In the professional horticulture, coco seems to become more important as a substrate, every year. Nevertheless experiences are not always positive and therefore we focus on 2 important characteristics of coco: the physical aspects and the chemical aspects. Because there are big differences in these two aspects, that vary between suppliers.
The physical characteristic Coco pith is extracted from the husk (around the coconut); this husk is separated in 2 materials: Coco fibers and Coco pith.
Coco pith: Because this is an organic material, we have to be aware that it will break down, especially when fresh husks are being used. For that reason Coco pith should be “aged” for several months to be sure that the final material is stable and will not break down during the culture.
It is not always easy to see if the coco pith is young or old; the color changes fast after drying in the sun but will be lighter than real “aged” material. Unfortunately some producers mix very old material (which is often sandy) with the fresh cocopith so that it looks as a good material.
Coco chips or “coarse coco”: Often the grower asks for a more coarse substrate. For that, coco chips can be used. The production is different from the coco pith; in this case the husks are cut into pieces and screened out into the right fractions. The chips cause good draining, because the water capacity is rather low.
Usually the producers use fresh husks to produce the chips. This will improve the fast production of “good looking” chips. The problem with these fresh chips is (again) the stability; because it is a young material, the chips can break down rather quickly. When this material is used in e.g. Grow Bags, the grower can see the decomposing of the chips, which sometimes makes a very wet substrate (is mixed with fine material) or the opposite when it is use as a pure substrate. The individual chips will retract and be lower in water capacity.
To determine the quality of your coco, you can ask for a “respiration-test”. With this test, the speed of decomposition can be checked. RHP in Holland has produced some standards already to avoid that too young material is used in the professional horticulture.
The chemical characteristic
The Coconut trees are very tolerant of salts, so if we analyze the coco pith or coco chips without washing them, the EC can be from 2 – 6 mS/cm. The problem is that the elements are mainly Potassium, Sodium and Chloride. Fortunately these elements (especially Chloride) are rather easy to wash out from the Coco pith and coco chips and to reduce the EC, the coco can be washed (or in some cases they are left for some time during monsoons). For cultures which are not very sensitive, “washed coco pith” can be used. The rule is than that the EC should be below 1,0 mS/cm.
Now, here is a subject that needs some extra attention, because huge differences can be found between suppliers, although all say that the EC is below 1 mS/cm. How is this possible ?
The reason is the way of analyzing; the minimum of 1 mS/cm is based on the extraction method of 1 : 1,5. This means that the lab takes 1 part of coco pith, adds 1,5 parts of de-mineralized water, this is mixed for some time and after that, the EC is measured in the water which drains out. Then the EC should be lower than 1,0 mS/cm.
Unfortunately there are different extractions used; there is the 1:3 method and the 1:5 method. For example, in the 1:5 extraction method, 1 part of coco pith is mixed with 5 parts of de-mineralized water. Of course the EC of the water, which is measured, is much lower.
For example: if EC in 1:1,5 extract is 2,0 mS/cm, then the EC in a 1:5 extract will be 0,7 mS/cm!
To avoid disappointment and errors in the culture, it is important that the grower is sure about the way the EC is measured.
For more sensitive cultures such as strawberries and young plants, cuttings etc, it is important to be sure a buffered coco pith is used. In buffered coco pith, the Sodium and Potassium is removed from the complex and it is safe to use for crops that are sensitive and crops that are not “over drained” much.
In general we can say that coco products are an absolute gain for horticulture as we use an organic material which would have been unused and left in the plantations otherwise. Nevertheless the grower is responsible for finding out if his new substrate is conform the needs of his crop.