Coco Coir as a Hydroponic Media

varying blends of coconut fibers, coconut husks, coco coir

Advantages and Disadvantages of Coco Coir

Coco coir, [ Coconut Fiber ~ Coconut Husks ] is gaining in popularity as a hydroponic growing Media. Coco Coir is a term used to denote a blend of Coconut peat/pith, coconut fiber and chips. All derived from the husk surrounding coconuts.

The coconut shells pith works like a sponge, in fact it is composed of a network of minute micro-sponges.

These natural micro-sponges absorb and retain up to eight times their own weight in water. Coco coir evolved to be a sturdy media, in nature it is the outer surface of the coconut, or coconut tree seed which typically floats on the ocean surfaces for many months before re-seeding on the next landfall.

The pith works like a sponge, bu the Fiber itself has very little water retention capacity. The fiber does however increase the capacity of the growing medium to retain air.

The Fiber degrades relatively fast which has a negative affect on the durability of the coco coir as a whole.

The Coco chips hold even less water than the fiber. but do positively affect the air retention capacities. The chips have the highest air to water ratio.

The moisture retention qualities and durability of coco coir make it an excellent planting medium for hydroponic gardens which works well in either passive or active hydroponic systems. It has an ideal pH range of 6.0-6.8 which also works to its advantage.

When not in use, Coco coir is easily aerated or re-hydrated as needed, in this respect it is highly versatile. However it does break down after several uses. Using coco coir once it has degraded is highly counter productive. One of the qualities of Coco coir is that it provides an insulating effect, it isn’t prone to overheating, this quality is negated as the substrate degrades.

Coconut coir is generally sold in bricks which expand when immersed in water. They typically expand up to 8 times their initial dry volume without becoming anaerobic. Anerobic meaning they are depleted of oxygen, and contribute to keeping the roots and system in general oxygenated – which is critical. It has roughly a 70-30 moisture-to-aeration level, although this ratio is somewhat variable.

Coco coir is completely environmentally friendly. It is a natural substance and adds no pollutants to the macro-environment as a whole, or to the micro-environment of your hydroponic setup.

Coco coir Promotes strong root growth .

The air and water retention qualities of coco coir are an asset in that they reduce maintenance that the hydro-grower sometimes neglects, and helps to correct some errors. Over watering with a warm nutrient for instance.

Coco coir has anti-fungal properties.

Coco coir has anti-fungal qualities that have been proven to protect plants from some, but not all root diseases. Pythium, Fusarium and phytophthora are some that it helps to suppress.

Unfortunately these same anti-fungal properties also contribute to some disadvantages of using coco coir. If you are using beneficial micro organisms such as bacillus, mycorrhizae and trichoderma , their progress will be inhibited, regardless of what the coco coir producers claim.

1. In Vitro Suppression of Soilborne Plant Pathogens by Coir
2. An antifungal peptide from the coconut
3. Antifungal activity of the alcoholic extract of coconut shell

Research indicates that the coir has an inhibiting effect on mycelial growth. It does not obliterate them, but only slows them down somewhat. If you are using any of these micro-organisms , you can still use them along with coco coir, but be aware that it will be more difficult to get a colony established.

Coco Coir is extremely lightweight.

That’s good and that’s bad. The lightweight aspect is self evident, however in addition to being lightweight it is also buoyant and does not always stay where its put. Mixing coir with perlite or even expanded clay pebbles is sometimes done for this and other reasons. Another reason is that coco coir suspended even a tad above its intended level has been known to be a haven for fungus gnats that sometimes are found near poorly maintained hydro systems. [Fungus gnats can be controlled by controlling algae buildup – See Algae in Hydroponics

Adding a shallow layer of clay pebbles on the bottom of the pot to aid drainage and oxygenation is a good idea also.

Coco Coir will store minerals

A plants roots uptake nutrients, that’s their primary function. In coco coir positively charged ions of any given nutrient will accumulate. If there is a concentration of any particular nutrient/mineral ion in the media, other [cat]ions will force them out and replace them. This natural behavior equates to a mineral balance in coco coir, leaving essential nutrients available for uptake by the plant.

Basically Coco coir has a relatively high Cation Exchange Capacity [CEC] which simply means it stores minerals well.

One exception to this “nutrient balance” theory is phosphorus and calcium. Coco Coir retains too much phosphorous and too little calcium. Some suppliers, aware of this, add additional calcium to their product. This can be good, and it can be bad. If they supplement the coir with too much calcium, it blocks potassium uptake resulting in a potassium deficiency. See – Hydroponic Nutrients. Quality Hydroponic-grade coco coir is supposed to be treated so that excess potassium as well as sodium has been eliminated.