In soilless hydroponics systems, the cache of nutrients in the soil is nonexistent, making it critical plants receive all of their resources through the solution circulating through their root zone.
This heavy reliance on a nutrient supply necessitates mixing and maintaining the perfect hydroponic nutrient solution for vigorous plant growth.
To make your own hydroponics nutrient solution for your growing system, it’s important to understand the influence nutrients have on plant growth and what nutrients are responsible for certain plant functions, what options are available for fertilizer sources, the impact water quality plays on the solution, and why parameters such as electrical conductivity, pH, and solution temperature are important.
The awareness of these concepts will give you the foundation to manage your hydroponics system successfully.
The Importance of Plant Essential Nutrients
All plants need certain nutrients for growth. These nutrients are considered plant essential and have specific roles within the plant. If any of the nutrients are deficient plant growth will be affected in some capacity; hence why you need to mix a perfect nutrient solution providing all of these nutrients.
Plant essential nutrients are classified as either macronutrients or micronutrients, based upon the relative concentration within plant tissue.
Regardless of their concentration within the plant they are all equally important.
Found in larger amounts within the plants, macronutrients are often involved in major plant process such as photosynthesis or are key structural components at the cellular level.
Plant essential macronutrients include nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur.
Nitrogen is considered the most key nutrient needed for plant growth. Its main responsibility in the plant is regulating vegetative growth.
Nitrogen is assimilated into amino acids, the building blocks of protein, it is a major component of chlorophyll, and it is necessary for many of the plant’s enzymatic reactions.
Phosphorus is a structural component in DNA and RNA and is needed for root growth and flowering.
Potassium isn’t a component of any plant parts, but functions by activating the enzymatic reactions that occur, making it imperative for the overall health of the plant.
Calcium holds together cell walls through the formation of calcium pectate, a pectin fiber. When deficient, new tissues exhibits distorted growth because of improper cell wall formation.
Magnesium is needed for many enzymes within the plant to function properly but its most important function is as the central, structural molecule in chlorophyll. Without chlorophyll plants cannot photosynthesize.
Sulfur is only required within plants in small amounts, but that doesn’t make it any less important than the other macronutrients. Through metabolic processes, plants break down sulfur into forms usable to build organic molecules such as vitamins and odoriferous compounds in onions and garlic.
The plant essential micronutrients are needed in much smaller quantities within plants, but their functions are just as critical as the macronutrients. Many of them function as activators of enzymatic reactions and include iron, manganese, copper, molybdenum, zinc, nickel, boron, and chlorine.
Even though these nutrients are needed in much smaller quantities, it’s important your hydroponics nutrient solution contains the correct ratio of micronutrients for plant growth.
Nutrient Solution Basics
Before making your hydroponics nutrient solution as a grower you should familiarize yourself with the fertilizers available for use, the importance of water quality, and why parameters such as electrical conductivity, pH and solution temperature are important.
There are many fertilizer sources on the market that will provide the plant essential macronutrients and micronutrients needed to mix your perfect hydroponics nutrient solution.
When it comes to choosing what sources to use you've different options to choose from, depending on your personal preference.
Conventional versus Organic Fertilizers
Conventional/inorganic fertilizers are made completely, or sometimes partially, from synthetic, manmade materials.
These inorganic fertilizers contain nutrients that are quickly available for the plants; quickly available nutrients mean plant deficiencies are fixed more rapidly, minimizing long-term effects. Inorganic fertilizers are cheaper to buy, and readily available for purchase.
Pros: Organic fertilizers are made from natural ingredients. They consist of the broken down remains of organisms or are a byproduct (i.e. waste) of the organisms themselves.
Cons: The downsides to organic fertilizers are a higher price tag, and nutrients are more slowly available for plant uptake after application.
Wet or Dry Fertilizers
Fertilizers come in either a granular or liquid form, both having their pros and cons.
Dry fertilizers are more economical to purchase and ship because their formulations don’t contain water.
They've a longer shelf life and can be purchased in bulk quantities. Many commercial growers opt for powder or granular fertilizers due to cost efficiency.
