Thatch is a concentrated layer of organic matter between the soil and the green surface.
This layer creates a cushion which not only slows down the green, but harbours fungi and unwanted insects. It can also become impervious to water.
All of this will impede the emergence of new leaf growth through the mat.
Thatch becomes a problem when it exceeds 10 mm. This accumulation of thatch can create an environment that affects sward quality in many ways:
- Excessive thatch can create a favourable environment for many pests and diseases.
- Thatch can influence water movement in and around the grass plant.
- Thatch can alter soil surface conditions, often producing a waxy layer that can prevent water movement into soils (dry patch).
- Thatch can influence soil temperatures.
- Thatch interferes with air movement around the grass plant.
- Thatch can affect mowing quality.
- Thatch can prevent effective use of chemicals and fertiliser applications.
- Excessive thatch affects bowl pace, bowl bounce and bowl roll.
- Thatch will also affect the traction and shear strength of the turf surface.
- Thatch will affect turf grass quality.
Mechanical removal of thatch
The method and type of machinery used will be dependent on:-
- Depth of operation.
- The amount of thatch to be removed.
- Surface damage.
- Retention of organic matter.
At renovation a Scarifier is used to remove thatch. On a normal size green one would remove anything between sixty and eighty barrows of thatch.
General
The commonly accepted time for thatch removal is in the autumn during the end of season renovations.
However, with the development of groomers and verticutting units on mowing machines thatch removal can be undertaken on a regular basis. In bowls situations these units are often used on a weekly or fortnightly basis.
The other recognized time is in the spring, but generally involves a lighter scarification to minimise any damage to the playing surface ahead of the new playing season.
Be careful not to overdo the scarification. Using a vigorous machine on a fine turf may have a detrimental effect.
Macro Thatch
This is a term used for the accumulation of dead material in the root zone.
Often as a result of compaction, the soil becomes acidic and prevents the breakdown of organic matter, leaving undecayed matter in the thatch.
If the greenkeeper has been top dressing on top of existing growing grass this becomes thatch in the root zone.
Apart from slowing down the green this macro thatch can significantly interfere with the healthy development of roots and grass.
Prior to the use of a scarifier to remove the thatch, one must check the root system is not too shallow and can be damaged by the blades penetrating the surface.