Issue 44: NFT Lettuce – Californian Style

Issue 44
January/February – 1999
Story Title: NFT Lettuce – Californian Style
Author: Roger Fox

In northern California, what started as a trial of “Aussie-style” NFT growing, has expanded into a combined fancy lettuce and hothouse tomato enterprise.

Outdoor NFT systems have never really been embraced by American growers – even in warmer regions. So when Michael Christian from American Hydroponics returned from a trip to Australia in 1994, he started thinking about how he could emulate the fancy lettuce systems he had seen “Downunder”.

Charged with the enthusiasm of a new idea, Michael and his business partner, Genaro Calabrese, started building 10 lettuce tables, a tank shed and other support structures on a small acreage outside Arcata, in Northern California, where American Hydroponics is based. For Michael and Genaro, both former builders, the project was fairly straightforward.

“We pretty much emulated the system we had seen in Australia,” Michael recalls, “and got it going with the prospect of breaking even financially. We wanted to learn about growing, just as long as it paid for itself, because the information we would gain from this would be really valuable to our business.”

With an expanding commercial arm to their hydroponic company, the partners saw in NFT an intensive growing method with great potential for lettuce production in many parts of the US. And the best way to establish its credentials was to actually have a system up and running.

The lettuce growing system they developed features 10 tables, 48′ in length, each comprising 8 channels. The whole operation runs on 200 gallons of nutrient, uses a simple 1hp. pump, and when fully planted is run by one person on only 20 hours a week. As a learning exercise and a display system that pays for itself, it has proved ideal.

In the near future, the scope of the operation is soon to expand. Having moved away from the retail side of the business, Genaro is now planning to run the lettuce farm as a full time business, in conjunction with an adjacent hydroponic tomato greenhouse. Already, there are plans to add another 20 NFT lettuce tables and start marketing the hydroponic produce into the populous areas of Santa Rosa and San Francisco further to the south.

Outdoor NFT – Californian-style
The lettuce seedlings are all raised on-site, in a small greenhouse dedicated to the purpose. The seeds are sown into oasis cubes and are subsequently transplanted into the growing channels, cube and all. By raising the seedlings on site, Michael believes they get the right level of control over the plants’ growth rate and their final quality.

“What we do in our seed house is heat up the root cubes and run lights. So by the time the seedlings get to the growing bench, they’ve already got a momentum going – and then we gain a week. Before we did that, we were pushing 14 weeks.”

Inside the seedhouse, under-tray heating keeps the root medium warm for the germinating seeds in winter. Metal halide lamps on a Suntrack light mover run all day in winter, when light levels are at their lowest.

“We have days in winter when you don’t see the sun – not a peep – and these plants are just ‘jamming’ in here,” Michael says.

The environmental controls of the seed house system let them produce perfect young plants with a good headstart. And a good start ultimately gives a good product, they have found. After two weeks in this environment, the seedlings are hardened off in another shed for two weeks, before being transplanted into the tables.

Outside in the benches, the lettuce are grown all year round – including right through winter. This is made possible by individual poly covers over the tables, an idea which Michael picked up from New Zealand. While snow doesn’t feature in this part of the US, winter brings a lot of rain and strong winds.

The covers are supported by a metal framework above the table, creating a sort of mini-greenhouse or ‘cloche’ when required. During the recent, very wet winter season in California, the covers were down for around 5 months. For wind protection, walls of wind mesh have also been erected around the growing area.

“We get about 80 mile-per-hour winds up here, so we really get hammered,” Michael says. “When we first put these in, we had lettuce flying everywhere!”

However, with the benefit of experience, Michael says he would do things differently next time, dispensing with the individual table covers, which can make harvesting difficult in bad weather, and instead running a cover over the whole area.

“What we would do again is cover the growing area with a clear-span of single poly, and then wind-shield the sides – probably with 10-foot side walls.”

The NFT system currently has a capacity of 4500 plants, and turns out around 1000 plants a week in summer, and 400-500 a week in winter. The turnaround time for a crop is 8-10 weeks in summer, and 12-14 weeks during winter’s grey and rainy cycle.

The lettuce are fed a two-part nutrient called ‘Evolution Solution’, which was specially developed for the purpose by American Hydroponics. The company now sells this formulation commercially.

