What Are Chelates?

Chelates are nothing new, but they’re not something you hear about everyday. Unless of course, you’re a grower or you work in agriculture. Chelates are one of the best advantages in your back pocket if you’re trying to ensure your plants can make use of all the nutrients you’re supplying them with. If you make your own fertilizer or nutrient solution, knowing the difference between chelated and non chelated minerals can make all the difference in your yield. 

Before we get started, let’s clear one thing up. Chelates is pronounced key-LATES, not che-lates.

Chelates – What Are They?

Minerals come in a wide variety of different forms. However, when you’re dealing with metallic minerals, like iron, or copper, you’re much more likely to see chelates come up. 

In short, chelates are minerals combined with amino acids to promote absorption. 

You can find a ton of different elements as chelates, but when it comes to agriculture, metallic elements are where you’ll see them most. There are multiple reasons why this is. First, metallic minerals are harder for plants (and humans) to absorb for use. Next, metals can become toxic in very little time because of their ionic composition. 

When these elements combine with amino acids to form chelates, they provide a sort of ‘buffer’ for the toxicity that plants otherwise experience. Chelates allow plants to absorb sufficient amounts of the minerals, without the ions that create a toxic environment. 

There’s another key role of chelates you should know about. Once they bond with a certain mineral, they can prevent it from bonding to another element. That might not sound like a big deal. However, when certain elements interact, they won’t dissolve in water anymore. This means they’re insoluble. To keep certain elements soluble (to dissolve in water), you need chelates. 

Take sulfur and calcium as an example. Your plants need both, so you have to have both in your nutrient solution. However, when they come into contact with each other, they form and insoluble compound (in this case, gypsum). 

Related: Nutrients for hydroponics

Common Forms of Chelates (Chelated Minerals)

In soil, some plants produce their own forms of chelates. This allows them to absorb minerals within the soil more easily. In water culture, chelates are more or less a staple of nutrient solution. There are several forms of chelating agents, but you might not want to assume they all work equally well. 

Even the pH of your solution, or the lights you use, can affect your chelating agents. Make sure your chelating agents work with your hydroponic conditions. 

The primary chelating agents include:

  • EDTA (Ethylenediaminetetraacetate)
  • EDDHA (Ethylenediaminedihydroxy-phenylaceticacid)
  • DTPA (Diethylenetriaminepentaacetate)
  • Humic acid
  • Fulvic acid

The first three are synthetic chelating agents, but they’re also the most widely used in agriculture, and hydroponics in particular. The other two, humic and fulvic acid, are biological chelating agents. These are present in nature, but you can also get them as a supplement to your nutrient solution. 

Let’s look at the main points about each type of synthetic chelating agent, so you can decide which to use:

Synthetic Chelating Agents

EDTA – (Ethylenediaminetetraacetic acid)

EDTA is a synthetic chelating agent often used in fertilizers, but also useful when metallic minerals build up to toxic levels. In fact, some studies show that with the addition of EDTA, plants suffering from copper toxicity may take in more copper, but experience less effects of toxicity. EDTA is also a popular agent for treating soil with high (toxic) levels of metals, because plants can take in those metals and remove them from the soil. This chelate does face some controversy, at least in soil use, as it doesn’t leave the soil with the metallic elements, which could cause long term environmental impacts. 

EDTA easily binds to any metallic element, but it tends to ‘gravitate’ towards iron (Fe) in particular. Chelating iron is one of the most common uses, but it works for others as well. 

The important thing to realize about EDTA is that plants don’t absorb it. Yes, it does bind with other elements. However, once the roots absorb whichever mineral the EDTA is bound to, the EDTA molecule goes right back into the solution. This can also be helpful when you have other elements within your solution that also work better with a chelating agent.

