THATCH

PART 1

Introduction

Thatch is the undecomposed or partially decomposed layer of living and dead grass stems, roots, rhizomes, stolons, and other organic matter that is found between the soil surface and grass blades.

Under some circumstances thatch can play a positive role in sports turf management, and this positive role has been given very little attention. A managed thatch layer can add just enough cushion to enhance the durability of the turf surface and keep a field playable under extreme conditions.

DEFINITION

Thatch is a tightly intermingled layer of living and dead stems, leaves, roots and other organic mater which accumulates between the soil surface and the grass blades.

• Thatch is a normal component of an actively growing turfgrass, and as long as it is not too thick, it can increase the resilience of the turf to heavy traffic.
• Thatch develops more readily on high-maintenance lawns than on low-maintenance lawns.
• Thatch develops as plant parts and other organic debris accumulate on the soil surface, when turf growth occurs at an excessive rate, and when both soil and weather conditions are unfavorable.
• Thatch becomes a problem when plant organic matter production exceeds the rate of decomposition. The rate of decomposition of the thatch layer depends on the turfgrass species, temperature, soil moisture level, soil pH, biological activity within the soil, and cultural practices.

Any turf grass species that spread by runners, either aboveground (stolons) or belowground (rhizomes) is likely to produce thatch. Bermuda grass and zoysia grass are all heavy thatch producers. This grasses respond well to aggressive fertilization, and under such maintenance develop moderate to heavy thatch

How thatch develops

Thatch develops when a turf grass producer surface organic matter at a rate faster than the organic matter can decompose. The major causes of thick thatch accumulation are management practices that reduce the population of organisms that decompose thatch. Research has shown that earthworm and microorganism activity play a vital role in preventing excess thatch accumulation.

Good aeration, soil pH around 6.5 and adequate moisture favour the build-up and activity of beneficial microorganisms. Thatch problems are sometimes common in acidic and compacted soils since a healthy microorganism population does not flourish under these conditions. Unbalanced fertilization and indiscriminate use of fungicides and insecticides play the most havoc on beneficial organisms in turf. Too much nitrogen can promote disease development. High nitrogen fertilization promotes lush, succulent growth that is more prone to insect pests and disease.

Regular mowing helps reduce thatch accumulation by returning relatively small pieces of leaf clippings, which can be rapidly decompose.

Soil types also affect thatch formation. Turf being grown on heavy textured soil usually developed thatch faster than the same turf on sandy soil. This is because sandy soil has better aeration and drainage characteristics.

Media Department; The RS Group.