Hydroponics Skills Checklist

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Form: Date:

Teacher:

INSTRUCTIONS

This workbook forms part of your assessment for this subject and MUST be completed and returned to your subject teacher.

HYDROPONICS SKILLS CHECKLIST

Set up hydroponics unit

Make a nutrient solution

Safe and clean use of tools

Plant crops

Care and maintenance of crops

Harvest crops

Clean hydroponics unit

WHAT IS HYDROPONICS?

Hydroponics is a form of “soil-less” growing of plants. It is not new. Many plants have been grown successfully without any soil since before World War II.

The basic principle is to supply the plant roots with water containing an appropriate balance of the nutrients needed for plant growth, using some form of inert substance as a holder for the moisture and support for the roots.

WHO USES HYDROPONICS?

Hydroponics may be used for:

• Commercial growing in various areas (e.g. lettuces and carnations)
• Cultivation in arid or polar areas (e.g. Middle East deserts, coral islands, oilfields at sea, isolated military bases and Antarctica)
• Work or hobby for disabled people in wheelchairs
• Domestic gardening (e.g. townhouses and units)
• Space colonies

A HYDROPONICS SETUP

Diagram of Hydroponics Setup here

The plant is placed in a container and the soil has been replaced by a stable inert material called the medium.

The medium:

• provides support for the root system
• retains some of the nutrient solution to be absorbed by the roots
• allows good drainage so the roots have enough air
• provides some protection to the roots against extremes of temperature
• should smell “fresh”
• should be moist but not crumble nor be dripping wet after watering

Unlike soil, the medium has no nutrient value. The nutrients needed by the plant must be constantly given in the form of a nutrient solution that has chemicals dissolved in water. In the diagram, the nutrient solution is being poured into the plant container from the jug. The same jug then collects the nutrient solution that drains through. It is again poured into the plant container. In this way, the medium is well stocked with both water and nutrients and the root system can help itself to both.

Because there is no soil, the hydroponics plant is less likely to suffer from diseases or pests.

Because the nutrient solution is at a relatively constant temperature, the hydroponics plant is less likely to suffer extremes of temperature.

Questions

1. What is hydroponics?
2. Who uses hydroponics?
3. What is the medium?
4. What are 2 things that the medium does?
5. What is the nutrient solution and what does it do?

REQUIREMENTS FOR HYDROPONICS PLANT GROWTH – 1. WATER

There should be adequate water otherwise the plant will waste energy growing roots to search for water. Lack of water can lead to a huge root system and a small above-ground plant. On the other hand, if the drainage is poor and the roots don’t receive enough air, the plant will also struggle.

Plants use a large amount of water. For example, a mature tomato plant uses about 2.5 litres of water a day.

The water must be as pure and uncontaminated as possible. A build-up of salt (e.g. in “hard” water with too many calcium and magnesium salts) will stunt or kill most plants.

REQUIREMENTS FOR HYDROPONICS PLANT GROWTH – 2. WATER-SOLUBLE NUTRIENTS

When the soil gardener puts manure on his/her rose bushes, the root system does not feed on bits of manure. First, the manure must be decomposed by bacteria in the soil to release the minerals or nutrients. Then, these are absorbed by the roots and passed up through the plant.

Scientists have worked out exactly which minerals are required by most plants. The minerals needed in largest amounts are nitrogen, phosphorus, calcium and potassium. The minerals needed in small amounts include sulphur, magnesium, iron, manganese, boron, zinc, copper and molybdenum. When a mineral is needed in very tiny amounts, it is called a trace element.

A well established hydroponics system feeds the correct nutrient mixture directly to the roots so that the plant gets enough “food”. The concentration of chemicals would need to be changed if the water used was impure.

REQUIREMENTS FOR HYDROPONICS PLANT GROWTH – 3. pH OF NUTRIENT SOLUTION

The pH of a solution is its measure of acidity or alkalinity. A neutral solution has a pH of 7. An acidic solution has a pH less than 7. An alkaline solution has a pH more than 7.

Most plants prefer a slightly acidic nutrient solution with a pH between 5.5 and 6.5.

