Light

For propagation purposes, fluorescent light is ideal operated for between 16 - 18 hour per day. The light should be operated on using an electronic timeswitch to ensure that the ON time and OFF time are the same each day. As fluorescent lights are of a low intensity they should be positioned as close to the plants as possible.

Temperature & Humidity

Maintaining constant temperature of between 20º - 28ºC encourages rapid germination and healthy seedlings. It is important to note that the faster clones or seedlings establish, the higher the success rate and the healthier the young plants will be. Temperature and humidity play an important role in successful propagation. Clones or seeds should be placed in a cloning chamber to promote a warm, moist environment. While humidity is important, monitor the chamber daily to avoid excessive condensation build up. As a rule, if water droplets trickle down the sides of the chamber, it is too wet and the vents should be opened, as extremes of temperature and/or excessive humidity will inhibit germination and the establishment of healthy seedlings.

pH

pH is important not just for established plants but also when propagating. Always maintain pH levels between 6.2 - 6.8 pH. pH levels should be tested and adjusted if necessary before sowing seeds and at least weekly throughout the growth of the plant. Incorrect pH levels can cause toxicities of some nutrient elements and cause other nutrient elements to be unavailable to the plants therefore adversely affecting plant growth.

Watering

Seedlings and clones need only a light mist spray to keep media moist and raise humidity, and provide food for the young plant. When misting, it is best to use a warmed 1/2 strength nutrient & Superthrive to avoid burning the tender young shoots.

VENTILATION

VENTILATION an average 10' x 10' foot vegetable garden will use from 10 to 30 gallons of water per week. Where does all this water go? It transpires and evaporates into the air. So basically, gallons of water will be held in the air. If this moisture is left in a small room, the leaves will get limp, transpiration will slow (remember the flow of water through the plant helps keep it erect) and the stomata will be stifled. This moisture mist be replaced with dry air that lets the stomata function properly. A vent fan that pulls air out of the grow room will do the job.

To be a Successful indoor gardener.

Successful indoor gardeners know that a vent fan is as important as water, light, heat, and fertilizer. In some instances it is more important. All greenhouses have large ventilation fans. It is sometimes said that the person with the most fans wins.

Vent fans are rated by the number of cubic feet of air per minute (cfm) they can replace or move. Buy a fan that will replace the volume (cubic feet) of the grow room air in about 5 minutes or less. The air that is pulled out is immediately replaced by fresh air which is drawn from little cracks under the doors or window sills. If a grow room is sealed tightly then an intake fan will probably be necessary to bring in fresh air.

A vent fan is able to pull air out of a room many times more efficiently that a fan is able to push it out.

To calculate the room size multiply width by height this will give you the total cubic footage of your room for example 10 by 10 by 8 = 800 cubic feet. Remember that you want your fan to exchange the air within 5 minutes so for a room that is 800 cubic feet a fan that is capable of moving 160 cfm is needed.

CIRCULATION

CIRCULATION if the air is completely still, plants will tend to use all of the C02 next to the leaf surface. When this air is used and no fresh air is forced into its place, dead air space forms stifling the stomata, slowing growth. Air also stratifies with the warm air rising and the cooler air settling towards the bottom of the room.. All of these potential problems are avoided by opening a door or window and installing oscillating fans. Air circulation is important for insect and fungus prevention. Mold spores are present in all growrooms.

What is STOMATA?

STOMATA are microscopic pores which are located on the undersides of the leaves. These stomata regulate the flow of gasses into and from the plant. These can get clogged with dust, filmy residues, pollen etc... So it is very important to have air movement to keep these pores clean and free.

Air Circulation

Fresh air is at the heart of all successful indoor gardens. In the great outdoors, air is abundant and almost always fresh. The level of C02 in the air over a field of rapidly growing vegetation could be only a third of normal on a very still day. Soon the wind blows in fresh air. Rain cleanses the air from dust and pollutants. The ecosystem is always moving. When plants are grown indoors the natural balance that is present out of doors must be achieved indoors by way of fresh air ventilation. You must take the task of bringing in fresh air seriously or else your green thumb is going to wilt and turn brown.
Fresh air is inexpensive and easy to find. An exhaust fan is the main tool used to satisfy this need.

In order to have a good flow of air through your growing environment, adequate air circulation and ventilation are necessary. Indoors, fresh air is one of the most commonly overlooked factors in contributing to a plentiful harvest. Experienced gardeners realize the importance of fresh air and take care in setting up proper air movement. Three factors affect air movement: stomata, ventilation, and circulation.

The Easiest Way of All

The easiest way of all, is great for people who just want to get rid of the heat and are lucky enough to live on a lake, stream or the ocean. All that is required is to string several hundred feet of garden hose from the pump in the reservoir, out into the lake and then back to the house where it is connected to the inlet to the lights. You then just pump the light cooling water from the reservoir, through the hose in the lake where it gives off its heat before re-entering the lights. No expense for cooling water, no fancy plumbing, no heat exchangers - just the lights, a pump, a filter, a small reservoir and some hose.

Lights as a Pool Heater

Another option is to waste the heat from the lights to a swimming pool. For people who don't have an in-ground pool installed in their back yard, a coated steel above-ground pool is a great alternative. They are cheap, easy to install, and enjoyable. You not only can get rid of the heat from your greenhouse or solarium, but you also get a heated pool.

Extra-low Water Consumption System

An interesting variation on a re-circulating system is one which allows use of city water without increasing facilities water consumption by much. It does this by tying the heat exchanger into the domestic water supply in such a location that whenever any water is used for any domestic purposes the light cooling system is also cooled. Depending on where one puts the reservoir it can also provide heating for a solarium or greenhouse too. While it does require a fair sized reservoir, a considerable number of lights can be cooled with very little extra water, which is a great advantage for the areas where water is metered.