Liquid fertilizer sources are popular with new growers. They are easier to work with, but have a shorter shelf life and are more expensive to purchase.
1-Part or Multi-Part
Fertilizers can be purchased as a “1-part” system that contains all of the nutrients needed in a single formulation or they can be purchased as a “multi-part”, meaning you may need to be two, three, or four different nutrient mixes to create a single solution.
New hydroponics growers like the ease and convenience of buying 1-part mixes that contain all of the nutrients they need for a solution.
The drawback with using a single nutrient mix is the resulting nutrient solution cannot be tailored to the developmental stage of your plants, and maximum growth may not be obtained.
As growers become more experienced they often switch to a 2-part or 3-part system. These multi-part systems allow you to customize the nutrient ratio depending on fluctuating plant needs, resulting in better growth.
No matter if you choose to go with synthetic or organic nutrient sources, if you choose to purchase wet or dry fertilizers, or if you choose to make your own nutrients or buy a pre-packaged formulation, the most important thing to look for are products marketed specifically towards hydroponics systems.
Fertilizers made for soil-based systems are not formulated to provide the same levels of nutrients, especially micronutrients.
Hydroponics gardening revolves around providing nutrients to plants through the water source, making it critical you start with clean, high-quality water.
Poor quality water will hinder plant growth from the beginning, making it difficult to maintain proper nutrient cycling.
Your most cost-effective water source is what comes from the faucet, but this might not always be the best-suited water for plants.
If you are in an area with “hard” water, the extra bicarbonates have to be neutralized before mixing a nutrient solution to reduce the pH level. But adding phosphoric acid to lower the pH will increase the water’s phosphorus level, potentially pushing it to a toxic level.
To avoid this, you can collect rainwater to use, purchase purified water, or install a reverse osmosis filtration system to reduce the dissolved solids.
Do not use mineral or spring water as it throws off the balance of the nutrients in the hydroponics system.
Solution Electrical Conductivity (EC)
Water, in its pure form, without any additives is a poor conductor of electricity. Synthetic fertilizers are made up of mineral salts.
When using them to create a nutrient solution these salts allow electricity to move through the solution, a capacity measured as electrical conductivity (EC).
Higher salt concentrations equate to a higher EC. By measuring the EC of a nutrient solution you can gauge the nutrient solution strength.
As a grower, it’s important to check the EC of your nutrient solution on a regular basis. Levels that are too high or too low can both negatively impact plant growth and require adjusting to keep the EC in the optimum range.
pH OF THE HYDROPONIC NUTRIENT SOLUTION
The pH of a solution is simply a measurement of how acidic or basic/alkaline the solution is and is calculated based upon the number of hydrogen ions it contains.
Solution pH is an important tool to growers as it gives an indication of how the water used to make a nutrition solution has been changed chemically.
It also indicates the availability of plant essential nutrients found in the solution.
If the pH of the hydroponics nutrient solution is either too acidic or too basic, a plant’s ability to absorb nutrients is significantly influenced, depending upon the hydrogen ion concentration and nutrient interactions.
At either end of the pH scale the plant essential macronutrients -- those needed in larger amounts for plant metabolic processes -- become tied up, making them difficult for the plant to absorb; the micronutrients needed become more available at these extremes, potentially becoming toxic to plants due to their abundance.
Therefore, when growing plants hydroponically, maintain a proper pH of the nutrient solution is vital to ensure nutrient availability isn’t compromised.
You should routinely test the solution pH, keeping it between 5.5 and 6.5 for optimal nutrient availability.
Not to be overlooked, the temperature of the nutrient solution directly affects plant growth, root health, and dissolved oxygen content.
Nutrient absorption is controlled by processes within the roots since plants cannot regular temperatures themselves they simply adapt to environmental changes.
At low temperatures, plant growth will slow. As temperature increases, dissolved oxygen decreases, but root respiration rates increase in conjunction, thus increasing the need for higher oxygen levels.
Higher temperatures also increase microorganism activity/metabolism and an increased prevalence of diseases such as pythium and other infections.
