What is Hydroponics?
Hydroponics is a method of growing plants in nutrient-rich water instead of soil. Hydroponics serves to solve issues that can occur in traditional soil farming like nutrient-lacking soil, drought, and flooding. Hydroponics allows plant roots to come in direct contact with nutrient-rich solutions while also providing direct access to oxygen. Everything a plant needs is provided through hydroponics, which allows them to save energy that is normally used to find food and water; this allows them to grow much faster. Plants grown in hydroponic systems have 20-25% higher yields than soil-grown plants. Additionally, hydroponic systems can use up to 90% less water than traditional systems, as unused water can be recirculated and returned to the system.
Overall Advantages and Disadvantages of Hydroponics
History of Hydroponics - Timeline
600 BC Hanging Gardens of Babylon
One of the Seven Wonders of the Ancient World, the Hanging Gardens of Babylon was one of the very first forms of hydroponics. Due to the lack of documentation from this time it is unknown today if the gardens were a poetic creation or a deliberate constructional design.
1100 Aztec Floating Gardens (Chinampa)
Chinampa is an agricultural technique that uses small rectangular areas of fertile soil on shallow lake beds in Mexico. This design most closely resembles today's Deep Water Culture hydroponic system.
1627 Sylva Sylvarum
The first new publishing that discusses growing plants without soil media is called Sylva Sylvarum written by Sir Francis Bacon.
1648 The 5-Year Willow Tree Experiment
This experiment was managed by the chemist, Jean Baptist van Helmont. The goal of the 5-Year Willow Tree Experiment was to determine if plants derive their mass from soil or water. He discovered that after 5 years, the tree had grown to 169 lbs just from water, no soil.
1930s Wake Island
Wake Island is a small, rocky island located in the Pacific Ocean. In the 1930s Pan American Airlines used the island as a refueling stop. Due to the nature of the island, hydroponics had to be used to grow food to supply the passengers.
1940s World War II
During WWII, military bases used hydroponics to supply food to troops stationed on rocky islands.
1982 EPCOT - Gardens of Tomorrow
The “Gardens of Tomorrow” was created by Disney. The garden features a number of different hydroponic applications.
Over the last several years, NASA has increased research within the fields of hydroponics and aeroponics for its Controlled Ecological Life Support System (CELSS).
Types of Hydroponics
Nutrient Film Technique (NFT)
Created in 1965 by Allen Cooper, the Nutrient Film Technique is today’s most commonly used hydroponics system. This technique uses 90% less water than soil systems. NFT systems provide a constant flow of nutrient-rich water directly to plant roots and returns the excess water to the nutrient tank.
There are also different types of NFT systems:
NFT Flat System: most common, used when space is not a factor
NFT A-Frame System: maximizes the number of plants per square meter, often used in rooftop farms or places where space is a factor
Vertical Pipe System/Vertical Farming: stacked in towers, used for indoor farming
The process of an NFT system is as follows:
Nutrients are mixed into a water tank to create a nutrient-rich water solution
A nutrient pump injects the nutrients and pumps the solution through the grow channel to the growing tray
The solution runs through the plant roots and is absorbed
Extra solution returns to the tank for reuse
Nutrient Film Technique Plant Spacing
Leafy Greens: 5 plants per 1m
Checkered: 4 holes per running meter
Two Phase Cultivation Systems
Phase 1 - Seedlings
Phase 2 - Mature Plants
Advantages and Disadvantages of the Nutrient Film Technique
The Dutch Bucket system is most commonly used for hydroponic container plants. Unlike other hydroponic systems, the Dutch Bucket system uses media for plants to have something to hang on to, allowing each bucket to act as a host for the media bed and for the nutrient water solution. This system features a single watering line and drainage line for multiple beds lined up together. The Dutch Bucket system is used for any indoor plant but works especially well with vining plants like cucumbers, peppers, and tomatoes. Vining plants can be trained upward to conserve space and add more plants. The media used in these systems can provide a buffer period of protection against possible electrical failure as soil holds enough moisture to supply the plant for a short time.
The buckets are placed in a series and share the same waterline and drainage line. The buckets can be set on tables, benches, and even the ground if needed. When connected in a series they should be staggered, alternating drain ports facing inward to make sure the drain line can serve all buckets.
Advantages and Disadvantages of the Dutch Bucket System
Media Based systems most closely resemble traditional soil planting methods. Nutrients are dissolved into water and held in the nutrient tank. The solution is then pumped to a drip manifold that distributes the solution to each plant. Excess water seeps through the media and returns to the nutrient tank to be reused.
