Degradation of Turfgrass Thatch by Earthworms (Oligochaeta: Lumbricidae) and Other Soil Invertebrates

Abstract

The importance of earthworms and other soil invertebrates in decomposition of thatch was studied in Kentucky bluegrass, Poa pretenses L., turf. Intact thatch was buried in nylon bags of different mesh sizes to selectively exclude certain components of the soil fauna. In a second experiment, thatch was buried in identical coarse mesh bags in either untreated plots or in plots from which earthworms had been eliminated with insecticides. Samples were recovered periodically for 23 mo, and net loss of organic matter was determined gravimetrically. Earthworms, mainly Aporrectolea Sp. (Oligochaeta: Lumbricidae), incorporated large amounts of mineral soil into the thatch matrix. In both experiments, rates of net loss of organic matter and of relative microbial respiration within remaining thatch were much greater when earthworms were present than when worms were excluded. Soil mesofauna (e.g., Cryptostigmata, Collembola) were less important than earthworms in the initial comminution of thatch. Preservation of earthworm populations should be an important consideration in controlling thatch accumulation.