Issue 25


Table of Contents:

  1. Points to remember when installing an NFT hydroponic system
  2. Not many greenhouses use solar energy exclusively...
  3. Here and there
  4. There's a "farm" in a basement in downtown Montreal
  5. Plant "smart valves" tell when a plant needs feeding
  6. Ensign wasp - beneficial insect of the month
  7. Think about it...


1. Points to remember when installing an NFT hydroponic system

  1. Your nutrient tank must have a fresh-water valve, fitted to makeup and keep up the initial volume of liquid in the tank.
  2. A venturi oxygenation system should be installed.
  3. The nutrient transport pump must be free from any corrosive or contaminating materials. Make sure you get one which is adequate in size for your operation. Also control taps should be installed in the feeding system to get adequate flow to each gully or feeding trough.
  4. NFT gullies should be flat-bottomed. Lettuce should have 4+ inches on the bottom; tomatoes, pepppers and cucumbers need 6+ inches. The gullies must be constructed so the gullies remain flat.
  5. The gully must not sag along its length and should be no more than 50 feet long with a slope of 1:40. Others claim twice that but they may be stretching the limits of NFT.
  6. A maximumm of 34 fluid ounces per minute should be the nutrient flow rate down an NFT gully. This will provide the necessary liquid film to provide maximum growth and air to the root systems of the plants.
  7. NFT gullies must be covered to prevent algae from growing on the root systems of the plants. But you still must provide some small openings around the stem entry to allow fresh air into the gullies.
  8. Make sure the plastic you use for the gullies is not toxic to the plants. To test any plastic (film or pipe) place a piece of it into a cup of boiling water and sniff the air above the mixture. You may have a problem if you can smell plastic or when after cooling you take a small sip and taste plastic. I said taste, not eat.


2. Not many greenhouses use solar energy exclusively...

But the Cheyenne Botanic Garden in Cheyenne, WY has been doing it for 25 years. And at winter temoeratures which fall to 30 degrees F below zero.

Other growers have had more or less mixed success with solar heating.

The cost of installation is still high when compared to regular utility prices. A photovoltaic panel costs $4 for each watt of power. By the time you add all the necessary extras, you're looking at $20 per watt of power. This is not conducive to being competitive although it could be the only practical option where you are too far from a power line or in a Third World country which needs development.

The solar energy is passive in the Cheyenne operation. A bare minimum of parts are used and these only for the office areas.

The walls of the greenhouse which face east, west and north as well as the foundation are insulated. Weather-stripping is used around vents, doors, windows and fans. The south side of the greenhouse is covered with polycarbonate plastic and glazing which is triple thick.

During the daylight hours heat is stored in drums which can hold 55 gallons of water. Water-filled fiber glass tubes are also used. The total average of stored water is 2.7 gallons per square foot of the southern exposure. When the temperature drops, the heat from the stored water is released.

Greenhouse angles are used to full advantage. The southern sun-facing wall is at a 45 degree angle. The water-filled barrels are placed at proper positions and heights along the other three walls to get or not get (for cooling) the sun during other times of the year.

The entire inside of the greenhouse is planted white to reflect heat to the barrels which are usually planted black.

Cheyenne Botanic Gardens has done quite well, even using solar energy to heat the water which is fed to the root systems of their plants and to run fans and open or close vents.

Nevertheless most passive systems such as this one are nowhere near as well controlled as your average well-designed commercial greenhouse operation. Solar power is good for giving frost free nights to a greenhouse and can be used for growing cool weather crops such as lettuce.

Some growers even find that under certain conditions a solar heated greenhouse can help beget a better crop. By specializing in appropiate plants and growing them under stressed conditions, the plants develop good root systems and do well when transplanted to someone's garden.

But mostly solar greenhouses are for hobby growers.

So you want a solar greenhouse and want to grow commercially? To start off you will need to have a minimum of 10-15,000 square feet where the economy of scale will work in your favor. You will also need a good store of cash to get the entire affair going and to keep it going.


3. Here and there

  1. Unless you're a commercial grower who uses large quantities of fertilizer, it's best to use fertilizer in liquid form which has already been very accurately pre-mixed by the manufacturer. Why? Because it is extremely difficult to get the trace elements mixed thoroughly in a batch of dry fertilizer. And if you don't get it mixed thoroughly, you will not have the trace elements evenly distributed throughout the mixture.
  2. . Our good friend, the Asiatic ladybug beetle, has made itself quite a nuisance this last fall. From Ohio to Colordao the beetle has clustered by the thousands on the outside and also inside houses and barns. Come winter, however, they will die off unless, of course, they are inside your kitchen or living room. There they become a nuisance instead of the beneficial we like to see among our plants.
  3. Polycarbonate sheeting is a good covering for greenhouses. It's durable and quite practical. Too provide an insulating layer, just use plain polythene plastic under the polycarbonate sheeting. And don't forget the small fan which supplies air between the sheets and keeps them apart.
  4. Cut flowers are quite the thing at the Karnup Flower Farm which is located south of Perth in Western Australia. Tunnel greenhouses are used to grow gerbera, limonium, gypsophula, foliage plants and alstroemeria. What I found most interesting was the growers' use of polyethylene covers with different colors for different crops. I suppose different plants require different bands of light spectra in order to flourish more abundantly.
  5. The most abundant source of water in Israel is salty or saline. And the man most responible for this saline water's use in hydroponic and soil growing is Dr. Meier Schwartz. He is responsible for the beginning of hydroponic farming using saline water. In 1950, he started out with about a 10th of a hectare. Now Israel hydroponic growers have 12,000 hectares under production. That's 24 times the commercial hydroponic growing space in the United States. Ah well, I guess we'll get the message one of these days.
  6. However, Florida seems to have the spirit. Hydroponic crops, including strawberries, now account for $14,000,00. Not much when you consider Florida's overall agricultural products to be $1.54 billion, but at least it's a good start. Now if only they could get their ballots in order.


