Issue 13


Table of Contents:


1. Seeds and their care

Growing plants from seed can be very profitable. Compared to buying seedlings, growing your own will give you plenty of healthy, quality plants for low cost. If buying seed from a commercial source, make certain you check the expiration date for viability on the package the seed comes in. In other words, don't hold seed over - use it, or lose it!

If you use your own seed, collect them only from your best plants. Do not use hybrid seed because they will not always breed true.

Some commercial seed is treated with fungicide - so wash your hands after planting. Store seed in the refrigerator or at room temperature. Don't open the package until you're ready to use all the contents.

There are various ways to plant seed, but hydroponically the best method is sowing directly (two at a time) into the medium cubes you plan to use. The medium used should friable enough to give sufficient air to root systems and to supply and hold nutrients and water for each feeding/watering period. Also the medium must be stiff enough to hold up the plant. The medium must be sterile.

You need to experiment with different media to see what fits your operation. Things to consider for each of the media would be aeration, liquid capacity, cleanliness, low cost and how easy it is to use.

There are several suitable media. They are rockwool (agricultural only), bark which as been composted, peat pellets and blocks, oasis blocks, pumice, sand, perlite, vermiculite, coir (which is coconut fiber), expanded clay and scoria.

But there are some things to watch out for when handling the above. Spray perlite first to settle any of the silica dust. Don't compress vermiculite because you'll ruin its structure. Sand should be used with other media and should be thoroughly washed. If you live in a warm climate, sprinkle coir on top of other media to keep the medium from drying out.

Be careful with pumice - it will get into your product when you harvest the crop. Make sure rockwool is wet before you handle it. Particles of bark can clog a feeding system, so you'll need a filter.

Again, there are different methods used for planting seeds. You can sow directly (for big seed) or sprinkled into trays (fine seed). Some crops, such watercress, onions, and beets won't put up with their roots being disturbed. For fine seed, after sowing in most media, cover with a finer layer of perlite or vermiculite. The depth of this covering should be twice the seed diameter and should be evenly spread.

All media should be heavily watered before sowing. After sowing, water in and cover with plastic or tissue paper to hold in the moisture. No need to water again until after germination. Remove cover when seedlings rise from the medium. No medium must be used which contains even a trace of soil.

It's a good idea to seed more than you need so you can thin out the weaker seedlings after germination. Rockwool, oasis and peat cubes must be thoroughly soaked before sowing. Punch a hole in each to fit the seed being planted. It's a good idea to pre-soak rockwool cubes with nutrient solution which has been diluted somewhat. Oasis cubes should be placed on a tray which has a bit of water in order to keep the cubes moist.

Some seeds come pre-treated or have hard shells. These should be placed in water for a full day before sowing. Or you can cut a nick in them to let water in. When in doubt, read the directions on the seed package.

Some seeds need light to germinate. But all seedlings need light after they spring above the medium. And they will need nutrient. The nutrient should be diluted after the first two leaves are completely formed. Some growers may use full-strength nutrient at this stage of growth, but it's best to not begin this until a week before placing the seedling into the main hydroponic greenhouse growing area.

Sometimes, if you're not watchful, your seeds won't germinate. This can be various things, among which are too much water, temperature too low, loss of seed viability from old seed or from a seed package which has been opened and lain around for awhile, damping off, and, yes, even mice or other varmints.

Damping off is one of the worst. This can occur during germination and the initial growth of the seedling. Symptoms of this disease are: seedling stem is girdled and stunted, seedling develops rot at medium's surface and falls over, seed decays and no seedling appears at all.

If damping off has already occurred, you may be able to save the day by using a fungicide to inhibit the process. But the most common-sense way is to start and do right from the beginning.

Don't overwater, have plenty of ventilation, have good drainage, don't plant or sow too deep, and watch how you handle the plants when transplanting. Always handle by the leaves, not the stem. Some media dry out too fast; others might have too much salts in them. That's why they say the devil is in the details. So be particular: make sure the medium is of highest quality and is sterile. A good fungicide spray wouldn't hurt either.

As in all things, cleanliness is everything! Make that a rule in your growing practices throughout your entire operation. You'll have a lot less headaches and more dollars in the pocket.


2. A little about greenhouse computers and controls

In most modern and profitable greenhouse operations computers which are integrated with one another manage the day by day control of growing factors which are needed for successful production. These include controlling climate, mini-climates, nutrient equipment and irrigation of crops.

With a high degree of accuracy and efficiency, such computer systems can give lower plant disease, better crop quality and quantity, and less use of energy. But you still have to do the thinking. To get such results you have to have experience and know what you're doing.