EDDHA (Ethylenediaminedihydroxy-phenylaceticacid)

EDDHA is often considered the most effective, and stable chelating agents for soil growing and agriculture. Because of its chemical compostion, it bonds much more tightly to elements such as iron (Fe) and has the ability to remain stable in even very alkaline environments. While it still works somewhat in more acidic surroundings, it does lose some of the stability that makes it so attractive to agriculturalists. Unlike other synthetic chelating agents, it has six molecular bonds. In comparison, DTPA has only five. This may seem like a small difference, but it actually gives EDDHA the ability to bond up to a hundred times stronger. 

EDDHA is best used in solutions with a pH measuring 4 minimum, and up to 9. For most plants, as long as the pH remains in this range, they can absorb all of the available iron. You can also use this synthetic chelating agent when plants continue growing, but have pre-existing damage to their root systems, and therefore struggle to take in sufficient nutrients. 

DTPA (Diethylenetriaminepentaacetate)

Next on our list of chelating agents is DTPA. With soil agriculture, DPTA may not be the very first choice, but it’s still high on the list. However, that really has more to do with working with difficult soils than creating a stable nutrient solution. In soil, it’s very difficult to control pH levels. However, in hydroponics, the grower has complete control of the pH, more or less. Because DTPA remains stable in the pH range between 4 and 7.2, it’s ideal for the majority of hydroponic crops. 

Because of DTPA’s most effective pH ranges, it’s a common favorite in aquaponics. Not only that, you can still be an organic grower and use it. DTPA is permissible in accordance with the USDA Organic Standards. 

Organic (Natural Chelating Agents)

Many plants produce their own chelates, although in some instances, it isn’t nearly enough to get the nutrients they need. In other cases, plants can have damaged or underdeveloped root systems, which also make it difficult to get certain micronutrients. Agriculturalists can add fertilizer with chelates to the soil, but otherwise, plants are on their own.

However, all’s not lost. Luckily there are also naturally occurring chelates, which we can now also use within our own homemade fertilizers. 

Fulvic Acid (FvA)

Fulvic acid isn’t present in soil on its own. However, it does come to be through natural processes. When plant or animal matter decomposes in soil, microorganisms transform some of this material into a humic material. Fulvic acid is an organic compound, which also means that plants can take it in, and use it in other ways. Unlike synthetic chelating agents, organic chelates enhance the overall health of the plant in a variety of ways, aside from allowing them to absorb more available minerals. 

Humic Acid

Humic acid is another organic chelate, and much like fulvic acid, it’s made through the decomposition process of animals and plants. This natural chelate helps plants thrive in environments with limited availability of certain nutrients. However, much like our other organic chelate fulvic acid, it also enhances the overall health of the plant, and can even help add biomass to plants. When properly used, humic acid can reduce the use of other fertilizers by up to 30%, and increase your overall yield by up to 70% more. 

Both fulvic acid and humic acid are commercially available. They most commonly come in powdered form. 

Frequently Asked Questions

What’s the difference between fulvic acid and humic acid?

One of the biggest differences between fulvic acid and humic acid is their molecular size. Where fulvic acids are fairly small molecules, humic acids are much larger. Another difference is in their potential applications. Humic acids work best in media, where plants’ roots can use them. Fulvic acids also work well in media, although they can also enter the cell membranes of plants’ leaves and provide important nutrients. 

Which chelate is best for hydroponics?

Because the effectiveness of any chelating agent relies heavily on the environment surrounding, the answer varies. One of the biggest things to consider is your target pH. Naturally, your target pH also varies depending on the plants you grow. For example, if you grow plants that need a very alkaline environment (above 7.2), DTPA won’t be your first choice. Instead, opt for a chelate that remains stable in alkaline solutions, like EDDHA. 

If synthetic chelates go back into the solution, is there a problem with build up?

If you were to use a system where you don’t change out your solution, but continue adding nutrients (and chelates), then they would build up. In soil, this can be more of a problem than in hydroponics. Because you change out your nutrient solution regularly, and add in fresh water, an excess of chelates isn’t likely- unless you add way too much from the start.