One of the problems with clay soil is its slow permeability resulting in a very large water-holding capacity.Because the soil particles are small and close together, it takes water much longer to move through clay soilthan it does with other soil types. Clay particles then absorb this water, expanding as they do so and further slowing the flow of water through the soil. This not only prevents water from penetrating deep into the soil but can also damage plant roots as the soil particles expand.