PHOTO: LINDSAY CORPORATION


PHOTO: RAINDANCER


PHOTO: MIKE MALONE PHOTO: BRIGGS IRRIGATION


WATER TECHNOLOGY ▶▶▶


The evolution of Variable Rate Irrigation


BY ANDREW SWALLOW I


t was developed in the late 2000s by three Massey University graduates who designed a patented system using solenoid valves at- tached to each sprinkler that are switched


on and off remotely by control boxes on the spans of the pivot. Each control box manages four sprinklers. The control boxes radio-link along the irrigator to a computer and modem at its centre. In turn, that ‘talks’ through ‘the cloud’ to the farm computer and/or the farmer’s mo- bile devices, relaying what’s applied and up- loading application prescription maps to control how much water should be applied. Stu Bradbury, one of those pioneers of the tech- nology and now a strategy advisor with irriga- tion specialists Lindsay, estimates 5-10% of all pivot and lateral irrigators in New Zealand now use some form of precision variable rate irriga- tion (VRI). Over the next five years, he expects that will increase to 15-20%, and environmental regulation could force even faster uptake. “But we’re campaigning for it to be farmer led,” he says. Precision variable rate irrigation is also be- ing widely adopted in Australia, as farmers with multiple crops and/or variable soils under their pivots seek to improve efficiency. Mr Bradbury says it typically costs around NZ$110/meter (of pivot) (€64.36/meter) to fit


Precision Variable Rate Irrigation (VRI), whereby every sprinkler on a pivot or lateral is individually controlled, is sometimes called ‘third generation’ or ‘full control’ VRI as opposed to sector or segment control.


a VRI system to a pivot, either at installation or as a retrofit. While some growers can see a re- turn on the investment in just one growing sea- son (For example, Canterbury seed grower Craige Mackenzie, Future Farming, April 2017), within three years is a more typical time frame. In addition to varying application rate according to soil water holding capacity and crop growth stage, VRI allows application rates to be changed as the pivot crosses the boundary from one crop to the next – even if that boundary runs at an angle to the pivot or is not straight. Sprinklers can also be programmed to shut off over water troughs and waterways to prevent contamination, and vary nutrient rates. To plan VRI applications, soil water holding ca- pacity information is derived from detailed soil survey data, where it exists. Alternatively, elec- tromagnetic (EM) scans delineate soil zones, which are then ground-truthed to derive soil available water capacity (AWC) values.


US adoption lags behind New Zealand Mr Bradbury’s colleague at Lindsay in the Unit- ed States, Brian Magnusson, says US adoption of VRI lags behind New Zealand and the UK and Europe are probably even further behind again. However, he too expects adoption to accelerate rapidly in the next few years. “Everybody’s heard of VRI now but there’s still education to be done in the US and other parts of the world about its benefits.” In the US the initial wave of users had areas they wanted to avoid watering. Now, adoption is in- creasingly driven by growers who want to make better use of irrigation water due to volume constraints and improved return on investment, he says. Software systems have also improved, so it is easy to make a new variable rate pre- scription for every crop and for every pass. For example, Lindsay’s new technology, FieldNET Advisor, generates real-time variable rate irriga- tion prescriptions based on crop growth mod- els, taking into account crop growth stage, soil type and weather data. The technology uses re- gional weather and soil moisture data and/or the grower’s own readings collected from


According to Stu Bradbury, strategy advisor at Lindsay Corporation, estimates 5-10% of all pivot and lateral irrigators in New Zealand now use some form of precision variable rate irrigation.


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New hardware such as Raindancer takes GPS located, real-time pressure readings to pro- vide proof of placement and/or automatical- ly vary speed of boom travel, hence the rate across designated zones of the field.


▶ FUTURE FARMING | 25 May 2018


Valley Irrigation, as well as Lindsay Corpora- tion and a couple of other companies now offer VRI systems in New Zealand.


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