Published by City Farmer, Canada's Office of Urban Agriculture


Oval Pipes Make Sense For Tropics

An Agrovision Publishing Report
Geoff Wilson,
Executive Officer (honorary),
The Urban Agriculture Network - Western Pacific Office,
PO Box 85, Mt Gravatt Central,
Queensland 4122, Australia.
Phone 61 7 3349 1422
Fax: 61 3343 8287
Mobile: 0412 622 779

Oval pipes make great sense for hydroponics in the tropics and sub-tropics. Three hydroponic growers around Brisbane, Australia, so testify. I visited them with Des Boxsell, the man who invented and patented to clip-together oval pipe system that seriously challenges makers and marketers of hydroponic growing channels of rectangular or round cross section. It is sold under the "EllGro" brand. name.

But there's more to it than enthused user testimonial hich, after all, can be dismissed by sceptics as justification of a investment decision. Des has created a system of service and practical information around his clip-together system which is generally unavailable from his competitors. It is winning him international sales -- and chagrined competitors are now being outsold around the Pacific.

The latest sales of the Boxsell oval-pipe system have been to Hawaii and Malaysia, with one in the offing in Indonesia when current troubles subside.

A major reason is that the oval-pipe system is more forgiving in the heat of the tropics and sub-tropics than NFT systems in channels of rectangular cross section.

To be efficient, rectangular cross section channels must be held perfectly level by substantial structures, otherwise the channel can warp or buckle so that nutrient flow is mostly along one edge, with none at the other (see diagrams).

Perhaps more importantly, channel of rectangular cross sections in NFT systems in tropic and sub-tropic installations also allow the nutriet to take up ambient heat far too rapidly. Cooling of nutrient tanks can be the cost penalty.

Des says: "In sub-tropical Brisbane, for example, anyone can have good hydroponic growing in winter, when temperatures are relatively mild.

"But the testing time is in summer, when too much heating of nutrient in channels can be a hydroponic lettuce grower's nightmare".

Because of this, round channels have been favoured by many Brisbane growers to provide better control over nutrient temperatures at the root zone. They provide a deeper level of nutrient that makes take-up of ambient temperature more difficult.

However, a number of Brisbane-based hydroponic growers are now keen converts to the Boxsell oval-pipe system. An oval pipe is less restrictive to root growth than either the rectangular or round pipes.

It also has the favoured volume of nutrient at the root zone that reduces the problem of over-heating of nutrient at the plant root zone.

Growers starting from scratch with the "Ellgro" system also love the lower supporting structure cost, with only one line of adjustable steel posts serving six, clip-together, oval channels six metres long. There's a great saving in setting up labour cost, and minor earth movements are forgiven by the oval pipe, whereas an NFT rectangular cross section can warp badly.

The Boxsell design also makes the structures and the pipes very portable, a point likely to find favour among growers with a desire to move now and again for whatever reason. Per-urban land or rooftop space can be hired, for example, rather than owned.

However, a clinching point about Des Boxsell's system is his information service to customers, before, during and after a sale. He's always available to customers for a helpful chat about any problems.

As a former practical grower, he can pass on most valuable (and accurate) advice on a host of subjects -- from how to guarantee clean water, nutrient regimes, use of probiotics, to sources of the best seeds for any locality. He also provides wise words about good marketing of the hydroponic produce.

Such service is rarely available from competitors because most of their sales staff have not had the practical growing experience. Des is always ready to experiment, and to apply lateral thinking to a grower's problem.

Three growers either north or south of Brisbane who are staunch supporters of the "Ellgro" system for all the reasons outlined. Two growers are changing from rectangular or round cross sectionn channels to the oval system, and one started with the oval system annd is about to undergo a threefold expansion of it.

The first grower is Rudi Heesman at Mt Nathan. He began with round pipes, changed to rectangular section pipes, and is now changing again to "Ellgro" oval pipes.

His reasons are:

He has 28,000 channel holes in which to plant 10 crops of lettuce a year. This is about twice the production of 140,000 lettuce a year, which Rudi regards as a viable hydroponic farm.

What began as a hobby has been made a major revenue earner for about 10 years. The labour input is about 50 hours a week over seven days. His growing time for each lettuce crop from seedling planting to picking is about 3.5 weeks in summer and about five weeks in winter. He aims to always obtain premium prices.

The second grower is Jim Blackley, at Wamuran, who has two hectares of land (about five acres) . Forty "tables" of hydroponic channels provide Mr Blackley with 15,700 growing holes for seven varieties, but he has plans to expand the investment to channels with 50,000 holes.

Current yields is around 160,000 lettuces a year. At present he sells whole lettuces to restaurants and retailers, delivering produce twice a week. But the job is a seven-days a week commitment for him and his wife, Kerry.

The third grower is Ken Goodhew, at Woodford. He began hydroponic growing as a hobby, but now has invested in the "Ellgro" system with more than 24,000 growing holes, which enables a production of around 240,000 lettuces a year.

His hydroponics bean on round pipes in towers of six. But Mr Goodhew is now convinced that the "Ellgro" system is right for sub-tropical Woodford.

"It takes only about a third of the work of other systems. It also has no nutrient heating problems in summer," Mr Goodhew said. However, to make sure that nutrient heating was not a problem, Mr Goodhew installed a cooling tower.

He and his wife, Annette, work a seven day week also, supplying restaurants year-round. They also deliver to Brisbane twice a week. Most days the start time is usually 4.30 am and the day often finishes after 7.30 pm

"It's the only drawback," he said.

The testimony from these three growers was convincing. Des Boxsell certainly has developed an innovation of importance to many hydroponic growers, especially those in hot climates. The pictures speak for themselves.

Microfarms With Great Returns

The "Ellgrow" hydroponic system using oval pipes has an attractive rate of return on capital on microfarms around Brisbane. On a site about the size of a house building block (a quarter acre or about 0.17 or a hectare) an investment of about $30,000 enables a hydroponic grower to grow and harvest hydroponic produce worth about $130,000 a year.

The net return, depending on cost control and marketing skills, tends to be from $50,000 to $75,000 a year.

The quarter-acre, open-air units can be operated easily by a couple, especially one with children prepared to pitch in to help with daily chores of planting out seeds and picking and packing.

On the downside, there has to be a seven-day-a-week time commitment. But such microfarms around peri-urban areas, or on commercial rooftops in shopping strips or shopping malls, could be the future for a great deal of fresh vegetable production.

A similar microfarm may soon to be set up in Mt Gravatt, a Brisbane suburb, on a purpose-built roof decking. In a feasibility study now being completed, the "Ellgro" system is being included with vermiculture and aquaculture.

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Revised Thursday, February 10, 2000

Published by City Farmer
Canada's Office of Urban Agriculture