At our August meeting this past Saturday, I shared with our members some of my experience and research on the topic of Hydroponics Gardening. Here is a basic framework of the items I covered.
(Credit for a great deal of this info goes to the book: Hydroponics, by Dudley Harris )
Definition:
HYDRO: Water
PONICS: Labour
Some say Hydroponics was used in the Hanging Gardens of Babylon. More recently, in the 1930’s, scientist Dr Gericke of California commercialised early lab experiments, which peaked public interest. The technology was also used extensively during war times.
The word Hydroponics is a misnomer, as it is generally used to describe all forms of soilless cultured.
Advantages
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No crop rotation
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Virtually no weeds and soil-born pests
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Uniform results
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Cleanliness
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Larger yields
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Less labour
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Better control
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Easy to start off new plants
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Upgrade poorly plants
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Arable land not required
Three Different Types
1. Water culture
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Least adabtable, not used to a large extent
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Modern variation called NFT (Nutrient Film Technique)
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Take a look at this fun idea for a home Water Culture using a collander
2. Sand/Vermiculite culture
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Solid media
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Overhead feeding
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Sub irrigation feeding
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Very easy for home grower
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nearest method to growing in soil
3. Gravel Culture
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Most widely used
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Sub irrigation
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External reservoir
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Nutrient pumped in, and flows back into reservoir
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‘gravel’ describes the size of the stone
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Advantages
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With this method, the old /new air exchange is very good
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The nutrients are re-used
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Gravel lasts indefinitely
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Highest cost outlay initially
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Product: Hydroton: Clay pebble
Small scale Hydroponics
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Use a container about 20/30 cm deep
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Any shape – a window box is a good idea
Container Materials and treatment
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Variety of materials:
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Wood, plastic, glass, asbestos cement, metal
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Paint the inside of the container with bitumen if necessary
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Plastic – no need to treat
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Wood – to prevent rotting
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Glass – to prevent light from affecting the pH of the medium and nutrient
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Galvanised metal – to prevent the effect on the zinc levels of the nutrient
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Asbestos cement – prevent the pH levels being affected
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Drainage
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Drainage is very important:
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6 mm holes
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Cover with nylon gauze
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Then add a 2.5 cm layer of stones, which are around 6/12 mm diameter
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Media material
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Variety of Media:
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Builders sand / Coconut husk / vermiculite / perlite
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Sand:
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Inert – ensure it doesn’t contain shell, which affects the pH levels
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Test this by placing a 6mm layer of sand in a glass tumbler
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Just cover with water
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Then add an equal amount of Hydrochloric acid (pool acid)
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If this effervesces, your sand unfortunately contains shell
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Coconut husk
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Buy a brick from nursery, and add to a bucket of water, until it expands completely.
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Great for summer, as it holds more moisture than other media
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Perhaps mix it with vermiculite and/or perlite to make it less absorbent
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Vermiculite
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Mica based – treated with high heat to make it more porous and absorbent
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Aerated – hold air and water well
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Collapses over time – replace every 18 months or so.
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Perlite
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Mined volcanic material
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Almost pH neutral
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Absorbs water well
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Can be a bit ‘fly away’ in wind
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Also collapses over time – replace every 18 months or so.
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Planting
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Seeds
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cover while germinating, with card or sheet of wood etc
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keep moist – extra overhead watering
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Seedlings – wash the soil off the roots if possible or if desired
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Bulbs, corms, tubers
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Cuttings – as in soil
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Adult plants
Food
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Buy Hydroponic nutrient powder from the nursery
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Follow the instructions on the pack for solution ratios
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Leave overnight after dissolving
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The nutrient reservoir or storage container needs to be
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Dark – light causes iron to be thrown out of solution
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Use bitumen to paint the container to darken it
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Seedlings – sometimes a half strength solution is better
Feeding Methods
Overhead
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Simply and easy
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Use a watering can
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Water till the medium is as wet as a wetted sponge rung out
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Getting nutrient on the foliage is not a problem
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You can optionally use fresh solution of nutrient at each feed – no need to store the nutrient
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Regulate the frequency based on wind and sun
Dry Feeding
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Easiest home method
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Sprinkle a pinch at the base of the plant – and water in
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Nutrient lasts around 2 weeks
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Can be a bit tricky with low growing plants like lettuce
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Use +- 15g/m2 ; A 90 x 20 cm window box would need around a teaspoon of nutrient
Sub-Irrigation
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Sealed tank
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Nutrient led in at the bottom, brought to a certain level, flows out again (into the reservoir)
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Success due to efficient old air/new air exchange
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Gravel is best – or sand
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First Setup
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Small containers – used sand as a medium
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Place them in a larger sealed outer vessel
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Add nutrient solution to the outer vessel
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Fill till containers are half submerged
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Leave for 30 minutes, and drain solution back into the reservoir
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Do this once a day
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Top the reservoir up with water in case of evaporation
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Replace the solution +- every 10 days
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Second Setup
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Larger sealed container
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Inlet pipe attached via tubing to the bottom of a bucket, filled with nutrient solution
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Place C shaped tiles or a U-trough along the length of the bottom of the tray
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Fill with medium and plant up
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To feed, lift the bucket so the solution runs into the reservoir
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Leave for 30 minutes, and drop the bucket for the solution to run out again
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Occasional overhead watering can be beneficial
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Drip-System
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Using irrigation tubing and a water pump, to pump water using drip nozzles onto the plants
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Once a day
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Re-use of solution stored in reservoir
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Less labour, and less waste and evaporation
The Wick System
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Don’t need to water/feed manually
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Great for going away on vacation
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Only need to top up reservoir, and change every ten days
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Encourages healthy level of constant moisture
You need:
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A pot with at least two holes (cover all but one of the holes with nylon gauze)
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In the other, place a plastic collar, and thread a nylon wick through it into the pot.
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Splay both ends of the wick
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Place the other end of the wick in the bottom of the nutrient reservoir
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Fill the reservoir with nutrient solution
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Plant up the pot with your choice of medium, and your plant
Important considerations
Light
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Consider the position of your plants – plant’s sun requirements
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Light encourages algae to grow on the medium – cover the exposed medium with card or stones
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Reservoir and container need to be darkened
Rain
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Harmless usually
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Can sometimes disturb seeds/seedlings – cover them with card
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If reservoir is not sealed, rain might dilute the nutrient solution – monitor and top up with nutrient
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Monitor for overflowing as well
Wilting
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Insufficient moisture – increase watering
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Constant wilting – sign that the container might be too small
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More severe wilting – could be bacterial wilting, or root rot
Flushing
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Flush the system with water every 6 weeks
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Gets rid of the built-up salts
Algae
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Harmless
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Can be a sign of poor drainage
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To prevent, cover the exposed surface with stones, or card
Staking
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Some media types cannot support stakes
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External support required
Wind
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Consider building a wind-break for the plants, without creating shade
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External staking once again might help
The future for hydroponics
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Overpopulation is increasing at such a rate that our ability to grow enough food to feed it is in doubt
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In year 1800, we had a population of 900 million
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In 2063 it is predicted that we’ll have 24 billion!!
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To house this population, arable land will be used for industry, housing, and buildings
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Raising crops hydroponically doesn’t require arable land
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With technology for converting salt to fresh water, we shouldn’t have a real shortage, on a large scale.
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Hopefully architects will by default design hydroponic tanks into their buildings
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Many people already raise fresh veg, herbs and fruit on their roofs. This could happen more and more.
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Basements, using artificial lighting are also an option for growing hydroponically
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All this will need government buy in and public education.
