Every living creature needs energy to live, develop and grow. For most living creatures the most important energy source is sugar (glucose). Green plants are the only ones capable of producing these sugars themselves. These sugars are produced from water, which is being absorbed through the roots and carbon dioxide, which is being absorbed from the air. In order to make sugar out of these matters, the plant needs light. This process takes place in the green pigment, (chloroplasts) and is called; photo synthesis. (photo=light, synthesis=produce, therefore photo synthesis means; produce through light).
As above, the plant needs light for its energy supply. Because we are talking about growing indoors, we will have to supply a light source. Normal lamps are less suitable for the job. A plant needs light of certain wavelengths, which are not or not present or strong enough in normal lamps. The some company’s. recommend the use of type SON T lamps. They are suitable for both the growth stage, as well as the flowering stage. Ballast’s are necessary for these lamps. Ballast’s of 600 watts have the most favorable output of delivered light per watt. Depending on the variety we recommend to use between 400 and 800 watts per m2. With insufficient light the plant remains light-green in colour and becomes unnaturally thin and protracted. The buds will also remain smaller with insufficient light.
The efficiency of the lighting in the grow room can be strongly increased by covering your grow room with reflective materials. You could paint the walls with mat white paint or cover the walls with white plastic. Ensure that the room can be easily cleaned because spraying might pollute the walls quite a bit. Most sorts of your “favorite plants” remain in their vegetative (grow) state when the light cycle is maintained at 18 hours. Your “favorite plant” is a so called short day plant, in this we mean that the plant will start flowering when we shorten the light period. Plants are initiated into the flowering phase by shortening the day period to 12 hours on and 12 hours off per 24 hours. Your “favorite plants” that originate from the tropics do not react to changing day lengths but flower after a certain time. That is logical if you realize that a day in the tropics lasts approximately 12 hours the whole year round. The lamp must hang at a distance from the plants that will not cause any scorching of the leaves. This distance differs with the wattage of the lamp. We recommend a distance of: 400 Watt- 45 cm; 600 Watt- 85 cm; 1000 Watt- 105 cm. Don’t hang the lamp any higher above the plants than necessary.
Carbon dioxide is absorbed by the plant through its pores. In small spaces, the present carbon dioxide will soon be used up. Therefore the air in the grow room has to be replenished regularly. For this you need to buy an exhaust fan. You have to make sure however that it is powerful enough to replenish all the air at least 20 times per hour. The fan can be connected to a time clock or thermostat and/or hygrometer. To provide for an optimal gas change for the plant we also recommend to place an oscillating fan in the grow room, in order to have a constant air flow along the plants.
In urban areas the carbon dioxide concentration might increase to a higher value than the normal 0.03% which is 300 ppm (parts per million). From regular horticulture we know that adding extra carbon dioxide to a concentration of 0.15% highly stimulates the growth and the speed of photo-synthesis. This results in faster and higher yields. This yield increasing effect is most powerful with intensive lighting and inert substrate cultivation, such as rock wool. Another effect that has been reported by growers is the fact that a higher carbon dioxide concentration makes the plants less sensitive to higher temperatures.
A third effect is that there is less need to ventilate (unless the humidity is too high) because you don’t depend on carbon dioxide from the outside air. In greenhouses the exhaust gas of oil-fired central heating is conducted back into the greenhouse. To raise the carbon dioxide concentration in grow rooms, it is usually supplied from bottles. There are two ways to provide for more carbon dioxide in the grow room.
