Properties of coir dust, and its use in the formulation of soilless potting media

Data from two experiments have shown that for adequate growth of Petunia ’Celebrity Salmon’ in soilless potting media based on or containing coir dust it was necessary to amend the media with Ca, S, Cu and Fe. When coir dust is used as a direct replacement for natural peat, about 10 mg/L medium extra N per week must be provided. The high K content of coir dust means that fertilizers need not contain as much K as is normally used for plants in media based on other products. The high Cl content of some coir products requires that they be leached if they are to make up a high proportion of a medium. The low CEC of the coir products (21–30 m.m (+)/L, compared with 78 m.m (+)/L for a peat), indicates a low ability to retain cations and to buffer against pH change. Two coir products had lower air‐filled porosities than did the peat tested and they retained more water at 10 kPa suction.