Severe reducing conditions and the production of FeS can occur in small pockets of buried organic matter produced as a result of thatch accumulation and using various topdressing materials. Normal aerobic conditions can be identified in close proximity to hollow-tine holes, highlighting the importance of this maintenance procedure.

Black layer is normally present between 1.2 and 5.9 inches in the soil profile. In some instances, severe reducing conditions can be established very close to the soil surface (within the first 0.4 inch). The effect of black layer at such a shallow depth can be devastating and result in total loss of turf cover.

This problem is often associated with algae proliferation on the surface of fine turf areas. The biofilm produced by the cyanobacteria seals the soil surface and thereby restricts air movement into the soil profile. The biofilm may also act as a readily available organic matter source for sulfur-reducing and other bacteria. Chemicals can control algae, and a dry surface can discourage algae formation.

High phosphate levels are also associ

ated with algae proliferation, and phosphate tends to accumulate near the soil surface, as it is very immobile. Therefore, keep phosphate applications to a minimum and make them in conjunction with hollow tining so that the fertilizer can be brushed into the tine holes.

Although black layer can cause severe damage to turfgrass, effective measures can be taken to prevent and correct the problem (see the sidebars).

This article first appeared in The International Turfgrass Bulletin Issue 211, the official magazine of STRI -- The Sports Turf Research Institute.

1. Berndt, W.L. 1987. Black layer formation in highly maintained turfgrass soils. Golf Course Management 55(6):106-112.

2. Hodges, C.F. 1992. Interaction of cyanobacteria and sulfate-reducing bacteria in sub-surface black-layer formation in high-sand content golf greens. Soil Biology & Biochemistry 24:15-20.

3. Nilson, S.M., and K. Denford. 1998. Effective management of black layer in golf greens: Anticipating black layer. Golf Course Management 66(12):62-63.