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GROWERS INFORMATION -
ARTICLE - GROWTH INFLUENCING FACTORS |
Growth Influencing Factors
By Cindy Rea
Courtesy Maximum Yield Magazine
Hydroponics is often referred to as controlled environmental
gardening. All conditions in a grow room are controlled by the
grower. The grower can simulate the seasons to replicate ideal
growing conditions for any individual species. This may give
some growers a bit of a God complex but where else can you
play Mother Nature?
Artificial grow rooms offer a tremendous opportunity to
produce maximum yields of selected plants at any time of the
year. Although the initial set up cost may seem a little
steep, the high quality, wonderfully delicious produce you
grow will quickly offset the expense. Home grown hydroponic
fruits and vegetables are a nutritious source of vitamin rich,
flavour packed foods.
To successfully produce a bountiful crop in hydroponic culture
requires some preparation. Ideally the growing environment
will start off sterile to eliminate any contamination from
preexisting foreign matter such as bacteria or fungus spores.
All new equipment should be washed in a weak solution of
bleach and water. Equipment that has been used in previous
growing applications needs a more thorough cleaning. A
disinfectant containing a viruscide and fungicide is
recommended.
Since you are ‘Mother Nature’ in your indoor hydroponic grow
room you must recreate all of nature’s fundamentals within its
walls. Wind, rain, sunshine, temperature fluctuations, light,
day/night cycle and nutrition are all part of the simulated
atmosphere in a grow room. These, along with oxygen (O2),
carbon dioxide (CO2), potential hydrogen (pH) are what are
termed Growth Influencing Factors or (GIF’s) among hydroponic
enthusiasts. As in nature, you will need to find the perfect
balance for each GIF and have all elements run in harmony. If
any of the GIF’s are missing or out of balance, growth will be
compromised and entire crops may be lost. The weakest link in
the chain determines the outcome of your best efforts.
A diary or journal is an essential tool for a serious grower.
Keeping precise records of fluctuations in the daily growth
influencing factors and their influences on crops is
important. It will help determine what is working and what is
detrimental to plants. A daily record of such things as
additives, reservoir conditions and other variables makes
troubleshooting much easier and the implementation of
corrective measures can be put into place swiftly, with
minimal damage to crops. An accurate record will ensure that
any problems are not repeated in subsequent crops.
Take your journal with you the next time you visit your local
hydroponic shop. The experts there will be able to advise you
if your crops are meeting their full potential and what you
may be able to do if they’re not.
The most important growth influencing factor (GIF) is light.
Lights range in size from 175 watt to 1000 watt. A 1000 watt
bulb will cover 16 to 25 square feet depending on the desired
light intensity. It is recommended that lights be used with a
reflector to maximize the full use of the bulb’s output. A
reflector will make sure all light is directed downward toward
your plants and not wasted throughout the room. The style and
size of the reflector you choose will depend on the size of
the lamp, desired light intensity and area of coverage. The
most efficient way to use any high intensity light is with a
light mover. Lights can be placed closer to the crop, stems
will be stronger and plant growth can increase up to 40%.
There are circular light movers that are capable of moving up
to three lights at a time or linear light movers on the market
today.
Seedlings respond to continuous light. Place seedlings in a
humidity tent under a fluorescent bulb 24 hours a day. Once
the first true leaves appear remove tent and cut light time to
18 hours. To propagate stem cuttings place them under a six
inch humidity dome and provide 18 hours of fluorescent light.
Use a rooting hormone to ensure good root development. This is
a crucial time in a plant’s life. Seemingly insignificant
changes could indicate potential trauma to young plants.
Recoding dates and procedures during the germination or
rooting stage will create a history and expectation for
ensuing crops.
For optimum growth at maturity supply up to 18 hours of light
followed by a six hour period of uninterrupted and complete
darkness for respiration to transpire. Respiration must occur
in every living cell if life is to be maintained and to allow
a plant the ability to use energy and thus grow and produce
flowers and fruit. Respiration occurs mainly during the lights
off cycle. Light requirements will vary with growth stages and
different plants.
Timers are the easiest way to automate your grow room. Plants
will respond to an accurate day/night schedule and watering
routine. With a timer you can establish a day/night schedule
that suits your schedule; it is not necessary to conform to
the outside environmental dark/light hours. (Plug in fans, air
pumps and drip irrigation pumps into the same timer as the
light).