4. There's a "farm" in a basement in downtown Montreal

And it's hydroponic. The outfit is called Fraicherbe and, especially for Canadians, the number is 514-938-0233. The owner, Greg Miller, can be contacted at .

What in the world did they do? Downtown is expensive isn't it? The Millers were lucky. They found a location with cheap electric power and lots of clean water. Using NFT troughs and eight sets of 1000 watt lights (metal halide), the Millers (read Fraicherbe) now grow basil and other herbs. Any excess heat from the hot metal halide lamps is vented outside.

The Millers are in the right location. Montreal chefs love the availability of freshs herbs so near at hand.


5. Plant "smart valves" tell when a plant needs feeding

It's called "needs-based" feeding and has been developed by Auto Pot Systems of Melbourne, Australia. Most hydroponic growers over-feed and over-water, but Auto Pot has eliminated these two problems.

(Like I've said many times before, the Israelis, the Australians, the New Zealanders, the Dutch, and others seem to have the agricultural horizon under their control. At least they have it within their reach.)

Auto Pot is manufacturing two basic systems which are neither run-to-waste or recirculating but something new. The first system is the use of pots in small modules - say two pots to a module. The second system is capillary tables with pots.

The pot modular system has two 10 inch pots inside a module to which a "smart valve" is attached. This valve controls how much nutrient solution will be allowed to go to a plant. A sensor in the vicinity of the plant tells the smart valve when nutrient and/or water are needed. The plant must use up all the nutrient and/or water before the smart valve will let it have more.

The capillary table is composed of modular trays with smart valves attached. Cotton matting is placed in the bottom of the trays. To prevent root systems from penetrating the cotton matting, a layer of weed mesh is added.

Potted plants are added to each module and the smart valves go to work. Nutrient is allowed to flow down channels in each tray and into the matting which will then be absorbed by the perlite in the pots. Just so much solution is allowed to go into the tray. No more is added until that is used up.

Consequently there is no wasted water or nutrient.

You also get great savings of labor and other costs in not having to "re-charge" the nutrient solution from time to time. Without any intervention of any kind, the plants are continually supplied with the proper nutrients and at the proper pH.

The only time something has to be done is to re-fill the nutrient tank.

Another plus is that nurseries can do away with overhead watering which can cause damage to the flowers of stock plants.

With both systems any kind of plant can be managed, including cactus. You just adjust the smart valve at the feeding level you want the plant to have.

Only regular city utility water pressure is needed ( about 13 psi) to run either system. Less capital costs, less plumbing and less operation costs make these Auto Pot systems quite attractive and something to look into.


6. Ensign wasp - beneficial insect of the month

These insects kill cockroaches. They will not harm you or your pets nor do damage to your property. You may find them flying about in a warehouse or even living in your home.

They are black and look like small spiders. Being anywhere from one quarter to three quarters of an inch in length, they have two sets of wings and three sets of legs. There are about 400 different species of the ensign wasp. Most live in the tropics.

In Canada and the United States, the ensign wasp lives mostly in the outdoors, but will enter your home if it believes cockroaches are to be find there.

The ensign wasp is a parasite. It lays its eggs inside the egg cocoons of cockroaches. The ensign wasp eggs awake and feed on the cockroach eggs before gaining adulthood.

The adult wasp likes flowers and the consequent honeydew. Its life span is about three weeks.

The ensign wasp is not a cure-all for a heavy cockroach infestation. They are more a deterrent - they keep the cockroach population in control. They are very good at finding well-hidden cockroach egg pouches.


7. Think about it...

What did the carrot say to the wheat?
Lettuce rest, I'm feeling beet.
- Shel Silverstein

I have a rock garden. Last week three of them died.
- Richard Diran

After all is said and done, a hell of a lot more is said than done.
- Murphy's Laws


bsaffell@mayhillpress.com...Last Update: 52008 copyright 1996 - 2008 by Hilmur Saffell

They are as follows:
"How to Start on a Shoestring and Make a Profit with Hydroponics"
"Big Dollars Growing Gourmet Salad Greens"
"Beneficial Insects - How to Mass Rear and Make a Profit"
If you would like a copy or copies of your own,

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