The USGA Putting Green Profile
Profile consist of the surface, root zone, gravel layer, drain lines and the sub grade
The USGA green when constructed properly creates a perched water table
In the root zone water will not move readily from small pores of the root zone to larger pores of the gravel layer until the finer layer is saturated with water to some depth.
Micro pores- pore that are filled with water not drained by gravity
Macro pores- pores that hold air water is removed by gravity
Saturated soil- all pore spaces are filled with water
Gravitational water- water that is removed by the force of gravity
Field capacity-when all micro pore spaces are filled with water and when the macro pores are drained by gravity and have filled with air
Adhesion- when water molecules stick to an object stronger than the force of cohesion
Cohesion when water molecules stick to them selves creates surface tension
Infiltration (hydraulic conductivity)-the rate at which water move into the soil
Peculation- the rate at which water moves through the soil
Perched water table occurs when fine textured soil is placed over coarse textured soil
Depth of perched water table is dictated by particle size of root zone and by the shape and size of the gravel laver (about 9 inches in a USGA spec green)
The capillary fringe and how water gets into drains
The lateral movement of water in soils is extremely slow- increase in slope adds to the height of the head, which increases pressure which forces the water down the slope
Free water- soil that is saturated- soil must be saturated before water will move in it
Capillary fringe- zone of quasi saturated soil above the free water zone- this water cannot move sideways in the soil- this water is a perched water table
Capillary fringe water cannot move into drains- water in the zone is held in place by the force of adhesion and cohesion and are stronger than the force of gravity
Air entry point- point above which the pull of gravity is strong enough to break the surface tension on the top of the menisci of the large pores, and water in these pores drains down the profile
The turf is now at field capacity large pores drained small pores filled with water
Capillary fringe height increases a soil particle size decreases
Compacted soils have less large pore space this also increases the height of the capillary fringe
The perched water table the concept and its use
Perched water table occurs when a fine textured soil is placed over a coarse textured soil
If the height of a capillary fringe exceeds the depth of the topsoil above the interface with the coarse material, the topsoil will never drain downward
USGA sands must be tested a two levels light compaction and heavy compaction if they vary greatly then the sand must be refused
The height of the perched water table can cause root zones to be droughty or too wet
Gravel affects height of perched water table- the finer the gravel the less height (more contact with the sand above it)