Zimmatic Variable Rate Irrigation by Precision Irrigation

Zimmatic Variable Rate Irrigation (VRI) is an add-on to a centre-pivot or lateral-move irrigation system that allows different amounts of water to be applied along any part of the length of the irrigator at any one time.

How does VRI work?

The Zimmatic Variable Rate Irrigation system provides precision control of all sprinklers on a centre-pivot or lateral-move irrigator. This is achieved by individually pulsing sprinklers on and off, while also controlling the system speed to modify the application depth along the length of the irrigator.

If you have a fast internet connection, you can watch the video in high quality by setting 360p to a higher value. As the camera zooms out, you will notice valves pulsing on and off on the span in the distance.

VRI system Components

The VRI system is a modular setup that consists of:

VRI controller. This controller is placed next to the irrigator’s main controller. It runs on 12VDC, controls the machine speed and sends out a wireless signal to control each individual sprinkler.
Wireless nodes. Each node is responsible for individual control of four sprinklers. It will either turn the sprinklers on, off or pulse at a dutycycle determined by the VRI controller.
Latching solenoid valves. Each sprinkler is individually controlled by a latching solenoid valve connected to one of four outputs on each node. The valve coil is 24VDC and requires a pulse in one polarity to open, and a pulse in the opposite polarity to close.
Wiring loom. Each loom is pre-wired into a node at the factory. The looms consist of a power cable that runs between nodes and four wires from the node that control each valve.
GPS. A GPS unit at the end of the pivot (or one GPS unit at each end of a lateral-move) sends a signal back through the wireless node network to tell the controller where the system is. The controller uses this position to calculate how to run the system.
PC Software. Every irrigation plan is made in FieldMAP farm mapping software, then loaded into the controller either via USB stick or wirelessly.

VRI hardware layout (click image to enlarge).

Benefits from VRI

Variable Rate Irrigation brings with it many direct and indirect benefits.

Click on an item to see more information.

Save Water

Desk top studies indicating water savings of 10-25% by quantifying all financial, environmental and social benefits of VRI, as well as identifying other potential benefits.

Decreases power consumption

Any area that requires less irrigation, or does not need watering saves water and associated pumping costs.

Changes application rate over different crops or soil types

Simple to isolate areas and treat them differently.

Increase crop yield

Crop yield increases from not over and under-watering different area.

Less track maintenance

Keeping tracks dry not only reduces wear and tear, but also saves animal hoof problems.

Reduces runoff and leaching

By not over irrigating specific areas, you can save valuable nutrients and water.

Optimised irrigation speed – quicker return times

Anywhere less water is required over the length of the machine, VRI can speed the machine up to apply less water rather than pulsing all of the valves so much.

Saves on fertigation and chemigation costs

Saves wasting fertilizer and chemicals where they are not needed.

Automatic pivot-lateral changeover

Save the time and hassle of changing sprinkler nozzles or valves on machines that do both pivot and lateral modes. VRI can take care of changing application rates to suit either pivot or linear mode without needing to switch a set of valves off. Rather, the VRI system simply pulses valves to make sure the correct application rate is applied along the length of the irrigator. This saves time and hassle, avoids potential mistakes and provides for much more even application of irrigation.

Provides web-based irrigation recording and reporting

Control and monitor your VRI system over a wireless or GSM internet connection.

Remote programming

Using a wireless or GSM connection, you can upload and select plans, plus monitor what your system is doing in real time right from your office.

Internet monitoring (optional extra)

Log in to the Precision Irrigation website and view where your irrigator is on a map of your farm. View current and historical positions, distances to hydrant change points, system pressure, calculated flowrates and plans being run.

Customer Testimonials

Brian Bosch, Dairy Farmer, Kahutara, South Wairarapa

Brian agreed to test out our VRI system when we were taking it from concept to prototype. His machine is now in its third season and still has the original prototype controller on it. We asked him after using it for two seasons what he thought of it and he said “I’m just driving down the cow track as we speak. The cows are walking under the irrigator on the dry track and it is irrigating the paddocks on either side… it’s just awesome! Keeping the tracks dry saves in track maintenance and cow lameness, as well as saving about 5% of water and pumping costs. It’s hard to put a value on the total savings, but definitely worth it. It also helps not having to work the pivot around the times when the cows are on the track going to and from the cowshed.”

Eric Watson, Cropping, Ashburton, Canterbury

Completed 1 season with 4 VRI systems, recently installed the 5th system.

“It’s a great system with a big future. Installing VRI was ideal for cutting out the overlaps inherent with my geo-lateral systems. Now that I have VRI, I couldn’t run the machines without it.”