(I) The cheapest way is to buy a pressure regulator that can be adjusted so that after ventilation (when carbon dioxide is dispelled from the room) the right amount of carbon dioxide will be released inside again. The exact quantity you need is something you have to work out yourself. You calculate this as follows: Length x Width x Height of the grow room in meters gives the volume of the room in cubic meters. One cubic meter is 1000 liters. If for instance you want to increase the concentration from 0.03% to the required level of 0.15%, you need to add 0.12% carbon dioxide. Suppose your grow room measures 2 x 2 x 3m , which is 12000 liters. 0.12% of 12000 liters is 14.4 liters. So to this room, 14.4 liters of carbon dioxide should be added to obtain an optimal gas concentration. This needs to be done after every exhaust period. This only needs to be done during the “day period”, because the plants only use carbon dioxide when the light is on. One kilo of carbon dioxide is approximately 500 liters. So a 10 kilogram bottle contains approximately 5000 liters. This means that a grow room of 2 x 2 x 3m needs two bottles per grow period.
(II) The second system to keep the concentration of carbon dioxide at the right percentage is by the use of a carbon dioxide meter and a computer controlled pressure regulator. The concentration of gas is constantly measured and the computer makes sure that with a too low concentration, the right quantity of gas is added. The ventilator could also be connected to this computer. This system is not cheap but once it has been installed you don’t need to worry about it anymore.
Temperature: If plants could be fussy about one main growing condition, it would be temperature. Aside from drying out the roots completely (not recommended unless you enjoy funerals !) the quickest way to create problems in your greenhouse is to mess with your plant’s temperature.
The bad news is : Letting the thermometer climb – or – drop by only a few degrees can make plants clench up and stop growing. The good news is : We know what they like. Here is a list of recommended temperatures for different stage of
growth in the garden.
Please note: The listed temperatures refers to TEMPERATURE AT THE TOP OF THE TOP OF PLANT not the floor , wall, or outside! Use a small thermometer on a bamboo stake for accuracy!
SEEDLINGS AND CUTTINGS 21 C (70 F) Day and night
GREEN GROWTH 30 c (85 F) days 18-21 C (65-70 F) Nights
FLOWERING AND CROP PRODUCTION 27 C (80F) Day
ROOTS (Green Growth and Crop Production) 21C (70F)
Do you know how to use it?
Most distributors of 35% food grade Hydrogen Peroxide recommend using 3-5 mls per gallon of solution. Here is what they don’t tell you, they do not know how it works in hydroponic situations and how it relates to nutrient solutions and delicate root hairs.
When Hydrogen Peroxide is added to water it creates a certain level of Ozone, Ozone will, having the opportunity, react with any organic compounds that are present and this is called oxidation. Hydrogen Peroxide is water with an extra oxygen molecule causing it to be unstable and when you add it to water H202 + H20 = H403, the 03 in the equation is ozone and requires oxidation to break it down into 02 which is stable.
The directions for use in hydroponics is 1 ml per gallon of water without nutrient present in the water, if you add Hydrogen Peroxide to your nutrient solution then you run the risk of the ozone reacting with the mineral salts allowing them to fall out of solution. Do not use more than this because it may break down the outer layer of the root hair making it susceptible to root disease which is in many cases the very reason you are using it. When used properly it will enhance your oxygen content of your solution. Another thing I need to mention is that when you add Hydrogen Peroxide to your water let it stand for an hour before you add your nutrient so as not to get any reaction.
1ml per gallon
let stand _ hour
add only to water.
-sufficient support for the plants
-appropriate distribution of air, since roots
-need oxygen and respire other gasses, such
-as carbon dioxide
-maximum water availability for the plant roots
-accessible nutrient solution with consistent
Liquid (non-aggregate) Hydroponic Systems
Deep Flow Hydroponics
The classic hydroponic system, where plants are supported so that their roots hang into a nutrient solution, is generally called “deep flow hydroponics”. This system is appropriate for hobbyists and large scale production of leafy vegetable crops. The system consists of horizontal, rectangular-shaped tanks lined with plastic. The nutrient solution is monitored, replenished, recalculated, and aerated. Commercial facilities are now quite popular in Japan. The rectangular pools act as frictionless conveyor belts where large, moveable floats of plants (lettuce) can be transported from transplant to harvest.
