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How To Choose the Right Hydroponic Nutrients and Fertilizers

How To Choose the Right Hydroponic Nutrients and Fertilizers

Having a deep understanding of hydroponic nutrients, which are necessary for plant growth and vitality, is vital for achieving success in hydroponic gardening.

This comprehensive guide dives into the intricate world of hydroponic nutrients, exploring their composition, their functions, and the vital role they play in fostering lush, thriving plants.

From understanding the essential macronutrients and micronutrients required for optimal growth to unraveling the challenges and solutions associated with nutrient availability, we embark on a journey that equips you with the knowledge you need to cultivate healthy and productive crops.

Hydroponic Nutrient Basics

Plants need nutrients to survive and thrive. 

In hydroponics, we need to put the perfect balance of nutrients into our systems, or our plants just won’t make it. We don’t get any help from the soil that naturally has some of these nutrients, so it’s all up to our fertilizer.

Before I break down everything you need to know about hydroponic nutrients, I want to show you which nutrients plants need specifically with a bit of info as to why your plants need them in the first place.

Primary, Secondary, and Micronutrients

There are different classifications of nutrients based on their importance in plant growth.

The primary nutrients are nitrogen (N), phosphorus (P), and potassium (K).

Secondary nutrients are essential for growth but in smaller quantities than the primary nutrients. These are calcium (Ca), magnesium (Mg), and sulfur (S).

Lastly, plants need a variety of micronutrients. As the name suggests, only a tiny amount of these nutrients are needed, making them less important than primary and secondary nutrients.

The micronutrients plants need are boron (B), zinc (Zn), manganese (Mn), iron (Fe), copper (Cu), molybdenum (Mo), and chlorine (Cl).

What is NPK?

NPK stands for nitrogen (N), phosphorus (P), and potassium (K). These are the primary three nutrients needed by all plants to grow and survive.

Because of its importance in hydroponic growing, you will see NPK referenced frequently. Understanding NPK is the first step in understanding plant nutrition.

Hydroponic fertilizers will usually have three numbers printed on the front of the bag or bottle, something like 4-18-38. This number represents the balance of NPK. This means 4% of the fertilizer is nitrogen, 18% is phosphorus, and 38% is potassium. 

Different Nutrient Needs of Leafy and Fruiting Plants

In general, nitrogen is the driving nutrient in foliage growth and therefore is especially important for leafy greens like lettuce, spinach, bok choy, and kale, as well as herbs and microgreens.

Leafy plants also do well with higher levels of potassium, which helps with many essential functions including growth and structure.

A good balance of nutrients for leafy greens is something like 8-15-36 which is found in this lettuce-specific fertilizer by Greenway.

This blend contains a complete nutritional formula with chelated micronutrients to ensure bright green, full leafy greens.

Or, for something more flexible, a ratio of 10-5-14 like in this MaxiGro all-purpose fertilizer for vigorous growth will work great for greens.

Fruiting plants, like tomatoes, cucumbers, strawberries, peppers, and the like, need a slightly different combination of nutrients. 

Starting with a higher concentration of potassium helps your plants during their fruiting stage. Potassium helps plants move water and sugar inside themselves, improving sweetness and overall quality.

As a plant comes closer to producing fruit, its nitrogen requirements increase. Giving plants adequate nitrogen at this stage will increase the size of fruits.

For a well-balanced fertilizer for fruiting plants, I’d recommend using a 4-18-38 blend. You will need to mix the main fertilizer with calcium nitrate and epsom salt before using it in your hydroponic system.

All three of those essential ingredients can be purchased in a bundle like this one from Mastergrow (more on how to use these below).

The Role of pH and EC

The pH and EC (Electrical Conductivity) are crucial parameters in hydroponics that significantly impact plant health and nutrient uptake.

Maintaining the appropriate pH and EC levels in your hydroponic system is crucial for providing plants with the right balance of nutrients they need for healthy plant growth.

Regularly measuring and adjusting these parameters based on the type of plant, its growth stage, and the nutrient solution used will help ensure that your hydroponic garden flourishes.

Let’s explore their roles and their relationship with hydroponic nutrients and plant growth.

pH in Hydroponics

Hydroponic system pH refers to the measurement of the acidity or alkalinity of a solution on a scale from 0 to 14.

In hydroponics, maintaining the correct pH level of the nutrient solution is vital because it directly affects the availability of essential nutrients to plants. 

Different types of plants have varying pH preferences, so it’s essential to tailor the pH to suit the specific type of plant you’re growing in your hydroponic garden.

