IrrigationNZ has spent the summer gathering data on farms around Canterbury to get a better, more accurate understanding of irrigation efficiency. The results, say INZ Project Manager, Steve Breneger, will provide a benchmark for progress.
“We’ve been on-farm for the past four months looking at how farmers are operating equipment, applying water, scheduling maintenance, monitoring soil moisture and run off – literally going through their farms with a fine-tooth comb. The data backs up what we already knew – that most farmers are operating within limits and are genuinely focussed on finding efficiencies.”
IrrigationNZ, in partnership with Environment Canterbury (ECAN), employed post-graduate Environmental Science students to undertake the four-month data collection. Their brief was to develop a clear snapshot of what was happening at farm level for a single zone (Ashburton).
“What we discovered during the programme was that most of the systems tested were within tolerance levels and over half of the respondents were undertaking some form of scheduling. On farms that weren’t meeting efficiency targets, the students then looked at potential causal factors.
“The value we gained was that not only did we have actual data from bucket testing, we also had insight from the students, they were able to add context and experience to gain a broader picture of what was really happening on the farm. Where they discovered some discrepancy between what the farmer thought they were applying against what they were actually applying, they were able to look at operational and maintenance factors as possible contributors.”
Enda Hawes was one of the farmers involved in the programme. He farms 360 hectares at Maronan, SW of Ashburton. He discovered his system wasn’t as efficient as he thought – “when the students first did the bucket test in January, it was only delivering 8.5mms. I should have been putting on 12.”
When the system was re-tested two months later, Enda thought he was applying 14.2 mms, in fact it was 12.2. “Clearly, we weren’t being as efficient as we thought. These results prompted us to have a look at what was going on and we discovered the system was losing pressure and was inconsistent at the far end of the pivot. We made a few adjustments and now we’re delivering greater efficiency all round. This process was great for proving the value of bucket testing.”
During the programme, students tested 244 systems on 131 farms. Primary land use included dairy, sheep and beef, deer and arable. Systems tested included centre pivots, laterals, travelling irrigators, hard hose guns and sprayline systems.
Distribution Uniformity (DU) is the key indicator for irrigation efficiency. Of the systems tested, 52% achieved good to excellent DU; 32% achieved fair DU and 16% achieved poor DU. Upon further investigation, possible factors contributing to poor DU were identified as being worn componentry, sediments in water supply and incorrect hardware being used.
In terms of Application Depth, which is a critical performance factor, of the systems tested, 37% achieved within +/- 10% of the desired application depth; 31% achieved +/- 25% and 32% achieved >+/- 25%. Contributing factors to poor results were identified as incorrect set up and commissioning during installation (including componentry), poor understanding of the system’s constraints, poor maintenance and technology failures.
“The programme really highlighted the importance of understanding your system and ensuring it is regularly maintained. In one case, we had a farmer whose DU and application depth showed poor results after the initial bucket testing. He discovered the operating pressure wasn’t high enough so he went out and replaced the regulators on his pivot and he got the service company to check the programmable set up and correct any errors. After re-testing, he’d turned his ‘poor’ result around- – achieving 99% of the target depth and overall DU of .85, which is considered excellent.”
Next summer, IrrigationNZ and ECan will extend the Irrigation Efficiency programme, employing more students to gather data from an increased number of zones.
Ultimately, says Breneger, this programme will tell a compelling story of change.
“We now have a benchmark to work from – we can clearly see where we started. Over time, we’ll be able to create a comprehensive, zone-specific snapshot of on-farm behaviour, which we can all use to effect positive behaviour change and support better environmental outcomes.”
ECAN Summer students, Will Wright and Beth Turner.
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