In 1949, E. P. Hume wrote an article in the journal Economic Botany extolling the horticultural virtues of a by-product of the coconut husk fiber processing industry. Coir is the name given to the fibrous material that constitutes the thick measocarp (middle layer) of the coconut fruit (Cocos nucifera). The long fibers of coir are extracted from the coconut husk and utilized in the manufacture of brushes, automobile seat and mattress stuffing, drainage pipe filters, twine and other products. Traditionally, the short fibers (2mm or less) and dust ("pith") left behind have accumulated as a waste product for which no industrial use had been discovered. Hume wrote of the excellent growth obtained with various plants when this Coir dust or, as he called it, "coco peat," was used as the growing medium. Hume was a prophet before his time. It is only in the last 10 years that his words of wisdom have percolated through the often conservative ways of international horticulture.

In the 1970's and 80's, initial tests in Australia and Europe indicated that coir dust could function remarkably well as a substitute for various peat products in soil less container media for plant growth. Several Dutch companies have in fact been using coconut Coco Peat in production media since the 1980's, and the Royal Botanic Gardens at Kew is currently shifting most of its plant production into Coco Peat-based media.

'Coir fiber pith' or 'coir dust' or Coco Peat produced as a bi-product when coconut husks are processed for the extraction of the long fibers. Coco Peat is the binding material that comes from the fiber extraction of the coconut husk. A very Special Grade of Coco Peat is washed, screened and graded before being processed into various Coco Peat products for Horticultural and Agricultural applications. Coco Peat is a multi-purpose soil conditioner and growing medium.

Coco Peat is very similar to peat in appearance. It is light to dark brown in color and consists primarily of particles in the size range 0.2-2.0 mm (75-90%). Unlike sphagnum peat, there are no sticks or other extraneous matter. Independent analyses of Coco Peat were performed in May and June 1991 at Auburn University, University of Arkansas, and A&L Analytical Laboratories (Memphis, TN). These results are summarized in Tables 1 and 2, and one manufacturer's technical data is also presented. G. C. Cresswell (1992) looked at Coco Peat in comparison to sedge and sphagnum peat products and concluded that it has superior structural stability, water absorption ability and drainage, and Cation Exchange Capacity compared to either sphagnum peat or sedge peat. Coir Peat tends to be high in both sodium and potassium (Handreck, 1993) compared to the other peats, but Na is leached readily from the material under irrigation (Handreck, 1993). The high levels of potassium present in coir dust are interesting to note, and may actually prove more a benefit than any detriment to plant growth. Coco Peat from sources other than Sri Lanka have also reportedly contained chlorides at levels toxic to many plants, thus it is very important that salinity in the raw material be monitored before processing into a horticultural amendment. It is evident, that chemical properties of this material can vary widely from source to source (Evans et al. 1996). The higher pH of Coco Peat may allow less lime to be added to a coir dust-based medium, though adding dolomite to container soils is more important for Ca and Mg nutrition than for elevating pH.

Sri Lankan data

       
Properties of Coir dust normally vary with the type of machine used to de-fiber the coconut husk. There are three major types of coir processed machines available in Sri Lanka. According to visual observation, Coco Peat emanating from the de-fibering machines are the best. Because they have several different types of dust particles which can produce macro as well as micro pores in the media.

Normally the Coco Peat is extracted from a process called retting. Retting involves soaking the husk in the water for a certain period until the fiber becomes loose and soft. The soaking is done in the cement tanks.( But in Sri Lanka most facilities use mud tanks to soak the husk) During the retting process, the husk become soft and a number of substances like carbohydrates, glycosides, tannin and nitrogen compounds are brought into the solution. The carbohydrates and nitrogen compounds are acted upon a great variety of anaerobic organisms, which produce various organic acids and gasses. When the fermentation progresses, the temperature of the husk increases, water become turbid due to gas formation, Lignin and pectin in the middle lamella of the husks slowly dissolves. Subsequently, the rate of fermentation slows down and water becomes clean without the evolution of gasses and the consequent frothing. At this stage the husk are ready for the removal of fibers. The time required for frothing is influenced by the various factors such as the stage of maturity of coconuts, microbial activity in the tanks, weather conditions and nature of the weather. (P.K.Thampan, 1987)

The retted husks are beaten in the machines called de-fibering or with wooden mallets (Patti kuttam). Broadly there are two major type of coir fibers. They are white and brown fiber. White fiber generated through the fresh husks de-fibering, and brownish are from soaked husks.