The solution conductivity is kept around CF11 (1.1mS/cm) and both conductivity and pH are automatically controlled via a Dosetronic unit, which provides a constant readout display of the values. Installing this controller has offered major operational benefits compared to hand dosing, as Michael explains.

“Now we’ve got the controller, we’re dumping about every 6 weeks. Before that it was about every 3 weeks, because it was hand dosed and everything got out of whack much quicker. The doser has made a huge difference.”

The nutrient concentrates are held in A and B tanks (30 gallons each) and the main nutrient tank has a capacity of 200 gallons and features a venturi valve for oxygenation, and a float valve for automatic water top up. A flow rate of 1 Litre per minute is used for the NFT system.

“We’re doing it slower and slower,” Michael says. “Grenville Stocker from New Zealand says the slower you can get it the better. We had one table just on a trickle and there was absolutely no difference between it and the one next to it.”

Meeting Market Demands
The enterprise started with a selection of 20 different fancy lettuce varieties, but this has now been fine-tuned to those that sell the best.

“We started with 20 varieties and we found out that the stores liked mignonette, butterhead, red oakleaf and cos, so we just reduced it down to those varieties. With the cos, we went through about 3 or 4 different varieties, till we honed that down to the best one.”

Michael is especially pleased with a recent red oakleaf variety they have secured – ‘Ferrari’ from De Ruiter Seeds.

“It’s a tight head red oakleaf, which is so unusual. We’ve tried 3 or 4 others, but there’s no way anything comes close to this,” he says.

The bulk of the farm’s lettuce production is sold through Farmers Markets, of which there are several in the area. These markets, Michael says, have become enormously popular in the US and, because the grower is selling directly to retail customers, they therefore get better prices.

For a period, the enterprise was also growing the Asian vegetable Bok Choy, specifically for some ‘up-market’ restaurant customers, who used it as a garnish.

“They actually wanted to buy it in flower,” Michael comments. “We would just turn the water off for 8 hours and then turn it back on and the plants would flower – we sort of shocked them into flowering!”

Getting the lettuce enterprise up and running has been an enormously satisfying experience for Michael and Genaro, and they claim it is the first ‘Australian-type’ system to be established in the US. And perhaps most satisfying, they have found it such an easy way to grow lettuce.

“The system is pretty basic – and so easy,” Michael observes. “People don’t realise that over here. And it’s still so uncommon – it’s like telling people about magic!”

“We have schools and various other groups coming through here. And I’ve sold several fairly good size systems to people just walking through.”

Forming another arm to the lettuce enterprise is a tomato production greenhouse, where cluster-type tomatoes are grown in perlite bags. The poly-covered greenhouse covers an area of 75′ by 30′, but production is soon to be expanded with the construction of a new greenhouse.

Cluster tomatoes, which are a size larger than cherry types, were chosen for their ease of packing and handling, according to Genaro. They are sold in small baskets, or punnets, again through the Farmers’ Markets.

“We went to cluster tomatoes because with the larger tomatoes you always have to grade them,” Genaro explains. “With these, there’s no grading – everything is useable.”

The aim of the tomato production cycle is to avoid the main ‘glut’ period of September, when tomato prices start to drop. Accordingly, planting takes place in February (before that, heating costs make it too expensive), and the fruit are picked from May to September. However, when the new greenhouse is completed, it will start to produce just as the September glut comes to an end. That means that both houses will be off-season, each complementing the other.

Greenhouse Systems
The existing greenhouse is a poly-tunnel structure, with an extensive system of fans for air circulation and venting in the summer. Hot air is drawn out of the house by two large extraction fans in an end wall, while at the same time inflatable poly tubes emit forced air down at the lower stem level of the plants. This low level air movement seems to have benefited the lower foliage of the plants, according to Genaro.

“The leaves are very healthy down below and I think it’s the air flow,” he comments. “There’s virtually no Botrytis or pythium anywhere, and the plants are over 6 months old – and we’ve just been through the wettest, worst winter we’ve had in years.”

However, the lack of roof ventilation is an oversight in the structure, and one Genaro plans to correct in his next house.

“The new house we’re building will be 10 feet high and have roof ventilation. I want a high house so I can have the tomato plants 3 feet higher – they are easier to work on,” he explains.

