Omarama farmers soak up irrigation advice

'Get to know your irrigation equipment better' was the clear message at a water efficiency field day held near Omarama in March.

Hosted by the recently formed Ahuriri Catchment Collective, the event was held at Twin Peaks Station before COVID-19 restrictions began and supported by Irrigation New Zealand and Environment Canterbury.

Steve Breneger, Technical Project Manager for Irrigation New Zealand, met with 19 interested Ahuriri catchment farmers to talk through practical tips to help reduce their water losses under irrigation.

The field day came about through recent on-the-ground work to help irrigators in the catchment operate sustainable farms with minimal environmental risks.

Key messages from the field day

  • Maintain your irrigation system to apply water efficiently.
  • Work with professionals and ensure that there's a clear understanding of what they will do for you.
  • Use your knowledge of soils, climate information and your irrigation equipment, to apply the right amount of water that will satisfy plant needs and minimise any drainage.
  • Keep good records to help you with your maintenance and irrigation decisions, and for supporting your audits.

Ensuring irrigation equipment is up to spec

Breneger told farmers to ensure their irrigation equipment could achieve the mandated 80% efficiency, and that farmers knew how their irrigators should be operated to reach this performance standard.

He said New Zealand irrigation standards and performance was amongst the top three internationally. "Design standards have been operational since 2012, to help us achieve our efficiency targets.

“You need to make sure that your new irrigators are designed to the NZ standards and when you install new irrigation, that your supplier commissions it to check it meets its design specifications. Also, they need to give you a full report on its performance, covering operating pressures, application rate and distribution uniformity,” he added.

When asked what farmers should do if they have an older irrigator that did not have a commissioning report, Breneger advised that farmers need to get a professional to carry out a capability assessment for them, which supplies similar information to a commissioning report. 

He noted that performance tests, which would include a bucket test, are there to identify performance issues that operators cannot see.

“Don’t carry out performance tests until you are sure you have fixed up everything that you can see, for example, blocked or missing nozzles and filters, faulty end guns and leaking hoses."

Assessing soil moisture levels

The farmers were keen to hear about how best to assess soil moisture and how to use that information to get the best value from their irrigation.

Advice given at the event was that soil moisture between the plants’ stress point and field capacity is the aim. Allowing a gap of around 20 percent below field capacity is important for reducing drainage risk in the event of rainfall after irrigation. In the peak of the irrigation season, farmers need to try and manage soil moisture closer to the fill point, and at 80% in the shoulders of the season.

The triggers to initiate the first irrigation at the start of the season are a combination of soil moisture and soil temperature. Breneger advised that 11 degrees Celsius was the recommended soil temperature trigger, if soil moisture levels were adequate. If the soil was dry, the soil temperature could be as low as eight degrees Celsius.

“Keep in mind that irrigation water will cool the soil and slow plant growth, and that this effect can last for up to four days,” he said.

The group then talked about the many soil-moisture probes and sensors available. Information was shared around gaining understanding on where they should be placed, that they need to be calibrated and that portable probes need to take 10 readings for each block to get good information for irrigation management.

Farmers had a good discussion about networking soil moisture sensors and the use of wireless connectivity to relay information between the outlying sensors and the main sensor.

Exploring water penetration

Field day hosts Mark and Bronwyn Becker also demonstrated how wet the soil became immediately after the irrigator had passed over the pasture.

With 5mm of irrigation water, the wetted area extended just over 60mm into the topsoil (after 2mm had been lost through interception by the pasture and evaporation on a sunny day with a slight breeze).

The conclusion was that there were times where applying 10mm per application would result in more water penetrating the topsoil and 20% being lost in evaporation and interception, rather than the 40% that was lost at the field day visit example.

The group also discussed options for managing irrigation, where there were farm tracks and different soil depths under the irrigation pivot.

Working towards a sustainable future for Upper Waitaki

Facilitator for the Ahuriri Catchment Collective, Stevie Young, outlined the goal of operating farms sustainably now and in the future, to support a sustainable community in the Upper Waitaki.

She said good on-farm management and business practices were important to achieving this.

Young is employed by Seed Force who support her in the role of the facilitator for the Collective.

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