The Fundamentals of Coir (the good, the bad, and the ugly).
The coconut palm, unlike many other plants’, is a salt tolerant plant. What happens with salt tolerant plants’ is that they uptake salt and displace it to areas of the plant where the salt can do the least harm.
In the case of the coconut palm the salt is displaced to the coir – the very thing that we use as a growing media. This means coir can contain high levels of salt (sodium chloride), something which can prove toxic to many/most plants.
On top of this coir contains large amounts of potassium and quantities of other elements. What this means is that coir requires special treatment to ensure a premium quality hydroponic media product is supplied to the end user. Analysis of Coco Coir Sample S 1978 P 126 K (Potassium) 3700* Na (Sodium) 2022 * Ca 119 Mg 104 Cu Zn 3.2 Mn 3.8 Fe 12.2 B 7 Cl (Chloride) 3498* All figures refer to parts per million (ppm). Above, is an analysis of one batch of hydrated coco coir.
It is easy to see that coco coir contains varying levels of micro and macro elements. The most significant elements in the analysis are the high potassium levels and the extremely high sodium and chloride levels (sodium chloride = salt). Potassium competes with magnesium and calcium while sodium competes with potassium for uptake. Furthermore, sodium chloride can be highly toxic to certain species of plants; even in relatively low levels, sodium chloride can have devastating effects on root health and development. For instance, this batch of coco coir caused phytotoxicity (yellowing of leaves, rusting/burning, sick plants etc) when trialled under controlled conditions next to another product that performed well.
Source of Material Coir derived from palms that are grown 50kms inland will have far less sodium chloride present than coir that is derived from palms that are grown close to the sea. That is, less sodium chloride present in the soil results in less sodium chloride in the coir. The origin of the coir is an important factor in determining the quality of the end product. Flushing and Buffering In order to prepare the raw coir product for use it is necessary to flush plentiful amounts of water through the product to wash out impurities (including sodium chloride). Premium grade coir is then buffered with various elements to prepare the coir for use. This requires flushing the coir with mineral elements in order to compensate for potentially problematic levels of sodium chloride and potassium (and other elements where required).
For instance, Iron is sometimes used to offset sodium chloride while magnesium and calcium is used to compensate for the naturally present, often high levels of potassium and phosphorous (While potassium and phosphorous are naturally used by plants and are beneficial elements, extreme levels of these elements can result in imbalanced nutrition and mineral element lockout). Typically, most suppliers of hydrated coir only flush the media and do not buffer it. This can prove detrimental to plant vigor and health, particularly in early growth.
Symptoms of toxicity include: • Rusting (particularly on leaf edges) • Yellowing • Slow stunted growth • Mineral deficiencies (due to uptake problems) • Purpling of stem Treatment/Age of Raw Product Coco coir has a shelf life where optimum performance is concerned (due to organic decomposition factors). Ideally the raw coir used in hydroponic medias should be less than two years old. Older coir is difficult to manage and will not last as long as newer coir.
Tips for using Coir Run-to-waste regime
After many years of experimenting in coir, both in indoor and outdoor settings, with various crops I have found that running a 25% - 30% waste regime is the most user friendly means of growing in coir. The 25 – 30% waste regime ensures that salt buildup in the media is kept to a minimum, and means flushing is typically never required; the agricultural standard being a 30% waste regime with the runoff being no more than 0.4EC higher than the original nutrient feed.
EC can be tested in the runoff and be compared to the nutrient EC. Air Porosity Typically, the bagged (hydrated) coir products sold via hydroponic outlets consists of fine particles and coir dust. While this means excellent fluid retention, it also means less than ideal air porosity in the media. Adding Perlite to the media will increase air porosity. A 60% coir to 40% Perlite mix being ideal (50/50 is also OK).
Another means of increasing air porosity is by mixing larger coir particles into the coir fines/dust, thus lifting the media and achieving a similar effect to a coir/perlite mix. pH Ideally, the nutrient should be maintained at between 6.1 (grow) and 6.3 (bloom). pH cannot be measured in the runoff. Ie. The runoff does not accurately reflect what is happening within the coir where pH is concerned. To test the pH of coir, take a sample of the coir from the root zone and add 1 part of coir to 5 parts of distilled water, shake and measure pH.
