The future of irrigation is here
Major research programme wraps up with a leading sensor technology system for irrigation scheduling
Introduction
A six-year research programme on irrigation has concluded with a big win for the agricultural industry - the development of promising new sensor technology systems that give arable, vegetable, and pastoral farmers the tools to use precision irrigation at sub-paddock scales.
The new technology systems work alongside existing irrigation scheduling technology, mapping and monitoring a field at sub-paddock scales and calculating exactly how much water is needed at the right time and place. It is a leading development for irrigation and field trials have proven to dramatically reduce water wastage, save users money, and minimise farm runoff.
Here’s how researchers did it.
THE SCIENCE FOCUS
Programme scientists at the Plant & Food Research trial site and rain shelter, Lincoln
New irrigation systems over the past two decades have given farmers and growers the ability to accurately apply water at appropriate intensities to a field or block of land.
This development occurred as the area of land being irrigated in New Zealand dramatically increased. But the amount of water required on different soil types and pieces of land varies from place to place, and without the correct application, users found too little or too much water could easily be applied with yield losses. Where too much irrigation was applied run-off and nutrient leaching resulted as well as wasted water. New irrigation scheduling systems were needed to help users make effective irrigation decisions to improve productivity and reduce these negative environmental impacts.
The MBIE-funded collaborative programme ‘Maximising the Value of Irrigation’ (MVI), led by Manaaki Whenua – Landcare Research, with Plant & Food Research and the Foundation for Arable Research (FAR), took on that challenge.
The programme began in 2013, and one challenge that researchers were tasked with was - evaluating variable rate irrigation (VRI) systems and developing new methods and sensor technologies to inform irrigation control systems.
THE FIELD TRIALS
Wireless soil moisture sensor network monitoring the soil moisture of a pea crop trial at Massey University.
“We designed, built, and used wireless sensor networks for near real-time monitoring at irrigation sites and sent this information via a smartphone app to participating farmers to inform precise irrigation schedules and monitor daily crop water usage.”
Soil moisture
One group of researchers conducted field trials at Plant & Food’s Experimental Station in Lincoln. The trials showed a water saving of between 9% and 30% when irrigation was varied according to different crop water demands monitored in different soil management zones at the site.
Researchers used high-resolution sensor mapping and in-field soil and crop sensor monitoring systems to assist with the precision irrigation.
“The sensor mapping used a vehicle mounted with GPS and an onboard data logger, and towed an electromagnetic sensor that sensed the soil and collected information on the differences in soil moisture and texture,” says MVI programme lead and Manaaki Whenua Landcare Research Scientist Dr Carolyn Hedley.
This sensor mapping system was trialed on six farms where researchers processed the survey data into management zones to record the main soil differences.
The soil variability was then characterized by physical soil sampling to measure drainage characteristics and how much water each soil zone could hold.
Soil and crop monitoring systems were designed to track the condition of soils and crops, and to inform irrigation scheduling decisions in a timely fashion.
“We designed, built, and used wireless sensor networks for near real-time monitoring at irrigation sites and sent this information via a smartphone app to participating farmers to inform precise irrigation schedules and monitor daily crop water usage,” explains Hedley.
Wireless sensor network installed into a carrot crop on a Hawkes Bay focus farm
“Replicated sensor monitoring sites were installed into each management zone defined by the sensor surveys,” she adds.
The app worked by measuring the soil moisture content of management zones in almost real-time and provided users with this information to guide precise irrigation schedules.
The new sensor technology and smartphone app were tested in three field trials on a range of different commercial-scale farms and showed promising results that saved water and almost completely stopped irrigation-related nitrogen leaching losses.
A wireless soil moisture sensor installed into a wheat crop sending data via cellular networks to apps and webpages
“In one trial, 150 mm of irrigation was uniformly applied to a barley crop over one irrigation season to maintain adequate soil moisture in the well-drained soil zones under the pivot, but a six hectare poorly drained zone was near saturation for most of the season and yields were significantly less (3 t/ha compared with 9 t/ha),” explains Hedley.
Trial results using soil moisture sensing showed that irrigation could have been reduced to this poorly drained soil zone by as much as 60 mm, to avoid over-wetting and possibly also increase yield.
Irrigation precision map updated every day to guide scheduling
“This equates to an unnecessary water cost of approximately $720 per year, (assuming ~$2/mm/ha/yr) and a conservative yield loss equivalent to approximately $2400 (assuming a yield penalty of 2 t/ha for the 6 ha zone) so that VRI could potentially save this farmer approximately $3000 a year at this site” adds Hedley.
Crop water usage
Alongside the soil moisture research, another group of MVI researchers used remote sensing methods to create a technique for monitoring daily crop water usage, to help calculate how much water a crop is using on a daily basis. Plant & Food Researcher Dr Hamish Brown explains:
“To know exactly how much water to put on a field, there’s two approaches you can take: you can measure the soil water content, which is generally what irrigation scheduling is based on; or you can measure how much the crop is taking out of the soil as a direct crop water extraction method. If you add that up daily you can calculate how much water you need to put back on the land.”
Researchers originally tested the technique in a rain shelter for two barley crop varieties.
They then applied different irrigation to each crop.
“We were wanting to create a technique that could be used as the equation for calculating crop water use at paddock-scale - the geospatial technology is there, but what we have done is provided the calculations to be able to take these data and turn them into useable and understandable information in relation to irrigation,” says Brown.
