Hydroponics

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Hydroponics

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Description Hydroponic Systems
Author(s)  Roger Mu


Hydroponics means growing plants without the use of soil for nutrients or support. Nutrients are delivered in a specially prepared mixture of water, and support is provided separately by various means.


Historical Examples of Hydroponics

The Hanging Gardens of Babylon, one of the Seven Wonders of the Ancient World, were built in a desert on the banks of the Euphrates River in modern day Iraq. Nebuchadnezzar II built them for his wife who longed for the lush landscapes of her distant homeland.

In China, floating gardens were used as early as 400 BC to grow water spinach (空心菜), water bamboo 茭白, and Chinese wild rice (菰).

The Aztecs built floating gardens on rafts (similar to those in China) on Lake Tenochtitlan to support themselves, eventually becoming a dominant civilization of North America.


Vocabulary

Nutrient Solution

Water mixed with hydroponic nutrients, either dry or liquid, that sustains plants with the essential elements and minerals needed to survive and grow. Soil fertilizer and water is not a suitable nutrient solution.

PPM/EC/TDS

Parts per million, electroconductivity and total dissolved solids. These are various units that measure the strength of nutrient solution. Distilled water has a PPM of 0, tap water has a PPM of 100-300 and nutrient solution for mature plants ranges from 800-1200, although higher concentrations are possible.

Substrate/Medium/Aggregate

An inert or neutral material that plant roots are surrounded by. It fulfills the support function of soil, but does not provide any nutrients and good mediums don’t influence the pH of the nutrient solution.


Advantages / Disadvantages

Advantages Disadvantages
Faster growth, shorter time until harvest High initial cost
No need for heavy and unpredictable soil; ability to grow where soil is not practical or available Appears technical, intimidating, even to soil gardeners
Less weeds, pests, and diseases Requires some special supplies and equipment, that may not be available
Less overall use of nutrients / fertilizers Some systems require electricity, which means power failure can lead to catastrophic results
Lower water needs, as low as 2% compared to soil
Can be setup anywhere; smaller carbon footprint from growing plants locally, rather than importing / transporting


Types of Hydroponic Systems

<-- Open, Aggregate                                      Closed, Non-aggregate-->
<-- Similar to soil gardening                            Different from soil gardening -->

Closed vs Open

  • Closed or recirculating systems describe systems in which plants are fed nutrient solution and the excess solution, or runoff, is collected and used again. Closed systems are more complex due to the changing nutrient strength and pH of the nutrient solution.
  • Open or run-to-waste systems collect the runoff, but it is not used to feed the plants in the system. These systems are less sensitive to medium composition and do not require constant pH and PPM testing.

Aggregate vs Non-aggregate

  • Aggregate systems support plants through the use of containers and neutral aggregates, or mediums, such as "rockwool", sawdust, sand, or coco coir, and fulfill the physical supporting function of soil. Aggregates can also act as passive irrigation and store small amounts of water in case of emergencies.
  • Liquid systems may also have a small amount of aggregate, but the majority of the plant roots are suspended in nutrient solution or mist.


Watering Systems

Hand Watered

Hand watered.gif

Hand Watered are generally open, aggregate systems. They are the simplest form of hydroponics that require no electricity or special equipment. They only need aggregate, nutrient solution, and motivation.

Drip

Drip are generally open or closed, aggregate systems. They use an automated irrigation system that drip nutrient solution to individual plants on a timer controlled feeding schedule. it is one of the most widely used system types for commercial production due to its simple design and ease of maintenance.

Wick

Wick.png

Wick systems utilize a nutrient reservoir placed beneath an aggregate container, and use capillary action to move nutrients up from the reservoir to the aggregate. Due to the passive nature of this system, water pumps are not necessary.

Deep Water Culture

Dwc.png

Deep water culture or DWC are generally closed, non-aggregate systems. DWC suspends plant roots in a reservoir of nutrient solution. Without an air stone, the system will consume zero electricity and some plants can do quite well. However, most plants will perform better with supplemental aeration from an airstone.

Nutrient Film Technique

Nutrient film technique.png

Nutrient film technique or NFT are generally closed, non-aggregate systems. NFT feeds plants using a thin film about 2 mm of nutrient solution streaming through a channel. Although NFT is often the "poster child" of hydroponics that most people imagine and a popular and cost effective system for large scale production, NFT systems are very susceptible to power failure, since plant roots will dry out quickly if the flow of nutrients is stopped for long periods.

Aeroponic

Aeroponics.png

Aeroponic are generally closed, non-aggregate systems. Aeroponics were originally developed by NASA for use in space. Aeroponics suspend plant roots in air and spray them periodically with a fine mist of nutrient solution. Although the most technically demanding and sensitive of all hydroponic systems, aeroponic systems are capable of achieving a 98% reduction in water needs compared to soil agriculture and offer superior oxygenation to the root zone.


