Advanced HydroponicsAdvanced Hydroponics. 1
Aggregate Culture. 10
Continuous Flow Systems. 12
Getting Started. 14
Nutrient Deficiencies. 16
Hydroponics is the process of growing plants in water. It typically refers to raising terrestrial plants that normally grow in soil rather than plants that are naturally aquatic. Hydroponics generally involves the use of a nutrient solution to deliver essential minerals to the plant. Many forms of hydroponics also use a soil-less medium, which allows the plants to take root.
Horticulturalists have known that soil is not essential for growing plants since the 18th century. Soil normally serves as a reservoir for minerals, which dissolve in water and allow the plant to absorb the minerals through the roots. However, it is also possible to dissolve the minerals in water artificially and eliminate the need for soil.
The primary reason for using hydroponics to grow crops is that the yield per unit surface area is potentially much greater.Hydroponics is useful in areas where soil is not readily available. It is also a common method of growing plants for teaching and research purposes.
- It is especially important to meet a plant’s requirements when growing it with hydroponics, since the lack of soil makes the plant more vulnerable to changes in the environment.
- Several specific systems exist for growing plants hydroponically, which primarily differ in precise method used to deliver the minerals to the plants. Starting the plants from seeds is an important consideration in hydroponics.
- A hydroponics engineer must also be able to identify specific nutrient deficiencies based on the plant’s appearance.
|Original Source: http://www.flairform.com/hints/nutrient_deficiency.htm|
Plants have generally have the same requirements for light, water, temperature and oxygen whether they are grown in water or soil. The lack of soil means they may require a growing medium, and the plants may also need some means of support. A hydroponics engineer must also pay particular attention to maintaining the method of delivering minerals to the plants.
LightHydroponic plants are often grown indoors, so they often require the use of artificial lights, to achieve their best growth. Most plants need at least eight hours of direct sunlight each day to thrive. Ordinary lighting is too weak for this purpose, so you may need grow lights that produce at least 1,000 foot-candles of light. Grow lights typically use sodium lamps that operate under high pressure, which are quite expensive. This type of lighting is normally used only serious hobbyists due to their cost.
Proper spacing is also important to ensure each plant in a hydroponic system receives adequate light, although the specific area depends on the particular plant. The minimum spacing is generally the same for plants in a garden. For example, tomato plants should have at least four square feet of space for each plant. Lettuce plants should be in rows at least nine inches apart with at least seven inches of space between each plant in a row. Cucumbers require at least seven square feet of space.
The plants in a hydroponics system generally do not grow as well during the winter, even when they are in a greenhouse. This is primarily due to the shorter days rather that the lower temperature. Poor weather can also reduce the availability of light for greenhouse plants in the winter. You should therefore avoid starting the plants in the fall and growing them in the winter when natural light is at its lowest level.
WaterThe difficulty in providing hydroponic plants with sufficient water depends primarily on the specific system in use. The water culture method easily provides plants with water, but adequate water can be a challenge when you use the aggregate culture method. This method requires you to estimate the water requirement of each plant. For example, a large tomato plant needs up to ½ gallon of water per day during hot weather. The plant roots can dry out and they may die when you use the aggregate culture method without providing adequate water. The lack of soil will cause the plant to recover from a low water level, even after you have restored the water to its correct level.
The quality of water is also an important consideration in hydroponics. A high alkaline content is often responsible for poor growth in these plants. A high salt content can make it difficult to maintain the proper level of nutrients, which may require additional expertise in chemistry. A high sodium level is especially common with water that has passed through a water softener. The total salt content in a hydroponics system should remain below 320 parts per million.
MediumA growing medium allows hydroponic plants to root but does not provide nutrition. The best choice of medium depends on the specific technique you plan to use. Common media in hydroponics include baked clay, coir, rock wool, perlite, vermiculite, gravel, packing peanuts and wood fiber.