When the pH of the nutrient solution is too high or too low, it can lead to nutrient deficiencies even if the nutrients are present in the solution.

This is because certain nutrients become less available for uptake by the plant’s root system when the pH is outside the optimal range.

For example, if the pH is too high, iron, manganese, and zinc can become less accessible to the plant, leading to their deficiencies.

Similarly, if the pH is too low, the availability of nutrients like phosphorus, potassium, and calcium might be compromised.

EC (Electrical Conductivity) in Hydroponics

Hydroponic system Electrical Conductivity (EC) measures the ability of a solution to conduct an electric current, which is directly related to the concentration of dissolved nutrients in the nutrient solution. 

EC is a valuable indicator of the overall nutrient strength in the solution.

As plants take in nutrients and water through their root system, maintaining the right EC level is essential for preventing nutrient imbalances and ensuring proper plant growth.

Monitoring EC helps prevent overfeeding or underfeeding your plants.

An excessively high EC can result in nutrient toxicity, where the concentration of certain nutrients exceeds the plant’s ability to absorb them, leading to burnt or damaged roots.

On the other hand, a low EC can indicate a deficiency in nutrients, hindering plant growth and development.

Relationship Between pH and EC

The relationship between pH and EC is intertwined. The pH of the nutrient solution can influence the availability of nutrients, while the EC value indicates the concentration of dissolved nutrients.

It’s important to note that the optimal pH range for nutrient uptake varies with the types of nutrients. When the pH is within the correct range, the availability of essential nutrients is maximized, allowing plants to thrive.

Types of Hydroponic Nutrients

There are different ways to buy your fertilizers, mainly, in liquid form, as a ready-made powder, or separated into different components so you can mix them yourself.

Liquid vs. Powder vs. Homemade

Liquid fertilizers are the easiest to deal with as very little preparation is required. The nutrients in these concentrates are pre-dissolved so vigorous mixing isn’t necessary. 

With liquid, you don’t need to go measuring and mixing several ingredients to get the right mix.

However, the downside of using liquid fertilizer is that it costs more to ship because of its water weight.

Also, you sacrifice some ability to customize the fertilizer like you can with homemade ones. Lastly, liquid fertilizers are usually the most expensive.

Recommended product: 

Powder fertilizers are pre-mixed bags of dry ingredients. All you need to do is dissolve them in water and you’re ready to go. 

These are still quite convenient as no complicated measuring, mixing, and balancing is required. You just follow the instructions on the bag and mix some of the powder with water.

Because they are completely dry, they are cheaper to ship than liquid fertilizers.

The only downside with powder fertilizers is they are pricey. Special pre-made blends cost a premium, just like with liquid fertilizers.

Recommended products: 

Finally, taking the DIY route will require a bit of work, but it can be rewarding. 

Many hydroponic growers swear by homemade fertilizer because it offers flexibility and great value. You won’t get a better price on fertilizer than if you buy bulk ingredients and make it yourself.

It isn’t as complicated as many imagine. You can buy a bundle of everything you will need all in one, follow the instructions, and mix them together without any special equipment.

Recommended product:

Keep reading for a full guide on how to use this Masterblend kit and mix your own fertilizer at home.

Adjusting Hydroponics Nutrient Solution

Adjusting hydroponic nutrient levels involves fine-tuning the nutrient solution to meet the specific needs of your plants at different growth stages.

Here’s a guide on how to adjust and optimize nutrient levels in your hydroponic system:

1. Monitoring Nutrient Levels

Regularly monitoring the nutrient solution is essential to ensure that your plants receive the right balance of nutrients for healthy growth.

You can use an EC meter (I like this one that also measures pH and TDS) to measure the concentration of dissolved nutrients in the solution. The EC value provides an indication of the overall nutrient strength.

2. Adjusting Nutrient Concentration

As your plants progress through various growth stages, their nutrient requirements change. Seedlings and young plants require fewer nutrients than mature ones. To adjust the nutrient concentration, you can:

  • Dilute the Solution: If the EC is too high, dilute the nutrient solution with water to bring the concentration down.
  • Increase Concentration: If the EC is too low, gradually increase the concentration by adding more nutrients to the solution.

3. Balancing pH

Maintaining the correct pH range of the nutrient solution is crucial for nutrient availability. Use a pH meter to monitor the pH level regularly. If the pH drifts outside the optimal range for your specific plant, adjust it using pH-up or pH-down solutions.

Different plants have different pH preferences, so be sure to research the ideal pH range for your chosen plant.

