Quick Dips

The Travelling Houmi Show

As El Niño puts the heat on New Zealand, scientists have turned to good old-fashioned Kiwi DIY ingenuity to help them find a way to save thousands of litres of water a day in vineyards, orchards and farms.

The "travelling houmi" -- a galvanised steel hoop driven by giant elastic bands and a windscreen wiper motor from an old Vauxhall -- is operating 24 hours a day at Montana's Brancott Estate in Marlborough, collecting information about sunlight falling on the grapevines.

It is part of a massive three week-long experiment, the first of its kind in the world, being carried out by HortResearch and scientists from the US and Canada.

"Irrigation accounts for 85% of world water use, so exactly matching irrigation with crop requirements is one way of making every precious drop count," says Dr Brent Clothier, head of HortResearch's Environment and Risk Management Group. "But before the correct amount of irrigation can be calculated, it's vital to find out how much water the plants use and how much the soil can store."

To find out, the scientists are using sensors that are just one millimetre wide inside the vines, through to scintillometers that scan over two kilometres above the vineyard to determine the rate and mechanisms of water consumption by grapes.

They also wanted to be able to get up close to the grapes and be able to move along the row of vines without getting tangled, so they could collect data on sunlight hitting the leaves. The job needed to be done non-stop for three weeks. They had the instrumentation, but not the means, to do it. Whatever they used also had to operate without mains power, and fit into the back of a van.

So Palmerston North HortResearch engineers built the "travelling houmi" from scratch. The hoop is 2.7 metres in diameter and stands 2.8 metres above the ground. Data loggers and sensors are attached and it runs on 18-metre tracks either side of the grape row.

Toothed belts attach to each side of the hoop and keep both sides travelling at the same speed, so it does not twist off the track. The power problem was solved by the old wiper motor and gearbox, which runs relatively slowly and so "fitted the bill nicely" according to Brian Jardine, who was largely responsible for the project. A solar panel means it can run all day and even generate some power to last into the night.