Re-circulating System

For those with a bit more concern for the environment or who want to keep water costs down, there are a number of cooling options which can cut down on the consumption of water and/or electricity. One of these is simply to use a re-circulating system which will allow you to use other sources of water and is in fact the system recommended by the manufacturers of the water cooled lights. The heat exchanger keeps the water flowing through the lights completely separate from whatever the cooling supply is, so the cold water can be from any source. Common examples are sea water, streams, lakes, wells or even swimming pools.

Water Cooled Lights

Since water cooled growing lights have been in use by the hydroponics industry for a number of years now, it seems like a good time to look at them more closely and the best place to start is by showing just how leading edge a development they are - probably much more so than most people imagine. Why do I say that? It is because I have in front of me, a scientific research paper from NASA, the people that send out the space missions. The author is a researcher at the NASA Ames Research Center, and the research was conducted in early 1996 at an Antarctic research station.
The project purpose was to develop a mini-farm sufficiently productive to supply food for a manned mission to Mars. It had to be energy efficient, small, light weight, and most importantly, highly productive - all desirable attributes for the home grower as well. The research was done using a high productivity growth chamber (CAAP chamber) fitted with lighting which featured " ....a recirculating water jacket that absorbs and removes non-photosynthetic energy". In plain English, they used water cooled lights - the same type of water cooled lights that have been available to home hydroponic growers for several years already.

To quote the report:

"The high-efficiency lighting system, providing unmatched photosynthetic radiation production and delivery efficiencies.........."

"The area required to produce the necessary human diet is much less in the CAAP"

"Yield expressed on an area, volume and integrated resource input basis are all greater for CAAP"

"Performance of the lighting system has been excellent........."

"The performance per unit area is so much greater in CAAP......."

Their conclusion at the end of the project was that even the results they got from this preliminary study met the minimum requirements for a mini-farm in space, something they had not been able to achieve with standard hydroponic practices and lighting,, and they saw many areas which they could still improve.

While growth chambers have been used for decades, the report stresses that it was through use of the water cooled lights that the performance has been optimized to the point that it may be feasible to grow the food in space. One has to think that if research scientists and engineers at NASA conclude that water cooled grow lighting has proven itself in their application, it is probably worth looking at for use in other applications.

Can home hydroponic growers benefit from these lights as well as NASA? Yes, because using a growth chamber doesn't require rocket scientists - there are several manufacturers of perfectly suitable growth chambers in Canada, the US, etc. How do the results obtained from these chambers compare to those of NASA? With billions of dollars to play with, NASA can spend a lot on fancy equipment and will probably do better than a home gardener, but still, the home gardeners have done very well and they got there long before NASA.

The growth chambers already available to the home grower have been shown by numerous growers to provide increases of about 30% - 50% beyond what was produced from standard hydroponic systems with everything else being the same - the same person doing the growing, the same strain of plants being grown, the same nutrients being used, etc. If the only thing they changed to obtain the increased production was to use a water cooled light equipped growth chamber, it suggests that using a similar growth chamber could provide anyone with a similar increase in productivity. What does a growth chamber consist of ? At its simplest, it's a box fitted out with everything needed for growing. It would have the light, fan, controls, ballast, watering and any other necessary equipment, already assembled.

One great advantage of these units is the ease of use. There is no trial and error period, or any of the trouble of installing a system assembled from parts. The growth chambers are already proven products with all the components provided, all sized properly and all assembled correctly. They can sometimes be purchased as kits for self assembly but generally they are sold in the completely assembled form so they are true plug and grow units - plug them into the power and water supplies and start growing.

And what are the advantages? Why should anyone bother with water cooled lights in a growth chamber if they've always grown OK without them before? There are many answers, but to quickly summarize:


1.Greater productivity at all times in a properly built growth chamber
2.Easier control of disease and insect pests
3.Increased efficiency of CO2 enhanced operations
4.Reduced size of the installation
5.Reduced ventilation needs and no noise, odor or light glare into the
surroundings
6.Better isolation of the growing environment from it's surroundings
7.Enables year round operation during any weather conditions.
8.Ability to use a modular, plug and grow approach for rapid, easy setup
and expansion.
9.Fast and easy teardown and removal when needed

Since use of the water cooled lights is what makes the growth chambers practical, some discussion of the lights themselves is called for. The hydroponic industry has had water cooled lights available to it for a number of years already and like any other new innovation they've had their teething pains. The initial offerings from several different manufacturers were either huge, heavy and difficult to handle, leaked constantly, were difficult to take apart for cleaning, prone to cracking and meltdown, or just too expensive but these problems all seem to have been overcome finally. The latest version on the market exhibits good design, ease of use, and finally a reasonable price for a complete package of parts - including a reflector.

The lights use standard HPS and Metal Halide lamps, which are fitted into a water jacket that removes the heat while still allowing all the visible light to reach the plants. This warm water can either be run to waste if there is no wish to use the heat in another application, or the heat can be recovered for use elsewhere. The number of cooling options is considerable.

Minor Elements

Manganese (Mn) – plays an important role in photosynthesis and chloroplast membrane formation. Needed at only ½ the rate of iron, its importance cannot be understated. Manganese also enters into the chemical reactions of oxidation and reduction. Deficiency – dead (necrotic) spots on younger leaves. Hard and woody stems, slow maturity. It is not very mobile in plants, so younger growth usually exhibits symptoms first. Toxicity – wilting and death in all but small quantities. Note: manganese is toxic in large amounts.

Boron (B) – is needed in small amounts. Boron aids in cell division and in transporting sugars through cell walls. It also aids in forming the amino acids – thymine and cytosine, important to DNA synthesis. Deficiency – affects new growth first. Black, brittle areas on leaf tips. Small, burned leaves with dead spots. Stubby brown and dead root tips. "Heart rot" in beets and "stem crack" in celery. Toxicity – above 10 PPM, dead leaf margins, wilting and quick death of the plant.