4. Addressing Nutrient Deficiencies

If you notice signs of nutrient deficiencies, such as yellowing leaves or stunted growth, it’s important to take action promptly. Based on the deficiency symptoms, you can adjust the nutrient solution as follows:

  • Nitrogen (N) Deficiency: Increase the concentration of a balanced hydroponic nutrient solution to provide more nitrogen.
  • Potassium (K) Deficiency: Add a potassium-rich hydroponic fertilizer to the nutrient solution.
  • Calcium (Ca) or Magnesium (Mg) Deficiency: Use a nutrient solution that includes calcium and magnesium, or supplement with a calcium or magnesium additive.

5. Maintaining Proper Ratios

Each type of plant nutrient serves a specific purpose in plant growth. It’s important to ensure that the nutrient solution contains the required nutrients in the right ratios.

This balance prevents one nutrient from interfering with the uptake of another.

6. Adjusting for Plant Type

Different types of plants have varying nutrient requirements. Research the specific needs of the plant you are growing, and tailor your nutrient solution accordingly.

For example, leafy greens might require higher nitrogen levels while flowering plants may need more phosphorus and potassium.

7. Considering Water Source

The water you use to prepare the nutrient solution can impact its composition. If your water source contains a significant amount of dissolved minerals, it can affect the overall EC of the solution.

Factor in the quality of your water source when adjusting nutrient levels.

8. Gradual Adjustments

When making adjustments to nutrient levels, do so gradually. Sudden changes can stress plants and lead to further issues.

Make incremental changes, and observe how plants respond before making additional adjustments.

9. Recording Changes

Keep a log of the changes you make to the nutrient solution, including adjustments to EC, pH, and nutrient concentrations. This record will help you track the effectiveness of your adjustments and identify trends over time.

A man using a TDS meter to measure the nutrient levels for small lettuce plants.

Common Problems Hydroponic Growers Have With Nutrients

Growers in hydroponics may encounter various challenges related to nutrient solutions and nutrient availability. Here are some common problems and their explanations:

1. Nutrient Imbalances

Nutrient imbalances occur when certain nutrients are present in excess or are deficient in the nutrient solution. This can lead to issues such as stunted growth, yellowing leaves, or reduced fruiting.

It’s essential to maintain a balanced nutrient solution with the appropriate ratios of essential nutrients for different growth stages.

2. Nutrient Deficiencies

Nutrient deficiencies manifest as specific symptoms, such as yellowing or discolored leaves, poor growth, and weak plants. Common deficiencies include a lack of nitrogen, potassium, calcium, and magnesium.

Regularly monitoring plant health and adjusting the nutrient solution composition can help prevent deficiencies.

3. pH Fluctuations

Fluctuations in pH can disrupt nutrient availability. When pH is too high or too low, certain nutrients become less available for uptake by plant roots. This can result in nutrient deficiencies even if nutrients are present in the solution.

Regularly measure and adjust pH to maintain the optimal range for nutrient absorption.

4. Nutrient Lockout

Nutrient lockout occurs when certain nutrients become unavailable to plants due to incorrect pH levels or the presence of antagonistic ions.

For example, excessive calcium can inhibit the uptake of magnesium, leading to deficiencies. Proper pH management and maintaining balanced nutrient concentrations can prevent nutrient lockout.

5. Overfeeding and Nutrient Toxicity

Providing too many nutrients or excessively high concentrations can lead to nutrient toxicity. This can cause burnt or damaged roots, leaf tip burn, and other symptoms of stress.

Using an EC meter to monitor nutrient strength and adjusting the concentration gradually can prevent overfeeding.

6. Poor Water Quality

The quality of the water used to prepare the nutrient solution can affect nutrient availability. Water with high levels of dissolved minerals can impact the overall nutrient concentration and balance in the solution.

Consider using filtered or purified water to prevent potential nutrient imbalances.

7. Incorrect Nutrient Solution Preparation

Incorrectly preparing the nutrient solution by adding too much or too little of specific nutrients can lead to imbalances and deficiencies.

Following manufacturer guidelines and accurately measuring nutrients when preparing the solution is crucial for achieving the right nutrient ratios.

8. Inadequate Mixing and Oxygenation

Properly mixing and oxygenating the nutrient solution ensures an even distribution of nutrients and prevents the buildup of stagnant pockets.

Inadequate mixing can result in uneven nutrient delivery to plants, leading to nutrient deficiencies in certain areas of the root system.

9. Temperature Fluctuations

Extreme temperature fluctuations can affect nutrient uptake and the overall health of the hydroponic system.

High temperatures can lead to increased nutrient uptake, potentially causing nutrient imbalances. Maintaining consistent temperatures within the optimal range supports optimal nutrient absorption.

