Black Layer

Condition on Greens!

Last year when our agronomist came to advise us on the condition of our greens, and the best course of action to take to produce a better putting surface, it was brought to our attention that the levels of thatch and black layer under the surface were contributing to a weak grass sward and poor roots.

This was a problem that the greenstaff were already aware of so the work to reduce these problems had already began. Black Layer is a solid layer of soil at different depths under the greens that locks up nutrients and roots and water will not penetrate through.

Black layer only occurs in anaerobic soil conditions. It is caused by a physical condition of the soil. If the soil does not drain quickly enough or impenetrable layers are present which restrict downwards water movement, it is likely that Black Layer will occur.

· When a root zone has excess water present, the water will push air out of the soil pore spaces. A root zone in this condition can be described as anaerobic.

· In an anaerobic soil, aerobic bacteria are replaced by anaerobic bacteria.

· Anaerobic bacteria produce Hydrogen sulphide gas, which has a characteristic ‘rotten egg’ smell. It is poisonous to grass plant roots.

· Hydrogen sulphide reacts chemically with metal elements such as Iron (Fe), creating black deposits, which form layers within the soil.

Possible causes of Black Layer:

· Poor rootzone mixture.

· Layering in the soil profile

· Buried thatch layers

· Compaction

· Soil panning.

· Incompatible top dressing

Conclusions

· Black layer only occurs in soils with excess water present.

· Black layer can be cured by improving drainage or increasing aeration.

· Sulphur does not cause Black Layer.

· Sulphur is an essential grass nutrient.

· Potassium nitrate does not prevent ‘Black Layer’

· Continued use of Potassium nitrate may cause soil de flocculation, which could increase the risk of ‘Black Layer’.

RGC Greenstaff