The Process of Chelating
Let's talk about bonding! One type of bonding that is important to learn in the cannabis industry is Chelating. Chelating is the process of a metal ion and ligand ion bonding. What is a ligand? Great question! It’s a molecule that has a strong attraction to metal ions. Why is it important to understand these two ions? It is due to the Macronutrients that the plants need in order to survive. While some Macronutrients are able to be taken up by plants normally such as Potassium, Sulfur, and Nitrogen, Metal ions such as iron, Manganese, zinc, and copper need extra help to be uptaken by the plant. This is due to other ions wanting to be evenly charged so they just steal any metal ions that can make them complete.
There are many chelant chemistries available but these three main ones are most important to growers; EDTA, DTPA and EDDHA. The most common one is EDTA also known as ethylenediaminetetraacetic acid; Try saying that three times fast! EDTA is very well liked due to its low costs and pH stability. This means the metal and chelant does not separate at a specified pH. The one exception would be a very hard water with a slightly alkaline pH (>7.0) but if you are watering your plants within a normal pH range, EDTA would be a great choice and is usually the number one pick amongst hydroponic growers.
Iron is much tougher to stay chelated and requires a little more elbow grease. For example is my reservoir is reading at a pH of 7.2 or higher and I have Fe(EDTA) and Mn(EDTA); the Mn(EDTA) will be fine but the Fe(EDTA) will most likely degrade and turn into an form that cannot be taken up by your plant. To help with this we turn to DTPA or diethylenetriaminepentaacetic acid. The main difference is that DTPA can survive much harsher alkaline environments than EDTA.
Lastly but certainly not least, the crème de la crème of chelants, EDDHA or ethylenediamine- N-N’-bis (2-hydroxyphenylacetic acid). This agent binds so well with iron that it is nearly impossible to remove it. It is stable within the entire pH range so if you’re really having issues with iron, consider this.
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