Issue 51: OH-Farms – Tropical Greenhouse Growing

Issue 51
March/April – 2000
Story Title: OH-Farms – Tropical Greenhouse Growing

Singapore has a range of tropical hydroponic technologies that work well. GEOFF WILSON visited an enterprise using a modified ‘dynamic root floating’ system (DRF), to produce pesticide-free vegetables.

Hot and humid climates demand modification of hydroponic systems. In Singapore, Oh Chin Huat Hydroponic Farms (Pty) Ltd, is one commercial enterprise that has successfully adapted its growing techniques to suit its climate.

Commonly called “Oh Farms”, this S$2.5 million investment comprises 215 tropical greenhouses, on 2.4 hectares of the 1500 hectares now devoted to the city-state’s six agrotechnology parks. Begun in 1991, the investment was boosted in 1996 after a S$2.2 million research project to develop hydroponic cultivation of aromatic herbs. This study met the objectives of extending the range of produce Oh Farms could offer customers, and upgrading the company’s research capabilities. Generous support and funding was obtained from the Singapore Government’s research and development assistance scheme. This led to a research advisory team that comprised management of Oh Farms, officers of the vegetable and foodcrop section of the Singapore Primary Production Department, plus consultants in plant sciences and chemistry.

Top: The Oh Farms enterprise was developed in stages between 1992 and 1995.

Bottom: Schematic view of the farm’s layout.
Computer technology helped design greenhouse structures that minimised heat traps and increased natural ventilation over the plants. Then, in 1998, a new growing system designed by Dr Kao Te-Chen of the Taiching District Agricultural Improvement Station in Taiwan, was introduced. The ‘dynamic root floating’ (DRF) system was modified somewhat, and built by Oh Chin Huat Hydroponic Farms, with the help of the Singapore Primary Production Department (PPD), to suit Singapore’s equatorial high heat and humidity. The R&D work carried out by the research advisory team also greatly helped with the aim of producing pesticide-free produce, something of great concern to the PPD, on behalf of Singapore’s people.

Each of the greenhouses comprises a gable-roof frame, made from light pipe, over which a rain-shedding plastic sheet is attached as roofing material, and insect-screening plastic mesh used for sides and ends. The structures each measure 2.1 metres wide by 18 metres long, with a gable height of 2.1 metres. They appear to be as easy to assemble as any child’s Meccano set!

Inside the houses are black plastic-lined troughs, containing nutrient solution to a depth of about 5 centimetres. It was felt that nutrient film technology (NFT) would be unsuitable, because of its uptake of high ambient temperatures. The troughs have supports for polystyrene trays with seedling holes which, after planting, are placed in the greenhouse until harvest.

Each greenhouse produces between 80 to 120 kilograms of vegetables, depending on the variety. Oh Farm’s workers harvest 10 greenhouses a day (the average yield is about one tonne of marketable vegetables a day) and replant them for the next crop. The average crop maturing time from seedlings raised on the property, is thus about 22 days.

According to Ore Yeok Keong, Executive Director of Oh Farms, about 75% of the company’s hydroponic produce goes to Singapore’s supermarkets, about 15% to wholesalers, and about 10% to food service customers such as hotels and caterers. He believes the modified DRF hydroponic system his company uses overcomes problems of tropical heat in the following ways:

*The spaced greenhouses have excellent air ventilation. The relatively small size of each unit allows the best use of wind movement, so that less heat is trapped inside the greenhouse.

*The culture beds are fully covered, and their unique design allows the nutrient solution in contact with the roots, to be maintained at 27 to 28°C. He said the air space above the nutrient solution in the troughs, stimulated vegetables to develop aerial rootlets which provide adequate oxygen to the root zone.

Another advantage of the DRF hydroponic system is that isolation of units prevented the spread of diseases if they broke out.

“Nutrient solution for each group of six greenhouses are supplied by one, isolated nutrient tank,” Mr Ore said. “The risk of disease break-out over the whole farm is minimised, so that production will not be disrupted completely in the event of infection.”

“We have chosen to formulate our own nutrient solution, after years of experimentation with vegetable growing in the hot tropics, ” he said. “All our nutrient chemicals are imported.”

Pesticide-free Produce
One of the major sales points for Oh Farms is that its hydroponic produce is brought to customers pesticide-free. This results from strict hygiene in the seedling nursery and growing unit, plus elimination of insect pests reaching the growing crop – the insect netting is extremely effective.

Mr Ore said that Oh Farms conducts farm tours, especially for students from Singapore’s many schools interested in learning about hydroponic technology.

“We educate our consumers that there is another, efficient way to farm vegetables, and get them to see, physically, that vegetables from our farm are really pesticide-free due to the unique way of cultivation,” he said.

“Oh Farms helps schools to set up a complete greenhouse unit using the DRF hydroponic system. We conduct lectures in conjunction with the teacher in charge, and we also guide them for two complete crops,” Mr Ore said.

The equipment for the system is made in Singapore and the estimated cost of a turn-key DRF operation is around S$1 million for every hectare of hydroponic farm (land supplied).

Oh Farms, who are the only company supplying fresh, local herbs to the Singapore market, is now expected to be one of the significant companies assisting the advance of tropical hydroponics around the world.

A Family Enterprise
Oh Ah Guan is the Managing Director of Oh Chin Huat Hydroponic Farms (Pte) Ltd, which is named after his grandfather. Like other Singaporeans who have moved into hydroponic investment since 1986, he was originally a pig farmer, rearing 22,000 pigs a year.

Singapore’s Government decided that the city-state had no room for pig farming, but it wished to encourage vegetable growing using hydroponic technology. Mr Oh saw hydroponics as a good business opportunity. He went to Taiwan to learn about hydroponics and the high technology vegetable growing being developed there.

Oh Farms started out growing tropical vegetables, but then switched to temperate climate salad vegetables such as butterhead lettuce. It now grows herbs as well, including rocket, dill and English chives.

Oh Farms is run by 12 family members, and the company has three directors other than Mr Oh. They are Ore Yock Lee, Ore Yock Pin and Ore Yeok Leong.

Oh Farms will be visited during the week-long Singapore Tropical Hydroponics Study Tour in August 2000 – see page 82 for details.