Coir is being marketed as a rooting medium for the hydroponic growing of plants. Growers need to be aware that coir is not a consistent substance in terms of its elemental content and physio-chemical properties, but will vary from batch to batch depending on the coir source and the procedures used for generating a rooting medium product. In addition, coir may also contain a substantial quantity of soluble organic compounds that can act as “chelating” agents, thereby affecting plant nutrient availability. Since coir has a high water-holding capacity, repeated applications of a nutrient solution will result in the accumulation of both soluble elements, increasing the EC of the retained nutrient solution, followed by the accumulation of precipitates of calcium phosphate and sulfate, trapping other elements, which in turn will impact the nutrient element status of the growing plant. Therefore, the management requirements for coir as a rooting medium are demanding in order to avoid potential nutrient element insufficiencies from occurring in the growing plant. Therefore, the elemental composition of an applied nutrient solution and its associated use factors must be such as to minimize the occurrence of nutrient element accumulation.
