Preparing and 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 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. 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?
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.
- Its 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 its 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, but it can also lock certain nutrients out, leading to deficiencies in your plant which will be displayed in various ways.
Coconut trees 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 sites are 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 fibres of the Coco Coir which can only be removed through buffering.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 fibres 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 Potassium in the media, 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 their plants are getting and prevents a build-up of salts. When buffering your Coco Coir, you are exposing the cation exchange sites to a solution that contains high concentration levels of the elements we 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.
Coco fibre acts like a peat fibre in the way that it binds and releases nutrients but also like an inner substrate, such as rockwool, in the way that it holds water. Coco substrate can act as a buffer, storing water and nutrients for the plants. Buffering can work in several ways. There are water buffers, pH buffers, nutrient buffers and coco buffers
What’s the difference?
Let's start with the water buffer, rockwool can hold about 92 % of its volume in water This water supply is available to the plants when its needs it, this is called a water buffer. Coco can act as a water buffer as well. It does not hold as much as rockwool, it only holds 66% of its volume in water but the water held by the coco is readily available to the plants.
Then we have the pH buffer, potting mixes are made from acidic peat, and because of this acidity, lime is able to bring to the right pH value. If you water the plant with a nutrient solution with a high or low pH the lime buffer will neutralise it. At least until the lime in the peat runs out. Potting mixes can help correct any mistake made by the grower. Coco is basically neutral in its pH value and will not neutralise the pH value of the nutrient solution, this means that the pH values are easier to control in coco; but is not as forgiving as potting methods. The next buffer is the nutrient buffer, substrates containing peat or mineral soil combine nutrients to the fibres or particles using the charge sites, these are the cation exchange sites, as mentioned earlier. The nutrients will later be released to the solution around the fibres in the soil. This mechanism is called slow release or equilibrium. All elements can be made available for the plants in a specific ratio. Coco has similar spaces between its fibres. These are already filled with potassium and sodium. As mentioned above, the excess sodium and potassium need to be removed by washing the coco with low EC water.
Finally, we have the coco buffer, as mentioned coco fibres also hold potassium this needs to be removed by calcium and magnesium, if this does not happen the fibres will draw calcium and magnesium out of the nutrient solution, so that is no longer available for the plants. Although the coco is buffered, it will always bind some calcium and magnesium from the nutrient solution and thereby release potassium. The coco substrate uses the potassium that is released for the generative phases as well. Since coco substrate absorbs enough water and does not need to be watered that much there is plenty of time for the coco to make this exchange.
Here are some how-to-steps on preparing and buffering your Coco;
1) First, the Coco must be rehydrated, tap water is perfectly fine for rehydration
2) The coco must be rinsed to remove the fine particles of dust; you can do this by using a strainer
3) The next step is to buffer the coco -double buffering is recommended
4) To start buffering you simply lower your fabric pot of coco into a bucket and then add enough buffering solution to completely submerge the potassium and sodium cation exchange sites with Cal-mag. Cover and let it and let it sit for 8 hours
5) After 8 hours, refresh the buffering solution. - By pre-soaking the coco like this, in a strong solution of Cal-mag, you ensure that the cation exchange sites are fully buffered. Once buffered the cation-exchange will no longer interfere with nutrition
6) Once the buffering solution is refreshed, put the coco back into the bucket and buffer it again-double buffering ensures further that the plants do not suffer any calcium or magnesium deficiencies
7) After the second buffer, the coco is ready. Only one step remains to ensure the coco is the optimal media for growing, and that is to mix it with perlite. A rough recipe that can be used is 6 quarts of perlite to 800g of Coco, just pour a couple of quarts at a time and mix thoroughly with your hands. Be sure to get all the way to the bottom of the pot! Perlite dramatically improves aeration and drainage.
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.
That concludes the guide to preparing and buffering Coco! For information on how to grow using the finer coco peat substrate please see our article “Growing hydroponically with Coco Peat”
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