Like all life on Earth, water is the cornerstone of a plant’s survival. In hydroponics, the water is the vehicle used to carry the nutrients, making them available for the roots to take in. With this in mind, it becomes obvious that water quality is paramount to a hydro-gardener’s success.
We categorize water into two descriptive terms – hard or soft. The calcium and magnesium concentration will be the deciding factor in which of the terms your water falls under. Having an abundant (over 300) parts-per-million (PPM, or measurement of the total dissolved solids) of these essential nutrients will make your water hard, while having a minuscule PPM will make your water soft.
In hydroponics, it is better to have a lower PPM in your base water, rather than a higher PPM. If you have hard water, a reverse osmosis filtration system is an invaluable tool to any serious gardener. A good tip is that the better water tastes to you, the better it will taste to your plant.
In hydroponics, there are tools to help a gardener take precise measurements of their water to enable them to succeed.
pH Meter: Potential Hydrogen (a.k.a. pH) is the scale used to measure the acidity or alkalinity of an aqueous solution. It’s measured on a scale from 1 to 14. Pure acid is a 1, pure base is a 14, and a neutral solution is a 7. Every point change on this scale exponentially multiplies the acidity or alkalinity by ten. This fact demands careful and exact measurement and observation, which is achieved with this invaluable tool.
Most plants grown hydroponically prefer a stable pH around a 6 with a .5 acceptable variance (i.e. 5.5-6.5). Since pH affects how well a plant can absorb each unique element, scientific testing has shown plants thrive on the higher threshold of this pH range in vegetative growth, and more acidic in the flowering stage. pH is safely manipulated and buffered using phosphoric acid (pH Lower), or potassium hydroxide (pH Raise). The meter must also be calibrated, at least once a month, to ensure accurate readings using a calibration solution.
EC (or TDS) Meter: Hydroponic nutrients, in the form of nutrient salts, are made up of a precise measurement of all nutrients and minerals needed to grow vegetables, fruits, and flowers. These salts are safe. Consider the pink Himalayan sea salt from your local whole food store. It is chock-full of minerals! Salts make liquid more electrically conductive. Therefore, the more hydroponic nutrient added, the more conductive your water is.
An EC (electrical conductivity) meter measures the nutrient (salt) strength via pulses of electricity. It then calculates the total amount of nutrients in your water, but doesn’t identify the individual nutrients present, or the portion they contribute to the whole. We measure TDS (total dissolved solids) in PPM, or parts-per-million. It is another way to express EC. You can find the PPM from the EC by multiplying the EC by 500 or 700 depending on what the conversion factor of your TDS meter is.
Hydroponic nutrients are a comprehensive soluble form of all the essential nutrition required to raise plants to their highest capabilities. There are primary nutrients known as “macronutrients.” Others we refer to as “micronutrients,” secondary nutrients, or trace minerals. All nutrients are either mobile or immobile.
Mobile nutrients are able to move about the plant as the plant sees fit. This means that the plant, identifying a mobile nutrient deficiency, will move the nutrient to the newest growth rendering the older growth damaged first.
Immobile nutrients do not move about the plant. These nutrients stay in their original placement, affecting newer growth first in the case of a deficiency.
Nutrients used in growing most plants almost always include:
Nitrogen (N): a mobile macronutrient that is required most heavily in vegetative growth. Nitrogen is also needed during the flowering phase in lower levels. Nitrogen is quickly depleted, and makes regular feeding necessary, especially in early growth.
Phosphorous (P): a mobile macronutrient important throughout a plant’s life. Fruiting and flowering plants need the highest levels of this nutrient that helps with germination, root growth, bud set, and production. There are also flowering additives containing very high levels of phosphorous.
Potassium (K): a mobile macronutrient that assists in the combination, production, and movement of starches, sugars, and carbohydrates. It also can aid a plant’s immunity to bad bacteria and mold issues.
Calcium (Ca): an immobile secondary nutrient that is as necessary as the macronutrients, and should be equal in concentration to phosphorous. Calcium creates cells, helps their integrity and growth. It also creates strong roots. Plants must always have calcium on their root tips.
Sulfur (S): an immobile secondary nutrient responsible for important protein synthesis. It is found in several amino acids, and is essential in oil and flavor production. Sulfur in the form of sulfates help to buffer pH, and is the building block of many vitamins and hormones. Vitamin B1, which aids in stress relief for plants, is one of the most notorious vitamins owing its debt to sulfur.
Magnesium (Mg): a mobile secondary nutrient that is the found in the central atom of chlorophyll molecules absorbing light energy for your plant. Magnesium is essential to a fruiting and flowering plant by transferring enzymes into carbohydrates and sugars that will become what your plant produces. Magnesium helps a plant make use of all other nutrients.
Boron (B): an immobile micronutrient that is one of the most understood as far as the scope of functions it performs in a plant. It is known as a needed piece of your nutrient puzzle! It’s needed throughout a plant’s life. Boron helps a plant’s calcium intake, cell growth, and RNA development.
Zinc (Zn): a mobile micronutrient that is infamous for deficiency in soil like ours in Florida! Zinc buddies up with magnesium and manganese to help with enzymes. Sugars and proteins owe a debt to zinc, as does stem growth and chlorophyll. Florida soil’s high pH (above 7.0) is to blame for the zinc deficiencies in our plants.
Iron (Fe): a mobile micronutrient that’s another casualty to high pH soil. It also plays a big role in chlorophyll and photosynthesis. Iron also has a role in a plants respiration, but is very difficult for a plant to intake, so it’s normally chemically-bonded (chelated).
Manganese (Mn): an immobile micronutrient that is essential to chloroplasts, which actually contain the chlorophyll. Manganese also helps with nitrogen and iron in chlorophyll production.
Chlorine (Cl): an immobile micronutrient that helps utmost with the osmotic pressure required to open and close the stomata on the bottom of the leaves, allowing the plant to transpire and release excess moisture. It also assists in root and foliage growth.
Molybdenum (Mb): an immobile micronutrient that converts nitrates to ammoniums. It’s needed only in very small doses, and is most effective in roots and seedlings. During your gardening career you will inevitably find different methods and products to use. The goal is to find the best quality nutrients that do not build up residue and salts that lead to extra time and labor. You should ask your local hydro professional for tips and advice in what will suit your hydro-situation best.
The inert mediums used in hydroponic growing have no nutrient content. Their purpose is holding and supporting the root system, and delivering oxygen, water, and nutrients in varying degrees. Factors such as the nutrient containment, the pH, as well as the composition and texture of a medium – all directly relate to the medium’s needs, and how well your plant will perform overall.
Soilless Mix is a term that normally refers to a medium that is a blend of peat moss, perlite, vermiculite, or coir. A single material is sometimes mistakenly called a soilless mix. It may be soilless medium, but it takes at least two of anything to make a mix!
Perlite is volcanic rock that can be used as an aggregate – a substance used to break up a medium with high moisture holding capacity. It’s also used as a stand-alone medium with fast drainage.
Vermiculite acts the opposite of perlite. It has a great ability to retain moisture. For this reason, one can use vermiculite to blend with perlite, soil, etc. when it drains too fast.
Peat Moss after being wet down has characteristics similar to soil. It holds a lot of moisture and has a fine texture, which is why it’s normally amended with perlite. Dolomite lime is usually added as well to add some micronutrient charge and raise the pH level of this naturally acidic medium.
Coco Coir (Coconut pith) is the ground up material from underneath the husk. It’s a very environmentally conscious choice for a medium, as it is one of the only portions left over in coconut processing. Unadulterated, it needs a calcium/magnesium charge, and a rinse to shed excess sodium content before use. Coir has natural antifungal properties and discourages algae growth – when added to the top of other growth mediums.
Expanded Clay (Hydroton/Hydrokorrels) is a rounded medium created by heating clay at a high temperature resulting in expansion. These porous, reusable beads allow for sharp drainage, nutrient uptake, and air capacity. Hydroton also provides great support for the root zone. You can add peat or coco coir to help retain more moisture and nutrient content around the root zone for plants to feed on between irrigations.
Rockwool (Stonewool) is a porous medium made by melting basalt rock using extreme heat and transforming it into a cotton candy-like material. It is then spun into a fibrous material that resembles fibreglass. This medium can hold 80% water, and 15% oxygen when fully saturated. Rockwool is arguably the most popularly used medium worldwide in hydroponic food production. It’s made into cubes, blocks, slabs, and a granular material. You must soak this medium before use in a pH of 5.5-6.0 for a length of time to neutralize its natural alkalinity.
These are by far not the only mediums used in hydroponics today but are the cornerstones. As hydroponic enthusiasts, we are always anxious to see what’s next. Testing new innovations always further the field of hydro-gardening and helps each grower see what works best for us.
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