The Fundamentals of Hydroponics

Tara | December 20, 2021
The Fundamentals of Hydroponics seedlings in hand
Introduction

Hydroponics is a type of horticulture which involves growing plants without soil under conditions intended to replicate and enhance a complex system of natural processes. Hydroponics enables growers to control and manipulate the key elements that create strong, healthy, high yielding plants. Some of the benefits of hydroponics include:

  • increased bio availability of essential mineral elements
  • larger yields
  • minimal wastage
  • high level of control over plant environment
  • improved efficiency - maximum yield per square metre
  • ability to manipulate conditions 
  • year-round crop production
  • allows crops to produced almost anywhere
  • reduced pesticide usage through biological pest control
Photosynthesis

The process of photosynthesis begins within the leaf structure of a seedling or cutting. Chlorophyll, the substance that gives plants their green colour, converts carbon dioxide (Co2) from the air, water (nutrient solution), and light into carbohydrates and oxygen (o2).

Light – Outdoors

Here, Mother Nature will determine many of the growth influencing factors. Lighting is the most critical of these factors, not only for energy supply, but for temperature control. Outdoor air may be fresh, but outdoors you cannot control other factors such as temperature, humidity, or wind.

Light - Indoors

An artificial source of light is supplied when growing indoors. Plants require 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.

Fluorescent

Fluorescent lamps are primarily used as a light source for seedlings and cuttings due to their low lumens per watt rating. There are a wide range of fluorescent tubes available, categorized by wattage, length, colour temperature and colour rendering index. The best suited tubes are those with a colour temperature of 5000 or greater, which is perfectly suited for early root and leaf development.

High Intensity Discharge (HID)

HID lamps are suitable for both the growth and flowering stages of the growth cycle. HID lamps have a higher lumens per watt rating than fluorescent lamps. HID lamps produce light by passing electricity through vaporized gas under high pressure. They require a precise starting technique provided through power boxes and special fittings and fixtures that house the lamps. Due to their high output, a large amount of heat is produced for every watt, so adequate ventilation is a critical when using HID lamps.

Metal Halide

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

High Pressure Sodium (HPS)

High Pressure Sodium lamps produce more yellow/red light which stimulates hormone production and a higher flower to leaf ratio. Therefore, they are perfectly suited for the flower stage of the growth cycle. HPS lamps have a higher output and last longer than Metal Halide lamps.

Light Emitting Diode (LED)

LED technology has progressed significantly in the last few years. The new generation of LED panels blow every other lighting system out of the water! LEDs put off less heat, use less power, are smaller and more durable and they last longer than other forms of lighting. LEDs also offer a full spectrum of light, and some models even allow spectrum variability.

We have performed comparison tests using an ARCEYE LED 450w board vs a 600w/400V top of the range digital ballast. The 600w digital ballast produced an average of 0.5 grams per watt vs the ARCEYE 450W which smashed it out of the ballpark at a whopping 1.5 grams per watt!

Nutrient Solution

In hydroponics, we feed and water our plants with a nutrient solution. This solution is comprised of water, nutrients, and additives. Nutrient solution 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 process 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. Feeding your plants is essential not only to photosynthesis but also to the transportation of the essential elements to the leaf structure.

Nutrients

Nutrients are fed to plants through the nutrient solution. They consist of elements that plants utilize to produce sugars and carbohydrates that in turn are changed into proteins and other complex substances. This process is an essential factor in plant growth.

There are six major (macro) elements:

  1. Nitrogen
  2. Phosphorous
  3. Potassium
  4. Calcium
  5. Magnesium
  6. Sulphur are the macro elements.

There are also six minor (micro) elements (also known as trace elements):

  1. Iron
  2. Manganese
  3. Boron
  4. Zinc
  5. Copper
  6. Molybdenum.

A high-quality nutrient will have the right balance of macro and micro elements. The elements in nutrients can be mineral or biological. Some nutrients will contain additional ingredients that promote plant health or increase yield such as sugar, kelp, enzymes and fungi.

Carbon Dioxide (Co2)

Carbon Dioxide is absorbed through the stomata and is essential for healthy plant growth. In an indoor growing environment, the air needs to be constantly exchanged to ensure adequate Co2 is available. Growing plants will rapidly use up Co2. Air movement (ventilation and circulation) is therefore critical in indoor hydroponic grow rooms. In hydroponic gardens that are not ventilated, C02 is sometimes supplemented using Co2 burners, bags, or cannisters. The more Co2 in the atmosphere, the faster and bigger plants grow.

Oxygen

Oxygen is released as a by-product of photosynthesis; however, in order for the root system to develop properly and absorb maximum amounts of the nutrient solution, oxygen must be present. Therefore, in hydroponics, it is necessary to oxygenate the nutrient solution – via air pumps, stones and optimal water temperature.

Temperature & Humidity

Optimal air temperate and humidity ensures that adequate Carbon Dioxide is available to the stomata. Excessively cold or hot temperatures reduce chemical/photosynthetic activity within the plant. Similarly, excessive humidity will reduce the plant’s ability to process Co2. This is because moist air suffocates the stomata, reducing its ability to collect the Co2 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 primary cause of 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 is considered ‘alkaline; and lower than 7 is considered ‘acidic’. Pure water has a pH of around 7. Most flowers and vegetables flourish within a range of 5.8 to 6.8. However, a pH of 5.8 – 6.3 is considered ideal.

In hydroponics it is necessary to monitor pH levels closely. Nutrients are more available when pH is maintained within the optimum range. During different phases of a plant’s life cycle some minerals will be used in greater quantities than others. When the mineral levels change, so does the pH. Accurate measurement and adjustment of the pH based on the growth cycle of the plant is a critical element in Hydroponics.

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.

Electrical Conductivity or EC is the means used for testing the levels of minerals in a nutrient solution. Measuring and adjusting the EC of your nutrient solution is essential to ensure your plants are not being over or under-fed.

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