Fertilizer vs. Hydroponic Nutrients
In order to begin a discussion on hydroponic nutrients, it’s important to first distinguish the difference between the terms fertilizer and hydroponic nutrient.
Fertilizer is intended to feed the microorganisms in the soil, such as beneficial bacteria and fungi. All of the living components in the soil must be protected, so fertilizer is lower in concentration compared to hydroponic nutrients. The microorganisms break down the fertilizer into a form that is usable by plant roots.
A hydroponic system is a sterile environment and there is no soil- therefore there aren’t any microorganisms for the plant roots to depend on. Hydroponic nutrients are directly absorbed by plant roots, which eliminates the middle step of those soil organisms. Hydroponic nutrients are higher in concentration because there are no organisms that need to be protected in these systems.
One last difference is the fertilizer and hydroponic nutrients are measured on two different scales: TDS and EC. We recommend only using EC, for the reason why read our article EC vs TDS
EC
Electrical Conductivity, or EC, is a measurement of the ionic activity of a solution. EC is measured using a probe that sends an electrical current into the water. EC is measured in microSeimens, or uS, and miliSeimens or mS. Hydroponic nutrient solutions should always be measured in EC.
When measuring your nutrient solution, it is important to first determine the EC of the water you are using. If you choose EzGro’s Vegetable Formula, for example, the recommended EC is 1575 uS. If you are using tap water and its EC is 100 uS, then the total EC of your solution should be 1675 uS.
Types of Water in a Hydroponic System
There are many types of water to choose from when sourcing water for your hydroponic system. Some are better than others, and now is the time to determine the differences. Rainwater is nature’s reverse osmosis (RO) water, and is the best choice for a hydroponic system. Believe it or not, well water tends to be the worst choice when choosing a source for your hydroponic system. Well water has been sitting in the ground, which means that anything in the ground can leach into the water and contaminate it. Our article Types of Water in a Hydroponic System has more information on this subject.
EzGro 3-Part Mixes: What are parts A, B, and C?
Our nutrient mixes are divided into three parts, A, B, and C. We do this to give you the most control over your nutrient solution, which results in healthier, more productive plants.
Part A combines all the minerals that are compatible with each other.
Part B is calcium nitrate or Ca(NO3)2, and cannot be mixed with Part A or Part C. If Part B is mixed with either of these two parts, a reaction occurs that solidifies it like a block of cement. The molecules bond, rendering it completely useless to your plants.
Part C is magnesium sulfate or MgSO4, also known as Epsom salt. No chemical reaction would occur if this was mixed with part A, but we like to keep these three parts separate because we want to give you the power to tweak your solution as you need to.
Parts B and C are crucial to plants when they are in the fruiting stage. Parts B and C should be increased when plants are fruiting so that you get the most out of your plants, and the nutrient mix.
In addition to the 3-part system, EzGro offers two different blends to give you exactly what you need. Our nutrient mixes use only the highest quality ingredients. We pride ourselves on higher quality- it’s what we expect in a product, and it’s what we trust for growing our own plants.
We have a Vegetable Formula that can be used with almost every plant. We also carry a Strawberry Formula that is lower in concentration so it’s meant specifically for strawberries. Strawberries are sensitive to high nutrient levels, so choosing the formula specific for them will save you money and provide the optimum low-level nutrients that your strawberry plants crave.
How to Mix: Powder to Liquid Concentrate to Working Solution
There are three steps in mixing nutrients for your system, and we’ve already completed the first for you by making the A mix which is a combination of necessary minerals for the plant.
- Powdered Concentrate: We’ve divided the nutrients into 3 parts so that you can add more or less of each, depending on your needs. This is a powder so it’s measured by weight, not by volume. When measuring the powder, be sure to use a scale and not a measuring cup.
- Liquid Concentrate: The next step is to combine each part with water, separately. One-gallon jugs are easy to find, inexpensive, and easy to store, so this is what we recommend using. As long as the container for the liquid concentrate is sealed when it is stored, it will have an indefinite shelf life. This is a concentrated version of your nutrient solution that is measured by volume using a measuring cup.
- Working Solution: The working solution is the nutrient solution in your reservoir. It is at the ideal concentration for your plant’s roots to uptake the nutrients. Reminder: always factor in the EC of your water! See the section on EC for more information about this. For information on mixing your liquid concentrate into a working solution, read on.
Closed System Flushing
Finally, let’s examine how important it is to flush out your nutrient reservoir, if you are using a closed system. Closed systems should ideally be flushed out each week. Though this may seem like a lot, there is a scientific explanation for it. Plants intake nutrients through their roots, just as we consume food through our mouths. Plants excrete waste salts in a process known as transpiration. These salts are excreted into the water that is part of your nutrient solution. The EC will rise when there are lots of waste salts in the water, but it is actually measuring the waste and not the fresh nutrients. Although the reading is accurate, the plants cannot use these salts.
