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  • Writer's pictureMike Casey

UFO Water Requirements - We got our consent approved!

The most important ingredients for horticulture are sun and water, and because Central Otago has plenty of sun, we also need plenty of water. Recently we received some good news that the Central Otago District Council had accepted our argument that UFO orchards require more water than traditional growing operations and that we had our water bore consented for the volume of water we needed for a full production cherry orchard in a few years time.

Water is always a considerable risk, especially when buying a property that doesn't have all the water consented for your future plans. Luckily, for us we were able to get a consent to drill a bore easily, we struck water on your first drilling attempt and, more importantly, our local government body accepted our argument to allocate the water-take we requested.

Striking water at 27 metres depth
Striking water at 27 metres depth

Although it wasn't expressly mentioned in the consent, I believe our approach of an efficient irrigation system and our renewable focus helped alleviate concern regarding over allocation of water for our project.

Completed Water Bore with 15kwh submersible pump
Completed Water Bore with 15kwh submersible pump

We opted for 2.3 mm ground based drip-lines. These drip-lines have integrated internal drippers which allow a total of 2.3 mm of water to flow out of them directly to the root zone of the trees.

Ground based drip lines
Ground based drip lines

1 mm per hectare is 10,000 litres per hectare and therefore we have the capacity to irrigate 23,000 litres per hour per hectare.

During peak production a UFO cherry orchard will require anywhere between 50000 and 65000 litres per hectare per day, or in our case up to 390,000 litres per day for our entire orchard. In other words, we are looking at close to around the clock irrigation during warm, dry peak periods and you can begin to appreciate the solar payback period is brief when you are replacing a diesel pump-set!

Increased Light means Increased Water

The UFO growing strategy allows us to plant 1650 trees per hectare based on a row width of 2.25 metres and 2.75 metres between each tree. This increased density leads to a higher yield per hectare and greater light inception, which means our demand on water increases significantly from traditional growing operations.

The science is fairly straight forward, light interception by planar canopies (UFO style) is 20% to 30% greater than conventional single leader trees^1. An increase in light inception increases tree yield and hence a matched increase in nutrients and water is required to maintain cherry quality and size.

On top of this, UFO orchards require more water in their earlier years as we grow the trees to fill their space allotment along the trellis system. The added leaf interception of light means our trees grow faster and reach maturity faster. I reached out to Greg Lang from Michigan State University for a quote to back this up.

“At orchard maturity, water use per hectare will be proportional to leaf interception of light, so the number of trees per hectare is less of an issue except during the orchard establishment years - that is, high density young orchards will require proportionally more water until they reach “maturity” (filling the space they have been allotted), and they will reach maturity proportionally earlier than a low density orchard. So, until maturity is reached, they would likely require a bit more than twice the water of a traditional orchard.” Greg Lang, Professor of Horticulture - Michigan State University.

  1. Light interception and yield of sweet cherry and apricot trees grown as a planar cordon orchard system design Schofield, Stanley, Shurmann, Marshall, Breen, Tustin, Alavi (all Plant and Food Research NZ)

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