Copper (Cu) – is needed in only small amounts. This metal aids in plant metabolism and general health. It helps ward off disease and pests, aids in the utilization of iron and the manufacture of enzymes. Deficiency – dark green, spindly young leaves. Plants are susceptible to disease and insects, wilt easily and exhibit stunted growth. Toxicity – dark roots, leads to an iron deficiency (interveinal chlorosis on young leaves).

Zinc (Zn) – is needed in small amounts for growth and chlorophyll synthesis. Deficiency – short stem internodes and a condition called "little leaf" or "rosetting" where the young leaves are spindly and twist around each other. Reduced or no bud formation. Mottled dead spots between veins. Toxicity – related to an acid pH, splotchy mottled leaves and wilting.

Chlorine (Cl) – this element controls water uptake and transpiration. Stimulates photosynthesis and is a major constituent of the anthocyanin molecule. Deficiency – plants wilt easily. Bronze colored leaves with dead or chlorotic spots, stunted roots with club-shaped tips. Toxicity – saline poisoning, small dark leaves, burned margins and wilting.

Molybdenum (Mo) – a catalyst needed in small quantities. It is involved in nitrogen fixation (assimilation) and in the manufacture of enzymes. Deficiency – causes nitrogen deficiency. Plants are light green, malformed and stunted. Causes the "whiptail" disease where young leaves are long, narrow and severely twisted, but not tightly bunched as in "rosetting" caused by zinc deficiency. Toxicity – very toxic to plants above 100 to 200 parts per billion (not much!). Causes iron and copper lockup and improper nitrogen utilization.

Cobalt (Co) – a constituent of vitamin B-12 and required for the fixation of nitrogen and DNA synthesis. Deficiency – causes pernicious anemia (lack of vitamin B-12) and improper nitrogen assimilation. Toxicity – all but the smallest amount causes quick wilt and death.

What is the NPK and how is relevant to a hydroponic nutrient? The NPK is the ratio of the levels of nitrogen, phosphorus and potassium. Note that the NPK is important in choosing the right nutrient for the proper stage of growth exhibited by your plants.

The nutrient solution in hydroponics, like the in-the-soil solution for traditional soil gardeners, provides the plant roots with water and essential elements. In hydroponics, the essential elements are added to the nutrient solution, using fertilizer (mineral) salts.

There are a number of hydroponic nutrients on the market these days but they mostly fall into one of four categories – they can be either liquids or powders, and these can be either a one or two part formulas. Most hydroponic retail centers offer a wide range of powder and liquid, one and two part, grow and bloom nutrients.

Powder nutrients are more concentrated than liquids and are usually less expensive. Powders should be dissolved in hot water to make a liquid concentrate, and not be used by adding the powder directly to the tank. This should be done to insure that the powder dissolves completely. If a liquid concentrate is to be made from a two-part powder formula, it is essential that the final volume of the two solutions be the same.

Liquid nutrients are more popular with most hydroponic gardeners because they are easier to use. Liquid nutrients can be added directly to the tank, while powders should be mixed separately then added to the tank. Also another thing to remember is that liquids should be shaken well before dilution, to get an even mix of nutrient chemicals by getting the sludge moving.

The strength of a nutrient solution is measured by its electrical conductivity (EC) and is of critical importance. Too high an EC results in vegetative growth at the expense of fruit or flower production and too low an EC produces weak, unproductive plants.

The EC can be expressed as TDS (total dissolved salts) or ppm (parts per million) depending upon the meter that is used. TDS is the concentration of s solution as the total weight of dissolved solids. These meters are widely used by hobbyists, and actually measure the electrical conductivity of a solution. They do this by measuring the amount of electric current a solution carries. The meters use a built-in conversion factor to express the electrical conductivity in TDS/ppm. The conversion factor for true TDS/ppm is expressed as:

True TDS/ppm = 640 x EC (mS/cm)

For example:

EC (mS/cm) x 640 = 640 True TDS/ppm

Toxicity – edges curl on leaves, small stems, signs of potassium deficiency.

Sulfur (S) – is a building block of amino acids and proteins. Used in small amounts, it aids transpiration and transport of other elements. Deficiency – rare, but young leaves turn pale green with yellowing along the veins, stems turn hard and woody. Plants are stunted and spindly. Toxicity – saline condition, wilting.

Iron (Fe) – is an important constituent of enzymes and plays a role in photosynthesis. Iron is not very mobile in plants and can be "locked up" if the pH goes much above 7. Deficiency – yellow or white chlorosis between veins of younger leaves. Stunted new growth with spindly stems. Flowers drop off before opening. Toxicity – deficiencies of other elements, brown spots on leaves.

Major Elements

Nitrogen (N) – a major element needed by all green plants. It is transported from older growth to new growth. Deficiency – lack of lush green color, especially in older leaves. Toxicity – soft, dark green leaves, long weak stems, poor root development and slow to maturation.

Phosphorus (P) – an important mineral that stores energy in plants and animals, also a flowering agent. Deficiency – stunted, dark green leaves. Lower leaves turn yellow and die. Leaves have brown or purple spots. Toxicity – small, curled new leaves. Early maturity, large root systems.

Potassium (K) – a nitrogen catalyst needed for enzyme manufacture. Needed in large quantities, although plants do not use a tremendous amount. Deficiency – brown, necrotic (dead) tips and edge margins on older (lower) leaves followed by yellowing of the entire leaf. Dead brown spots on older leaves. Slender, weak stems and small seeds. Toxicity – saline condition, marginal leaf burn, wilting and drying due to poor water uptake.

Calcium (Ca) – helps form the structural parts of the plants (it is a major element in cell walls). Counters acidity (low pH). Deficiency – new growth affected first. Root tips turn brown and die. Hard, stiff new leaves with dead edges and brown spots. Stems are stunted and woody, blossoms fall off. Little or no fruit. Toxicity – rare, but can cause an alkaline (high pH) condition, wilting, iron and potassium lockup and deficiencies. Calcium is not very mobile in plants.

