Soils and drainage

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A soil ped, which is sub-divided into Granular and Crumb, having rounded surfaces and is common in topsoil (A Horizons). A Granular structure is relatively small and compact within an aggregate, being less porous than a Crumb structure which is more porous, and this is represented by a good topsoil that has good organic matter content and an active soil fauna and micro-organisms. This is the best structure for most soils, especially turfculture.

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Small to large stones. Gravel is a material with a diameter between 2 and 64mm. It is categorised using the Udden-Wentworth scale as granular gravel (2 to 4mm diameter) and pebble gravel (4 to 64mm diameter).

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A layer of free draining material usually gravel or stone, about 100 to 150mm in depth. It is sometimes installed on specially constructed sports pitches beneath the root zone material, being separated from this by a blinding layer. This may also be referred to as a Drainage Raft or just a Raft.

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Excess water within a soil which will drain away and which is unavailable for use by a plant. It is water which is temporarily present between the states of Field Capacity and Saturation Point.

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A drainage system where the lateral drainage trenches and pipes are in a grid like pattern, being parallel to each other. They will typically join perimeter drains at 90 degrees. This is also called grid iron or parallel drainage.

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All water which is stored below the ground in rocks or other geological strata. The water within a water table can be classed as ground water. A formal definition is, 'All water which is below the surface of the ground and in direct contact with the ground or subsoil'; Flood and Water Management Act 2010 (S5 (4)).

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The material in which a plant grows.

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An open channel or ditch which allows water, especially excess water, to flow from a field or drainage system.

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A Calcium Sulphate mineral which has been used as a fertiliser on sodic soils. It is also sometimes called Sulphur of Lime.

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The Humic or Humus horizon within a soil profile. Where present, it forms part of the O Horizon.