What is hydroponics?
The word, Hydroponic, comes from Latin and means working water. Simply put, it is the art of growing plants without soil.
When most people think of hydroponics, they think of plants grown with their roots suspended directly into water with no growing medium. This is just one type of hydroponic gardening known as N.F.T. (nutrient film technique). There are several variations of N.F.T. used around the world and it is a very popular method of growing hydroponically. What most people don’t realize is that there are countless methods and variations of hydroponic gardening. For more information on the various methods which can be used to grow hydroponically please either call us (0208 644 3780) or email us (firstname.lastname@example.org)
Why does Hydroponics work so well?
That’s simple. If you give a plant exactly what it needs, when it needs it, in the amount that it needs, the plant will be as healthy as is genetically possible. With hydroponics this is an easy task; in soil it is slightly more difficult.
With hydroponics the plants are grown in an inert growing medium (please see our medium page) and a perfectly balanced, pH adjusted nutrient solution is delivered to the roots in a highly soluble form. This allows the plant to uptake its food with very little effort as opposed to soil where the roots must search out the nutrients and extract them. This is true even when using rich, organic soil and top of the line nutrients. The energy expended by the roots in this process is energy better spent on vegetative growth and fruit and flower production.
If you grow two genetically identical plants using soil for one and hydroponics for the other, you will almost immediately see the difference this factor makes. Faster, better growth and much greater yields are just some of the many reasons that hydroponics is being adapted around the world for commercial food production as well as a growing number of homes, hobby gardeners.
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Understanding the environment in which you grow your plants and how to manage it within a specific set of parameters is paramount to obtaining the best results. The conditions needed for sustaining healthy plant growth can be divided into 4 main categories; light, temperature, humidity and atmosphere.
“When each of these environmental variables is set correctly yield improvements will follow”
Light is the single most important thing for you to consider. Obviously, if you wish to grow plants in your basement for instance, you will have to provide all the light yourself and you will need to provide a lot if you are to recreate the conditions of a summer’s day. Fortunately, modern horticultural lighting is more than capable of doing this in an efficient and cost effective manner.
One can start by assuming that you have no natural light whatsoever in your chosen growing area. Obviously, if you have a window or skylight, this will reduce the amount of light that you have to provide but in most cases, this is not especially significant. There are other problems associated with using natural light, such as the inability to control the hours of darkness. The easiest and most efficient way to grow plants indoors is to do it in a dark area and provide all the light yourself. For greenhouse growers, the need to use extra light is limited to the darker months of the year.
Another thing to consider under the heading of light is the level of reflection in your growing area. A well designed grow room will get the maximum benefit from the light that is used in it and it is of great importance to get the best reflection of available light.
Temperature is another important design parameter of your grow room and it is something that must be borne in mind from the beginning. Most plant species will grow most effectively in the temperature range of 20-28°C, the mid-twenties being optimal. It will not be difficult to maintain this sort of temperature in your room while the lights are on as they are a great source of heat as well as light. If temperatures should become too high, a simple extractor fan should serve to reduce them. This extractor can be easily linked to a thermostat to ensure that your room never reaches the high temperatures that can have a negative effect on growth rates. When your lights are off, however, you can expect a gradual decline in temperatures. In the colder parts of the year, they will drop well below the ideal growth range. Recent research has shown that night cycle temperatures are just as significant as day cycle temperatures in plant production and it is in fact the relationship between them that has most effect on the final shape and productivity of the plant. It is important to avoid large temperature fluctuations between the day and night cycles as this can lead to weak and poorly formed plants. It is ideal for most species to try and bring day and night temperatures as close together as possible and this is not as difficult as it sounds.
Humidity is another important consideration in grow room management. If it is allowed to get too high for prolonged periods, it will cause problems both in your room and among your plants. The main danger is the development of Botrytis or grey mould among the flowers or fruit. This organism thrives in conditions of high humidity and will quickly spread and ruin a crop. Plants of the melon family and strawberries are particularly susceptible to fungal diseases and should be provided with a dry environment. The cautious grower will always monitor the humidity in his grow room which is measured by another simple device called a hygrometer. This is a dial type instrument that can be mounted on the wall next to the Max-Min thermometer and will give a constant and accurate reading of humidity. The ideal humidity for normal plant raising would not be much above 50%. If it rises above this, the grower will normally operate his extractor fan until it has been reduced. To keep this potential problem under check, it is advisable to avoid leaving water on the floor which can then evaporate and raise humidity. Any water or nutrient solution that spills or overflows should be wiped up promptly and nutrient tanks should be covered at all times. Any water that is left exposed to the heat from your grow lights will rapidly evaporate and add to the humidity levels.