This may sound like a lot of maintenance, but once you develop a routine it will be very quick and straightforward. After filling the Patio Garden’s reservoir, just wait until the solution level drops down to the bottom. This will happen in about a week. At this point, just refill with fresh water, add nutrients, and you’re ready to go. The Backyard Garden has two tanks side-by-side. Run one tank down to the bottom, and then refill from the second tank. This method makes sure most of the nutrients are used up before ever adding more.
Once per month after the nutrient reservoir has been nearly run dry, add fresh water and run through the system. This water should be pumped out into a garden bed to clean your system, and fertilize your soil garden. This solution has a low concentration, which makes the perfect fertilizer for plants grown in soil!
One myth about hydroponics is that it is wasteful because the reservoir needs to be emptied constantly. When you use this method, plants use all of the nutrients, whether they are in a hydroponic system or in your soil garden, and none of them are released as runoff.
A fundamental distinction in plant nutrition lies between soil-based fertilizers and hydroponic nutrient solutions, particularly in how nutrients are delivered and made available to plants.
In soil systems, fertilizers primarily support a complex ecosystem of microorganisms, including bacteria and fungi. These microbes mediate nutrient cycling by converting organic and inorganic compounds into plant-available ionic forms through processes such as mineralization and nitrification. Because fertilizers must maintain microbial viability, they are typically applied at lower concentrations to avoid osmotic stress or toxicity within the soil microbiome.
In contrast, hydroponic systems are largely abiotic (sterile or near-sterile) environments that lack these biological intermediaries. As a result, nutrient solutions must supply fully soluble, plant-available ions directly (e.g., NO₃⁻, K⁺, Ca²⁺). This eliminates the microbial conversion step and necessitates higher precision and often higher concentrations of nutrients, as there are no biological buffers.
This distinction is well-supported by plant physiology research, which demonstrates that roots absorb nutrients exclusively in ionic form regardless of the growing medium.
Electrical Conductivity (EC) as a Measurement Tool
In hydroponics, nutrient concentration is most accurately monitored using electrical conductivity (EC) rather than total dissolved solids (TDS).
EC measures the ability of a solution to conduct electricity, which is directly proportional to the concentration of dissolved ions. It is expressed in microsiemens per centimeter (µS/cm) or millisiemens per centimeter (mS/cm).
Scientific Basis:
- Ionic compounds dissociate in water into charged particles.
- These ions carry electrical current.
- Higher ion concentration → higher conductivity.
Practical Application:
It is critical to measure the baseline EC of the source water before nutrient addition.
Example:
- Source water EC = 0.10 mS/cm (100 µS/cm)
- Target nutrient EC = 1.575 mS/cm
- Final EC = 1.675 mS/cm
This adjustment ensures accurate nutrient dosing and avoids under- or over-fertilization.
Water Quality in Hydroponic Systems
Water quality significantly influences nutrient availability and system performance.
Common Water Sources:
- Rainwater: Often considered ideal due to low dissolved solids, similar to reverse osmosis (RO) water.
- Tap water: Variable composition; may contain chlorine, bicarbonates, and dissolved salts that affect EC and pH.
- Well water: Frequently contains high levels of dissolved minerals (e.g., iron, calcium, magnesium) and potential contaminants due to groundwater leaching.
Verification:
Studies in hydroponics and controlled environment agriculture consistently emphasize that low initial EC and minimal contaminants are optimal for precise nutrient management.
Three-Part Nutrient Systems (A, B, and C)
Commercial hydroponic formulations are often divided into multiple components to prevent precipitation reactions and allow flexible nutrient management.
Composition:
- Part A: Compatible macronutrients and micronutrients.
- Part B: Typically contains calcium nitrate [Ca(NO₃)₂].
- Part C: Contains magnesium sulfate (MgSO₄·7H₂O), commonly known as Epsom salt.
Chemical Justification:
Certain ions, particularly calcium (Ca²⁺), react with sulfate (SO₄²⁻) or phosphate (PO₄³⁻) to form insoluble precipitates (e.g., calcium sulfate or calcium phosphate). These precipitates are not bioavailable and can clog systems.
Separating these components prevents:
- Nutrient loss
- Equipment damage
- Reduced plant uptake
Nutrient Requirements During Plant Development
Plant nutrient demands vary by growth stage.
- Vegetative stage: Higher nitrogen demand for leaf and stem growth.
- Fruiting/flowering stage: Increased need for calcium and magnesium to support cell wall development and metabolic processes.
Empirical studies in plant physiology confirm that calcium deficiency during fruiting can lead to disorders such as blossom end rot, while magnesium is essential for chlorophyll function.
Nutrient Formulations
Different crops require tailored nutrient concentrations.
- General vegetable formulations: Balanced nutrient profiles for a wide range of species.
- Strawberry-specific formulations: Reduced EC levels due to strawberries’ sensitivity to salinity.
Verification:
Research shows that excessive salinity (high EC) can reduce water uptake due to osmotic stress, particularly in salt-sensitive crops like strawberries.
Nutrient Solution Preparation
Hydroponic nutrient preparation typically involves three stages:
- Powdered Concentrates
Dry salts are measured by mass, ensuring precise stoichiometric ratios.
