Buffered Coir Pith Blocks
Coir pith is high in sodium and potassium, it is treated before use as a growth medium for plants or fungi by soaking in a calcium buffering solution; most coir sold for growing purposes is said to be pre-treated. Once any remaining salts have been leached out of the coir pith, it and the cocochips become suitable substrates for cultivating fungi. Coir is naturally rich in potassium, which can lead to magnesium and calcium deficiencies in soilless horticultural media. Coir fiber is rarely used as a potting material, except for orchids, and does not need buffering, as it has a very low cation-exchange capacity (CEC) capacity, hence not retaining salts.
Coir does provide a suitable substrate for horticultural use as a soilless potting medium. The material's high lignin content is longer-lasting, holds more water, and does not shrink off the sides of the pot when dry allowing for easier rewetting.