Buffering Coco Coir
With the increase in buffering supplements being sold worldwide, it is clear that growers are becoming aware of the importance of buffering of your Coco Coir media. Today we take a closer look at exactly why it has such a big impact on your yields…
Coco Coir is a by product of industries who use Coconut. It’s an organic product that comes from processing the Coconut’s husk from Coconut tree plantations that are mainly located in tropical and sub-tropical regions.
To get the Coco Coir from the Coconut husk it goes through many stages of grading processes – aging, washing, buffering, drying, grinding and compressing into different sizes and grades of Coco Coir, namely Fine and Coarse. Processing the Coco this way ensures that the chemical and physical characteristics of the Coco are altered to ensure the best quality Coco Coir for growing plants in.
So you may be asking yourself – Why even bother with buffering Coco to prepare it for optimum plant growth? Is growing in Coco Coir really worth it? Why not just use another hydroponic medium?
Well, here are some reasons why…
- It’s a by-product from another industry.
- It has an ideal pH.
- It holds 22% air even when fully saturated.
- It has excellent drainage properties.
- It’s anti-fungicidal properties help plants to get rid of soil-borne diseases.
- 100% renewable.
- Easy to hydrate.
- Fewer weeds to remove.
- Environmentally friendly.
Organic matter and Coco naturally have negative charges on it’s surface that attract cations (positively charged ion). The total number of cations that anything can hold onto or exchange are referred to as the Cation Exchange Capacity or CEC. So basically, CEC will help us to determine amount of nutrients that the media can hold onto before it starts leaching.
The CEC of Coco Coir is anything between 40-100meq/100g (meq or milli-equivalent is used to measure the cation exchange capacity). This means that Coco can hold onto nutrients very well but it can also lock certain nutrients out too leading to deficiencies in your plant which the plant will display in various ways.
Coconut tree’s have a naturally high tolerance for salt (sodium chloride) and therefore most plantations grow abundantly along the coast. This in turn means that Coco’s cation exchange complex is naturally saturated with Sodium. Coco coir’s CEC also naturally contains large amount of Potassium and low amounts of Calcium and Magnesium. These 4 cations are the most important cations when buffering Coco.
Initially, Coco Coir has a salt content or Electrical Conductivity level of 2 to 6 mS/cm which is far too high for a growing medium. High quality Coco Coir should be washed thoroughly until an E.C of below 1mS/cm is reached. Even after washing, there will still be Sodium and Potassium in the complex of the Coco Coir which can only be removed through buffering.
Now I need to explain that there is a big difference between washing and buffering Coco. Washing the Coco Coir will allow the water soluble elements to be removed but buffering will remove elements that are naturally bonded to the cation exchange complex of Coco.
The goal is to lower the amount of CEC sites that have Potassium and Magnesium attached. Potassium can be attached to up to 40% of the sites and Sodium can be attached by up to 15% of the sites. This is very important because if 40% of the exchange is holding Potassium that means that there is 40meq/100g of media of Potassium which is a single-charge molecule. Hydrated Coco Coir should make 12-15L of medium per 1kg of dry, compressed Coco Coir. It may not sound like a lot but it would mean that there is as much as 1.56g of Potassium per 100g of media. If you compare this 1.56g to 0.22g (220ppm) of Potassium that you would normally be using in a well balanced nutrient feed, you can see where this would be a problem.
Buffering is especially important for growers who have a recirculating system as it gives them more control over how much Calcium your plants are getting and prevents a build up of salts.
When buffering your Coco Coir you are exposing the cation exchange to a solution that contains high concentration levels of the cations we do want on the sites, being Calcium and Magnesium. Cations that are already bonded to sites are quite difficult to remove and therefore a simple washing of your Coco Coir won’t do much to change the makeup of the undesired cations. Washing will only change the E.C but not the CEC of the Coco.
Sodium, Magnesium, Potassium and Calcium will all be absorbed at different rates even if they were all introduced into a solution at the same concentrations. Calcium and Magnesium are absorbed at double the rate due to them having a double-positive charge while Potassium and Sodium have a single-positive charge ( Ca++ , Mg++ , K+ , Na+ ). Buffering products that have high levels of Calcium and Magnesium have a slower buffering rate but they help to effectively create a lower Potassium and Sodium percentage on the exchange and offer beneficial Magnesium to the CEC. This ensures that any nutrient mixes you use are going directly to the plant instead of amending the Coco’s CEC.
Nutrient Lockout and Plant Deficiencies
Using Coco that has not had it’s complex buffered is going to create a very unsuitable grow medium for any plant. The positively charged cations such as Calcium and Magnesium are going to have a stronger attraction to the Coco complex where it will become unavailable to the plants and nutrient lockout will occur. This will cause Potassium and Sodium, which are less attached to the complex, to be displaced into the solution and be taken up by the plants instead of Calcium.
Calcium is crucial for a plant’s growth and is involved in almost every aspect of a plant’s development. Your plant will show Calcium deficiencies in a few different ways if you pay close attention. New leaves may appear crinkled and distorted while they might also show dead spots where the leaves will turn brown and die-off.
Most Coco Coir on the market these days is washed but it may not be nutrient buffered so please make sure you know exactly what your buying.
Information sourced from: