After a month back out in the field it’s become clear there is an urgent need for tailored advice and services. Irrigation and Irrigation good management practice advice is all about what works for the farm in question not a blanket recipe.
We visited a client last week where the audit requirement was to ‘Do a Bucket Test’ to calibrate their system, and ‘Put in Soil Moisture Monitoring’ – the blanket approach. Both good things to do but were they the right actions for the situation?
They’d had a go at a bucket test but couldn’t make much sense of the results so had given up… they’d also bought a sensor which was giving them data but they were struggling to relate the information to their scheduling. These are not uncommon situations.
The client had a 60 hectare k-line system delivering 65 mm on a 12-day rotation. First impressions were the system was well designed, operated and maintained, particularly given parts of it were over 15 years old. A check of the as built design, then flow and pressure tests to audit the system confirmed good design.
But yes there was still improvement to be made. Putting things simply there’s two components to getting your irrigation right (achieving Irrigation Good Management Practice). Knowing when to turn the taps on and off and ensuring your system is up to scratch.
For knowing when to turn on and off there was a lack of any tangible evidence and detailed understanding around what they were doing but it was obvious from the conversation they weren’t just turning it on and leaving it running for the season – they’d worked out a basic system that accounted for rainfall. Hence the action to install a soil moisture meter. The sensor purchased was a manually read, single point measurement providing soil moisture status at the point of measurement and time. For the older k-line system with typically poor uniformity issues this data was of limited value.
So what is best in this situation? We proposed two options
- Using a soil moisture probe the better approach is to have a hand held probe taking multiple readings over the same area every few days and then average your results to produce a trend over time
- Or simply running a daily soil water balance – recording inputs (rainfall and irrigation) and outputs, in this situation daily Potential Evapotranspiration values.
Given the situation – a cut and carry low intensity grazing system – my preference is option 2 with the proviso of soils information being included.
Regardless of your monitoring system the one thing you must always do is understand how much water your soil holds – which involves digging a hole. It turned out there were a couple of very different soil types being irrigated on the property. One area had a moderately well drained 60 cm silt loam and the other a 30 cm stony sandy loam over stones (it was surprisingly uniform in both areas). The rooting zone in both cases occupied the full depth of the soil profile. This indicates deficit irrigation had been occurring – the roots had gone looking for water. The soil was the critical piece of information missing from the farmers equation.
So what did this all mean? Was the system up to scratch? System design was good hydraulically, but a more in-depth analysis of the soils meant that the management needed to alter. For the shallower soils applying 65 mm at a time was too much which means a move to twice a day shifting or reducing the current application depth over the 24-hour run-time plus adding additional lines to reduce the return period to 6-8 days.
Running a water balance for both soil types to work out when to start and stop irrigating is the most appropriate way to schedule irrigation for this property. A better investment to help with this would have been a weather station. The actions identified in the audit were nothing unusual but, in this situation, an alternative approach was needed to better tailor the spend and achieve the right result.
It was a great afternoon at a stunning location and the client must have also enjoyed the session as they mucked-in with the testing and picked our brains as to what they needed to do – the homemade chocolate chip muffins afterwards were also much appreciated!
There is a growing need out there for people on the ground that know how to trouble shoot and problem solve irrigation. This is the gap in the market the Water Strategies team will fill. It’s about putting in place the right solution for each farm.
Water Strategies consists of ‘four middle-age blokes that know stuff’… and before we get slated for that statement please be assured we are actively working on our diversity policy – there will be a number of ‘ladies that know stuff’ joining our team in the not too distant future!
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