Baked ClayBaked clay is a common choice for hydroponic systems that require tight control over the nutrients in the water. This material has a neutral pH, does not react easily with other materials and does not have any nutritional value. The manufacturer forms the clay into small pellets and fires them in a kiln at a temperature of 2,190 degrees Fahrenheit. The pellets expand in response to the heat, causing them to become porous. They will not shrink over time, although the shape of the pellets may be irregular. Baked clay is easy to clean and sterilize, typically with bleach, vinegar or hydrogen peroxide. This property makes it an ecologically sustainable material. The biggest disadvantage of using baked clay is that root tips may penetrate the pellets, which can inhibit the growth of the plants.
CoirCoir is the fibers from the outer shell of a coconut. It is also known as coco or coco peat when it is ground to a fine texture. Commercial coir that is to be used as a growing medium in a hydroponic system typically contains colonies of fungi in the trichoderma genus. These fungi protect the roots from bacterial infections and help them to grow. Coir absorbs excess water, making it difficult to over water plants that grow in this medium. Coir can also store excess minerals until they are needed by the plant.
|Choir Fiber Displayed on Broken Coconut|
Rock WoolRock wool is made from filaments of molten rock, usually basalt. It is generally inert to chemical and biological activity, and is the most common medium used in hydroponics. Rock wool has a long history as a successful hydroponic substrate but it is also a possible carcinogen.
PerlitePerlite is a type of volcanic rock that comes from molten lava, which is composed of basalt, granite and obsidian. The high temperature of the lava causes these materials to fuse together in a process known as fusionic metamorphosis. This change also causes the rock to expand and form small, glass-like pebbles.
Perlite can be used as a hydroponic medium in loose form, but it may be packaged in plastic sleeves. It is also a common ingredient in potting soil where it reduces the density of the soil. Perlite is very light in weight and may float to the surface of the water, especially with hydroponic techniques that use drain or float feeding. Pumice is similar in composition to perlite, but it is made from frothy and has a lower density.
VermiculiteVermiculite is also a volcanic rock formed by fusionic metamorphosis. It is similar to perlite, but has a greater ability to absorb water. This property allows vermiculite to store water and nutrients, which is especially useful for passive hydroponic techniques. Hydroponic growers often need to add perlite to vermiculite to increase the amount of air available to the roots of the plants.
GravelGravel is a collection of rock fragments that can vary greatly in size and composition. The gravel used in hydroponics is small, typically the size of the peat. This media is most common in any traditional gravel filter bed that circulates water with electric. The primary advantages of gravel are that it is inexpensive, drains well and easy to clean. However, it is also heavy and requires a stronger container than other containers used in hydroponic. Gravel does not absorb water, and is suitable only for hydroponic techniques that provide water continuously. Brick shards are generally similar to gravel, although they require additional clinging and may change the pH of the water.
PolystyrenePolystyrene is a type of plastic readily available in the form of packing peanuts. They are primarily used in closed tube systems, where the excellent drainage of polystyrene is in a band. Polystyrene is also very light in weight, which generally make it unsuitable hydroponic techniques that use open containers. Plants grown in polystyrene can absorb this material, which may make it unsuitable for growing plants intended for consumption. It is important to ensure that packing peanuts are made of polystyrene, as biodegradable peanuts will decompose into sludge.
Wood FiberWood fiber is extracted from wood with friction and steam. This organic substrate is popular in hydroponics, because it is inexpensive and can maintain its shape for a prolonged period.
AerationAir is essential for plants to carry out photosynthesis. Plants that are rooted in loose soil generally require no special measures to obtain adequate aeration. However, plants will quickly exhaust the air in the water with some hydroponic systems. This requires the grower to introduce supplemental air, typically by bubbling it through the nutrient solution. Continuous flow and aeroponic systems do not require supplemental air since they provide a constant supply of water with fresh air.
NutritionAll plants require specific elements in order to live. Soil normally provides these elements in adequate amounts, often without the need for fertilizer. Hydroponics engineers must specifically supply these elements to their plants. The primary elements that plants require include nitrogen, potassium, phosphorus, calcium, sulfur and magnesium. Additional elements such as iron, seeing, copper, manganese, chlorine, molybdenum and boron are required only in trace amounts.
TemperatureThe temperature requirements for hydroponic plants are generally the same as they are for plants that grow in soil. Most plants can grow over a relatively wide temperature range, but only achieve their best growth within a narrow range of temperatures. For example, a cool weather vegetables such as spinach, or let us grows best at a temperature between 50 degrees Fahrenheit and 70 degrees Fahrenheit. Warm weather plants may grow best at 80 degrees Fahrenheit or higher.
