Outdoor Living: Hydroponic Nutrients

The definition of hydroponics – the growing of plants, using mineral nutrients, without soil.

But the real value of nutrients in the hydroponic system is better defined by using the phrase, “using only fully available nutrient minerals.”

For example, the highly important element phosphorus may be present in soils, but it is often locked, or “fixed” to soil particles so tightly, that it is often not properly available for absorption by the plant’s root system.

In the case of Nitrogen (N), if microbial colonies that are required to convert organic forms of nitrogen to plant available inorganic forms are absent or limited in size, the availability, type and concentration of this important element can be limited.

In hydroponic systems, growers can control not only the type and concentration of nutrients but also their availability. Nutrients are added directly to the plant root system. This results in significant energy savings since the plant does not have to use its energy to support photosynthesis and other reactions and processes required to build extensive root systems required by plants grown in soils.

This energy savings often results in improved whole plant growth, development and yield compared to soil grown systems. Root systems of hydroponic plants are also routinely healthier and more efficient and root systems of plants grown in soils.

Organic Hydroponics

There is a long-standing debate as to whether soilless hydroponic systems can ever be completely organic. For the most part, this debate is the result of disputed ideas about what organics really means. Even in the commercial horticultural world, things are not clear-cut when it comes to what is and what isn’t considered organic.

Traditional hydroponic nutrients are made from fertilizers such as calcium nitrate, potassium nitrate, monopotassium phosphate, iron chelate and many others that, when dissolved into water, dissociate into ions ready for immediate uptake by plants. This is what allows for such rapid and balanced plant growth.

While the reasoning behind whether hydroponics is organic is still under debate, hobby growers need not bother with the large-scale logic. Instead, they should decide what organics means to them and follow techniques to fulfil their own ideas.

For some growers, producing organic and natural crops from an indoor garden simply means avoiding the use of toxic chemicals such as synthetic pesticides, fungicides and sterilization agents. These types of growers choose to focus more on natural approaches while fully embracing hydroponic methods.

For others, growing organically means incorporating the use of organic nutrients combined with beneficial microbial populations like the methods used by soil-based organic producers. Unfortunately, it’s not just a simple case of switching from traditional, fertilizer-salt-based nutrients to organic ones since many early hydroponic systems were never designed to be used with organic compounds and many growers have run into huge problems and ruining crops when trying this.

Replacing highly effective and carefully calculated fertilizer salts with organic nutrient sources is not easy. Manufacturers of hydroponic fertilizer products go to great lengths to get the ideal parts per million of each nutrient ion in their products, so plants grow as fast and balanced as possible.

With organic nutrient sources, it’s impossible to be so precise, so mineral deficiencies within organic hydroponic systems are often an issue. Also, organic nutrients contain a great deal of carbon, which non-organic nutrient products do not provide. This carbon is an ideal source of food for microbes in the nutrient solution and root zone, feeding both beneficial and pathogenic fungi and bacteria.

If unwanted microbes begin feeding on the carbon from organic nutrient sources, things can get a little toxic, creating slimy nutrient solutions, anaerobic root conditions, diseases and even plant die back. To avoid these problems, organic growers just starting out should begin slowly and with systems known to have a better success rate.
There are a few different approaches to obtaining and using organic nutrient sources in a hydroponic system. It can be difficult to get a balanced and suitably high ratio of all the essential minerals from organic sources alone, so experimentation with different products is helpful. There is a range of liquid organic nutrient concentrates on the market, as well as some fertilizer salts that are considered organic and naturally occurring to help boost growth where required.

The plants never must starve or wait for nutrient ions to become available. However, calcium nitrate and many others used in traditional hydroponic systems are not considered organic, but synthetic or man-made, and are not part of an organic system.

Generally, sulphate trace elements, such as iron sulphate, copper sulphate, zinc sulphate, manganese sulphate and magnesium sulphate (Epsom salt), are allowed under organic production, so these can be used to help round out any deficiencies that may occur with organic nutrients.

An organic base product (often a concentrated fish emulsion base or similar) blended with an organic liquid calcium is a good place to start. An organic nitrogen product may be required later on. Growers should aim to use products that have been designed for soilless systems wherever possible.

The main difficulty with running organic systems is obtaining sufficient amounts of nitrogen and calcium, which are required in large amounts by plants. Organic systems rely on microbes in the root zone to convert organic compounds into plant-available nitrogen sources and sometimes this process does not occur fast enough for uptake.

Calcium is difficult to obtain rapidly from organic nutrients as it relies on the breaking down of calcium-containing materials such as limestone. Growers who have hard water sources containing naturally occurring calcium have a major advantage in this case because this form of calcium is readily available for plant uptake.

It is possible to make an organic nutrient solution completely from raw materials rather than relying on commercially bottled products. While liquid bio-digesters that turn raw organic materials into usable plant nutrients have been used by some growers, the more reliable method for smaller systems is vermiculture (worm farming).

Vermiculture is a highly efficient way of processing high-mineral raw materials, such as manures, limestone, blood and bone, fish meal, seaweed meal, guano and others, into usable, mineralized hydroponic nutrient solutions that also provide the benefits of a diverse population of beneficial microbes.

The successful use of vermiculture to process organic fertilizers relies on two things. First, the vermicast must be processed to completion and then extracted into water for use in a hydroponic system. The extract or liquid draining from the vermicast system should not be used as a nutrient solution until the vermicast itself has been fully processed.

Many worm juices on the market are highly diluted and often not balanced enough to use as a stand-alone nutrient solution. Second, the quality of the raw materials going into the vermicast system will determine how balanced the final nutrient will be. High-mineral sources, such as fish, blood and bone meal are often dried and ground into products, while food scraps, weeds and vegetation contain only low levels of minerals and will not make a nutrient solution concentrated enough for most hydroponic systems.

One of the main problems with organic nutrients is concentration. Most organic liquid products are not as concentrated as standard, salt-based fertilizer formulations, so plants may become weak, stretched and more prone to disease.

Growers need to be aware of what underfed plants look like and boost nutrient concentrations as soon as these conditions are detected. Nutrient additives and boosters, such as humic and fulvic acid, are a good addition to organic systems as they help facilitate nutrient uptake and are generally considered organic.

EC and pH Levels

Electrical conductivity (EC) and pH control is also different in organic hydroponic systems. Many organic nutrients don’t conduct electricity, so EC readings may not be a true indication of the concentration of an organic solution. A garden’s pH levels also tend to run higher in a healthy, organic system than many growers are used to maintaining in standard hydroponics.

Since pH-lowering acids commonly used in hydroponics such as nitric and phosphoric acids are not organic, pH is best left to stabilize on its own. Some organic nutrient products naturally have a high pH, so growers should try to select those that have a more suitable pH range for use in soilless systems.