Growing greens without soil

Ian Kerr standing among the hydroponic units. Photo: Catherine Fry.

Waipa landowner Ian Kerr has several enterprises on his 22 hectare block near Lake Karapiro, but the pure, well balanced water found on the property proved to be the perfect mix for growing hydroponic plants.

A 40m by 20m, double-tunnel, commercial greenhouse is home to a thriving hydroponic plant business. At any one time Ian has 10,000 units growing, with a maximum capacity of 15,000 units. The seasons dictate what is grown, so the produce varies through the year.

Natural order

“They’re all grown without the use of pesticide and fungicide spray,” says Ian. “We aren’t certified organic but it is definitely a big plus. I use companion planting where it helps, and sparrows and spiders provide good pest control. I’m a great believer in using the natural order of things as much as possible.”

Scrupulous cleanliness is crucial, with the gullies being water blasted between crops, and the flooring of weed mat covered with crusher dust changed every couple of years to prevent soil-borne bacteria and fungi establishing.

The system is fairly automated once set up. Heat control in the greenhouse is important as when the temperature rises above 18 degrees Celsius the plants are in danger of wilting. The greenhouse sides are rolled up and they run fans. When the temperature drops below 18 degrees Celsius, it is a little more complex.

“Under 18 degrees Celsius slows growth,” says Ian. “We have heaters that automatically kick in to warm the nutrient. As long as the plants have warm feet they keep growing, even if the air temperature is colder.”


The water from the property is so balanced it doesn’t need anything added other than the secret nutrient formula, which is mainly fish fertiliser and kelp powders. The plant is very dependent on power for the water pumps and for the computer that monitors the pH of the nutrient, adjusting the levels of the each nutrient as required. Alarms go off if there are problems and the computer also generates reports.

The greenhouse has three possible zones, meaning that three different nutrient mixes can be controlled and monitored at any one time.

“Water use is extremely efficient,” says Ian. “Old water is recycled, tested by the computer and topped up with nutrient as required. We replace the water completely each month.”

Despite sounding complex, Ian only spends around 20 hours a week tending to the plants, and that includes time at the farmer’s markets selling the produce as the Lettuce Man. Ian is one of the founder members of the Hamilton and Cambridge Farmer’s Markets. He puts the success with this business down to a few factors.

“A daily walk-through – as you can’t beat a visual on the plants – our amazing water, lots of luck, and playing them good music 24/7.”


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