The other environmental control, of course, is winter heating, for which propane gas is used as the fuel source. Unfortunately, cheaper natural gas is not available at this location – “it’s about $40,000 away,” Genaro comments wryly. The hot air is piped through the ground level poly-tubing, and gradually rises through the house.

The tomato seedlings are raised in Grodan blocks, which are subsequently placed into the bags of perlite. Generally, the perlite medium can be re-used for at least three years without any problems, but curiously it was in the very first year of operation that disease problems developed.

“The worst infestation I had was in the first year I grew with brand new perlite bags, when the perlite and greenhouse were as sterile as they could be. I had a lot of problems with Tomato Spotted Wilt Virus.

“The second year I had very little virus, the third year none at all and I have not had any for several years now.”

Needless to say, the first lot of perlite bags were disposed of – “I wasn’t taking any chances,” he says.

Also, to counter nematode problems in the media, the perlite bags can be inoculated before planting, with a special bacteria for the purpose, sold as ‘Guardian’.

No pesticides are used in growing the tomatoes, which adds greatly to their sales appeal. The biological agent Encarsia is used, as well as sticky traps for white fly – thrips are rarely encountered.

General management of the crop includes layering the tomato plants – “training the vine to the twine”, as Genaro says – and stripping the bottom leaves off the plants once a week.

The drip irrigation of the plants is not controlled by a time cycle, but by light intensity. A light sensor sends a millivolt signal to a the control unit, called a “Solar 3B”, which calculates the number of solar units in the greenhouse. As these solar units accumulate, the irrigation system is turned on and off. It’s a light sensitive system, rather than a time sensitive system.

“You can set the amount of solar units to trigger it and then it turns on and turns off, in this case for 96 seconds. And you can change that – to be more or less frequent and more or less duration.

“If it’s feeding a little bit too much – and you’re getting a bit more run-off than you want – then you scale it back a bit.”

The tomatoes are fed a two part nutrient, which was formulated for the enterprise by Grenville Stocker, from Stocker Horticultural in New Zealand. The feeding is operated through a fertiliser injector.

“It’s straight in-line injection,” Genaro explains. “The line pressure operates the unit and the A and B concentrates are mixed in with the water in pre-set proportions.”

Nutrient strength for the tomatoes is kept at around 1400-1600 ppm (2.1-2.5mS/cm).

Packaging and Marketing
The greenhouse is entirely planted with the tomato variety Aranca, based on its “excellent flavour”. Selling to the general public through Farmer’s markets, a much more personalised scenario than selling to a supermarket, means flavour and quality are all important to sales and repeat business.

“People are really happy with the flavour,” Genaro comments. “We actually trialled 8 tomato varieties last year, of which this was one, and we just liked the taste of it.”

The tomatoes are attractively presented too. They are sold in small wooden baskets, or punnets, made from Poplar wood which, while considerably more expensive than plastic, give the product the right image of pesticide free and vine-ripened – all popular imagery with the discerning public. Also, in practice, Genaro finds that people at the markets will often pour the tomatoes into a bag and hand back the punnet. Hence, he is often able to re-use them 3 or 4 times.

“The average use of each box is between 3 and 4 times. Recycling is pretty pervasive in our society now – if people have the choice, they’ll invariably do something to reuse or recycle. Its way beyond the point where you have to convince anyone.”

The European practice of selling cluster tomatoes still attached to the stem, was not worth the extra effort, Genaro found.

“Picking clusters didn’t do a thing at the market – and they’re a pain in the neck to handle.” he observes.

One of the main problems was getting every tomato on the cluster to ripen evenly and at the same time – it is far easier to simply pick ripe fruit from all over the plants to pack into punnets. Given the lack of marketplace price advantage, it was simply not worthwhile. Of far more significance to the market is the lack of chemicals used in growing the produce.

“I feel good about saying mine is all pesticide-free,” Genaro comments. And so, it seems, do the customers. Tomato production will be doubled next year, when the new house comes on line, to meet market demand.

Genaro believes that this part of northern California is heading for an expansion of intensive agriculture, as traditional pursuits like cattle ranching and potato growing give way to more concentrated forms of production. Having established the first outdoor NFT lettuce system of its kind in California – and probably the US – he and Michael have proved that this type of hydroponic growing can work and work well, provided the right level of crop protection is provided.

As more growers also become convinced, the scope for a ‘hydroponic conversion’ of the US salad market is great indeed.