Paul Reese from Irrigation New Zealand says a lot of effort is going into developing clever, precise irrigation technologies in NZ and around the world with water quantity and quality factors at the forefront of thinking.
Getting just the right amount of water in the right place at the right time is the aim, not only so it doesn’t waste water but also to prevent nutrients being washed out of the root zone.
In pursuit of that aim, there are new developments across the irrigation spectrum, from technologies that focus on the soil, to efficient water delivery infrastructure, to the pumps or systems that bring the water from its source.
Reese says developments include real-time soil moisture and plant status information that feeds directly back to the irrigator operating systems, with programmes being developed to manage the irrigator settings.
Soil moisture information coupled with weather data and plant-focused infra-red technologies could provide ongoing information so the irrigator and irrigation rates are adjusted as the irrigator moves over the paddock.
Fertigation technologies also fit with that kind of development.
Having accurate information is essential to improve precision from any baseline and Reese says the mandatory installation of water meters is opening farmers’ eyes to that.
New consents now commonly have a total annual water allocation included, rather than simply a rate, and farmers have to keep a close eye on how much water they are using to ensure they can get right through the season.
Scheduling irrigation based on soil moisture, particularly in the shoulders of the season, is increasingly being used.
Reese says that’s likely to be where most farmers could initially make the biggest gains in improving water use.
Soil moisture probes could be used to measure soil moisture levels regularly at specific sites onfarm, with measurements taken on the predominant soil type. More varied soil types would have multiple sites.
Permanently installed tapes that measure soil moisture based on measures of electrical transmission give real-time soil moisture readings. Aquaflex operates using this system, with the readings plotted graphically so farmers can access the information easily on their computers or mobile devices and adjust irrigation to maintain soil moisture between refill and field capacity points.
Soil temperature information is also collected and used to help in the decision-making process.
Variable rate irrigation is being used to improve efficiency, reduce water wastage and nutrient loss, and free up water.
Electro-magnetic (EM) mapping is used to provide accurate and detailed soil type advice to link with variable rate irrigation systems. It uses electro-magnetic fields, emitting them into the soil and then measuring how far the field can travel in the soil profile.
The variations in electro-magnetic conductivity are linked to water-holding capacity variations that can be correlated with soil types. Lighter, sandier soil will have lower conductivity while heavier clay soils have high conductivity.
The mapping can be finely detailed and give an intricate picture of where soil types and properties change. When used with GPS and variable rate valve technologies on irrigators rates of irrigation can be set to alter as they pass over the various soil types.
Sarah Elliot from Precision Irrigation says early Landcare Research studies found that generally water savings of 10% could be made where average water-holding capacity of the soils on a farm varied by 50mm, with those savings rising to 15% if the variation in water-holding capacity was 100mm.
Elliot says three farms in Canterbury and North Otago that use Precision Irrigation VRI technology and have average water-holding capacities of between 71 and 125mm found water savings of 27-35% from soil variability alone.
Other benefits farmers with VRI commonly find include a decrease in power consumption, reduced track maintenance costs, and reduced runoff and leaching.
Reese says new environmental regulations require more evidence of good practice and farmers are likely to have to show they understand the fundamentals of soil and water dynamics.
They include an understanding of what the soil’s water holding capacity is, infiltration rates and how to manage soil moisture so that field capacity isn’t frequently breached.
Making more data readily available to farmers is important and projects are underway to increase weather stations so that information such as rainfall, soil temperature, evapotranspiration, wind speed, wind direction and air temperature can be accessed.