Questions

1. About how much water does a mature tomato plant use in a day?
2. What are nutrients that are required in large amounts by plants?
3. What is the name given to nutrients that are required in very small amounts only by plants?
4. If a plant has leaves that are small and yellowish, what element/s could it be lacking?
5. What is the pH favoured by most common plants?

REQUIREMENTS FOR HYDROPONICS PLANT GROWTH – 4. TYPE OF MEDIUM

Although soil contains nutrients and organisms (e.g. earthworms) that are useful to plants, it also contains many fungal diseases and pests (e.g. weeds).

A suitable medium should:

• give adequate support for the root system and the plant
• be stable and not break down quickly
• have absorb and store water
• have good drainage
• be porous enough to allow good circulation of air around the roots

Examples of media that can be used for hydroponics are:

• Sand (cheap and plentiful but dries out easily)
• Scoria (crushed volcanic rock that is often used by commercial growers but it is heavy)
• Vermiculite (crushed mica rock with a flaky brown appearance that retains water well – up to 50% of its weight - but must be mixed with perlite or scoria for hydroponics)
• Perlite (crushed light volcanic rock that is cheap, absorbs water well and lasts a long time)

We use Perlite in hydroponics. The advantages of using perlite are that it is:

• quite cheap (when bought in bulk from large hydroponics suppliers)
• lightweight
• easy to use
• relatively stable and lasts 1 to 2 years
• drains well
• absorbs 27% of its weight in water
• not penetrated by other minerals

Be careful of 2 things when using Perlite:

1. There are two forms of perlite – the hydroponics type and the type used in seed-raising mix and for striking cuttings. Be sure that you buy the correct type.
2. Care should be taken when handling fresh dry perlite as its fine dust is irritating and potentially damaging to the lungs if inhaled. To settle the dust, the required amount of dry perlite should be poured into a plastic bag in the open air. Lightly spray inside the bag with a garden hose while moving the perlite about. Don’t add too much water or the bag will become too heavy.

Questions

1. What is the brand name of the medium used for hydroponics at school?

2. Write down 3 advantages of using Perlite.

3. What other media can be used for hydroponics?

4. Is the Perlite used in hydroponics the same as the Perlite used for seed-raising soil mix?

5. Care should be taken when working with dry Perlite as its dust is irritating to the lungs. What should you do?

REQUIREMENTS FOR HYDROPONICS PLANT GROWTH – 5. WARMTH AND SUNLIGHT

The best all-round temperature for most plants is 22oC. If the temperature falls below 15oC or rises above 30oC, plant growth slows.

On the whole, plants will accept as much sunlight as possible as long as they are not being “cooked”. However, different colours of troughs are recommended for different climates. In colder and temperate regions, the troughs should be black to absorb more sunlight. In warmer areas, troughs should be white to reflect excess sunlight.

REQUIREMENTS FOR HYDROPONICS PLANT GROWTH – 6.AIR

In garden soil, earthworms make air pathways for air to reach the roots. Hydroponics plant roots also need good drainage and air supply to prevent the growth of mould.

Above the root level, good air circulation is achieved by removing dead or excess leaves.

Hydroponics units should be raised above the ground and this helps with good air ventilation.

REQUIREMENTS FOR HYDROPONICS PLANT GROWTH – 7.DISEASE AND PEST CONTROL

A healthy protected plant is less likely to suffer from disease. If the plant is receiving the correct amount of water and nutrients and is isolated from outside potentially disease-carrying plants, it is less prone to disease.

To isolate hydroponics plants from outside diseases, you should:

• place the hydroponics set-up in an enclosed area such as a shade-house
• ensure that they receive the correct nutrient solution
• have good drainage
• remove dead or dying plants
• remove excess leaves
• remove any pests (e.g. snails, slugs, aphids, cabbage moths, mites and grasshoppers)
• ensure that the hydroponics set-up is raised above the ground (Note that snails and slugs cannot crawl easily over coarse sand so this could be placed beneath a ground level set-up)
• use clean tools and ties just for hydroponics (e.g. not the secateurs that are used for outside plants)

REQUIREMENTS FOR HYDROPONICS PLANT GROWTH – 8. SHELTER AND SUPPORT

Strong winds and rain strain a growing plant. Some shelter is needed to protect from these.