Flood and Drain

Flood and Drain are closed and aggregate systems. Flood and drain, or ebb andf flow, systems bathe plant roots and aggregate and then drain back into a reservoir several times every hour, either by timer or through a siphon.

Aquaponic

Aquaponic.gif

Aquaponic are closed and aggregate systems. The majority of aquaponic systems are flood and drain. The major difference between an aquaponic and hydroponic system is that an aquaponic reservoir also contains fish, which provide nutrients for the plants and eliminate the need for nutrient solution. Other reservoir based systems, such as NFT and DWC can also be used.


What can you grow

In general, almost any plant can be grown hydroponically, but some plants perform better than others.

  • Leafy vegetables, such as lettuce and herbs, do especially well in hydroponics.
  • Fruiting vegetables, such as tomatoes and peppers, also do well in hydroponics, but have more requirements that must be fulfilled to grow well.
  • Root vegetables, such as carrots and onions, can be grown in hydroponic systems, but often perform better and require less work when grown in soil.


Growing Process

Propagation

The first step of the growing process is creating seedlings or clones. Seedlings are started from seeds (germination) while clones are made from cuttings off of mature plants.

When germinating seeds, providing the ideal temperature is critical and a heating mat can drastically increase success, especially in winter and early spring. Once they have sprouted, they must immediately be provided with good light, or else they will stretch towards a light source, creating ‘leggy’ seedlings which are poorly supported. Good air circulation must also be provided not only for air but also to stimulate thick stem growth.


Cloning involves cutting new growth from a mature plant and giving it conditions that will allow it create roots to make it an independent plant. The easiest way is to take the cutting, stick it in water and cover with clear cling wrap. Replace the water every 2 days and after a week, new roots will be visible. The use of a specialized cloner and cloning gel can increase success rate.

Many seedlings/clones can be packed in a small area since each one is quite small, but as their leaves grow larger and wider, the next step will become necessary.

Transplanting

The second step of the growing process is transplanting seedlings and clones to progressively larger containers so that they won’t be competing with each other for light and also to stimulate root growth, until they are transplanted into their final container.

For example, 12 tomato seedlings can be germinated in a 12 cell starter tray. At about the 3rd or 4th week, they will be transplanted into a 75 mm diameter pot, then 2 weeks later they will need to be transplanted to a 225 mm pot, then 2 weeks later they can be transplanted into their final 400 mm container.

Transplanting can sometimes stress seedlings, known as transplant shock, especially if roots are damaged or left out in the air for too long. However they will recover after a few days of appearing visibly ‘unhappy’ (droopy leaves, no new growth).

Vegetative Growth

The vegetative phase of plant growth begins at germination and ends once the plants begin flowering.

During this phase, plants focus on growing new leaves and shoots, and are hungry for nitrogen, which is the basic building block of leaves and shoots. Plants grown with artificial lights can be ‘turbocharged’ by giving them 16-24 hours of light every day, allowing for more growth than naturally possible with sunlight.

For leafy vegetables, it is important to keep them in this phase as long as possible. Older leaves can be harvested and consumed and new leaves will grow again to replace them. Once they begin to show flower buds however, the entire plant should be harvested, since flowering often causes the taste of the leaves to become bitter.

For fruiting vegetables, it is important to carefully monitor the plant’s growth. As it grows taller, supporting the plant with stakes, string or a trellis may be necessary. Also, old leaves and new shoots should be pruned to maximize growing efficiency.


Flowering

Flowering begins when the plant begins producing flower buds, which then produce flowers, which eventually produce fruit. For artificially lit gardens, flowering can be induced by giving the plants 1-2 days of total darkness and then a 12 hour light cycle.

During this phase, plants focus on producing as many flowers as possible and directing growth towards any fruit from those flowers. Potassium and Phosphorous are the critical nutrients needed during this phase. Flowering plants desire 12 hours of light and 12 hours of dark to rest.

Fruiting plants will continue to increase the size of fruit until visible ripening signs are shown. For example, peppers set fruit and start off as green but once they begin to turn red, they should be harvested.

Similar to the vegetative phase, providing supplemental support for the plant will be necessary for good results and new shoots should be pruned so that all of the nutrients can be focused on developing fruit.


Harvest

The final step for the growing process is harvesting. For fruiting vegetables this means cutting ripe fruit from the plant and for leafy vegetables this can either mean cutting off old growth or harvesting the entire plant.

Fruiting vegetables will remain in the flowering phase as long as the temperature and light hours it desires are maintained, two things which can easily be controlled in an indoor system.

Using temperature and light control, it is possible to continue harvesting fruit throughout winter.

Like professional athletes however, plants have a limited life span of stellar performance and sometimes it is more practical cut down an old plant so that a younger plant can replace it.



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