SupportThe soil also provides physical support for terrestrial plants. Hydroponic plants typically must be fastened to a vertical structure to keep them upright. This generally requires the gardener to use stakes or strings.
Hydroponic systems deliver water to the plants with a variety of methods. The type of container that holds the plants also depends on the specific system. The general types of hydroponic systems include aeroponics, aggregate culture, aquaculture and continuous flow.
AeroponicsAn aeroponic system involves growing the plants in a closed container. The container must also be kept dark to prevent algae from growing on the surface of the nutrient solution. The roots are kept at 100 percent humidity with a misting system that keeps them from drying out. The containers may vary in size and shape depending on the specific plants, and may be lined with plastic. Tomatoes require a tall, narrow container to support their vines. Shorter plants such as strawberries grow best in an A-frame container that makes better use of space.
Aeroponics is an advanced hydroponics systems that requires an experienced grower. The spray nozzles must be positioned so that it directly sprays some portion of the roots. They may spray water on the roots continuously or intermittently. A typical pattern turns the sprayers on for 20 seconds, then off for 40 seconds. The spray mixture often contains a fungicide to prevent the exposed roots from rotting.
Aggregate CultureThe aggregate culture method involves growing the plants in an aggregate material instead of water. This hydroponics system requires two containers. One container holds the aggregate material the plants and the other container holds the nutrient solution. A pump delivers this solution to the roots on an intermittent basis to provide the roots with nutrition and moisture. The solution then drains from the aggregate container, allowing the roots to receive air.
An aggregate culture system typically pumps water to within an inch of the surface of the aggregate bed before it is allowed to drain from the container. The specific material may be any type of inert rock that does not contain calcium. Common choices include silica gravel, basalt and granite. Experimental agriculture systems may use other substances such as crushed marble, perlite or Styrofoam.
It is important that the surface of the bed remain dry to restrict the growth of algae. The aggregate material must be coarse to provide rapid drainage of the container, typically with a diameter of at least ¼ inch. Larger material requires a more frequent delivery of nutrient solution, whereas smaller material takes longer to drain. Aggregate culture often uses a gravity-feed system. The nutrient solution flows from the nutrient tank to the aggregate tank by gravity over a period of about 10 minutes. The solution then drains from the aggregate tank into a storage tank over the course of 30 minutes. A pump delivers the solution back to the nutrient tank to repeat the cycle.
AquacultureAn aquaculture system completely immerses the roots of the plant in a nutrient solution at all times. Hydroponic growers often start plants in fine media such as perlite, sand or vermiculite until they reach a certain size. They can easily wash this media from the roots and move the plants to an aquaculture system.
Aquaculture hydroponics systems are the easiest to implement on a small scale, but it needs a large amount of water. The specific design can vary considerably, so long as it meets a few basic requirements. An aquaculture system must support the plants above the nutrient solution. It must keep light away from the solution to prevent the growth of algae. Aquaculture also requires a method of continuously aerating the roots.
The container for an aquaculture solution is typically made of concrete or wood. A wood container will need to be sealed to protect it from the nutrient solution, usually with asphalt or plastic. It is essential to use a type of asphalt that does not contain tar or creosote, which will leave a film on the surface of the water. The size of the container can vary considerably, but it typically has a diameter of two to three feet and a depth of up to one foot. A mature tomato plant should have a container of at least two gallons. Common containers for an aquaculture system include an aquarium, wading pool or plastic pail. The container is typically covered with a sheet of plywood or Styrofoam to keep light away from the nutrient solution. Drill or punch holes with a diameter of about 1 inch to accommodate the plants.
Short plants like spinach and lettuce usually can support themselves but tall plants such as tomatoes require artificial support. Pack cotton or some other flexible material around the holes to hold the stems of tall plants in place. Plants that grow vines such as tomatoes and cucumbers will also require additional support as they grow. This generally involves tying the vines to an overhead support.