There are also different types of Media Based systems:
Recovery Drip Hydroponic System: closed loop system, more efficient as the excess nutrient water is returned to the nutrient tank and recycled, requires regular inspection as nutrient concentration diminished over time
Non-Recovery Drip Hydroponic System: drain to waste system, does not recycle water nutrient solution, requires less maintenance as nutrient levels remain consistent, minimizes the risk of spreading plant diseases
Advantages and Disadvantages of Media Based Systems
Aeroponic systems provide continuous saturation of roots with drops, mist, or fog of a nutrient-rich solution. Plants are grown with their roots suspended in the air. This offers great aeration to the plant and does not require substrate. As the plants are suspended in air, they have access to 100% of the available oxygen and carbon dioxide, which greatly reduces rooting time. The main advantage that aeroponics has over hydroponics is that hydroponics is limited to the fact that 1kg of water can only hold 8kg of air. Aeroponics uses 65% less water and uses a quarter of the nutrients used in hydroponic systems. Aeroponically grown plants do not suffer transplant shock and the ability to spread plant diseases is greatly decreased. Any plant species can be grown with aeroponics as everything in the system can be fine-tuned.
Advantages and Disadvantages of Aeroponic Systems
Deep Water Culture
In Deep Water Culture systems, plant roots are suspended in a well-oxygenated solution of water and nutrients. Air is pumped into the nutrient solution by an air pump and air stone that prevent the plants from drowning.
Advantages and Disadvantages of Deep Water Culture Systems
Electrical Conductivity (EC)
Electrical conductivity (EC) is the primary variable when measuring water and managing nutrients, and is the measurement of the strength of a nutrient solution. The speed that nutrients are absorbed by plants varies (for example, nitrogen (N), is absorbed more quickly, while calcium (Ca) is absorbed slowly). EC rises because plants are absorbing water quicker than nutrients. This tends to happen in hot weather as plants are trying to stay cool, and can be combated by adding more water to the nutrient solution. EC drops when plants are absorbing nutrients quicker than water. When this occurs, more nutrients should be added to the solution. EC meters are used to test if the EC levels of the water are the same as the EC levels of the specific plant. Plants can be categorized into low, medium, and heavy feeders.
Potential Hydrogen (pH)
Potential hydrogen is a unit of measurement that measures how much hydrogen is in a liquid and how active those hydrogen ions are. In other words, pH is the measure of acidity or alkalinity of a solution. pH is measured on a scale of 0-14, with 1 being very acidic, 14 being very alkaline, and 7 being neutral. Hydroponic plants tend to prefer slightly more acidic solutions with a pH between 6 and 6.6.
Nutrients are the building blocks of plant growth. Hydroponic fertilizers provide everything that plants would normally get from the soil. When mixing hydroponic fertilizers, it is very important to pay attention to mixing instructions and ratios. In soil, nutrients interact with other nutrients differently which affects the nutrient availability to plants.
This chart explains how different elements interact with one another. The green lines represent elements that complement each other and the red lines represent the elements that ‘antagonize’ each other. For example, Calcium can cause a Phosphorus deficiency, and adding Magnesium will counter the deficiency.
Antagonism: Decreased nutrient availability to the plant due to the action of another nutrient
Synergism: Increased nutrient availability to the plant due to the increase in the level of another nutrient
Dissolved Oxygen (DO)
Dissolved oxygen (DO) is the amount of oxygen dissolved in a solution.
What Affects Dissolved Oxygen?
Temperature - Higher temperatures have less capacity to hold dissolved oxygen
Electrical conductivity (EC) - the higher the EC, the lower the oxygen concentration
Ways to Increase Dissolved Oxygen
Water movement - prevents existing dissolved oxygen from dissipating
Air pumps and air stones - create and release air bubbles
Electrolysis - rather than creating bubbles that can float to the surface and escape, O2 systems release tiny hydrogen and oxygen molecules that dissolve into the water (Note: This is highly effective but costly)
Ozone - O3 is 13 times more water-soluble than O2. O3 will also simultaneously disinfect water
Concentrated O2 - same idea as above, but using O2 instead of O3
In comparison to soil-grown methods, hydroponics is a time-tested, efficient way of saving water and maximizing plant yields. Utilizing one (or several) of the aforementioned techniques can provide you with more control over your plants. Additionally, if you have concerns about nutrient-lacking soil, drought, flood conditions, or the use of pesticides, then hydroponics may be the watering application for you!
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