The fourth variable that needs to be taken into account at the design stage is the atmosphere or air in the grow room and it is here the grower is often faced with a dilemma. On the one hand there is a strong requirement for a continuous supply of fresh air. Growing plants need a constant supply of carbon dioxide to maintain growth. CO2 is present in normal fresh air at the rate of around 330 parts per million (ppm). If you try to grow plants in a closed and sealed room you will quickly run into problems. As the plants grow they will rapidly use up the available CO2 which can drop to less than a third of normal levels within one hour. At this point, plant growth will effectively cease. To maintain normal atmospheric levels of this essential gas, the grower would be advised to run an extractor continuously as well as providing an input point, such as an open door or window, for the fresh air to enter the room. The problem with this of course is that the extractor will reduce temperatures and the grower may not wish to run it any more than necessary to maintain temperatures in the desired zone. It may also not be convenient to leave a door or window open on a long term basis. Fortunately, modern technology has provided simple answers to the grower’s dilemma as carbon dioxide can be added to the atmosphere in the grow room which reduces the need for fresh air being brought in.
Nutrients are the basis of any hydroponic system and since we need to meet all of the plants nutritional requirements, it’s important to know what you are supplying and what can go wrong. With any nutrient solution the two factors to keep in mind are firstly the composition of your nutrient – does it contain all of the elements required for plant growth in the correct ratios. And secondly, with your balanced and complete nutrient solution, what strength or ‘EC’ should it be running at for your particular crop, stage of growth and type of hydroponic system, and how do we measure this.
The nutrient solution – composition
Many growers prefer to buy a ‘pre-mixed’ nutrient solution which simply needs to be diluted (for liquid concentrates) or dissolved in water before use. Often these ‘pre-made’ nutrients come in 2, 3, 4 or even more ‘parts’ so a grower can change the ratio of the mineral elements to allow for either vegetative or fruiting growth or for different crops. There are many excellent brands of these pre-mixed nutrients on the market (such as Ferro, Hydrotops, House &Garden, Dutch Pro and Canna).
The levels that these elements are present in your hydroponic nutrient tend to vary between brands, since there is no one single recommendation for concentrations. Many nutrients may also contain some of the ‘beneficial elements’ such as Nickel (Ni), Cobalt (Co), Silica (Si) or Selenium (Se). While these are not ‘essential’ (plants will still grow without them), they can be beneficial to many crops.
Whether you make your own nutrient solution from the different fertilizer salts, or buy a pre-made brand, problems can, an often do, arise with deficiencies of one of more of the nutrient elements. Common reasons for this are that (1) the nutrient strength may be too low, resulting in insufficient nutrients for the plants in general. (2) The nutrient formula you are using may not be completely balanced, and one (or more of the elements) may be deficient. (3) Occasionally, growers may unintentionally leave out one of the fertilizer salts or the wrong fertilizer was used when the nutrient formula was weighted out. And just to complicate matters further, even if your solution is well balanced, sometimes environmental and internal plant conditions prevent the uptake of certain nutrients and deficiency symptoms then result.
Signs of Deficiency
Each of the mineral elements required by the plant has its own set of ‘deficiency signs and symptoms’ and growers can learn to identify many of these. Many of the signs are similar in appearance, but others are very distinct and most good gardening and hydroponic books will detail what these signs are. Briefly the deficiently symptoms for each of the elements are listed below (these may vary slightly between different plant species and depending on how severe the deficiency is):
Nitrogen (N): Plants are short; leaves tend to be pale green-yellow in colour, especially on the older foliage. On tomato plants, the undersides of the leaf and stems can develop a purple coloration.
Phosphorus (P): Plants are usually stunted, and a dark green colour. Symptoms occur on the older leaves first and plant maturity is often delayed. Phosphorus deficiency in some plant species can be due to conditions being too cold for uptake of this element, rather than a lack of phosphorus in the nutrient solution.
Potassium (K): The older leaves become yellowed with scattered dark (brown or black) spots, followed by tissue death. Severe deficiency will stunt the plant and all foliage will become yellowed and curled. On lettuce the leaves may take on a yellowed, bronzed appearance starting on the older foliage.