Magnesium (Mg) – is important in photosynthesis and the chlorophyll molecule where light energy is converted to chemical energy. Chlorophyll gives plants their green color. Deficiency – chlorosis (yellowing) of older leaves between the veins. Later, leaf tips curl, entire plant turns yellow and dies. Magnesium is mobile and is transported from older to newer growth. Old growth is affected first.

Nutrients are an essential part of healthy plant growth.

For a plant to grow, it requires the correct temperature and humidity, moisture, light, air, certain mineral salts (nutrients) and the absence of pathogens (disease causing organisms).

Plant nutrition is the science which studies what plants eat, or more to the point which nutrients the plant takes from its surroundings, in what amounts, under what conditions and how what the plant takes is used in growth and development. This is of great importance to anyone who is interested in maximizing the genetic potential of his/her plants.

A hydroponic nutrient solution is composed of water, dissolved air and a dozen or so essential elements in their proper proportions. The essential elements, or mineral elements that must be present for proper plant growth and development are nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), calcium (Ca), sulfur (S), iron (Fe), manganese (Mn), boron (B), copper Cu), zinc (Zn), molybdenum (Mo), and chlorine (Cl). The letters in parentheses are the chemical symbols for each element. In addition to these elements, hydrogen (H), oxygen (O2) and carbon (C) are also essential elements which can be found in the air and the water.

The elements that make up a nutrient solution are broken up into two different categories depending upon their relativity to the total make-up of the nutrient solution. Hydrogen, oxygen, carbon, nitrogen, phosphorus, potassium, magnesium, calcium and sulfur are required in relatively large amounts and are so called macroelements (major elements), while iron, manganese, boron, copper, zinc, molybdenum and chlorine are required in relatively small amounts and are so called microelements (minor elements).

Hydroponic nutrients should be complete, containing every essential element, both major and minor, required by all green plants for optimum plant growth. The nutrient should be well balanced containing enough of all essential elements so no deficiency occurs, while not containing too much of any element that might lead to a toxicity. Also the nutrient should be pH balanced and buffered preventing the pH from drifting too high (alkaline) or too low (acid). The last and maybe most important requirement is that the nutrient solution be water soluble with minimal or no residue. The mineral salts used should readily dissociate into elemental ions and not contain any toxic chemicals or elements like heavy metals (lead, mercury or tungsten). This is controlled by the selection and purity of the raw ingredients used.

Drip Irrigation Technique (DIT)

Drip Irrigation Technique (DIT) Grown in inert or organic material and the nutrient solution are fed around the root system 6-7 times a day, in drops or trickles. This technique is called as Drip Fertigation Technique.

Root Mist Technique (RMT)

Root Mist Technique (RMT) A nutrient mist solution is sprayed every 4-5 minutes onto the roots of the plants that hang from frame in a root chamber. This technique is known as Aeroponics. This technique is good for starting roots, cuttings and also for extracting (milking) in the pharmaceutical industry.

Nutrient Film Technique (NFT)

Nutrient Film Technique (NFT) This technique helps the root system with a thin film of nutrient solution which is always in contact with the roots while the nutrient solutions circulates and the root surface is exposed to air.

Aerated Flow Technique (AFT)

Aerated Flow Technique (AFT) A modified version of DFT, the nutrient solution is amply aerated by special mechanisms. The Japanese Kyowa Hyponica Technique is somewhat similar to AFT.

Fog Feed Technique (FFT)

Fog Feed Technique (FFT) This technique is similar to RMT but the nutrient solution droplet size is very minute. This technique is good for plants having aerial roots. Example: orchids, anthuriums, etc.

Deep Flow Technique (DFT)

Deep Flow Technique (DFT) The depth of nutrient solution (4-6 cm) is circulated around the roots either by gravity or by using a pump. This technique is also referred to as Dynamic Root Floatation Technique and as Raceways Hydroponics.

Ebb and Flow Technique (EFT)

Ebb and Flow Technique (EFT) Flood & Drain Technique EFT is the same as Static Aerated Technique SAT, but the nutrient solution in drained off 3-4 times a day to permit the roots to breathe.

Static Aerated Technique (SAT)

Static Aerated Technique (SAT) Also referred to as a Passive Technique. Plants are grown in a depth of static nutrient solution, which is aerated by providing air space in the root zone or by pumping air into the nutrient solution in the tank. This is a basic method of hydroponics.

Dissolved Solids in Water (TDS)

Bad water can cause big problems. Pure water is often not available to hydroponic growers. Almost all domestic water supplies contain certain "dissolved solids," minerals that cannot be filtered out in the way that particles can. Generally these conditions won't cause too much trouble. A simple pH adjustment will usually correct an imbalance caused by "hard" water.

However, there is a limit. In some areas the amount of total dissolved solids or of specific elements in the water supply can combine with elements in the nutrient solution resulting in nutrient lock-out. This may occur when well water is used to mix nutrient solution or where the municipal water supply is very hard. Water containing more than 50 parts per million (ppm) of calcium and magnesium (called "total hard- ness") can create serious problems. Other common elements that may be present in hard water include various carbonates, sulfur, sodium, iron and boron.

Your municipal water supplier can provide you with an analysis of your water supply. If you are using well water, there are many laboratories that can provide you with an analysis if you send them a sample. If the news is bad, it may be necessary to collect rainwater (a good idea wherever possible), install a reverse osmosis filtration system, deionization system, steam distillation system or use purified water (not mineral or "spring" water).

Dissolved solids (ppm) can be measured by using an instrument called a conductivity meter. Pure water will not conduct electricity. The higher the amount of dissolved solids the solution contains, the higher its conductivity will be. Thus, the conductivity meter can measure the electrical conductivity in the solution and interpret that measurement as ppm. Generally this method is the best available to the home grower to measure water quality before nutrients are added and to identify dissolved solids (ppm) after adding the nutrient mix.

