Many years ago, I wrote one of my first articles, on “Coconut Coir Dust Mulch in the Tropics” and published it in Humus News, a trilingual (Dutch, French, English) magazine from Comité Jean Pain, a Belgian non-profit association that has trained people from across the globe on making compost since 1978.
So, a couple of years ago when one of our Indian video partners decided to make a training video on composting coir dust, I dug up my old article, and was pleasantly surprised to see that it still contained useful information.
Coconut coir dust or coir pith is the material that is left over after the fibres have been removed from the coconut husk. Coconut factories often have no idea what to do with this waste, so in many coastal areas in the humid tropics one can find heaps of this natural resource.
Whether economical or ecological motives are the driving force, in low external input agriculture systems in the tropics, farmers often use biowaste for soil conservation and sustainable land use.
While coir dust has negligible amounts of nitrogen, phosphorous, calcium and magnesium, making it a poor source of nutrients, it can store up to 8 times its dry weight in water. By applying a 15 cm thick layer of coir dust mulch around coconut seedlings in Sri Lanka, irrigation needs could be reduced by up to 55%.
In a pineapple coconut intercrop during the dry season, my coir paper reported that the top soil layer had a moisture content of 49% under the mulch, compared to 10% under a sandy ridge of the same height.
When coir dust mulch is applied to salt-sensitive plants, care has to be taken that the concentration of salt is not too high. The highest salt concentrations, though still low, are mainly observed in coir dust which is fresh and from coastal coconut trees. This salt concentration can be reduced by leaving the material in the rain, before applying the mulch in the field or nursery.
In a commercial tree nursery in Kenya, germination of cashew seeds is enhanced by applying a coir dust mulch. Besides, roots are not damaged after transplanting, thanks to the loose structure of the coir dust. Weeds in cashew plantations in India are suppressed by applying a layer of 7.5 cm of mulch in a 1.5 m radius around the trees. In Sri Lanka, this kind of mulch is mainly used in semi-perennial crops like pineapple and ginger. Coir dust mulch suppressed some of the world’s worst weeds.
Besides suppressing weeds, coir dust mulch also helps to establish cover crops. Herbaceous legumes are often used as cover crop under coconut in Sri Lanka, but they are suppressed by weeds in dry weather. Applying coir dust tackles the weeds, but favours the leguminous cover crop during the dry season.
Coir dust consists mainly of lignin, a woody substance which is poorly biodegradable. About 90% is organic matter and the C/N ratio is extremely high (>130). The low pH of 4.5 – 5.5 offers an extra protection against biodegradation, as many micro-organisms do not survive once the pH drops below 4.
Slow biodegradation of organic mulches has been recently more and more looked for, especially in the humid and sub-humid tropics, where fast mineralization of the organic matter and leaching of minerals are big problems.
While coir dust can easily be applied as a mulch, the recently produced Access Agriculture video suggests that it is better to compost the coir dust first when one wants to use it to improve the soil structure. The video shows how one can easily make one’s own organic decomposer that is rich in good microbes to break down the lignin.
Coir dust, being important to control weeds, improve soil physical conditions and increase water retention capacity, should be regarded as an important resource for soil conservation and sustainable land use in integrated cropping systems, and not as waste.
The use of coir dust in the tropics, however, is not only hindered by a lack of knowledge, which the video aims to share, but is also seriously threatened as coir dust is increasingly exported to Europe where it is used as a horticulture substrate.
Further reading
Van Mele, P. 1997. Utilization of Coconut Coir Dust Mulch in the Tropics. Humus News, 13(1), p. 3-4.
Related Access Agriculture video
Coir pith – from waste to wealth
