Nutritional Requirements of Plants
Whether a hobbyist or professional grower, it is important to understand the nutritional requirements of plants in order tomaximise quality and yield. Plants require 17 essential elements to grow and reproduce. They are called essential elements because without even one of them, plants weaken and die.
Three of the essential elements, hydrogen, oxygen and carbon are “free”. They come from the water and air, and they account for about 95% of a plant’s dry weight. In nature, the other 14 essential elements come from dissolved minerals in the soil and decaying organic matter. Since hydroponics grows plants without soil, all of the essential elements must be dissolved in water in a form that the plants can readily absorb.
Essential Elements in Their Ionic Form
A good hydroponic nutrient formula provides all the essential mineral elements in their ionic form. Ions are small, inorganic molecules that carry a tiny electrical charge. Some ions are positively charged and are called cations (pronounced cat-ions). Other ions are negatively charged and are called anions (pronounced an-ions). Dry fertiliser salts are neutral because the positive and negative ions are bound together to balance each other out. But once the fertiliser dissolves in water, the ionic bonds are broken and the molecules separate back into their ionic forms. Plant roots can easily absorb ionic nutrients, so plant growth is greatly accelerated in hydroponics.
Grow and Bloom Formulas
For the hobbyist, premixed hydroponic nutrient formulas are the easiest to use. A “grow formula” is used at the vegetative growth stage, providing the extra nitrogen that plants need for strong and vigorous growth. At the fruiting and flowering stage, the grow formula is removed and a “bloom formula” is used in its place. Bloom nutrients are higher in phosphorus and potassium, stimulating the plant to produce a bumper crop of fruit and flowers. During heavyproduction, a “boost formula” is sometimes used for topping off the reservoir. A boost formula is high in potassium, but it contains no nitrogen. Since tomato plants in full production could remove large amounts of potassium from the reservoir in a matter of days, a potassium boost puts back in what the plants took out, helping to improve fruit quality. If the reservoir were topped off with a standard bloom formula between reservoir changes, excess nitrogen would tend to build up in the tank while the potassium was drawn down. The bloom formula would begin to look more like a grow formula to the plant, and the energy of the plant would go towards more vegetative growth instead of fruit production.
Hydroponic Fertilisers vs Chemical Fertilisers for Soil
Hydroponic fertilisers are not the same as chemical fertilisers for soil. First of all, agricultural fertilisers usually focus on N-P-K and rarely contain all of the essential elements plants need, particularly calcium, magnesium and beneficial trace elements. Furthermore, agricultural grade fertilisers often have unacceptable levels of chemical impurities such as lead and arsenic. Mineral salts used in hydroponic fertilisers must be very clean, usually technical grade or laboratory grade, and they focus on providing the perfect balance between all of the essential elements, not just N-P-K. By giving the plants exactly what they need when they need it, the health and vigour of the plants are improved, providing exceptional quality and yield.
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