrate the soil), LEPA / LESA sprinkler irrigation is more likely to cause issues such as puddling, runoff and compaction of the soil. For this reason, a LESA / LEPA irrigation system should only be installed in fields with a fairly flat topography. On sloping terrains, a fixed spray irrigation system is not usually recommended, due to the increased risk of erosion this irrigation method inevitably entails.

Irrigation Spray Heads for LEPA / LESA Irrigation

Building the perfect LEPA / LESA irrigation system with Komet’s LEPA / LESA sprinklers

Komet’s pivot irrigation product catalog includes several fixed-spray and bubbler options that are specifically geared towards LEPA / LESA irrigation: The Komet Precision Spray (KPS) series comprises three LESA sprinklers with fixed spray patterns – a 360° standard model, a 180° part circle sprinkler for dry wheel track applications, and a dual model for high-flow machines – and two bubbler variants – vertical and wide bubblers. The KPS series is complemented by a number of separately available deflectors with varying numbers of flat (FL) or concave (CC) grooves.

While the above-mentioned LESA sprinklers (360° / 180° / dual) are each geared towards their own specific area of application – with different sprinkler head spray patterns, trajectory angles, nozzle ranges and deflector compatibilities – they are, in fact, based on the same core body. What is more, every KPS model features an integrated storage for an additional nozzle. This makes it easy to swap irrigation spray head nozzles at later stages of the growing season (for example, once the germinating seedlings have matured), and ensures that the intended nozzle will be fitted to the correct outlet. Furthermore, the KPS body comes with an integrated cleaning pin, which is the perfect size for freeing the sprinkler nozzle’s opening of possible blockages and debris.

As for Komet’s LEPA irrigation segment: Komet currently offers two KPS bubbler models – the KPS Vertical Bubbler, and the KPS Wide Bubbler 60” – which operate at very low pressures, and are once again based on the same core body.

The KPS Vertical Bubbler is suitable for circular crop rows only. It is designed to deliver water into the furrows in the form of a straight, narrow stream, directly targeting the root zone of the crop. The Vertical Bubbler is compatible with an extensive range of different deflectors. For ultimate flexibility, the KPS Vertical Bubbler can even be converted into the ‘standard’ KPS sprinkler with a 360-degree fixed spray pattern: This is achieved by simply removing the bubbler cap, and turning the respective deflector upside down.

The KPS Wide Bubbler 60” is suitable for straight as well as circular crop rows. Like the KPS Vertical Bubbler, the Wide Bubbler distributes water straight into the furrows between the crop rows – however, it does so with a wider, dome-shaped irrigation pattern, and at a lower instantaneous application rate. This can be advantageous in the case of more compact soils, as the Wide Bubbler’s larger irrigation pattern and lower kinetic energy reduce the potential for runoff. Its more expansive and more even coverage also makes the Wide Bubbler better suited to applying chemicals and fertilizers directly to the soil surface. The KPS Wide Bubbler 60” is only compatible with one deflector (type: ’FL33’, i.e.: flat, with 33 grooves) – which can also be turned upside down to ‘transform’ the Wide Bubbler into a standard, 360-degree KPS fixed spray irrigation sprinkler.

The KPS models can be installed on all drops – with the exception of the KPS Part Circle fixed spray irrigation sprinkler: As with all sprinklers with a 180-degree spray pattern, the KPS Part Circle is limited to rigid-hose installation, as the gravitational effects of its one-sided irrigation output would otherwise cause it to become tilted.

To find out more about LESA / LEPA irrigation and a broad range of other irrigation-related topics, why not take part in one of our Komet Academy sessions? In this ongoing series of free webinars, our irrigation experts share their in-depth expertise with audiences around the world. The Komet Academy is entirely product-neutral, and an excellent opportunity to expand your knowledge on all aspects of successful irrigation with a center pivot system.