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DIY Hydroponics - The Nutrient Solution

CF TruncheonIn most hydroponic systems the nutrient solution is really just water with fertilizer added. The nutrient solution and its delivery to the plants root system form the core of hydroponics and the success of your crops will depend on your ability to guage what the nutrient solution is delivering to your plants. If the nutrient solution is too weak the plants will be deprived of elements necessary for their healthy growth. If the nutrient solution is too strong the plants roots will be burnt. Either way their growth will be stunted. How do we measure effectively the strength of our hydroponic nutrient? The most common way to test your hydroponic solutions strength is using a gadget called a CF truncheon. A CF truncheon is usually about a foot long with a number of LED's up the side that light up to indicate the strength of the solution. What the truncheon actually measures is the electrical conductivity of your nutrient, the higher the conductivity the more nutrient salts are present in the water. Simply dip the appropriate end of the truncheon into the nutrient solution and give it a few seconds to adjust to the temperature. The LED's next to the nutrients strength will light up or blink.

Most truncheons have a number of different scales on the side. Which you use is up to the individual. I use the CF scale (conductivity factor), others may prefer the EC (Electro-Conductivity) or PPM (Parts Per Million) scales. PPM appears to more popular in the US and CF is used just about everywhere else.

Different plants need different nutrient strengths as they have different requirements and this is more obvious with vegetables than flowering plants or ornamentals. Strawberries as an example are bitter tasting if grown with a CF higher than 24 and lettuce will most definetely benefit from being down around the 6 mark. Tobacco and most flowering plants will grow well at a CF of 18 but most weeds, particularly that whacky one, will grow with a CF of 22-28 without any ill effects. If you are unsure as to the best nutrient strength for your favourite plant experiment and make notes as to what you have done. Observe the plants, are they pale and slow growing? Try increasing the nutrient strength. Did they start out dark green then the leaves curled over and they died? The nutrient was too strong.

NutrientsAlways use the highest quality nutrient solution available to you and make sure that it is a complete formula containing all of the necessary macro- and micronutrients. It is very common for nutrients to be available in two types, one type for vegetative growth which contains more of the nutrients necessary for rapid growth and good plant development and the other for the flowering stage, containing more of the nutrients required for good flowers or fruit. Use the one most suitable for the stage of growth your plants are in. A hydroponics shop is by far the best place for your hydro supplies. A buffering solution such as Bio Earth Sea Acids can increase crop yield quite markedly by keeping the nutrient PH level around the optimum, which is 6.0 - 6.5 for many plants. Add the sea acids first as it contains nutrients as well that will increase your CF then add the nutrient. Most off-the-shelf hydroponic nutrients are two part solutions and you should allow it to mix well with the water before measuring the CF. A few millilitres of superthrive is also a good addition to your nutrient solution and you can really see the difference in the health of your plants when you start using it. The barest minimum that your garden requires is the hydroponic nutrients and if you dont feel the extra expense is warranted you can skip the extras and still get reasonable yields.

The hydroponic nutrient solution in your tank should never be allowed to drop below 15 degrees celsius (60 degrees Fahrenheit) or nutrient uptake will be aversely affected. Ideally the nutrient solution should be between 18-24 degrees celsius (65-75 degrees fahrenheit) and it is easier to heat the nutrient solution that it is to heat the whole room up in winter. An aquarium heater with an adjustable thermostat will keep your tank in the right range. An important thing to bear in mind that the water will evaporate from the nutrient solution but the nutrients will not, effectively making the solution stronger. This is more apparent when the tank is heated and the room is cold. Measure its strength at least every second day and add additional water if it gets too strong. If you dont have a cF truncheon you can compensate for evaporation by topping the tank up with plain water but bear in mind that this may weaken your nutrient solution.

Controlling your pH level can be important, particularly if you are not using a buffering solution and your chosen plant requires very acidic nutrient. Most plants will grow happily in a pH level of around 6-7. Water generally has a pH of 7 so you can get away with a plain water and hydroponic nutrient mixture in your tank. Most plants will grow ok if the pH is less than optimal however nutrient uptake is inhibited. Your hydroponic supplier can provide chemicals which can help you adjust the pH of your tank and I have used these in the past with great success. The best advice for beginners is select crops that will grow in the 6.0-7.5 range and simply not worry about the pH level until you have gotten more adept an hydroponic gardening. You can focus on squeezing the most out of your plants when you have become more proficient.

Over a very short period of time the carefully balanced nutrient solution you have mixed will become depleted of some nutrients more than others because the plants naturally will absorb what they need more than than what they dont. Some gardeners change their nutrient solution every 5 days or so. I dont recommend going longer than two weeks before completely removing the old nutrient, cleaning the tank if it is possible to do so and then mixing fresh solution. It is also good practise to flush the whole hydroponic system out by replacing the nutrient solution with fresh water and running your pump for 24 hours straight to loosen and remove built up nutrient salts. This should be done every four weeks or so. Passive hydroponic users can flush their pots under gentle running water or simply feed the plants plain water periodically to achieve the same results.

As a final extra touch for an active hydroponics system such as flood and drain or top feed is to consider getting an aquarium aerator and putting it into your tank. It will keep your nutrient solution well mixed and aerated.

Foliar Feeding

Foliar feeding makes nutrients immediately available to your crops by misting the leaves with fertilizer or nutrient solution using a hand or pump sprayer. The nutrients are absorbed directly into the leaves.

This can be immediately usefull if your plants have become sick or the nutrient levels in your media have built up to the point where they are toxic to your plants. If this is the case the media is leached (flushed with several litres of water, soaked and flushed again) and the plant is then foliar fed to directly deliver nutrients to the leaves. Foliar feeding can have an almost instant effect and leaves that were pale green and dying can return to a lush green state in the space of less than a day.

Some growers periodically foliar feed to keep the plants growing at their best however be fairly warned that it is easy to over foliar feed your crops. If they are foliar fed to much the nutrient solution, particularly if it is a weak mixture, can leach the nutrients from the leaves and cause your plants to become very sick and unproductive. A mixture that is too strong can block the stomata in the leaves leaving the plants unable to photosynthesise.

As a general guide allow your plants to grow to at least two weeks of age before you start foliar feeding and never foliar feed at less than five day intervals. Mix the nutrient solution you intend to foliar feed with at twenty five percent of the strength that you would apply to the roots. So as an example if the recommended nutrient strength for your crop is a cF of 20 then mix your foliar feed to a cF of 5.