- Liquid Concentrates
Each component (A, B, C) is dissolved separately to prevent chemical reactions. Concentrated stock solutions are stable when sealed and stored properly.
- Working Solution
Diluted to the desired EC for plant uptake. Accurate dilution requires accounting for initial water EC.
Closed System Dynamics and Flushing
In recirculating (closed) hydroponic systems, nutrient solution is reused, which introduces challenges related to ion imbalance and waste accumulation.
Plant Physiology:
Plants absorb nutrients selectively, leading to:
- Depletion of some ions
- Accumulation of others
Additionally, plants release excess salts and metabolites through transpiration and root exudation.
Result:
- Rising EC does not necessarily indicate usable nutrients
- Accumulated salts may be non-essential or harmful
Maintenance Protocol:
- Weekly refresh: Replace depleted solution with fresh nutrients
- Monthly flush: Run clean water through the system to remove accumulated residues
Environmental Insight:
Contrary to common belief, properly managed hydroponic systems can be resource-efficient, as nutrient solutions can be reused and even repurposed for soil fertilization at lower concentrations.
Key Takeaways
Hydroponic nutrient management requires:
- Understanding plant nutrient uptake at the ionic level
- Monitoring EC for precision control
- Maintaining water quality
- Preventing chemical precipitation
- Regular system maintenance to avoid ion imbalance
These principles are grounded in plant physiology, chemistry, and environmental control, making hydroponics a highly efficient and scientifically robust method of cultivation.
References
- Marschner’s Mineral Nutrition of Higher Plants — Marschner, H. (2012). Mineral Nutrition of Higher Plants (3rd ed.). Academic Press.
- Hydroponic Food Production — Resh, H. M. (2013). Hydroponic Food Production (7th ed.). CRC Press.
- Plant Physiology and Development — Taiz, L., Zeiger, E., Møller, I. M., & Murphy, A. (2015). Plant Physiology and Development (6th ed.). Sinauer Associates.
- Food and Agriculture Organization — FAO. (2013). Good Agricultural Practices for Greenhouse Vegetable Crops.
- University of Arizona Controlled Environment Agriculture Center — Jensen, M. H. (1997). Hydroponics Worldwide.
- North Carolina State University Extension — NCSU Extension. (n.d.). Nutrient Management for Hydroponics.
Before learning about hydroponics, it’s important to understand the difference between fertilizer and hydroponic nutrients.
- Fertilizer is used in soil. It feeds tiny living organisms like bacteria and fungi. These organisms break the fertilizer down into nutrients that plant roots can absorb. Because it must protect these organisms, fertilizer is usually low in concentration.
- Hydroponic nutrients are used in systems with no soil. Since there are no microorganisms, the nutrients must be in a form that plants can absorb directly. This means hydroponic nutrients are more concentrated.
Measuring Nutrients: EC
Hydroponic systems use a measurement called EC (Electrical Conductivity).
- EC tells you how many nutrients are in the water.
- It works by measuring how well electricity flows through the solution.
- More nutrients = higher EC.
Important Tip:
Always measure the EC of your water before adding nutrients.
Example:
- Water EC = 100 µS
- Target EC = 1575 µS
- Final solution = 1675 µS
Types of Water for Hydroponics
Not all water is the same. Some types work better than others:
- Rainwater – Best option. It is clean and natural.
- Tap water – Okay, but check its EC first.
- Well water – Usually the worst choice because it may contain unwanted minerals or contaminants from the ground.
The 3-Part Nutrient System (A, B, and C)
Hydroponic nutrients are often divided into three parts to give you more control.
- Part A: Contains minerals that can safely mix together.
- Part B: Contains calcium nitrate. It must be kept separate or it will harden and become unusable.
- Part C: Contains magnesium sulfate (Epsom salt).
Why keep them separate?
Mixing certain parts too early causes chemical reactions that make nutrients useless to plants.
During Fruiting:
Plants need more nutrients when producing fruits.
- Increase Part B and Part C for better growth and yield.
Different Nutrient Formulas
There are different blends for different plants:
- Vegetable Formula – Works for most plants.
- Strawberry Formula – Lower strength because strawberries are sensitive to high nutrient levels.
How to Mix Nutrients
There are three main steps:
1. Powdered Concentrate
- Nutrients start as powders.
- Measure by weight, not volume.
2. Liquid Concentrate
- Mix each part (A, B, C) with water separately.
- Store in sealed containers.
3. Working Solution
- This is what goes into your system.
- Always adjust based on your water’s EC.
Flushing a Closed System
In a closed hydroponic system, water is reused. Over time, waste builds up.
- Plants release waste salts into the water.
- These salts increase EC but are not useful nutrients.
Why flush the system?
To remove waste and keep plants healthy.
How often?
- Weekly: Let water level drop, then refill with fresh water and nutrients.
- Monthly: Run clean water through the system to wash it out.
You can reuse this leftover water to fertilize soil plants, so nothing goes to waste.
Key Takeaway
Hydroponics may seem complicated at first, but it becomes easy with practice. By understanding nutrients, water quality, and system maintenance, you can grow healthy and productive plants without soil.