Optimum nutrient solution temperature depends on the type of plant you're growing and the developmental stage it is in.
Keeping your solution reservoir between 63 and 72°F will meet the growing needs of most plants.
Some cool-season crops such as lettuces and carrots growth the best with solution temperatures around 68-70°F; cannabis prefers solution temperatures ranging from 60-75°F depending on the stage of plant growth.
Most plants prefer a warmer nutrient solution during germination, propagation, and early vegetative growth. As they mature the temperature can be dropped, providing more oxygen for increased respiration rates.
Plant nutrient requirements also fluctuate depending on the plant variety, its development stage, and the environmental conditions, creating a shifting requirement for nutrient concentrations in the hydroponics nutrient solution.
Early in the developmental stages of plant growth, nutrients taken in by the roots are transformed into carbohydrates through photosynthesis for vegetative growth.
A milder, or lower concentration nutrient solution -- low to medium EC of 1.2 to 1.6 -- promotes vegetative growth.
Flowering and Fruiting
Plants that've moved from a developmental stage where they are growing vegetatively to flowering and then fruiting can handle full strength EC in the nutrient solution.
As flowers and fruits develop gradually increase the EC of the nutrient solution it to make more difficult for the roots to take in water.
The resulting plant stress condenses sugars in the fruits, and more antioxidants such as lycopene and vitamin C are produced.
Low EC will present as calcium deficiency, and create tip burn on the foliage. The tip burn makes herbs more susceptible to fungal diseases such as powdery mildew.
Growers will utilize a higher EC (1.8 - 2.2) to avoid this. Short day plants (less than 10 hours of light) can handle an EC up into the 3.2 - 3.4 range.
Mixing the Solution
When working with nutrient sources that contain such little amounts of certain micronutrients -- because that is all your plants need -- your solution needs to be mixed correctly.
Follow the instructions on the label closely for dosing rates (or start off with a more diluted concentration), especially if you're a beginner grower.
- Sterilize all of the containers or reservoirs you'll be mixing the nutrition solution in and all measuring utensils or other apparatus you'll need. You want to avoid cross-contamination or introducing foreign substances into your nutrient solution. Then rinse all of the components really well to remove all traces of the disinfectant/sterilizer.
- Fill containers/reservoirs with your preferred water source making sure to know a close approximation of the volume. If using water treated by a local municipality, allow it to sit overnight for the chlorine to off-gas and dissipate.
- Measure dry fertilizers according to weight using plastic scoops, a calibrated scale, and sterilized filter papers; measure liquid nutrients according to volume using a graduated cylinder or beaker.
- After carefully measuring, add nutrients one at a time (if using a multi-step system add micros, bloom, then grow in that order) to the water. Exercise caution to avoid having fertilizers come in contact with your skin or breathing in the dust of dry fertilizers.
- After each fertilizer has been added to the water mix it in well using a plastic paddle or spoon, creating the solution.
- Check the nutrient solution pH, and bring it to 5.5 to 6.5 if it is out of range.
- Adjust the solution temperature up or down, putting it in the appropriate range for the plants you're growing and their developmental stage.
How I mix my hydroponic nutrients solution for best results for growing, Video guide.
One of the most important aspects of growing plants hydroponically is ensuring the plants receive optimal nutrition through the nutrient solution supplied to their root zone.
Making the perfect hydroponics nutrient solution means as a grower you must understand plant essential nutrients, the nutrition requirements of the plants you're growing, and the important attributes your solution must maintain such as EC, pH, and temperature.
Understanding these principles, coupled with constant monitoring and proper adjustment of the nutrient solution will accelerate and maximize plant growth and resulting yields.
Lindsey Hyland grew up in Arizona where she attended University of Arizona’s Controlled Environment Agriculture. She has supplemented her formal education by working on various organic farms, including spending a semester abroad in India.
Growing and/or raising just about anything gets her excited. She is especially passionate about environmental justice and low-tech, sustainable ways to better run small-scale farms and homesteads. Lindsey started Urban Organic Yield to discuss gardening tips and tactics.