The nutrient solution in an aquaculture solution may continuously aerated by immersing a perforated hose in the solution. A pump can then deliver air directly into the solution. The rate of air flow is important, since too little air will not provide sufficient aeration and too much air can damage the roots. An aquarium pump may suffice for a small aquaculture system, but a large system may require a commercial air compressor. Add water to the container each day to keep the level constant. You will typically need to replace the nutrient solution every two weeks when you start the plants and decrease the frequency to once a week once the plants mature.
Continuous Flow SystemsA continuous flow system delivers a continuous flow of nutrient solution over the roots of the plants. This is the most common commercial method for raising plants hydroponically. A continuous flow system delivers the solution with a pipe. Small plant such as spinach and lettuce typically use pipe with a diameter of two inches, while large plants such as tomatoes may require a pipe with a diameter of a six inches. The pipe should be on a slight slope to allow the nutrient solution to flow freely across the plant roots. The pipe will have a row of holes drilled into the top, typically with a diameter of a least one inch.
The grower typically starts the plants in the root cubes until they reach a certain size. The plants are then inserted into each hole in the pipe. Small plants will be able to support themselves, while tall plants will require support with string or wire.
The nutrient solution in a continuous flow system is stored in a tank. It flows by gravity or is pumped through the pipes to keep the roots continually bathed in a nutrient solution. The solution then travels back to the storage tank and repeats this process. Supplemental aeration is not necessary with a continuous flow system since the nutrient solution aerates itself when it returns to the storage type.
The pipe used in a continuous flow system can be made of several different materials. Polyvinyl chloride is a popular choice since it is commonly used in plumbing systems. The primary disadvantage with PVC pipe is its relatively high cost. PVC pipe must also be cleaned after raising each crop to prevent the spread of disease. A cleaning solution consisting of one part bleach and nine parts water is often used for this purpose.
A continuous flow system may also use nutrient film to deliver the solution. This material is a black plastic film formed into a flexible tube with holes at regular intervals. A wooden tray must support the two since nutrient film is not rigid. The primary advantage of nutrient film is that it is considerably less expensive than PVC pipe.
Plastic corrugated drainage pipe may also be used in a continuous flow system. A horizontal pipe carries the nutrient system, which typically has a diameter of two inches for small plants and six inches for large pipes. This pipe has holes cut along the top of a diameter of about two inches. Vertical plastic drainage pipes are placed into these holes and filled with peat moss. The plants are placed into each of these vertical pipes. Capillary action carries the nutrient solution through the peat moss and brings the solution to the roots. Hydroponic growers typically start the plants with another method, although they may also plant the seeds directly into the peat moss.
Hobbyists often need to run their hydroponics system outdoors, although commercial operations typically take place in a greenhouse. Common locations for a private hydroponics system include a patio, rooftop or back yard. The starting schedule for outdoor plants is generally the same whether they grown hydroponically or in soil. The primary steps for starting hydroponic plants are germination and making the nutrient solution. The identification of nutrition deficiencies is also an essential requirement for growing plants hydroponically.
GerminationHydroponic growers can generally plant large seeds directly in aggregate culture systems since an aggregate medium will hold the seeds in place. These seeds can germinate normally and the grower can thin them according to the normal schedule for that particular species. Smaller seeds typically must be started with other techniques and transplanted to the hydroponic system when they are large enough to withstand the conditions of that particular system. All plants will need be started elsewhere and transplanted if you are using a water culture system.
Hydroponic plants generally should be started in a manner that keeps the roots exposed if you are going to grow them in an aeroponic or water culture system. Plant the seeds in a starter medium such as perlite, coarse vermiculite or quartz sand. Water the seeds according to their normal starting requirements and keep them covered with moist paper towels. Remove the paper towels after the plants germinate and thin them as usual. Keep the seedlings moist with a nutrient solution since the starter medium does not provide nutrients. This solution should be ¼ the normal strength since the seedlings are not strong enough to benefit from the full-strength solution. Wash the starter medium from the roots when they ready to transplant to the hydroponic system. It is not necessary to wash every particle of the medium from the roots.
