Trevor Croll Home Page
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.
View the instruments we supply from our home page.
Not all meters are the same. Know the differences and what is measured.
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
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.
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.
Photosynthesis occurs within the general temperature range of 5 and 45 degrees Celcius
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 footcandles with the temperature about 30 degree Celcius. ( 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 from Wet-and-Dry Bulb Readings
Disease and pestilence
Sterialization 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 7.
Dealing with insects and fungus. Some simple remedies.
Insects and their pests: Department of Entomology North Carolina - Insect Notes
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.
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 preditor.
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
References Practical Hydroponics & Greenhouses http://www.world.net/hydroponics
Prepared by Trevor Croll,
42 Pearse Street, Keperra, Queensland Australia, 4054.
Phone 61 7 3855 1115