10. Poor Root Health

Unhealthy roots can struggle to absorb nutrients efficiently. Root problems can be caused by factors like poor oxygenation, root diseases, or incorrect watering practices.

Regularly inspect roots for signs of health, and address any issues promptly.

The Best Hydroponic Nutrients By Plant Type

The best hydroponic fertilizer for leafy greens and herbs like lettuce, spinach, kale, endive, swiss chard, arugula, basil, dill, mint, and parsley is all about stimulating foliar growth and getting those leaves built up fast. 

For leafy greens and herbs, I recommend using this Lettuce Greens and Herbs Mix. You will need to combine the two parts of this powdered fertilizer, but all you need is a bucket and measuring cup. This bag makes 128 gallons of nutrient solution.

For fruiting plants, you will need a slightly different mix of nutrients. The structure of fruiting plants is different from that of leafy vegetables—fruit size, color, and flavor all improve with the right balance. 

For tomatoes, I recommend the Greenway Biotech Tomato Mix. Compared to mixing the ingredients yourself, this fertilizer is super convenient. Everything has been specially formulated and pre-mixed specifically for tomatoes, all you need to do is add water. 

Peppers need a similar ratio of nutrients but do better with more nitrogen and slightly more potassium. For large, full-flavor peppers, you should use the Greenway Biotech Pepper and Herb Fertilizer. This is another simple “just add water” mix that anyone can use.

For hydroponic fertilizer for strawberries, more nitrogen is needed, and extra boron helps to get the berries growing fast.

An easy choice is Greenway Biotech Strawberry Fertilizer. This blend is crafted for perfect strawberry growth. And just two pounds of the stuff makes 400 gallons when mixed with water.

Homemade Hydroponic Fertilizer DIY Recipe

For this recipe, I will be using the Masterblend Combo Kit which includes a 4-18-38 general vegetable and tomato blend, 15.5-0-0 calcium nitrate, and epsom salt.

Buying these ingredients unmixed and in bulk will save you a ton of money in the long run.

All you will need is a 3-5 gallon bucket or similar container, measuring cups, and purified water.

Step 1: Pour one gallon of distilled or reverse osmosis water into a clean bucket.

Step 2: Add 600 grams of Masterblend 4-18-38 Tomato & Vegetable Formula. Mix well. 

Step 3: Add 600 grams of Powergrow 15.5-0-0 Calcium Nitrate. Mix well.

Step 4: Add 300 grams of epsom salt. Mix well. 

This recipe makes a hydroponic fertilizer concentrate, so just one gallon of what you make is good for 250 gallons of nutrient solution. All you need to do is dilute it with water.

To make a general-purpose nutrient solution, add one tablespoon of fertilizer concentrate to one gallon of water.

Other Commonly Used Hydroponic Additives

Hydroponic additives play a significant role in enhancing plant growth, root development, and overall plant health in hydroponic systems. Here’s an overview of some common hydroponic additives, including mycorrhizae and root stimulants:

Mycorrhizae

Mycorrhizae are beneficial fungi that form a symbiotic relationship with plant roots. They extend the root system’s reach, increasing the plant’s ability to absorb water and nutrients from the nutrient solution. 

Mycorrhizae are particularly advantageous in hydroponics as they compensate for the absence of natural soil microbial communities. They enhance nutrient uptake, improve water retention, and aid in plant resilience against stressors.

Adding mycorrhizal inoculants to your hydroponic system can greatly benefit plant growth. Mycorrhizae help solubilize nutrients, making them more accessible to plant roots. They also contribute to disease resistance and overall plant vitality.

Root Stimulants

Root stimulants are additives designed to encourage strong root development, which is critical for optimal nutrient absorption and overall plant health.

These stimulants typically contain compounds that promote root growth, enhance root branching, and improve the root system’s ability to take in water and nutrients.

Root stimulants can be particularly beneficial during the early stages of plant growth, helping young plants establish robust root systems.

As the roots grow more vigorously, the plant can access nutrients more efficiently, leading to accelerated growth and better overall performance.

Humic and Fulvic Acids

Humic and fulvic acids are organic compounds derived from decomposed plant and animal matter. They contribute to soil and hydroponic system health by improving nutrient availability and retention.

These acids enhance the cation exchange capacity of the growing medium, making nutrients more accessible to plant roots.

When added to the nutrient solution, humic and fulvic acids can improve the solubility of minerals, chelate micronutrients, and stimulate microbial activity. These effects collectively contribute to improved nutrient absorption and better plant growth.