“We were wanting to create a technique that could be used as the equation for calculating crop water use at paddock-scale - the geospatial technology is there, but what we have done is provided the calculations to be able to take these data and turn them into useable and understandable information in relation to irrigation.”
Dr Peter Jamieson (ret.) (L) and Plant & Food Research Dr Hamish Brown (R) testing the new sensor technology on a crop at the Lincoln trial site
“We started by working in fixed points in the trial area to develop the technique. We devised multiple experiments in which we applied treatments to create different rates of water use, to work out how much water a crop is using,” he explains.
“One crop received a small amount, another a moderate amount and then there was one that was fully irrigated and so we got nice patterns of differences in canopy temperature throughout the season. We were able to combine all our data to create some equations and give a really good estimate of the amount of water that the barley crop was using on any given day,” says Brown.
“We then tested our technique outside the rain shelter on a range of crops using different variables. We found that we reduced the water use a little bit in the heavy soil, but in the light soil there was a considerable reduction in water use with no yield reduction in the crop, which is promising,” he adds.
Crop sensor measuring canopy temperature
Researchers found that their method reduced drainage to near zero and concluded that it could substantially reduce the environmental impact of irrigation.
Maximising the Value of Irrigation
THE ON-FARM IMPACT
Maize crop
“You always think ‘the soil is dry, run the irrigator over it and job done’ but actually no, it’s not accurate enough."
Effective irrigation for crops such as wheat, corn, grass seed, and potatoes has been a significant problem for farmers around the globe for centuries.
It’s a delicate balance to get the correct amount of irrigation onto the land without dramatically reducing production, wasting water, and causing unwanted runoff.
Developing technologies to measure accurate real-time soil moisture and crop water use is of immense value to farmers and growers making irrigation decisions.
Canterbury farmer Steven Bierema
Canterbury farmer Steven Bierema has relatively flat and even land, but soil moisture sensing has given him an additional tool for improved irrigation scheduling.
“You always think ‘the soil is dry, run the irrigator over it and job done’ but actually no, it’s not accurate enough,” says Bierema.
“With irrigation scheduling, you can track that soil moisture content and make sure that the soil moisture is adequate for plant growth. We run five irrigators on the farm with three soil moisture probes. We want to increase that because it really does give us a better view of what crops use and what growth stages they are at,” explains Bierema.
The technology has also been trialed on a Hawkes Bay farm with a large area of land to irrigate but a very limited amount of water available.
Although that farm has a mixture of different soils, farmer Hugh Ritchie still found the technology effective.
“Different crops and different soils in a paddock have different moisture requirements at different times, so having the ability to apply the water more effectively and efficiently at those different places means you get more efficient use of the water. You are optimising the crop performance with that water – because you are not getting it too dry or too wet, the crop potential is maximised,’ explains Ritchie.
“Over time the new software control models almost took over the irrigator, prescribing what the model thought would be the best for the crop at the time given the current and past weather,” he adds.
Variable Rate Irrigation for effective irrigation
THE INDUSTRY VOICE
Canterbury plains
Irrigation usage remains a hot topic in New Zealand. Long variable dry summer conditions coupled with increased demands mean irrigation is now essential for consistent and quality food production on the east coast of New Zealand. Since the late 1970s the area of farmland in New Zealand under irrigation has doubled every 12 years. The latest figure published in this year’s Environment Aotearoa report reveals that 747,000 hectares of land were being irrigated in 2017, and this figure is expected to reach over a million hectares by 2035.
Preserving New Zealand’s water resources and enabling farmers to have access to the amount of water they need is an ongoing discussion between regional councils and industry groups. The two groups agree that high-resolution sensor-informed smart irrigation scheduling has the potential to help make informed decisions for precision irrigation at sub-paddock scales, and FAR say adopting this research could be the answer.
“Irrigation is seen as a contentious issue and adoption of the outcomes of this research should alleviate public concerns over potential wastage of New Zealand’s natural resources and the risk of unintended environmental pollution,” says the Foundation for Arable Research’s CEO, Alison Stewart.
“Sensor technologies that support growers being able to optimise their water use will deliver multiple on-farm benefits including water savings and reduced nutrient losses. The effective uptake and adoption of precision irrigation technology will be crucial to maintain New Zealand’s primary sector’s license to operate,” she adds.
Stewart says that while the industry is well aware of the potential benefits of smart irrigation scheduling, the next challenge will be for farmers and growers to be able to integrate them into their farm business in a cost-effective way.
Maximising the Value of Irrigation is a collaborative research programme funded by MBIE and led by Manaaki Whenua – Landcare Research, Plant & Food Research and the Foundation for Arable Research (FAR). It also includes researchers from Lincoln AgriTech, Massey University, and the University of Southern Queensland. FAR chair the Programme’s Industry Advisory Group, with representatives from the Vegetable Research and Innovation Board, Irrigation New Zealand, Dairy New Zealand, Ministry for Primary Industries, Hawkes Bay Regional Council. Environment Canterbury.
We would like to acknowledge participation by our focus farmers – without whom this research would not have been possible. We also gratefully acknowledge collaboration with Agri-Optics, HydroServices, Waterforce and Lindsay NZ.
Story map & article: Suzette Howe
Imagery/videography: Bradley White & supplied
