Black Layer

Black layer can have serious consequences for the health of all turf types. The name comes from the symptoms of black layer, namely the blackening of the subsoil in, or under, the rootzone. Turfgrass that grows on top of this black layer may show signs of poor health as the root health is affected. When soil samples are taken with an auger, the affected zone has a black color and a ‘rotten egg’ smell.

What does black layer to your turf:

1. Black layer can have serious consequences on the health of turf. It is important to understand the causes of this problem, and the methods used to control and prevent future occurrence.
2. Black layer only occurs in anaerobic soil conditions. It is caused by a physical condition of the soil.
3. If soil drainage is insufficient, it is likely that anaerobic conditions will develop and encourage black layer.
4. Anaerobic bacteria produce hydrogen sulfide gas, which has a characteristic “rotten egg” smell.
5. Hydrogen sulfide is poisonous to grass plant roots.
6. Hydrogen sulfide reacts chemically with metal elements such as iron (Fe), creating black deposits which form layers within the soil.

Approach

1. To control black layer it is essential that you treat the cause of the problem and not the symptoms.
2. Use a good-quality rootzone material.
3. Minimize layering in the soil profile through compatible top-dressing and mechanical action.
4. Minimize thatch in a programmed approach; minimize compaction and soil panning.
5. Use a penetrant wetting agent to improve water through the rootzone.
6. Sulfur does not cause black layer; it is an essential grass nutrient. Potassium nitrate does not prevent black layer. Continued use of potassium nitrate may cause soil deflocculation, which could increase the risk of black layer (J.B. Beard).
7. Continue the normal program but ensure good cultural practices.