Few well designed tests have appeared assessing the performance of Coco Peat as a plant growth medium.

Cresswell (1992) compared Coco Peat to both sphagnum and sedge peat as a growing medium for Broccoli, Tomato and Lettuce seedlings. He found earlier germination and greater size and uniformity of seedlings germinated and grown in Coco Peat.

Handreck (1993) tested growth of Petunia x hybrida 'Celebrity Salmon' in 5.6:1 (v:v) mixes of either Malaysian coir dust, Sri Lankan Coco Peat, or a sphagnum from Sakhlin, Russia and silica sand. He observed equal growth when all three mixes were adjusted to pH 6 and total plant nutrients were supplied, but varying performance with changes in nutrient regime. He concluded that plants in Coco Peat-based media require more Ca, S, Cu and Fe, but less K, than those grown in peat. He also observed greater immobilization of soluble nitrogen with Coco Peat than peat moss, an observation confirmed by Cresswell (1992).

Trials at Whittle College in England with several woody ornamentals in various Coco Peat blends indicated that Coco Peat performance was comparable to sphagnum peat. Unpublished technical reports from other institutions in England have indicated similar results with a wide range of greenhouse crops.

Another experiment was conducted to test the efficacy of Coco Peat as a peat substitute in replicated trials at the University of Florida Fort Lauderdale Research Center (Meerow, 1994, 1995). Ixora, Anthurium, majesty palm, and Pentas were grown in container media that differed only in the peat fraction (40%). One mix utilized sphagnum, the second Florida (sedge) peat, and the third, Coco Peat. The Pentas, Ixora and majesty palm all grew much better in the Coco Peat mix than in sedge. Interestingly, the Anthurium grew almost as well in the sedge peat mix as in the Coco Peat. The Pentas, majesty palm and Anthurium grew equally well in the Coco Peat medium as in the sphagnum medium. Only the Anthurium showed slightly better top growth in the sphagnum mix. The sedge peat-based medium had the greatest percent air space and the lowest water-holding capacity of the three media at the initiation of the trials, but at termination, showed considerable reversal of these parameters. The Coco Peat-based medium showed the least change in these parameters over time. The higher initial air porosity of the sedge-based medium may have been conducive to better initial root growth of the Anthurium, as this plant is epiphytic in nature. No evidence of Cl or Na toxicity was observed on the plants in this study grown in the Coco Peat-based medium, and conductivity measurements indicated low levels of total dissolved salts. More informally, he had noticed that seeds sown in a 1:1 (v:v) mix of Coco Peat and perlite seem to develop larger root systems than those germinated in 1:1 sphagnum and perlite.

An experiment was conducted by L.H.J.van Holm & M. Fernando to evaluate the response of Albizia falcataria to dual inoculation with vesicular-arbusculer Mycorrhizea (VAM) and a Rhizobium strain. The potting medium consisted of compost, coir dust, and soil. Previous literature had showed an inhibitive effect of compost on the spread of mycorrhizal infection. An experiment was undertaken to ascertain whether a biological or physiochemical parameter in either of the two organic substrates was inhibitive to VAM fungal spread. All coir dust treatments and autoclaved compost media demonstrated no reduction of colonization compared to the control (Soil), indicating no physiochemical inhibition. They produce a greater colonization percentage at all harvests except the forth harvest in which colonization was reduced in the autoclaved compost medium. Hence coir dust appeared most suitable for the culture of VAM fungi owing to it’s lack of biological inhibition and it’s advantageous physiochemical properties.

