4 minute read
Hydroponics a focus in controlled-environment growing
HYDROPONICS A FOCUS IN
CONTROLLED-ENVIRONMENT GROWING
Words by Geoff Lewis. Photos by Trefor Ward
Cody McNaughton with an injection manifold for an inline ’3 part plus ph’ injection system
There is a surprising amount going on in Tirau – a small but growing south Waikato town halfway between Hamilton and Rotorua. Among the activity is PGO Horticulture, a business that combines a mix of garden supplies, electronics and plumbing.
Technical director, Neville Stocker, is the second-in-line for the three-generation business and has “absorbed chemistry by osmosis.‘ Son of British immigrants in the early 1970s, it all started with Neville‘s dad, Grenville Stocker who was an industrial chemist working for Dominion Salt at Mount Maunganui. He had access to an atomic absorption spectrograph which could give quick analysis of water samples, and quickly realised how accurate water analysis was imperative in the increasingly popular hydroponics sector. Hydroponics is an agricultural system growing without soil by feeding plants a carefully formulated and monitored solution of nutrients dissolved in water.
A form of closed-system growing, hydroponics holds a variety of advantages over growing in soil and the outdoors. It is not dependent on the vagaries of the weather and a defined amount of water can be recycled, with nutrients that have not been picked up by the plants filtered out. Water use is greatly reduced, and nutrient run-off minimised, with many recirculating systems having no run-off. It is far easier to control nutrients and keep plant pests and diseases at bay rather than dealing with the random factors delivered in the natural environment.
Being able to control the majority of growing factors in an operation allows for far greater crop yields than can be achieved by other means.
Solar-powered hydroponics systems are currently being studied by Elon Musk‘s SpaceX organisation as a means of growing food for future colonists of Mars too. However, in earlier days, Stocker found himself the target of terse comments at times, even having hydroponics compared with ‘black magic‘.
Neville Stocker demonstrating the use of the Autogrow ‘MultiGrow‘ controller made by Autogrow Systems Ltd Northshore and an iHydro unit made by Electronics Ltd Christchurch LED Grow lights that can be tailored to the needs of a customer‘s specific crop
“I would be abused,” says Neville. “The perception was that the system was unnatural, and the public‘s awareness of hydroponics meant the quality of tomatoes was blamed on hydroponics. But it is resource efficient, creates minimal runoff, and can make growing pesticide-free easier. The grower can grow what the buyer wants.“ Stocker says hydroponics are amenable to many crops, widely used by big growers of capsicum, tomatoes and chillies and are now booming in the berry industry. A large proportion of salad and culinary herbs are produced this way too. Watercress is a great example, as it cannot be ‘quality assured‘ if gathered from a natural stream. The system has become critical to growers growing for specialist buyers like big fast-food outlets that require consistency of product. The progressive banning of ozone-depleting Methyl Bromide, a once popular soil steriliser used for outdoor crops, also hastened the move indoors to controlledenvironment growing, Stocker explains. “You have to forget what you learned about growing in soil,” he says. “In a closed system, you measure the electrical conductivity of the solution to determine the quantity of minerals in it. If you‘re controlling electrical conductivity and pH [acidity/alkalinity] of the solution, you know how and when plants absorb nutrients and learn to put in what the plant wants. “PGO Horticulture makes a replenishing mix which is relative to what the plants are taking out and creates mixtures tailored to the needs of different growers in crops including lettuce, culinary herbs, salad greens and watercress. “I haven‘t built a greenhouse system in eight years that hasn‘t captured all the run-off. A lot of growers are getting into recirculation and aim to minimise root and vegetative growth and maximise yield. One of our strawberry growers was getting 1.5 kgs per plant last season, where growers commonly would be aiming for around 1kg.“ PGO Horticulture works closely with greenhouse and tunnel house builders supplying equipment and designing systems which has seen them contracted to design and supply hydroponic systems in India, the United States, the Philippines, Indonesia and Nuie.
Currently the business is keeping a careful watch on its raw material supply situation due to uncertainties around the supply of phosphoric acid from China. Phosphoric acid is commonly used to control pH levels in hydroponic systems.
