Accumulation of thatch in a distinct and restrictive layer is a symptom of an imbalance between tissue production ( primarily root, stolonS, and rhizomes ) and decomposition in the ecosystem. Tissue production in cool season grasses is most rapid in cool weather, and tissue decomposition is most rapid in hot weather. Thatch decomposes rapidly during hot periods if adequate water and nitrogen are available and if the pH of the thatch is in the slightly acid to neutral range. Hence, it is advisable to ensure that water, pH, and nitrogen levels are favorable during the summer to help decompose thatch. Regulation of these factors may also promote some diseases, however because some facultative parasites are active decomposers of organic litter.
When thatch decomposition has been suppressed, mechanical removal of thatch by mean aerification and vertical mowers may become necessary. Top dressing is particularly effective in managing thatch. Thatch decomposition maybe suppressed by:
- Low soil temperature
- Conditions under which the turf is kept continually wet or very dry
- Excessive acidity (pH < 5,5) as a result of failing to apply lime
- Removal of clipping and allowing nitrogen to become depleted in thatch during periods of high temperature
- Application of excessive amount of nitrogen, especially in water soluble and acid reacting ammonium-based fertilizer
- Repeat application of fungicide or certain insecticides, nematicides, and herbicide before or during summer, when most thatch decomposition usually occurs