It is critical that the nutrient solution not exceed the plant's tolerance for dissolved salts. That tolerance can range from extremely low for some plants such as orchids, to a very high for salt-tolerant crops such as barley. Unless you know the specific tolerance of a given crop, it is best to use a nutrient between 800 and 1,200 ppm.

When in doubt, remember that it is always better to apply too little nutrient than too much. The typical "dose response" curve of plants to variations in nutrient concentration shows three distinct and sharply defined zones: a "deficient zone" where there are insufficient nutrients for healthy plant growth; a "tolerant zone" in which sufficient nutrients are available; and a "toxic zone" where nutrient concentration is too high (too strong) for healthy plant growth.

A complicating factor in determining nutrient strength is that not all salts give equal electrical conductivity readings at specific concentrations. For example, monopotassium phosphate, a common salt used in the composition of plant nutrients, offers very poor conductivity and is practically invisible to conductivity meters. Nutrient solutions containing high monopotassium phosphate levels will appear to be much weaker than they actually are. It is important to be aware that this type of nutrient is stronger than it appears to be, based on your readings.

Always follow the manufacturer's recommendations for mixing nutrient, then measure the conductivity of the resulting solution. This will tell you what "indicated ppm" should be for that particular nutrient solution when mixed with your water supply, although "actual ppm" is probably higher.

As plants consume nutrients and water, the nutrient strength will change in the hydroponic reservoir. In hot, dry regions it is common for plants to transpire lots of water; if you measure the ppm you may find that it rises. It will be necessary to top off the reservoir with water and bring the indicated ppm down to a reasonable level. In cool, humid environments you may find that the ppm drops; this is because the plants are consuming nutrients and not transpiring lots of water. It will be necessary to top up the reservoir with nutrient solution in order to bring the indicated ppm up to its proper level.

A fast growing crop can consume huge amounts of nutrients. If you have a small reservoir it is important to change the solution frequently. Depletion of the solution will result in slow, spindly growth and sickly plants. A large reservoir in proportion to the total bio-mass will not have to be changed as often. Small plants, or naturally light feeders will deplete nutrients more slowly. Different types of plants have differing nutrient needs. The composition of nutrient solutions for all types of plants will contain the same elements as the list at the beginning of this article, however, the ratio of these elements can differ greatly. These variables can be striking when the nutrient needs of one type of plant are compared with the needs of another.

For example, orchids prefer a nutrient that is not only mild (low ppm) but also of a different NPK ratio in comparison to a high metabolism plant such as a fruit producing annual which must complete its entire life cycle within one growing season - from seed germination, through seedling, vegetative growth, flowering, fruit and seed production. Moreover, the fruiting annual which is going through this high-speed metamorphosis in less than one year will also have greatly differing nutrient needs during the various stages of its life cycle.

During rapid vegetative growth a plant can use lots of nitrogen, but a flowering or fruiting plant needs more phosphorus and magnesium. Hydroponic cultivation enables the grower to provide different diets for the crop at different times during the growth cycle. One of the great advantages of hydroponic over soil cultivation is the ability to manipulate nutrient concentrations for enhanced plant growth.

There are manmade nutrient formulations on the market that provide the same NPK combination throughout the plant's life cycle. The best of these are crop-specific formulations. Many manufacturers produce a particular product for orchids, another for tomatoes and perhaps another for indoor ornamentals.

These products will provide reasonable nutrition for the particular crop for which they are designed. However, since it is not possible to alter the NPK combinations during the various phases of growth, it is not possible to perform "nutrient manipulation" with general-purpose products. A multi-stage nutrient that permits adjustment of total ppm and NPK ratios will help you gain the full advantage from your hydroponic system.

What is pH all about?

Maintenance of the proper pH in the irrigation stream helps prevent chemical reaction of fertilizers in the irrigation lines. High solution pH can cause line clogging precipitates to form. Correct pH level ensures that phosphates remain in the more soluble hydrogen form and that minor elements are more available for plant uptake. Minor element deficiencies can result from high pH. What is pH? The abbreviation pH stands for "Potential Hydrogen" and refers to the concentration of positively charged hydrogen ions (H+) relative to negatively charged hydroxyl ions (OH-), in a substance. Hydrogen ions are acidic in nature while hydroxyl ions are basic or alkaline in nature. The pH scale, which measures the concentration of hydrogen ions runs from zero to 14 with 7 being neutral (equal number of H+ and OH- ions). Any value below 7.0 indicates acidity and any value above 7.0 indicates basic or alkaline conditions.

An acid such as Nitric Acid (HNO3) or phosphoric acid is a substance which, when added to water, breaks apart or "ionizes" to provide hydrogen (H+) ions. A base ionizes to provide hydroxyl ions (OH-). The terms strong and weak applied to acids indicate the degree of ionization they undergo. A strong acid such as hydrochloric in a dilute solution undergoes 100% ionization whereas a weak acid like acetic exhibits only 4% ionization. In North America most water supplies are alkaline. In addition plants tend to make the root environment more basic. When a plant takes up nitrate ions, which are negatively charged, the roots shed negatively charged hydroxyl ions to maintain electrical balance. This raises the pH of the root environment. When positively charge ammoniumions are taken up, positively charged hydrogen ions are shed, acidifying the root environment.

When deciding on a pH correction program, the pH of the water is not the only thing to consider, Buffering capacity (the ability of the water to resist pH change) has to be taken into account. The buffering capacity of water is related to the amount of bicarbonate (usually calcium bicarbonate) that is present. If there is a lot of bicarbonate present, much more acid is needed because of the reaction that takes place between the bicarbonate and the acid. The acid that Is added initially to water containing bicarbonate is Used up in this reaction. The hydrogen ion from the calcium bicarbonate molecule (above) and the hydrogen ion from the nitric acid molecule (above) combine to form water. This means that the hydrogen ion from the acid is locked up and therefore does not lower the pH. Once sufficient acid has reacted with the bicarbonate present, any additional acid added will contribute hydrogen ions to lower the pH; therefore, the more bicarbonate that is present, the more acid wit) be needed before free hydrogen ions are available to lower the pH.

