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Overview of Hydroponics

The key to successful hydroponic gardening is understanding how a plant produces food and grows.

The manufacture of food for either a seedling or a cutting starts within the leaf structure of the plant. Chlorophyll, the substance that gives plants their green colour, converts carbon dioxide (CO2) from the air, water (containing nutrients), and light energy into carbohydrates and oxygen (02).

This process is called Photosynthesis.

From this point on a complex process will determine the success or failure of your plant’s growth.

Hydroponics is the method or science in which you can supply all the essential elements to this complex system, along with natural sunlight and/or artificial lighting.

Plants are supported in a hydroponic system and nutrition is provided by water soluable, bio-available elements in conjunction with sunlight or an artificial light source. Because hydroponics provides the plant with well-balanced nutrition, hydroponic gardens can achieve amazing results!

Benefits of Hydroponics

  • High bio availability of essential mineral elements.
  • Larger yields.
  • Minimal wastage.
  • High level of control over plant environment.
  • More intense growing techniques requiring less space.
  • Ease of manipulation of essential elements for maximum yield per square metre. Year round crop production.
  • Growing can be facilitated almost anywhere.
  • Less pesticide usage through biological pest control.

Essential Elements

Light – Outdoors

Here, Mother Nature will determine many of the growth influencing factors. Lighting is the most critical of these factors, not only for its energy supply but also for temperature control. Outdoor air is usually fresh but can become uncontrollably humid, arid, cold or windy.

Indoors

Here we must supply a light source. A plant needs a certain colour spectrum of light to promote optimum levels of photosynthesis. A plant in a vegetative state will perform best under a blue spectrum of light, while the same plant in flower will perform best under a red spectrum of light. Light spectrum colours are measured in nanometers. Intensity of light is measured in lumens. High Intensity Discharge (HID) and certain fluorescent lamps are the indoor gardener’s lighting tools.

Fluorescent

These lamps are most efficiently used as a light source to root cuttings, grow seedlings and provide enough lighting for some indoor plants.There is a wide range of tubes available and they are categorized by wattage, length, colour temperature and a colour rendering index.The best suited tubes are those with a colour temp of 5000 or greater, which is perfectly suited for early root and leaf development.

HID

High Intensity Discharge lamps are excellent for the growth and flowering stages of a plant due to their high lumens per watt rating (whereas fluorescent lamps are more suited to the early stages due to their low lumens per watt rating). HID lamps produce light by passing electricity through vaporized gas under high pressure.They require exact starting requirements through power boxes and special fittings and fixtures to house the lamps. Due to their high output a large amount of heat is produced for every watt, so ventilation is a critical factor that needs to be looked at.

Metal Halide lamps create an abundance of blue light that makes them best for vegetative growth, promoting short internodal spacing and therefore excellent plant structure.

High Pressure Sodium lamps produce more yellow/red light which stimulates hormone production and a higher flower to leaf ratio. HPS lamps have a higher output and last longer than Metal Halide. Because of this HPS are the most popular lamps available.

Water / Nutrient

Water is drawn up from the roots through the stem into the leaves where it joins with CO2.Tiny pores on the underside of the leaf aid in this process called photosynthesis. In order for this to occur the leaf’s interior tissue must be kept moist.These tiny pores called the stomata open and close to regulate the flow of moisture, preventing dehydration. They also regulate the outflow of water vapour and waste oxygen.

It can be seen that the water/nutrient system is essential not only to photosynthesis but also to the transportation of the essential elements to the leaf structure that enables photosynthesis to occur.

Nutrients consist of elements that the plants utilize to produce sugars and carbohydrates that in turn are changed into proteins and other complex substances.This process is an essential part of growth.

There are six major (macro) elements and six minor (micro) elements that are also known as trace elements. Nitrogen. Phosphorous, Potassium, Calcium, Magnesium and Sulphur are the macro elements.The micro or trace elements are Iron, Manganese, Boron, Zinc, Copper, and Molybdenum.

A good nutrient solution will have the right balance of all the Macro and Micro elements.

Carbon Dioxide (CO2 ) /Oxygen (O2)

Carbon Dioxide as previously mentioned is absorbed through the stomata and is essential for healthy growth. In any enclosed growing environment the air needs to be constantly exchanged to make sure adequate CO2 is available, as it is very quickly used up by rapidly growing plants. Air movement (ventilation and circulation) is therefore critical.

Oxygen as previously mentioned is released as a by-product of photosynthesis; however, in order for the root system to develop properly and absorb maximum amounts of water and nutrient, oxygen must be present in the solution. Therefore water oxygenation – via air pumps and water temperature – is critical to achieve vigorous growth.

Temperature / Humidity

In order to have Carbon Dioxide available to the stomata reasonable air temperatures and humidity levels are required. Excessive temperatures reduce chemical/photosynthetic activity within the plant. Similarly, excessive humidity will reduce the plant’s capabilities to process CO2.This is because moist air suffocates the stomata, reducing its ability to collect the necessary amounts of carbon dioxide needed for vigorous growth. In addition to this, moist air reduces the plant’s ability to transpire.Transpiration is the movement of water from the roots to leaf surface – driven by evaporation. At high humidity, evaporation is low so transpiration slows down. As a result of this, growth is adversely affected.

Temperature affects the root system differently from the stem, leaf and flower structures. Excessive water temperatures will reduce available oxygen to the root zone.The root system can become damaged as a result of this, which in turn affects the plant’s ability to uptake nutrition. Oxygen starvation as a result of excessively warm water is the key reason for root rot in hydroponic systems.

pH

pH is the measure of the acidity or alkalinity of the solution. A neutral solution has a pH of 7. Higher than 7 becomes alkaline and lower than 7 becomes acidic. Pure water has a pH of around 7. Most flowers and vegetables flourish within a range of 5.8 to 6.8. 5.8 – 6.3 is considered ideal.

The successful hydroponic gardener will keep a very close eye on the pH, as the nutrients are available in their greatest amounts when the pH is maintained within its optimum range. During different phases of a plant’s life cycle some salts will be used in greater quantities than others. Because of this, the salt levels will change and the pH will alter.Therefore accurate measurement and adjustment of the pH along with regular water and nutrient maintenance will provide optimal growth rates.

Conductivity / EC / CF

These measurements refer to the total strength of the nutrient solution. As a plant goes through its various growth stages its nutrient requirements change. Different nutrient strengths and NPK ratios are necessary to provide maximum yields.

Conductivity is the means used for testing the levels of mineral salts available to the plant.