Nutrient Film Technique
A modification of the deep flow system is called “nutrient film technique”, where a thin film of nutrient solution flows through plastic lined channels, which contain the plant roots. The walls of the channels are flexible; this permits them to be drawn together around the base of each plant, excluding light and preventing evaporation. For lettuce production, the plants are planted through holes in a flexible plastic material that covers each trough. Nutrient solution is pumped to the higher end of each channel and flows by gravity past the plant roots to catchment pipes and a sump. The solution is monitored for replenishment of salts and water before it is recycled. Capillary material in the channel prevents young plants from drying out, and the roots soon grow into a tangled mat. This method is mainly used for tomatoes.
Aeroponics is another technique, where nutrient solution is sprayed as a fine mist in sealed root chambers. The plants are grown in holes in panels of expanded polystyrene or other material. The plant roots are suspended in
midair beneath the panel and enclosed in a spraying box . The box is sealed so that the roots are in darkness (to inhibit algal growth) and in saturation humidity. A misting system sprays the nutrient solution over the roots periodically.
The system is normally turned on for only a few seconds every 2-3 minutes. This is sufficient to keep roots moist and the nutrient solution aerated. Systems were developed by Dr. Merle Jensen at the University of Arizona, for lettuce, spinach, and even tomatoes, although the latter was judged not to be economically viable. In fact, there are no known large-scale commercial aeroponic operations in the United States, although several small companies market systems for home use.
In aggregate hydroponic systems, a solid, inert medium provides support for the plants. As in liquid systems, the nutrient solution is delivered directly to the plant roots. Aggregate systems may be either open or closed, depending
on whether surplus amounts of the solution are to be recovered and reused. Open systems do not recycle the nutrient solutions; closed systems do.
In most open hydroponic systems, excess nutrient solution is recovered; however the surplus is not recycled to the plants, but is disposed of in evaporation ponds or used to irrigate adjacent landscape plantings or wind breaks. Because the nutrient solutions are not recycled, such open systems are less sensitive to the composition of the medium used or to the salinity of the water. These factors have generated experiments with a wide range of growing media and the development of more cost-efficient designs for containing them.
There are numerous types of media used in aggregate hydroponic systems. They include peat, vermiculite, or a combination of both, to which may be added polystyrene beads, small waste pieces of polystyrene beads, or perlite to reduce the total cost. Other media such as coconut coir, sand, sawdust, are also common in some regions of the world.
For growing row crops such as tomato, cucumber, and pepper, the two most popular artificial growing media are rock wool and perlite. Both of these media can be used in either closed or open systems (gravel is not recommended as an aggregate in either system). Both media are lightweight when dry, easily handled and easier to steam-sterilize than many other types of aggregate materials. Both can be incorporated as a soil amendment after crops have been grown in it.
Rock wool, or stone wool, is produced from basalt rock, and can come as spun wool, resembling fiberglass, or it can be granulated, offering an alternative to perlite and vermiculite in terms of water holding capacity and aeration. Stone wool has a high pH, generally greater than 8.0, however, it has essentially no buffering capacity, meaning it will not affect the pH of the nutrient solution nor will it affect any other media it is mixed with, such as peat moss (which has a pH of 3.8 to 4.5). Stone wool can be purchased in prepackaged “slabs (commonly 15 x 7.5 x 100 cm long), ready to use, or as bulk granules for those growers who wish to mix their own soil less media.
Perlite is usually bagged in opaque white bags with drip irrigation tubes at each plant and drainage slits in the bags. Perlite is an inert media providing excellent aeration and water holding capacity. As in rock wool, it can be steam sterilized, re-bagged and reused several times.
When both perlite and rock wool are used as closed systems, great care must be taken to avoid the buildup of toxic salts and to keep the system free of nematodes and soil born diseases. Once certain diseases are introduced, the infested nutrient solution will contaminate the entire planting. In addition to the common practice of sterilizing the re-circulating solution, there is current research exploring the use of surfactants to control certain root diseases. Such systems can be capital intensive because they require leak proof growing beds as well as sub grade mechanical systems and nutrient storage tanks.