Many fertilizer components are acidic and lower the pH, while others are alkaline and raise the pH. To achieve the proper pH with fertilizer alone, however, would require water with little to no bicarbonate present, When nitric acid ionizes, it provides nitrogen ions as well as hydrogen ions; phosphoric acid provides phosphorous. Which acid should you use? Consider the following: Plants use more nitrogen than phosphorous. In addition, high phosphorous levels can cause the formation of calcium and magnesium phosphate; a hard, scale-like precipitate than can coat, and eventually plug, feed lines. It may, according to speculation, even coat plant roots, blocking air passages. Further, high phosphorous levels can hinder the uptake of some minor elements, We believe phosphoric acid should be used only if the amount of acid required is constant and the level of phosphorous provided by the phosphoric acid will not create excessive phosphorous levels in the solution. If you are using a "proprietary" blended fertilizer such as 20-20-20, phosphoric acid should likely not be used at all, as the levels of phosphorous in the blend are usually at an optimum level.

It seems nitric acid is the better choice in many instances. Bear in mind that nitric acid is more dangerous to use. Nitric acid is highly corrosive and produces poisonous fumes when exposed to the atmosphere in the concentrated form. A spray mask, eye protection and rubber gloves should be worn when handling it. Nitric acid is much less hazardous once diluted. Concentrated nitric acid should be stored in sealed glass or stainless steal containers.

Potential Hydrogen can be important for more than fertilization and irrigation. It also plays in the use of some pesticides. Alkaline water can break up the molecules of certain pesticides in a process called alkaline hydrolysis, reducing the activity of the chemical. This problem is heightened if the tank mix will be sitting for any length of time prior to application and if ambient temperatures are high. There are other greenhouse compounds rendered more effective if the water added to is pH corrected before hand.

Finally, at the end of a crop, low pH can be used to clean irrigation lines and dripper tubes of any scale that might have formed. This is done by charging the lines with a low pH solution (3-4) and letting it steep overnight. The lines should then be flushed thoroughly before being put back into regular use.

Hanging basket tomatoes

Here are some tomatoes (variety Tumbling Tom) grown by Kath in Linlithgow, near Edinburgh. They are planted into some of our Self-watering Hanging Baskets and fed our Tomato Liquid Feed. This is a great idea if you don’t have much space and miss the just-picked flavour of home-grown tomatoes.

Kath says:"I really was amazed at how easy it all was to do and I'm sure the tomatoes taste better than our greenhouse soil-based ones. Will be trying it again next year."

Grower’s Diary

It was about this time of year, last year, that my pond bound fish prayed daily for a giant iceberg to make its way up from the Southern Ocean. The temperature in my greenhouse reached an all-time high of 119 degree’s F. The tomato plants thought it was Christmas Day each and every day. This year the plants, especially the one’s grown from seed, are having a bit of an up hill struggle. Each day the weather man promises them sunshine, most days he is getting it wrong. Being an honest Leo I must confess to my own contribution to their misfortune. It was only yesterday that I realised I was giving them the wrong nutrient mix – ‘A’ and ‘B’ only. I should have added liquid feed ‘C’ at the third leaf stage, which was a month ago ! This, of course, applies only to those tomato plants which have been brought on from seed.

The other Tommy plants, which were purchased as established young plants, are doing remarkably well and are about two feet tall ( the seeded plants are little more than three to four inches high ) and well into their flowering stage. You may recall that I have attempted an experiment with three tomato plants of the same variety, Beefsteak, in pyramid pots. One is sitting in coconut fibre, one in vermiculite/perlite, and the third is in a sharp/soft sand mix, all being fed the same liquid feed. The plants in the coconut fibre and vermiculite/perlite pots are racing away as if their backsides are on fire, and are beginning to bully neighbouring tomato plants for space. The tomato plant set in sand is a sad tomato plant, and I think it only a question of time before it becomes a deceased ( as in dead ) tomato plant. But I am prepared to accept full responsibility for it’s eventual demise, and I promise to do better next time.

Which brings me to the peppers. The Capsum peppers ( grown from seed ) are not doing too well either, yet ( and understandably so, no doubt ) the Yellow Luteurs, bought as established plants, continue to reach upwards to glory. The Beetroot, Carrots, Spring Onions and Radishes ( all grown from seed ) are now ready for a little thinning – especially the Radishes. Still in the propagating stage are Leek, Parsnips and two types of Lettuce. The Mixed Salad lettuce have produced a nice green carpet over the propagating tray, but the Salad Bowl lettuce ( with the exception of just two little plants ) refuse to come out and join in the fun. Not all the Leek seeds are making a show, hopefully time will produce better results. The Parsnips are looking good, and I have built a Parsnip growing tray, with the use of drain-piping, and await the young seedlings to reach a better maturity so they can be transplanted into their individual drain-pipes.

Now there’s a thought that might boggle the mind – if you want to grow a parsnip, get a drain-pipe.

Augmentation

Augmentation involves releasing natural enemies into areas where they are absent or exist at densities too low to provide effective levels of biological control. The beneficial insects or mites used in such releases are usually purchased from a commercial insectary (insect rearing facility) and shipped in an inactive stage (eggs, pupae, or chilled adults) ready for placement into the habitat of the target pest. Augmentation is broadly divided into two categories, inoculative releases and inundative releases.

Inoculative releases involve relatively low numbers of natural enemies, and are intended to inoculate or an area with beneficial insects that will reproduce. As the natural enemies increase in number, they suppress pest populations for an extended period. They may limit pest populations over an entire season (or longer) or until climatic conditions or a lack of prey results in population collapse. Generally only one or two inoculative releases are made in a single season. In contrast, inundative releases involve large numbers of natural enemies that are intended to overwhelm and rapidly reduce pest populations. Such releases may or may not result in season-long establishment of natural enemies in the release area. Inundative releases that do not result in season-long establishment are the most expensive way to employ natural enemies because the costs of rearing and transporting large numbers of insects produce only short-term benefits. Such releases are usually most appropriate against pests that undergo only one or two generations per year.

