November/December – 1997
Story Title: Booyong Hydroponics
Author: Steven Carruthers
STEVEN CARRUTHERS reports on a hydroponic lettuce and flower facility that uses bacterial and fungal organisms to control plant disease.
Some would argue that one of the strengths of hydroponics is its sterile environment, and the notion of exposing growing systems to bacterial and fungal organisms would be self-defeating, if not sacrilegious. However, there is a growing number of growers who report that certain micro-organisms when introduced into the system, do much of the work in helping plants produce better root systems and more vigorous and healthy foliage. Anecdotal evidence also points to a reduction in diseases such as Fusarium, Pythium spp, and Verticillium spp. According to one grower, the good bacteria seems to overwhelm the bad bacteria within the growing system.
“If ever we get a pythium problem now, it just means I haven’t been using enough bacteria,” explained the principal of Booyong Hydroponic Farm, Keith Suttenfield.
Situated in the heartland of the Northern Rivers, New South Wales, the Booyong hydroponic farm fills a much needed niche in the local and export markets for fancy lettuce and cut flowers. Equal distant from Lismore, Ballina and Byron Bay, it was here that Keith and Vivian Suttenfield decided to build a commercial hydroponics facility in 1985.
“We started off with two crops – strawberries and flowers. Within 2 days of planting the strawberries we had flowers, and within 5 weeks we had our first fruit, but we soon worked out that the labour cost of picking and packing was going to take away any possible profit,” said Keith.
After 9 months, Keith pulled the plug on the strawberry crop, but continued to grow flowers which were well received by the local market. Within a year he had doubled his flower production, and replaced his strawberry crop with head lettuce grown in gravel culture.
“We always liked the idea of having two separate crops, but we had enormous problems growing head lettuce. It was just a battle. We grew them for 2 years and probably didn’t make any money,” Keith lamented.
Keith and Vivian gradually replaced the head lettuce with fancy varieties. Today, the farm has a production capacity of 40,000 fancy lettuce and 35,000 carnation plants.
At the young age of 37 years, Keith is one of the founding fathers of the Australian Hydroponics Association and Lotus Red Network, a group of hydroponic growers who have combined their skills and resources to export fresh produce to Asia. He was first introduced to hydroponic techniques as a child in his native America, but never thought he would have the opportunity to work his own hydroponic holdings. Arriving in Australia in 1979, Keith and Vivian first established an oyster processing and distribution business on the north coast, before opting for a lifestyle change.
“We wanted to get into horticulture, and hydroponics offered quicker returns than growing tree crops which we also looked at,” explained Keith. “The technique also appealed to me.”
Keith and Vivian brought with them from the oyster business the skills in handling perishable products, and operating a direct marketing business. They also attribute their success to good on-farm management practices, plant observations and intelligent interpretation.
With all the support mechanisms, such as tanks and packing sheds, the Booyong hydroponic facility takes up 5 acres (2ha), which is terraced over a steep slope.
The flower facility consists of 10 sheds of varying size with carnation plants grown in Growool (rockwool) slabs for up to 18 months, producing 40-50 blooms before they are replaced.
The irrigation is controlled by a computer system that initiates the day’s first irrigation at 4am. From this point onward, irrigation cycles are controlled by a solar trigger linked to the computer, which measures the solar radiation in terms of calories. Once the calorie count reaches 200, the system initiates another irrigation cycle to 22 points throughout the facility.
The pH and conductivity dosing is also controlled by the computer system, however Keith prefers to manually control the lettuce nutrient
“We like to let the lettuce plants have a lot to drink during the day, especially in summer, and give them a good feed at night,” Keith explains.
The carnation plants are looking particularly good for this time of year (early winter). According to Keith the volume of buds is something he would only expect to see in October (early Spring).
“I think this has come about for two reasons,” Keith explains. “We had an unusually warm end-of-autumn, and we’re using a different foliar spray feed regime.
During the Autumn, Keith sprayed his crop with a high mixture of phosphorus and potassium (Foliar Spray PK2510). A second schedule of foliar spray was used in early winter, using potassium sulphate to build up the potassium levels. Leaf samples are taken every 3-4 weeks and the foliar spray regime adjusted accordingly.
“After looking at other crops, I feel that I’ve got an advantage – something’s happened that’s better,” Keith commented.
Carnation cuttings are imported directly from Europe via a Brisbane propagator, using the latest plug technique from Holland. The propagator has access to some 200 varieties of carnations, which has allowed Keith to expand his range of flowers. Chrysanthemums are also grown for the Mother’s Day market.
The fancy lettuce system utilises NFT (Nutrient Film Technique). With the exception of one small area, the bench-height tables are covered with retractable thermal shadescreens, which reduces plant stress during the height of summer when outside temperatures are typically in the high 30’s (°C), and sometimes up to 55°C inside the sheds.
“The thermal shade screens make a huge difference in summer,” commented Keith, “and as far as personal comfort is concerned, it’s so much more comfortable when they are across.”
Although Keith and Vivian initially propagated their own lettuce seedlings, they have found they have better quality control by buying seedlings in. “I have a far wider range of varieties to choose from, and it allows me to increase product uniformity by culling seedlings before they reach the adult tables,” Keith explained.