In other words, if you already produce crops with high quality, then the addition of computer control systems can only help you do it better. And they'll save you from having to be everywhere at once. You have the choice: you can do everything manually, or have a computer system do it partially or all the way. Some growers start out with a partial system setup and gradually "feel" their way into a completely integrated setup.

The trend however is for complete computer control. This would include cooling systems, thermal curtains, water managing quality, lighting, fertilization, root zone temperature management, storage of heat, and the use of carbon dioxide.

Actually, when your operation gets large enough, its time to seriously consider the introduction of such a computer system. It will certainly give you time to breathe.

But how everything works is still up to you, no matter how complicated everything becomes. You have to decide what you want, how you want things to work, by what and when.

The great advantage of such control systems is you can orchestrate how the systems should respond and coordinate themselves under various environmental conditions, such as storms, frigid weather, cloudy conditions, etc. You personally might find it an impossible task to keep up with such emergency situations.

In addition, you can adjust everything according to seasonal variations. Also you can take one particular factor such as heat control and set it up to vary with temperature, humidity, day and night crop needs, lighting and ventilation. You can even set up alarms for certain specified conditions.

One important item would be the ability to have the computer keep records of what happened. So when you grew a particularly good crop you would know exactly how to duplicate those conditions for the next crop. Conversely, such accurate record keeping cam help you know what factors (when and where) make for a poor or just ordinary crop.

You can refine the system to such a point that you can adjust and control it from inside or out - or even by remote control from anywhere else you can imagine.

Now wouldn't that be a happy state of affairs?


3. More lighting techniques

Sometimes it's necessary to augment your lighting, especially on rainy days or when the weather is overcast for period of time. This is when you need to have additional knowledge close at hand.

For any given situation you need to know how many lights you need. The following formula gives the lumens you need. This is usually between 20 to 60 watts for every square foot. Take your greenhouse room or area to be lighted and multiply the square footage by 20.

The answer will tell you how many watts of lighting you will need. You need to know the number of lights you want, the wattage for each light and the length and width of the room you intend to work in.

There are ways, of course, to enhance the results. Light manufacturer web sites are a good resource for gaining information. But be certain you are reading only the latest information as light usage has changed somewhat over the years.

Measuring light is different than the wattage of the lamp which puts out the light. Instead of using foot-candles, we now measure light output by what is known as PAR (photosynthetically radiation). PAR is measured in micromoles (uMOLS). Micromoles are determined with Quantum meters (or meter) which cost around $150.

Using PAR, you'll find that the long favored sodium lamps can now be challenged by halide lamps. Many commercial growers are now using halide lamps because the newer warm color halides can give PAR outputs near to or equal to the older sodium lamps.

In any case, a light won't do nearly as well without a well-designed reflector as one which has that reflector. Without proper reflectors you will get an uneven balance of light across your crop.

Some reflectors are designed to give high light levels while others are constructed to spread light evenly over a crop and at a lower ceiling or raised height. Newer light fixtures are designed to be easily lowered and raised with remote ballast system controls. In other words, you want the lights to be easily installed and maneuvered. What's more, a lot of greenhouse and lighting manufacturers can help with the layout of your lighting program.

Though the installation cost of high output lighting is high, it more than pays itself off many times over by helping to save a crop in inclement weather. In short, a good lighting program can not only save you money in the long run, it can also help you make a bundle of profits with quality crops and the right timing.


4. Short descriptions of various hydroponic techniques

Deep Flow:
Nutrient a few inches deep is swirled around the plants' roots. This done with a gravity drain and a pump.

Static Aerated:
Plant roots lie in a nutrient solution which is aerated by a pumping system. You can also aerate the nutrient while it is still in the tank.

Nutrient Film:
Nutrient solution flows thinly past the root system. The exposed part of the root system is exposed to air.

Aerated Flow:
This is Deep Flow modified. The nutrient solution is aerated with various pumps and mechanisms. It's a large "table", several inches deep in nutrient. The crop floats on styrofoam sheets on top of the nutrient. The nutrient is aerated from below. This method, among others, is discussed at length in my book on hydroponics (see http://www.mayhillpress.com/hydroponics.html).

Ebb and Flow:
The plants sit in pots or in a medium. Nutrient is pumped into the "table" on which the pots sit or into the medium to a level where the roots of the plants can soak up the nutrient and then the nutrient is drained away back into its tank. This is done several times a day by a timer. Also called "Flood and Drain".

Drip Irrigation:
Just as it says. The nutrient is "dripped" at regular intervals around the base of the plant on top of the medium. This process is usually done with a timer 5-7 times a day. Very popular technique among growers.

Aeroponics (or Ein Gedi):
Plant roots are suspended from a platform and in the dark. Then a mist of nutrient is sprayed continuously upon the roots. Used a lot in Israel.


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,

Payment Processing