Wednesday 23 September 2015


Being an Irrigating Farmer has many benefits with increased land value and production to less reliance on rainfall events being at the top of the list.
But with these benefits comes responsibilities and duties to ensure success at being an irrigating farmer.  So, what is involved?

1. Regular System Maintenance

1.       Irrigation System checks should be undertaken pre-season and at least twice over the irrigation season.  This involves doing pressure tests, checking sprinklers and nozzles, cleaning out filters, checking and fixing leaks.  Click on the link below for checklists and guides.

2. Irrigation Evalulations

Irrigation Systems need to be evaluated much like getting a vehicle Warrant of Fitness.  Evaluating your system allows you to check that it is working to the design specifications and performing as you would expect.  High distribution uniformity (how evenly the system applies water) is the key to achieving an efficient and effective irrigation system.  

Ideally, irrigation systems should be ‘farmer’ evaluated annually using the ‘Irrig8lite’ guide -  

Should your system show low performance, a full system evaluation should be undertaken by a qualified evaluator:

3. Measuring Soil Moisture

Measuring your soil moisture is the BEST way to manage and schedule your irrigation efficiently.  If you don’t know what your soil moisture content is, it is likely you are either under irrigating or over irrigating which can be detrimental to your crop and/or the environment.  There are a number of options when it comes to measuring soil moisture whether it be an on farm service or telemetered continuous soil moisture sensors.  

The Irrigation Season has already arrived for some and is fast approaching for others.  If you haven’t completed your pre-season system maintenance checks already, now is the time to do it!

Tuesday 15 September 2015

EM Surveying and Water Holding Capacity

In recent weeks we’ve been through the calendar of EMSurveying, A day in the life of an EM Surveyor and The value in ground-truthing your EM Survey in amongst other informative posts from Lindsay NZ and HydroServices. This week we’re going to shed some light on how an EM Survey by Agri Optics can be used to evaluate water-holding capacity of the surveyed area.
Predominately our clients ask us to conduct an EM survey for them to determine the differences in their soils with a view to varying their irrigation depths on the different soil types; however we can adapt the EM Surveys for many different uses, one of these being to evaluate water-holding capacity variation.

The DualEM sensor works by emitting an electro-magnetic field into the soil and measuring the returning conductivity of the soil. The conductivity of the soil in New Zealand is affected mostly by soil texture and the amount of water the different soil textures can hold (the more water the soil can hold the more conductive it is). The readings can also be influenced by salinity, however other than a few isolated areas in NZ we don’t have an issue with salinity affecting the readings. 

Figure 1: DualEM sensor being trailed behind our light weight Polaris

To fully relate the EM readings to water holding capacity (WHC), ground-truthing is needed to quantify the actual WHC at different locations as the EM Survey only measures relative difference of one area compared to another. As we have mentioned in previous blogs we create a map of EM zones and within that locate sample sites for each zone to be ground-truthed. The ground-truthing is then carried out by typically HydroServices using their neutron probe and our agreed protocols. They then provide us with the water-holding capacities for each different depth. From this we then create a map of WHC variation across the surveyed and provide a report back to the client of these additional maps with description on correlations of WHC and EM and recommendations on how these maps would be used to implement more efficient irrigation.  

In addition to getting accurate WHC maps and the associated report back the client can also use the ground-truthing sites to help site soil moisture probes and if the probes are installed before the ground-truthing is completed, the ground-truthing reading can also be used as one of the field calibration readings for the soil moisture probes.  

Figure 2: Water-holding capacity map created from an EM map

All of this information helps the client get the most of their EM data and make efficient use of their water by matching the water to the different zones and then monitoring moisture levels with their moisture probes. If the 2015/16 season is going to be as dry as forecast then making every drop count will be crucial. We not only conduct the EM surveying we can now also provide our clients with AquaCheck soil moisture probes to help manage your irrigation as efficiently as possible. Visit our website or give Jemma or Chris a call to discuss any of the above.  

Tuesday 8 September 2015

Variable Rate Irrigation Pioneers

Ashburton cropping farmers Eric and Maxine Watson (Rangitata Holdings) were the South Island’s original Precision VRI pioneers. Ordering four VRI systems in 2008, after only two systems had been built and tested less than twelve months earlier, Eric and Maxine took a lot of trust and belief that the system would achieve what Precision Irrigation claimed.

This 3 News clip has been bought out of the archives from 2008. Eric and Maxine Watson along with Stu Bradbury, one of the engineers who developed the technology, showcasing the first system up and running in the South Island. And the results exceeded their expectations. The Watsons now have seven out of their nine lateral-move irrigators fitted with Precision VRI. 

The Watsons farm 490 hectares on the Canterbury Plains, with annual rainfall of 600mm, growing a wide range of crops on different soil types. In 2005 Rangitata Holdings water right restricted their annual and daily water take, so they started looking for ways to stretch their available irrigation water. With an annual water volume of 1,183,500m³, 3.7mm per hectare per day and 5ha of irrigator overlaps, VRI was considered as the solution to save water where it was being wasted. An unlooked-for advantage was the negated need for turning taps off and on when watering in pivot mode.
At least partly as a result of maximising water efficiency, and being able to prove minimal wastage, ECan raised the Watsons’ annual water volume to 1,420,000m³, 4.1mm per hectare per day. This consent only permits pumping 270 litres per second across all pumps. When one irrigator is watering in an over-lap situation or using different rates over different crops, they are able to use the saved water to turn on another smaller irrigator elsewhere on the property, thus ensuring soil moisture levels are maintained at critical times.

“It’s a great system with a big future... Now that I have VRI, I wouldn’t want to run the machines without it.”

Caption: Eric and Maxine say that the Growsmart Precision VRI system exceeded their expectations allowing them to maximise the use of their limited annual water volume allocation.

The couple’s dedication to efficient water use has seen them recognised with numerous awards including the 2011 Canterbury Ballance Farm Environment Award and the Environment Canterbury Water Efficiency Award. The Watsons say they were just doing what was needed to get the best out of their limited water take. Once they identified the greater efficiency with Growsmart Precision VRI, the opportunities snowballed. 

Eric and Maxine had the property electro-magnetically (EM) mapped and the soil water holding capacities quantified. Soil moisture sensors were installed to measure the actual moisture content of the soil. This allows the Watsons to schedule the correct amount of irrigation to individual zones which is then applied by the intelligent Growsmart Precision VRI system. This results in the crops getting the exact quantity of moisture required and no water is wasted. Resulting in a considerable saving of 15% of water that can then be used elsewhere.

"Being able to match application rates to the exact amount of water needed to ensure the soil has enough moisture is important to water efficiency and means that over-watering of crops is eliminated."

For More information contact your local Zimmatic by Lindsay irrigation dealer or visit