Hydroponics - growing plants using
a nutrient solution.
Instrumentation in hydroponics is controlling pH
and Conductivity while ensuring the
plants have the right nutrient mix, environment, support and hygiene.
TPS has a range of instruments for
Hydroponics, designed specifically for that purpose.
Not all meters that measure nutrient strength are the same. You must
know what your instrument is actually measuring.
Hydroponics is a technique that uses nutrient-enriched water rather
than soil. The major advance of hydroponics is the ability to control the
plant's environment increasing productivity in all seasons.
Plant productivity requires:
Water, Light, Dark, Nutrients, Warmth, Humidity, Support, Fresh air, Protection
from wind, Carbon dioxide, Oxygen, Nutrient Temperature, pH, Genetic makeup,
Disease free and Cleanliness. The result is a productive plant with a healthy
root environment and a healthy leaf structure.
Plants need nutrients
A plant lives and grows by taking up nutrients
from soil moisture and carbon dioxide and oxygen from the atmosphere.
Plants can suffer from nutrient deficiencies. Good hydroponics farming
is being able to recognize nutrient deficiency symptoms
early. Getting the correct nutrient formulation for
the particular crop improves productivity.
Plants varieties each have their own preferred Conductivity
range. Know your plants.
pH dramatically affects plant nutrition.
If pH is too high plants suffer from iron, manganese, copper, zinc and
boron deficiencies. If the pH is too low plants suffer from phosphoric
acid, calcium and magnesium deficiency. At lower pH fungal diseases flourish.
Healthier plants have more sugars. Plant health can be measured using
refractometers to measure sugar levels in the
plant leaf.
There are three basic methods of starting or propagating
plants.
Growing Conditions
Most plants require support for either the root
system or the stem or both.
There are a number of Hydroponics techniques such as Nutrient film,
Rockwool, Aggregate, wick systems, bag culture, aeroponics, in water aeration
etc.
A quality and quantity of light is required. The light needs to be at the
blue end of the spectrum. Special globes or lights are required for exclusively
indoor growing. A dark period every 24 hours is required so that the plant
can stop photosynthesis and produce the sugars required for growth. TPS
have a Light meter, model MC-88.
Photosynthesis occurs within the general temperature range of 5 and 45 OC.
Normal concentration of carbon dioxide gas in the atmosphere is about 340
parts per million. Enrichment is usually aimed at producing 1300 to 1500
parts per million of carbon dioxide gas whilst the light intensity is about
40,000 lux (3800 foot-candles) with the temperature about 30 OC. Levels above 2000 parts per million become toxic to the plant.
Levels of carbon dioxide below 200 parts per million can cause some plants
to stop growing.
Relative Humidity is also an important parameter which must be monitored
regularly. TPS have a Relative Humidity meter, model MC-83.
Disease and pestilence
Sterilisation is used in closed hydroponics systems to keep the
level of pathogens low. It is important to "know thy disease". Some pathogens
have lipto-proteins in their cell walls. The addition of a little detergent
can solve some disease problems. Nutrient sterilization
is another technique. The addition of killing chemicals to the nutrient
solution is another. Many pathogens do not do well in high value nutrient
solutions with pH values above pH7.
Plants have differences
Plants are grouped into three main biological classifications as far as
carbon dioxide fixation is concerned - C3, C4, and CAM. These are the different types of bonding
sites (receptor sites) for carbon dioxide. Once the bonding process is
complete a series of chemical reactions occur to break down the carbon
dioxide and water to create carbohydrates. An enriched carbon dioxide atmosphere
can give an increase in photosynthesis of between 30 and 60%. Increasing
the carbon dioxide can also increase the water use efficiency - Under normal
carbon dioxide atmospheric conditions carbon dioxide diffuses into the leaf while water
travels up the root system and transpires through the stomata. In a carbon
dioxide enriched environment the stomata shrink so that the plants transpire
less water - they become more water efficient.
Plant Genetics
Genetic engineering has started a whole new activity - Gene hunting. The
hunting for genes in some other species that can be moved into another
species and give that species a major advantage. Cotton is benefiting from
the addition of a gene from a bacteria that produces a protein that kills
cottons major predator.
The genetic makeup of the plant can play an important role in the overall
growth performance of a plant. Plants are selectively bred for certain
desired characteristics. Tulips and Roses are a common example of breeding
for colour and stem length. Early fruiting varieties of Tomatoes are grown
to take advantage of market prices.
References: Practical Hydroponics & Greenhouses
Copyright © 1996, 1997, 2001 TPS Pty Ltd
