Variable Rate Irrigation (VRI)

PRECISION IRRIGATION

A center pivot system is retrofitted to control irrigation application with GPS guidance by span or individual sprinkler, depending on the type of VRI system.

With VRI, the center pivot applies varying amounts of water across irrigation management zones to address variations in the field, helping farmers determine where to irrigate.

VRI enables farmers to apply customized rates of water based on individual management zones within a field. VRI has economic, agronomic, and environmental benefits. Enhancing the precise placement and amount of irrigation through VRI can conserve water and reduce input costs. VRI improves water use efficiency by irrigating precise amounts according to soil and crop needs. Using VRI conserves water, and it may also reduce runoff and leaching of nutrients.

SPEED CONTROL OR ZONE CONTROL

There are two ways to implement VRI: speed control or zone control. Speed control VRI divides the field into pie slice-shaped sections, and the user can vary the speed in each of these sections. Zone control VRI divides the field into irrigation management zones that are delineated on a software-based mapping program and then uploaded to the pivot.

Irrigation Management Zones are delineated based on soil types, topography, hydrology, and other features. With VRI, the center pivot applies varying amounts of water across the irrigation management zones to address variations in the field, helping farmers determine where to irrigate. The animation above demonstrates how VRI operates across variations in a field.

estimated cost

The cost of VRI varies significantly. Speed control VRI is often a feature of remote irrigation tools and is included in a suite of other tools for $2,500 - $5,000. For zone control VRI, farmers do have the options of installing a partial or modular VRI system (only implementing GPS controls on a specific set of sprinklers rather than the full system). Partial VRI expenses range from $5,000 - $15,000. A full VRI system may cost anywhere between $20,000 - $45,000 depending on the length of the pivot.

efficiency

Researchers have determined VRI may reduce water use by 15% on average. This also varies greatly depending on field conditions and VRI management.

Variable Rate Irrigation for Agriculture video