Hydroponic Nutrients

More than 98% of any plant is made up of water, together with carbon which is obtained from carbon dioxide in the atmosphere and is present in all living things. Other elements which are essential to the growth of all plants are:
Hydrogen - from water
Oxygen - from air and water
Nitrogen - needed most when the plant is producing leafy growth
Phosphorus - important for root growth
Potassium - influences flower and fruit production and produces more robust leaf growth
Calcium - important for the structure of plant cell walls
Magnesium - required for chlorophyll production. Chlorophyll gives leaves their green colour and is needed for plants to get energy from light

As well as these major elements, plants need trace elements such as Sulphur, Iron, Copper, Chlorine, Manganese, Zinc, Boron and Molybdenum in minute quantities. There are several more elements that have been shown to be beneficial to the plant or to improve the nutritional value of a food crop but are not essential to growth, for example Silicon, Selenium, Iodine and Nickel.

When a plant is grown in soil, the roots absorb whichever of this range of inorganic minerals is present and available in the soil. Some of the minerals present in soil, however, may not be in a form that the plant can absorb easily and availability can also be affected by the pH of the soil.

In a hydroponic system, the complete range of nutrients is supplied by a feed solution specially formulated to provide the same nutrients as would be found in soil, but in such a way as to make all the nutrients readily available to the plant via its roots. Because the added feed supplies all the nutritional requirements of the plant, there is no need for a growing medium such as soil or compost. Some hydroponics systems use an inert medium to support the plants while others use no medium at all.

In small hydroponic systems the concentrated nutrient solution is diluted with water which is then added to the system by hand. In larger, automated systems a tank is connected directly to the mains water supply and kept continuously topped up with water. Nutrients are added to the tank to achieve the desired strength; this can be checked using a conductivity (EC) meter. If the reading is below the optimum level more feed is added to the tank until it is back in the optimum range. The EC ranges for many different crops are widely available in literature about hydroponics.

At the Achiltibuie Garden we check our automated systems every two days during the warmer summer months and less frequently in cooler times of year; this is enough to ensure that the plants have all they need. It only takes a couple of minutes to check and top up, so very little labour is required to maintain the systems. The pH (a measure of how acid or alkaline a solution is) is also important because it affects whether nutrients are available to the plant. Bare-root systems (those with no growing medium) are especially susceptible to fluctuations in pH, so we test and adjust those if necessary.

Our own nutrient solution range is a product of research from many sources into what different plants need and was developed at the old Hydroponicum in Achiltibuie. It is varied to suit different crops: salads and herbs have to produce the maximum amount of good quality leaves, but strawberries and tomatoes require to produce lots of flowers and to set good flavoured fruit, so they need a different nutrient mix. We use (and sell) two different formulations: general purpose feed and tomato feed.