Water meters attached to two laterals designed with 40lps sprinkler packs show that on average one machine is doing 32lps and the other 36lps due to irrigating to the crop and soil types.

“I have no doubt that our annual water allocation stretched much further with VRI this year. I’m not that computer literate, but it’s pretty easy to use.”

Johnny Fraser, Cropping, Otane, Hawkes Bay

Zimmatic pivot with Maxfield corner-arm, in its third season.

“With pumping costs of approximately $1/mm/ha, if I don’t need to irrigate 20ha beneath part of my pivot and I’m putting on say 20mm per pass, that’s a $400 saving in pumping costs each pass.”

In the 2009-2010 irrigation season Johnny reckons he used approximately 1/3 less water than he would have used if he didn’t have VRI.

“Of the things you apply to your field that you have control over, fertilizer and spray are fairly forgiving and not too detrimental to your yield if you muck them up, but the one thing that will get you is over or under watering. The biggest bang for your buck is getting your water right.”

“Variable Rate Irrigation definitely works, there’s no doubt about that”.

“An added advantage is that most machinery is designed to work in rectangular blocks. With VRI you can still plant and work in rectangular blocks, then you program the pivot to work around your blocks, rather than cultivating in segments.”

EM Mapping of soils for Variable Rate Irrigation control

In variable soils, common practise is often to irrigate everything for the soil that requires the most water. This is inefficient and results in much of the field being over-watered.

For heavily variable soils, and electrical conductivity soil survey and resulting EM (Electro-Magnetic) map can be used to identify the boundaries of the varying soils. Massey University and Landcare Research have been working with Precision Irrigation to utilise these maps for calculating where water should be applied under variable rate irrigation. Research shows that the available water capacity of varying soils can be calculated and then correlated to the EM map to create a spatial Available Water holding Capacity (AWC) map. This map can then be loaded into the VRI control software to calculate how much water should be applied in different areas beneath the centre-pivot irrigator.

The above map shows a field split into several irrigation zones based on soil types. This map is extrapolated from an EM Map that has been ground-truthed and was used in conjunction with a wireless soil moisture sensor network to calculate how much irrigation should be applied to the crops beneath the irrigators.

Precision Irrigation Video Gallery

Click an image to view the video.


VRI pulsing over several sprinklers	Last several spans of pivot pulsing with VRI

Simulation showing VRI applying different rates of water over wet and dry land	VRI turning irrigator off as it passes over a track

Single Sprinkler pulsing on and off	VRI switching valves off over a dry-zone

Irrigating Potatoes with Precision VRI while baling pea straw beneath a Zimmatic Center-Pivot	Precision Variable Rate Irrigation irrigating beans while keeping cultivated area dry

Variable precision irrigation in New Zealand seen as part of the International Farm Management Congress

Span pulsing valves on and off

Valves are pulsed on and off with different duty-cycles to adjust the amount of water that is applied under different parts of the irrigator.

Several spans pulsing valves on and off

Valves are pulsed on and off with different duty-cycles to adjust the amount of water that is applied under different parts of the irrigator. If you look down to the end of the irrigator as the video zooms out, you can see the valves on the corner-arm span pulsing.

Variable Rate Irrigation Simulation

VRI software does some image processing to calculate what rate to irrigate different parts of the area beneath the irrigator. The farmer can then view a simulation to see how much water is going to irrigated and where, and view the total amount that is going to be irrigated in a cycle.

Water off over track simulation

Water is switched off as irrigator approaches track. Valves switch back on on the other side. This can be programmed for tracks, waterways, buildings, yards and any areas beneath the irrigator that do not require irrigation or need to remain dry.

Single sprinkler actuating on and then off with VRI

When instructed by the VRI central controller, the solenoid valve latches open and then latches closed.

Sprinklers near programed dry-zone

As the irrigator approaches an area that it has been programmed to keep dry, sprinklers turn off and remain off until it has passed the area. This is commonly done over tracks, gate-ways, troughs, waterways, buildings and any other areas that do not need water on them, or are required to remain dry. For example, wheat near harvest can be kept dry as crops on either side of it are irrigated.

Irrigating Potatoes with Precision VRI while baling pea straw beneath a Zimmatic Center-Pivot

Precision Variable Rate Irrigation by Lindsay enabling New Zealand farmer Johnny Fraser to irrigate his potatoes while baling pea straw beneath the same center pivot irrigator.

Precision Variable Rate Irrigation irrigating beans while keeping cultivated area dry

New Zealand farmer Eric Watson keeps his ground that he is cultivating dry while applying irrigation to beans. Both areas are beneath the same irrigator. Made possible with Precision VRI by Lindsay.

Variable Precision Irrigation In New Zealand

Variable precision irrigation in New Zealand seen as part of the International Farm Management Congress.