The unique crop, soil, topography, and other characteristics of every farm present a strong case that each field should be irrigated to its individual needs. Variable rate irrigation (VRI) systems offer growers the opportunity to customize water application based on specific field conditions and other unique needs of their farm.
Not only has precise water application been shown to positively impact yield potential, additional benefits include greater water use efficiency (WUE) and resource use efficiency (RUE).
Another advantage of VRI is it’s not a one-size-fits-all solution for every farm. While every manufacturer’s offerings vary slightly, there are different options. Valley Irrigation, for example, offers three primary ways growers can incorporate VRI into their pivot irrigation system for best results.
Start with Application Speed
The first and most basic level of VRI is adjusting application speed. The pivot system can be programmed to speed up or slow down the amount of water applied as field characteristics and water requirements change. For greater customization, a system can even be specified to change water application midway through a field, if needed, to accommodate a multi-crop field, low area, or other unique need.
With speed control, a grower isn’t changing how much water is used, rather changing the rate at which water is applied for greater WUE. This control can also be useful for growers who chemigate with their pivot systems, with the same functionality allowing better RUE for chemicals, fertilizer, and electricity.
Because the prescription is easy to write, application speed is the simplest way to incorporate VRI into an operation. A grower simply needs a general overview of field characteristics to write a good prescription. While simple, speed control is still an effective use of VRI, with the opportunity to accommodate various unique field characteristics.
Graduating to Zone Control
A pivot is divided into zones, with each zone including half a dozen or more sprinklers. Using GPS technology, VRI zone control allows for water application to reduce or shut off entirely in a specified zone vs. the entire system.
In a similar way to application speed, zone control provides a level of accuracy that improves both WUE and RUE. However, because of the added customization down to each zone, the effectiveness of these benefits is even greater.
Zone control requires a bit more effort to create a proper prescription, including a more detailed snapshot of the field to identify smaller areas where application would not be effective. Because of the added complexity, it’s often the next step for growers who have had success with speed control prescriptions. And similar to application speed, zone control is a highly-effective way to apply VRI to a field and accommodate unique characteristics.
Adding Individual Sprinkler Control to the Mix
Taking zone control to the next level, one of the latest VRI advancements within the past year is individual sprinkler control made possibly by GPS technology. Valley irrigation offers a system, the Trimble Irrigate-IQ, that allows this level of precision application. While spacing varies from pivot to pivot, generally, sprinklers are spaced around eight-feet apart. Just as the name implies, the system allows control over each individual sprinkler, providing application accuracy within feet.
To get the maximum potential from a VRI system, a grower would incorporate a complete agronomy plan, including evaluating soil data maps, topography information, yield data, and other field specifics, along with a combination of application speed and zone control, and the precise accuracy of individual sprinkler control.
With the added effort and accuracy comes the highest expectation of WUE and RUE. This level of VRI is most valuable for multi-crop fields, those with variable soils, and fields that have a mix of high, dry spots and low, swampy areas. Because of the level of data and analysis required, an agronomist, service provider, or other trusted advisor would most often assist a grower in implementing a VRI plan of this level.
From water conservation and yield potential, to saving labor, materials, and costs, VRI is an opportunity worth exploring for every grower, whether adding to an existing pivot system or incorporating into a new one.
–by Brian Boyne, Technology Service Manager of MVI and based in Wadena, MN. Learn more about variable rate irrigation and complete center pivot systems from MVI by visiting www.rdoequipment.com/irrigation/mvi/products