Precision Irrigation Gives Central Otago Farmer Peace of Mind
Oct 28, 2020
One way to cope with the changing climate and the usual vagaries of the weather is to build fat into the system. If you grow more feed than you need and carry a comfortable number of stock, you won’t end up close to the edge.
Another way is to control the environment.
Hamish and Jan Mackenzie own Kyeburn Station in Central Otago, they do both.
Kyeburn Station is 3300 ha and carries 200 Angus cows and up to 9000 ewes, crossbred or half-bred merinos. It is in the Maniototo, which is a dry region that gets 500 mm of rain a year with little or none of that falling in summer.
The property has 260 ha of river flats, with two Zimmatic centre pivots that irrigate about 180 ha, which gives Hamish peace of mind.
The irrigators guarantee enough feed to fatten stock and carry cows and ewes over winter. Sometimes there is too much growth and they have to top the pastures, but that is okay because they are building carbon in the soil and maintaining a safety margin.
The ability to irrigate crops is one source of security; another is having precise control over that irrigation.
One of the centre pivots is equipped with Zimmatic Precision VRI, which means it can apply water at variable rates according to a prescription map.
Hamish can target the application of water depending on the soil types in different parts of the paddocks, the type of crop, and its stage of development. For example, lucerne needs less water than pasture, and he can turn the water off cereals as they approach harvest.
Water is turned off permanently over tracks, gateways and boggy areas.
The brain of the system controls the speed of the pivot and valves on each individual sprinkler, which pulse on and off to ensure the correct amount of water falls on each area.
The Zimmatic Precision VRI system was installed in 2015, and the following year they added FieldNET. This is a remote irrigation management tool.
If Kyeburn Station had reliable cell phone coverage then Hamish could be controlling the whole system from his smart phone when out on his farm. But he can still use FieldNET to operate the Precision VRI system from his home computer.
He sets up his maps and rates, transfers it to a memory stick and plugs it into the control panel.
Kyeburn Station generally needs irrigation from mid-September through to May. It is used to fatten stock and produce silage and brassicas for winter supplements.
The Zimmatic Precision VRI system can be set up to adjust application depths according to readings from soil sensors, but Hamish has chosen to do it manually. If it rains, he turns it off.
Hamish and Jan have a water allocation of 521 litres/second from the Kyeburn River. Since using Zimmatic Precision VRI, their actual take has dropped to 431 litres/second. Theoretically, they could irrigate more land with the water they save, but that is not the aim. Hamish wants the security and reliability, not life on the edge.
Using less water saves electricity, so they have quickly recovered the cost of the variable rate irrigation system.
Two years ago Hamish and Jan took their security a step further and put in a buffer dam next to the pump. The dam holds 270,000m3and the pivot uses about 5 million litres per day, giving them enough water for two months.
“If there are water restrictions out of the river, we can still irrigate. This is what everyone has to do.”
The pressure is on around the country to care for water supplies – both what is taken out and what is allowed back in. Their Zimmatic system keeps Hamish and Jan ahead of council regulations because they use what they take and they take only what they need. There is little or no run-off.
The Precision VRI technology was developed by two Kiwi engineers and eventually acquired by US company Lindsay Corporation, which produces Zimmatic centre pivots and other irrigation technology.
“Zimmatic are really good irrigators and they are reliable. I get good backup from Lindsay. Most of the time they can explain anything over the phone,” Hamish says.
“They are a good bunch – really practical and always willing to help out. But the pivots are that reliable you hardly ever talk to them.
“With the Zimmatic centre pivots and the Zimmatic Precision VRI we are self-sufficient. We have not bought in feed for a long time because of the reliability of our water supply.
“I would hate to farm now without it.”