The distinction between inoculative and inundative releases is not absolute. Many programs attempt to blend long-term establishment with short-term results. In addition, conservation and augmentation may be used together in a variety of ways to produce the best results.

Conservation

Conserving natural enemies is often the most important factor in increasing the impact of biological control on pest populations. Conserving or encouraging natural enemies is important because a great number of beneficial species exist naturally and help to regulate pest densities. Among the practices that conserve and favor increases in populations of natural enemies are the following: (1) Recognizing beneficial insects. Learning to distinguish between pests and beneficial insects and mites is the first step in determining whether or not control is necessary. This circular provides general illustrations of several predators and parasitoids. Picture sheets available from the University of Florida feature common pests of many crops and sites. Insect field guides are useful for general identification of common species (see Borror and White, 1970). (2) Minimizing insecticide applications. Most insecticides kill predators and parasitoids along with pests. In many instances natural enemies are more susceptible than pests to commonly used insecticides. Treating gardens or crops only when pest populations are great enough to cause appreciable damage or when levels exeed established economic thresholds minimizes unnecessary reductions in populations of beneficial insects. (3) Using selective insecticides or using insecticides in a selective manner. Several insecticides are toxic only to specific pests and are not directly harmful to beneficials. For example, microbial insecticides containing different strains of the bacterium Bacillus thuringiensis (Bt), are toxic only to caterpillars, certain beetles, or certain mosquito and black fly larvae. Other microbial insecticides offer varying degrees of selectivity.

Other insecticides that function as stomach poisons, such as the plant-derived compound ryania, do not directly harm predators or parasitoids because these compounds are toxic only when ingested along with treated foliage. Insecticides that must be applied directly to the target insect or that break down quickly on treated surfaces (such as natural pyrethrins or insecticidal soaps) also kill fewer beneficials. Leaving certain areas unsprayed or altering application methods can also favor survival of beneficials. For example, spraying alternate middles of grove rows, followed by treating the opposite sides of the trees a few days later, allows survival and dispersal of predatory mites and other natural enemies and helps to maintain their impact on pest populations. (4) Maintaining ground covers, standing crops, and crop residues. Many natural enemies require the protection offered by vegetation to survive. Ground covers supply prey, pollen, and nectar (important foods for certain adult predators and parasitoids), and some degree of protection from weather. Most studies show greater numbers of natural enemies in no-till and reduced tillage cropping systems. In addition, some natural enemies migrate from woodlots, fencerows, and other noncrop areas to cultivated fields each spring. Preserving such uncultivated areas contributes to natural biological control.

Maintaining standing crops also favors the survival of natural enemies. Where entire fields are cut, natural enemies must emigrate or perish. Alternate strip cutting (with time for regrowth between the alternate cutting dates) allows dispersal between strips so that natural enemies remain in the field and help to limit later outbreaks of pests. (5) Providing pollen and nectar sources or other supplemental foods. Adults of certain parasitic wasps and predators feed on pollen and nectar. Plants with very small flowers are the best nectar sources for small parasitoids and are also suitable for larger predators. Seed mixes of flowering plants intended to attract and nourish beneficial insects are sold at garden centers and through mail order catalogs. Although no published data document the effectiveness of particular commercial mixes, these flower blends probably encourage a variety of natural enemies. The presence of flowering weeds in and around fields may also favor natural enemies.

Artificial food supplements containing yeast, whey proteins, and sugars may attract or concentrate adult lacewings, lady beetles, and syrphid flies. As adults these insects normally feed on pollen, nectar, and honeydew (the sugary, amino acid-rich secretions from aphids or scale insects), and they may require these foods for egg production. Lady beetles are predaceous as adults, but some species eat pollen and nectar when aphids or other suitable prey are unavailable. The proteins and sugars in artificial foods provide enough nutrients for some species to produce eggs in the absence of abundant prey. Wheast®, BugProTM, and Bug Chow® are a few of the artificial foods available from suppliers of natural enemies.

The practices listed above must be judged according to their impacts on pest populations as well as their effects on natural enemies. Practices that favor natural enemies may or may not lessen overall pest loads or result in acceptable yields. For example, reduced tillage favors beneficials but also contributes to infestations of such pests as the common stalk borer and European corn borer in corn. Moreover, tillage decisions may be influenced more by soil erosion and crop performance concerns than by impacts on pests or natural enemies. Flower blends and flowering weeds can serve as nectar sources for moths (the adult forms of cutworms, armyworms, and other caterpillar pests) as well as beneficials. The ultimate goal of conserving natural enemies is to limit pest problems and damage to crops, rather than simply to increase numbers of predators or parasitoids. Pest densities and crop performance are factors that must be included in any evaluation of the effectiveness of natural enemy conservation efforts.

Classical Biological Control

Importing natural enemies from abroad is an important step in pest management in part because many pest insects in the United States and elsewhere were originally introduced from other countries.
Accidental introductions of foreign pests have occurred throughout the world as a result of centuries of immigration and trade. Although the foreign origins of a few recently introduced pests such as the Asian tiger mosquito, Russian wheat aphid, and Mediterranean fruit fly are often noted in news stories, many insects long considered to be serious pests in this country are also foreign in origin. Examples of such pests include the gypsy moth, European corn borer, Japanese beetle, several scale insects and aphids, horn fly, face fly, and many stored-product beetles. In their native habitats some of these pests cause little damage because their natural enemies keep them in check. In their new habitats, however, the same set of natural enemies does not exist, and the pests pose more serious problems. Importing and establishing their native natural enemies can help to suppress populations of these pests.

