Question

The topsoil of golf course putting greens typically is sand, as this substrate promotes rapid drainage of water and is relatively insensitive to compaction by foot traffic. A disadvantage of a sandy topsoil is that it does not store much water, causing problems for the grass growing on the greens. This issue can be partially eliminated by installing a layer (horizon) of gravel beneath the sandy topsoil during construction of the putting green. Explain why the gravel layer helps the retention of water in the sandy topsoil.?

Answer 1

The gravel's particles are much more closely packed together like clay soil so water will find it difficult to penetrate it and drain into the ground. Water will therefore gather on the gravel but beneath the sandy topsoil.

This will allow for the roots of the grass to penetrate past the sandy soil and get to the water that is on the gravel thereby ensuring that they remain hydrated and healthy.