What is coir compost?
Coir compost or coconut coir is a soil amendment made from the hard inner shell (brown fibers) of the coconut. It is shredded or ground up and compressed into a brick and then packaged. You must soak it in water and let it expand before using. I bought some online for $10 for a 10lb brick.
Coconut coir can transform dry, sandy or clay soils into rich, moist garden soil. Coir is very fibrous and will alter the texture of soil from dry compacted to loose, airy and moist. The fibers stop the soil from compacting like rock plus it retains moisture so the soil does not dry out as quickly. Coir can hold up to 6 times its volume in water. The fibers of coconut coir not only allow water to drain through because they create air pockets but also allows air to penetrate the soil. Coconut coir holds 1000 times as much air as soil.
To a minor degree, coconut coir adds organic material to the soil which provides nitrogen and carbon to plant roots. But it does not provide much in the way of nutrients so you need to fertilize with compost and/or worm castings.