Seedlings that will be transplanted to a continuous flow system should be started in a root cube. This cube will provide the seedlings with the extra stability and support they will require when you move them to the tubes of the continuous flow system. A root cube is made of a sterile material such as cellulose fiber, plastic foam or compressed peat and vermiculite. Containers made of pure peat or peat and perlite will disintegrate when you place the in a continuous flow system and may clog the pump.
SolutionsPre-mixed nutrient solutions for hydroponic systems are readily available and relatively inexpensive. Advanced growers may also want to mix their own solutions. This allows them to experiment with different mineral concentrations, typically to optimize a plant’s growth producing a deficiency symptom. A nutrient solution contains macronutrients and micronutrients. Macronutrients are measured in relatively large quantities and the precise amounts of these substances are not critical. Micronutrients are measured in small quantities and the measurement must be accurate to ensure good plant growth.
The ideal nutrient solution varies by plant but the following recipe is easy to prepare and provides good result for a broad range of plants. The salts in this recipe are commonly available and supply all the macronutrients required by most plants.
The macronutrients for this recipe include the following:
- Calcium nitrate – 7 teaspoons
- Magnesium sulfate – 4 teaspoons
- Potassium nitrate – 4 teaspoons
- Potassium phosphate – 1 teaspoons
The magnesium sulfate and potassium phosphate should be reagent grade while the calcium nitrate and potassium nitrate may be fertilizer grade. Reagent grade chemicals are significantly more expensive than fertilizer grade chemicals. Dissolve each ingredient separately in a glass of warm water before adding it to 24 gallons of water.
The micronutrients in a nutrient solution are used in small amounts and must be measured precisely. These ingredients should be reagent-grade chemicals, which are available in chemical supply stores or hobby shops.
The micronutrients in a nutrient solution include the following:
- Boric acid - ½ pint
- Copper sulfate - ½ teaspoon
- Iron sulfate - ½ pint
- Manganese Chloride - ½ pint
- Zinc sulfate - ½ teaspoon
Dissolve these ingredients in warm water before adding them to the nutrient mixture. You may not need to add copper sulfate or zinc sulfate if you are using tap water, since tap water normally contains these compounds as impurities. Add sufficient water to the nutrient solution to bring the volume to 25 gallons.
Substitute an iron chelate for iron sulfate if your water has a pH above 7.0, meaning that it is alkaline. Prepare an iron chelate by adding 1.5 ounces of iron EDTA to five quarts of water. Mix this solution thoroughly and add ¼ pint of this solution to the main nutrient solution. Prepare other iron chelates so that the final nutrient solution contains 1 part elemental iron per million parts of nutrient solution.
Plants will release waste products into the nutrient solution as they grow, which will cause the water to become more alkaline, meaning the pH will increase. Hydroponics growers will typically add sulfuric acid to the nutrient mixture as needed to lower its pH to between 5.5 and 6.5. Large hydroponic systems may require growers to add acid to the nutrient solution every day.
Growers may also add potassium hydroxide to the solution to increase its pH. Add water as needed to keep the level of the solution constant. Replace the entire nutrient solution every two weeks for seedlings. Replace the solution each week once the plants begin growing.
Nutrient DeficienciesNutrient deficiencies are more common when growing plants hydroponically, since the grower must add the nutrients artificially. Each deficiency produces a specific set of symptoms, so an experienced grower can often identify the deficient element by observing the plants. However, it is important to note that these symptoms may have other causes besides nutritional deficiencies.
The non-metals needed by plants include boron, potassium, and sulfur. A boron deficiency can cause shoot tips to die, and it will cause the petioles and stems to become brittle. A lack of potassium can cause the margins of the leaf to become yellow and continue towards the center. It may also result in dead areas near the margins and tips of the leaves. A potassium deficiency can make the lower leaves become mottled. A lack of sulfur causes the upper leaves to be light green and the leaf veins to be lighter than the rest of the leaf.
The primary metals needed for healthy plants include iron, manganese and magnesium. An iron deficiency causes the parts of the upper leaves that are between the veins to turn yellow while the large veins remain yellow. The tips and edges of the leaves may also die. A lack of manganese or magnesium may cause the upper leaves to develop dead spots. The small veins in the upper leaves may also remain green, giving the leaves a netted appearance.