Normally the use of organic manure as an alternative for expensive imported fertilizers is not popular. Because the amount of nutrients released after decomposition is very slow. It is reported that the microbial activity determines these parameters to a great extent. Therefore investigation was conducted by Dr.K.A. Nandasena & Mr. L.H.J.van Holm to study the active fraction of soil organic matter & to determine the potential nitrogen mineralization in soil. Rice straw, Coir dust, farm yard manure and Gliricidia sepium leaves were monitored after incorporating in three soils with different contents of organic matter. Organic matter addition increased CO2 production in all materials except in Coco Peat. Increasing the dose of incorporation enhanced the effect. Fresh rice straw Gliricidia sepium had a higher effect than the farm yard manure & Coco Peat. Higher microbial population was observed when Coco Peat was added and the number increased slightly with the dose. Fresh organic matter increased all fractions. But fiber rich Coco Peat enhanced mainly the humic fraction which has very high benefit to live soils.

Sri Lanka have also reported contained chlorides at levels toxic to many plants, thus it is very important that salinity in the raw material be monitored before processing into a horticultural amendment. It is evident, that chemical properties of this material can vary widely from source to source (Evans et al. 1996). The higher pH of coir dust may allow less lime to be added to a Coco Peat-based medium, though adding dolomite to container soils is more important for Ca and Mg nutrition than for elevating pH. Cresswell did find that a small amount of nitrogen drawdown (N kept from availability to plants during decomposition of organic amendments low in nitrogen) occurred with Coco Peat, but typical production fertilization practices would likely compensate for the small amount of resulting N loss. At present, it is unclear how else fertilization regimes may need to be adjusted, if at all, in media comprised chiefly of Coco Peat.

Coco Peat doesn’t contain enough plant nutrients, hence, immediately farmers may need to add fertilizer to the crop otherwise decomposition of the materials can take place, temporally N deficiency may occur.(M.Arenas & C.S.Vavrina, 2002)

Further research has shown that Coco Peat requires pre-treating before its use as a growing medium. Early attempts failed due to the high potassium and sodium content naturally found in the coir dust. When the growers added calcium or magnesium to the substrate the potassium and sodium was released causing damage to the plant (,www.hydroponics.co.uk/organic_growing media)

Washing

Most of the Poly-phenolic compounds are easily water-soluble. So by adding more water to the Coco Peat and allow it to drain will wash off most of polyphenolic compounds.

Recycling the pounded water

Recycling the soaking water at the correct time will be the most economical way to reduce the toxicants in fresh coir dust. So, coir mills should have the facility to recycle water or remove small amount of water from the tank and put new fresh water to balance the volume.

Adding some synthetic compounds

 By adding CaNO3 to the fresh coir dust, it will enhance the calcium level in the product as well as facilitate cation exchange with Ca. So Ca will be absorbed to the colloids & release most of the salts from Coir dust like Na, Fe..etc .

Composting the Coco Peat.

This will help to increase the nutrient status of the product as well as reduce most of the polyphenolic compounds due to oxidation. This kind of value added Coco Peat has very big demand in the market because they are pretty close to the mined peat.

Comparison of Coir dust & Peat

Value-added Coir dusts:
Coco Peat contains very high amount of Lignin. Hence Coco Peat takes decades to decompose. Studies by various institutions have resulted in methods to speed up process of decomposition (Lignin reduction) by fungal/ Microbial culture.
Coco Peat doesn’t contain enough plant nutrients, hence farmers need to add fertilizer to the crops, otherwise  decomposition of the materials will commence, temporally N deficiency may occur. (M.Arenas & C.S.Vavrina, 2002)
Further research has shown that Coco Peat requires pre-treating before its use as a growing medium. Early attempts failed due to the high potassium and sodium content naturally found in the coir dust. When the growers added calcium or magnesium to the substrate the potassium and sodium was released causing damage to the plant (,www.hydroponics.co.uk/organic_growing media)
Hence, effective value adding processes should contain suitable measures to keep way from all the above problems of Coco Peat