Keith and Vivian also grow a small range of herbs.
With scarce water resources, the Booyong farm relies on bore water, drawn from one of the deepest bores in the district (550ft). The water is pumped to a concrete tank (227,300L – 50,000 gal capacity), which is enough water to last 2 weeks in the event of breakdowns. The water contains small quantities of sodium (about 100ppm), and almost the same again of chloride. With a cF of 45 before nutrients are added, Keith understands the necessity to adopt good management practices to reduce salt build-up. These include ‘bleeding’ of the lettuce system regularly, unless there has been high levels of rainfall which tends to flush the system anyway. The carnation plants are also given plenty of fresh water with each irrigation, which results in more than the average run-off.
“Unless you keep a good regular program of flushing, there is a build-up of salts, not just of sodium and chloride, but potassium and nitrogen as well,” observed Keith.
In the early days, Keith and Vivian thoroughly cleaned the lettuce system between crops; anything they could do to minimise the transfer of disease was no effort. But all that stopped 3 years ago when they started using Amnite 100, a blend of 23 beneficial bacterial and fungal organisms.
Beneficial bacterial and fungal organisms are marketed in Australia under different names including Amnite 100, Get-Back-Teria, Ag-Bact L, Organosol and OGP, among others. Initially, it was used as a foliar spray, and put through the lettuce root zone, but Keith found the foliar spray caused too much bacteria on the leaves of the lettuce. He now restricts the friendly micro-organism to the root zone. For the flower crop, Keith uses the micro-organisms as a foliar spray, rather than through the roots where they tend to block the drippers.
“One very clear problem that it cleared up amongst the flowers is botritus, and whenever I don’t have enough bacteria, the botritus returns,” commented Keith. According to Keith, the ‘friendlies’ make the nutrients in the solution more available to plants, however he warns that the micro-organisms will not work properly outside of certain temperature parameters, or if there’s not enough oxygen in the system.
“I have found it definitely works for me, and we’ve found certain ways to apply it which helps it to work better, added Keith.
Gravel Filtration System
The lettuce system incorporates a fast-flowing gravel filtration system. Using a 1000 litre fibreglass tank, the filter consists of a series of different size gravels, from fine through to coarse grade. An inlet pipe extends across the diameter of the gravel filter, its underside peppered with large holes to disperse the nutrient solution across the breadth of the gravel filter, at a rate of 3 litres per second. The inlet pipe is covered with a ‘pantyhose’ stocking to act as a fine filter. The filter system is used to distribute the beneficial micro-organisms throughout the system.
“The gravel filter is an excellent area for the bacteria to exist,” Keith explains, “and I feel I’m getting the same type of result as the sand filtration system (Practical Hydroponics & Greenhouses – September/October 1995 – Issue #24), but at a much faster rate.”
Testimony to the health of the biofilter is evidenced by the colony of worms that live within the gravel.
“People say that inorganic fertilisers are not in ‘sync’ with normal biosystems, but to find worms in the gravel filter indicates to me that it is a very healthy system,” commented Keith.
Although there has been little scientific work done to support the claims of products such as Amnite 100, there is a wealth of anecdotal evidence to suggest these products deserve closer scrutiny.
The symbiotic relationship between plant root systems and beneficial bacteria and fungi is widely recognised by many horticulture growers. It is now understood that there are extensive interrelationships between micro-organisms and plant roots. Some examples include seed innoculants which are used to sow legumes to provide nitrogen fixing bacteria for their roots; the use of beneficial fungi like actinomycetes spp, which are used as an adjuvant to fertilisers applied to fields; and vescular arbuscular mycorrihizae (VAM), which plays a critical role in helping plant roots extract nutrients from depleted soils.
It is known that crops like lettuce, grown in recirculating NFT systems, eventually accumulate large populations of pathogens such as Fusarium, Pythium spp and Verticillium spp. They cause destruction of roots and leaves, leading to plant death. In some horticultural applications, treatment often involves the use of agricultural surfactants, which are used to suppress the development/reproduction of such pathogens. However, surfacants are not registered in New South Wales for use in hydroponic nutrient solutions, with the exception of Agral 500.
Surfactants mimic the hormone oestrogen. When they get into the aqueous environment, they contaminate marine and riverine animal species causing males to lose their ability to produce testosterone, thereby having a feminising effect. This problem has been clearly demonstrated in the Florida Everglades where alligators are failing to reproduce.
Medical scientists know that our intestines are full of millions of bacteria, which are responsible for many of the reactions that occur during digestion. They assist us in assimilating the nutrients in our food. It is now recognised that as we age, it is harder to maintain the population of friendlies in our gut. A depletion of beneficial bacteria leads to replacement and colonisation by harmful bacteria and fungi. An example is candida albicans, a harmful fungus that lives in the gut, producing harmful toxins that circulate in the bloodstream. This is why we are encouraged to eat yogurt daily, to replenish the friendly bacteria and maintain the balance.
Much work still needs to be done to fully understand the complex interrelationships between friendly micro-organisms and plants. Although controlled scientific experiments using products such as Amnite 100 have so far proved inclonclusive, strong anecdotal evidence suggests that these organisms seem to play an important role in the control and prevention of plant disease in hydroponic applications.