Some plants with tall stems (e.g. tomatoes and carnations) need to be supported by a trellis of wire or similar system. This helps their leaves to absorb sunlight for photosynthesis.

QUESTIONS

1. What does the word “optimum” mean?
2. At what temperature do plants grow best?
3. In our school set-up, we have white-coloured trays. Why?
4. Our school hydroponics set-up is above the ground. Why?
5. What can occur if the roots are not well drained?
6. State 4 ways to prevent hydroponics plants becoming diseased.
7. Our school set-up is in a sheltered courtyard. What are 2 advantages of this?

REQUIREMENTS FOR HYDROPONICS PLANT GROWTH – 9. SOWING SEEDS

Advantages of sowing from seed rather than seedling are reduction of cost as well as disease.

Direct Sowing - In warmer weather, seeds can be directly sown by sprinkling them in on top of the perlite which is placed in Jiffy pots, and then covering them with a thin layer of more perlite. Normal nutrient solution will be too strong for seedlings so a quarter strength solution should be used initially and gradually increased in strength as the plant grows.

Seed Germinating Mixtures - In commercial hydroponics, seeds are germinated in separate trays in a special mix (70 to 30 mixture of vermiculite and fine grade perlite) or in lightly packed granulated growool. The advantage of separate trays for seed-raising is to choose the healthiest seedlings for transplanting.

Whatever method is used, it is essential that the seeds do not dry out.

REQUIREMENTS FOR HYDROPONICS PLANT GROWTH – 10. TRANSPLANTING SEEDLINGS

If a seed-germinating mix containing soil has been used, the soil must be washed off before transplanting.

Transplanting requires very gentle treatment so that the roots are not damaged. Seedlings must be carefully teased apart from each other.

The nutrient solution used initially for seedlings should be a quarter strength and then gradually increased.

REQUIREMENTS FOR HYDROPONICS PLANT GROWTH – 11. GENERAL MAINTENANCE

• The pump should be checked daily.
• The nutrient solution should be checked daily to ensure that the roots are moist.
• The perlite medium should be wet – not dripping wet and not crumbly. It lasts 1 to 2 years.
• In any recycling system, the nutrient solution should be replaced at least every month. In summer, this may be as often as every 2 weeks.
• Filters should be cleaned monthly.
• Every 2 months, copious amounts of fresh water should be circulated to remove mineral build-up. The surface medium should be hosed thoroughly and all returned water discarded. At this time, all parts should be scrubbed (e.g with a toothbrush) to remove any build-up.
• Every 2 years, the perlite medium should be replaced.

Questions

Complete the following table about general maintenance of hydroponics.

ADVANTAGES OF HYDROPONICS

• Crops can be grown in areas where normal cultivation is difficult (e.g Middle East deserts, coral islands, oilfields at sea, isolated military bases and Antarctica).
• It is easy to test the nutrient supply for pH and levels of minerals.
• Hydroponics allows more crops per season, particularly with fast-growing crops such as lettuce.
• Soil-borne pests and diseases are less of a problem.
• Less labour is required for irrigation, fertilizing and weed control.
• Plants can be harvested more easily and cleanly.

• Higher yields are obtained from a small area of land.

DISADVANTAGES OF HYDROPONICS

• Hydroponics is expensive to set up. For this reason, many commercial growers usually grow high-value crops such as tomatoes, carnations, strawberries and lettuces.
• Most hydroponics systems require daily attention. If a pump breaks, the whole crop may be lost.

• A high level of technical knowledge is required when treating nutritional disorders of plants or making specific solutions.

2 TYPES OF HYDROPONICS SET-UPS

1. Tank Culture – where the nutrient solution is relatively still and is held in tanks in which the roots are covered

2. Flowing Culture – where the nutrient solution flows past the roots in shallow troughs

THE SCHOOL’S HYDROPONICS SET-UP

Our school uses the flowing culture method where nutrient solution is poured along long shallow troughs that are tilted downwards at a slight angle. (The fall of the trough should be 1 in 25.) The collected nutrient solution is then pumped back to the high end of the trough for recycling.

The medium used is perlite in small Jiffy pots.

The nutrient solution is a prepared powdered mix that is universally used for many vegetables and flowers. Follow the directions for dilution on the container.