Nutrition is the second most important GIF and will be an
integral part of your hydroponic gardening success. Plants
grow faster in hydroponics because their food supply is
constantly available. In the basic hydroponic system plants
are fed by passing the nutrients over the roots or flooding
around the root area at regular intervals, and then later
draining off. In a soilless mix plants can be hand watered
from the top as you would with a regular soil container.
Electrical conductivity (EC), measured in milliMhos, is the
measure of electrical conductance of the total dissolved
solutes (minerals) in the solution. The optimum EC range
varies among different plants. While EC measures the total
dissolved minerals in a solution it does not identify the
amounts of specific elements present. Therefore, it is easier
to achieve the ideal EC using premixed two-part hydroponic
nutrient formulations than attempting to create your own
formula using individual components. It is necessary to change
the nutrient solution weekly to ensure that plants receive the
specific elements required. Nutrient formulas may also be
adjusted between the vegetative and flowering stages. EC
testers are the most accurate way of monitoring and
maintaining a desirable nutrient level in your reservoir.
It is very important to keep track of any additives used for
growth enhancement. Note the date they are added and what
effect they have. Indicate any visible changes that occur
immediately after additives are used, such as leaf colour or
shape. If a sudden adverse reaction takes place quickly flush
or leach with a solution designed to rinse roots.
pH is the measure of alkalinity or acidity of the nutrient
solution and is an important consideration in hydroponics. The
ideal pH level for most plants is between 5.5 and 6.5. If the
pH is not within this range plants will not be able to absorb
nutrients at the maximum level. pH should be tested on a daily
basis using an inexpensive test solution or a pH meter. Even
seemingly small pH fluctuations can have a big impact on
plants’ ability to utilize nutrients. The pH is easily
adjusted with a pH Up or pH Down solution to obtain the
desired level. pH can be tested using a simple litmus paper,
or a pH meter may be used for exact digital readings.
Photosynthesis is the production of sugar from two simple raw
materials - carbon dioxide and water - in the presence of
chlorophyll with sunlight (or artificial light) as the source
of energy. Carbon dioxide (CO2) is vital to the plants’
survival. The normal atmospheric level is about 340 parts per
million (ppm). Research has shown that plants are able to use
more CO2 than is available in the atmosphere (up to 1500 ppm)
to grow larger and faster. CO2 enrichment in your grow room
has the potential to dramatically increase your yield with
little cost. A CO2 injector should be used in conjunction with
an exhaust fan to ensure all CO2 is exhausted between cycles.
The injector should be installed above the lights because CO2
is heavier than air and will float down through the plants,
resulting in maximum intake.
It is absolutely essential to have good ventilation with an
incoming supply of fresh air (oxygen) as plants will soon
consume all the CO2 in an enclosed environment. Plants could
not complete respiration or utilize the food produced by
photosynthesis unless they have a good supply of oxygen. An
oscillating fan in the room will simulate the wind reducing
ambient leaf temperature, restoring CO2 to the leaf zone and
strengthening the stems. It will also make sure there is good
distribution of fresh air throughout the room and help control
humidity levels.
Atmospheric temperature must be monitored and controlled
within the room. As in the outdoors there needs to be an air
temperature differential between the plant’s perceived daytime
and nighttime. When there is light the plant considers it
daytime and the temperature should be maintained around 18 -
25oC, with nighttime temperatures between 12 - 18oC. (This may
vary slightly for different plants.) An independent thermostat
should be placed among your plants to ensure temperature
regulation.
Plants grown hydroponically are usually strong and healthy
making them less likely to fall prey to insect infestations.
However there is always the risk of infiltration by some
tenacious species of undesirable pest. Biological controls
such as ladybugs can be used to help safeguard crops against
whitefly and thrips and beneficial predator mites may be used
to help control spider mites. With severe infestations
non-systemic chemical interventions may be required. Different
methods of extermination are used for different conditions.
Conditions in your growing environment such as temperature
will greatly affect the severity of the pest problem. Your
diary will become an invaluable reference of all these
variables.
Hydroponic gardening needn’t be complicated. However, if you
wish to produce crops commercially or in large quantities
journaling is strongly recommended. Documenting successes and
failures will help build a gardening history that will ensure
your personal gardening growth. |
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