Sulphur: Deficiency of sulphur is not common – there may be a yellowing of the leaves, first seen on the new growth.
Magnesium: Deficiency is common on tomato crops with the older leaves developing yellowed areas between the veins which stay green.
Calcium: Young leaves are affected before older leaves and become distorted, small in size with spotted or necrotic (dead) areas. Bud development is inhibited and root tips may die back. Tip burn on lettuce is a symptom of calcium deficiency but is also caused by other factors not associated with a solution deficiency. Blossom end rot of tomatoes is also caused by a deficiency of calcium within the fruit tissue (not necessary in the nutrient solution), and is more of a ‘calcium transport’ problem within the plant under certain environmental conditions.
Iron: Deficiency shows as a distinct yellowing between the leaf veins which stay green, on the new growth and younger leaves (this distinguishes it from magnesium deficiency which shows first on the older leaves). On crops such as tomatoes, iron deficiency may show when conditions are to cold for uptake, rather than be caused be an actual deficiency in solution.
Chlorine: deficiency shows as wilted leaves which then become yellowed and necrotic, eventually turning a bronze colour. Roots become stunted and thickened near the tips.
Manganese: Initially, an interveinal yellowing on the younger or older leaves, depending on the plant types. Brown, dry areas may develop and leaves may drop.
Boron: Plant size is usually reduced; the growing point may die back. Root tips often become swollen and discoloured. Leaves eventually become thickened, brittle, and may be curled with yellow spotting.
Zinc: Short plants with a reduction in internodes length and leaf size. Leaf edges may be distorted or puckered, Yellowing between the leaf veins may also develop.
Copper: Deficiency is rare, but young leaves may become dark green and twisted or misshapen, often with brown, dry spots.
Molybdenum: Older leaves develop interveinal yellowing, progressing to the younger leaves. Leaf edges may develop scorching or cupping of the leaves.
Solution strength – under and over use, measurement
Provided the nutrient you are using is complete and balanced, the concentration or strength of the solution has major effects on plant growth and development. This is why it is essential to be able to measure solution concentration, using a meaningful unit of measure. Many growers will still be working in ppm, using TDS meters, however there is now an industry move to standardize the unit of solution measurement to EC (electrical conductivity) which is a more accurate and meaningful way to monitor your nutrient. All a TDS or ppm meter actually does is to measure the EC of the solution, then use an approximate conversion figure to convert this to PPM. The problem arises is that this conversion figure is never very accurate, as different nutrient solutions with different compositions of nutrient elements will have different PPM values so using one conversion figure can be extremely inaccurate. What the plants root system is actually responding to is the EC (or osmotic concentration) of the nutrient so this is what we should measure. There are a number of different EC (sometimes called CF) meters, and the ‘water resistant’ pen type meters are commonly used by growers. Depending on where in the world you are, the units expressed on your meter may be different, however it is easy to convert between the different units of EC.
Running the correct EC for your particular crop and system is important. Some crops such as lettuce and other greens prefer a much lower EC than fruiting crops such as tomatoes, and each crop has its own ideal EC range for optimum growth. When the EC is being run to high for a particular plant, this will show as visible symptoms within the crop. A high EC, effectively puts the plants under ‘water stress’ since the plant cells begin to lose water, back into the more concentrated nutrient solution surrounding the roots. As a result the first sign of nutrient ‘overuse’ is plant wilting, even when supplied with sufficient nutrient solution. If the high EC conditions are not too severe, the plants will adjust to these conditions and you may see growth which is ‘hard’ in appearance – often a darker green then usually, with shorter plants and smaller leaves. When the EC is being run to low, the opposite occurs – greater amounts of water are taken up, growth will be soft and floppy and often a lighter green in appearance.
Fruit will have less flavour and the quality of the whole crop – in terms of dry matter, shelf life, firmness and colour will be reduced. Since other factors affect EC also, such as water uptake from the solution, concentrating the (nutrients) during warm periods, or (nutrient) uptake, dropping the EC under different environmental conditions it is vital that the EC is measured, monitored and adjusted on a regular basis.
By focusing on the two most important solution factors – (nutrient) balance and (nutrient) concentration, the hydroponic solution will give maximum growth and yields. When things do go wrong, being able to correctly identify a deficiency symptom before it begins to severely affect your plants is also important, so as always, closely watching what your crop is doing is a growers best line of defence against solution problems.