Seaweed Extracts

Seaweed extracts, often derived from kelp, are rich sources of growth-promoting compounds like auxins, cytokinins, and gibberellins.

These natural plant hormones influence cell division, elongation, and differentiation. Seaweed extracts are known to enhance root growth, flowering, and fruiting.

Adding seaweed extracts to the nutrient solution can lead to increased nutrient uptake, improved resistance to stress, and overall plant vigor. They are often used as foliar sprays or incorporated into the nutrient solution.

Enzymes

Enzymes are biological catalysts that accelerate chemical reactions. In hydroponics, enzymes are used to break down organic matter, converting it into forms that are more easily absorbed by plants.

Enzymatic additives can enhance nutrient release from organic matter in the growing medium and facilitate nutrient uptake.

Enzymes can also help maintain a clean and healthy root zone by breaking down dead root material and preventing the accumulation of organic debris that could lead to disease.

pH Buffers

pH buffers are used to stabilize the pH of the nutrient solution. They help prevent drastic fluctuations in pH that can negatively impact nutrient availability. pH buffers ensure that the nutrient solution remains within the optimal pH range for nutrient uptake.

Incorporating these hydroponic additives into your nutrient management strategy can lead to improved plant health, stronger root systems, and increased nutrient uptake.

As with any additives, it’s important to follow manufacturer recommendations and monitor plant response to ensure the best results.

Questions About Hydroponic Fertilizer

Do you need different fertilizers for different hydroponic methods?

The hydroponic fertilizer you use depends on the plants you’re growing, not the system that you use. 

Plants’ nutrient requirements are the same regardless of whether they are in a Kratky, NFT, or aeroponic system.

That being said, different hydroponic systems are suited for different types of plants. For example, Dutch buckets, also known as bato buckets, are ideal for fruiting plants like tomatoes, cucumbers, squash, and peppers.

These plants need different nutrients than herbs and leafy greens, especially during fruiting when extra nitrogen is key.

So you won’t be picking a fertilizer based on the system you use alone, but what grows well in that system, and ultimately what you decide to put in it, will dictate what fertilizer you use.

Can you grow hydroponics without nutrients?

All plants require nutrients, regardless of whether they are grown in soil, hydroponic systems, or out of a crack in the concrete. You can’t grow any plants without nutrients!

If you were to put a seed or seedling into plain old water without a nutrient solution, it simply wouldn’t grow. The plant would lack the building blocks and fuel that it needs to grow, bear fruit, and survive.

Can I use regular fertilizer for hydroponics?

You can use a fertilizer designed for soil in hydroponics, but it may not be worth the trouble.

The first problem is that regular fertilizer is made to be used in the soil which naturally has nutrients in it. Hydroponic fertilizer is designed to deliver 100% of the nutrients the plant needs. This makes the quantities of nutrients in these products quite different.

Secondly, most soil fertilizers are supposed to be used infrequently. Because of this, they slowly release nutrients.

For example, many soil fertilizers contain urea and ammonia salts which need to be broken down by microbes in the soil slowly to provide nitrogen.

Hydroponic systems have no such microbes and hydroponic plants need instantly available nutrients.

A misconception that I hear from time to time is that it could be cheaper to use regular fertilizer instead of hydroponic fertilizer.

The prices of the two classes of fertilizer are already comparable, and when you factor in the extra work you will put in to make sure your soil fertilizer is perfectly balanced for your hydroponic plants, it isn’t worth it.

If you want to save money, buy raw fertilizer ingredients in bulk and mix them yourself at home.

Can you use tap water in hydroponics?

If you are going to use tap water in a hydroponic system, you must first test it and treat it.

Tap water has been treated to kill harmful microbes that can make people sick. To do this, the processing plants add chlorine, chloramines, and aluminum sulfate, which you definitely don’t want.

Also, water may come out of your tap at a pH that will harm the plants you are growing.

The best course of action is to use distilled or reverse osmosis water in hydroponics. But, if you insist on using tap water, you will have to go through a few steps to prepare it first.

How do you make tap water safe for hydroponics?

The first step is removing the chlorine. If you leave tap water out in the sun for about a day, UV rays from the sun will break down and remove the chlorine. However, in large quantities, this can be very difficult.

Or, if you want to remove chlorine and chloramine together in one blow, you will need to buy a bottle of chlorine remover, like this.

To balance the pH of your water, you can use the same pH up and pH down you already use in your hydroponic system to balance nutrient solutions.

Lastly, if you have hard water in your tap, you will likely need to purchase an expensive water softener. 

For many growers, especially on a small scale, the best course of action is to use distilled or purified water instead of treated tap water.