Importation typically begins with the exploration of a pest's native habitat and the collection of one or several species of its natural enemies. These foreign beneficials are held in quarantine and tested to ensure that they themselves will not become pests. They are then reared in laboratory facilities and released in the pest's habitat until one or more species become established. Successfully established beneficials may moderate pest populations permanently and at no additional cost if they are not eliminated by pesticides or by disruption of essential habitats.

Importation of natural enemies has produced many successes. An early success was the introduction of the Vedalia beetle, Rodolia cardinalis, into California in 1889 for the control of cottony cushion scale on citrus. For over 100 years this predaceous lady beetle from Australia has remained an important natural enemy in California citrus groves.

Although the importation of new natural enemies is important to farmers, gardeners, and others who practice pest management, the scope of successful introduction projects (involving considerable expertise, foreign exploration, quarantine, mass rearing, and persistence through many failures) is so great that only government agencies commonly conduct such efforts. Introducing foreign species is not a project for the commercial farmer or home gardener.

Types Of Biological Control

Biological control, sometimes referred to as biocontrol, is the use of predators, parasitoids, competitors, and pathogens to control pests. In biological control, natural enemies are released, managed, or manipulated by humans. Without human intervention, however, natural enemies exert some degree of control on most pest populations. This ongoing, naturally occurring process is termed biotic natural control. Applied biological control produces only a small portion of the total benefits provided by the many natural enemies of pests.
There are three basic approaches to the use of predators, parasitoids, and competitors in insect management. These approaches are (1) classical biological control--the importation and establishment of foreign natural enemies; (2) conservation--the preservation of naturally occurring beneficials; and (3) augmentation--the inundative or inoculative release of natural enemies to increase their existing population levels. Broad definitions of biological control sometimes include the use of products of living organisms (such as purified microbial toxins, plant-derived chemicals, pheromones, etc.) for pest management. Although these products are biological in origin, their use differs considerably from that of traditional biological control agents.

Beneficial Insects and Mites

Many insects and related arthropods perform functions that are directly or indirectly beneficial to humans. They pollinate plants, contribute to the decay of organic matter and the cycling of soil nutrients, and attack other insects and mites that are considered to be pests. Only a very small percentage of over one-million known species of insects are pests. Although all the remaining non-pest species might be considered beneficial because they play important roles in the environment, the beneficial insects and mites used in pest management are natural enemies of pest species. A natural enemy may be a predator, a parasitoid, or a competitor.

Rockwool, Geolite & DFT Irrigation

Rockwool will allow the grower an easy set-up, since it is pre-formed and modular. It holds a tremendous amount of water and offers a buffer against drying in the case of electrical outages or pump failures. Rockwool slabs may be used successfully in a "hand-water" system since they stay moist so long. Rockwool will will maintain a 60/40 water to air ratio even when completely saturated, which makes for extremely healthy root growth. For starting seedlings and cuttings, rockwool is without equal. Rockwool is not degradable or reusable and must be repurchased for every use.

Geolite is a ceramic, kiln-fired pebble developed specifically for plant growth. It is completely inert and sterile and each piece is completely rounded so it will not cut roots. It is light weight and holds a small amount of moisture between irrigation cycles. It may be cleaned and reused again and again, so it is an economical choice. Geolite is not a good choice for most hand-water systems, as it does not provide enough of a moisture buffer. It may be difficult for anyone who is physically challenged to clean and rinse without assistance.

DFT Irrigation, or "media-less" culture, will be the most economical method of growing as it only requires 1" rockwool starter cubes. This can be an excellent choice for some growers, but beginners sometimes find that they are less successful with a media-less system as it does not buffer the roots against temperature changes, nutrient strength changes and uneven watering the way that rockwool and geolite will. This is a consideration for growers who experience frequent power outages and for beginners who will be more prone to initial mistakes, such as leaving a pump unplugged! Actual growth in these systems is excellent and DFT irrigation is a good choice for many conscientious growers.

Experiments to Try

Many interesting experiments suitable for science fairs and for school or p-H projects can be performed with soilless culture. Two experiments, the first dealing with pH levels and the second with nutrient materials, are outlined here. You may want to work out variations of these experiments or try others of your own.

Experiment l: pH Levels
Use the nutrient solution given in the Nutrient Solutions section or a solution prepared from commercial premixed nutrients. Pour the solution into three containers. Adjust the pH of the solution in the first container to between 5.5 and 6.5. This solution is the "check" or "control" for the experiment. Lower the pH of the solution in the second container to less than 4.0 by adding small amounts of dilute sulfuric acid. Raise the pH of the solution in the third container to 8.0 or higher by adding a dilute sodium hydroxide (NaOH) solution. Test the pH of the solutions with an indicator.

The following plants do well at a pH range between 5.5 and 7.0: carrot, coleus, cucumber, geranium, orange, pepper, petunia, strawberry, turnip, and violet. Grow a plant from this list in each of the three solutions. Choose only one kind of plant (pepper, for example), and be sure the plants are about the same size. If you use seeds, plant them all at the same time.

Observe the difference in growth between the plants in the three solutions. Typical results are shown in Figure 1. You may want to set up various pl l ranges to find the best pH in which to grow a particular plant.

Figure 1. Effect of various pH levels on the growth of lettuce

Experiment 2: Nutrient Levels
You will need to prepare three nutrient solutions for this experiment. The first solution is a premixed nutrient solution or the "standard" solution listed in the nutrient solution tables. To prepare the second solution, use twice the recommended amount of each nutrient. For the third solution use one-half the recommended amounts of the nutrients. You will probably not want to prepare 25 gallons of each solution. The amounts of salts and water may be reduced by one-half, one-fourth, or even more as long as you mix the proper proportion of ingredients for each of the three solutions.

Be sure to grow the same kind of plant in each container so that you can compare results between the plants (Figure 2). If you transplant into these containers, choose plants that are uniform in size. By varying the nutrient and pH levels and observing the effects of these changes upon the plants, you can determine the proper pH and nutrient levels for a particular plant.

Figure 2. Effect of various nutrient levels on plant growth.