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Abstract
A simple assay, based on soil burial tests, was developed to determine the activity of cellulolytic microorganisms in compost. The assay used filter paper as the cellulose substrate. The filter paper was buried in compost and incubated in the dark for 10 days at 30°C. The amount of cellulose degraded was determined by the difference in dry mass of the filter paper, before and after burial, and the cellulolytic activity was expressed as percentage cellulose degraded in 10 days. The assay was applied to visually mature composts from various sources that differed in raw material composition and treatment. The results were compared with those obtained from a cress (Lepidium sativum, L.) germination and growth experiment carried out with the same composts and with the microbial activities of the composts determined by a fluorescein diacetate method. The fresh mass of the cress roots was negatively correlated with the cellulolytic activity of the composts. A positive correlation existed between the cellulolytic activity and the microbial activity of the composts. It is suggested that cellulose degradation could be one of the factors responsible for ‘latent toxicity’ exhibited by some visually mature composts.
Acknowledgments
The financial support of the National Research Foundation of South Africa (NRF) is gratefully acknowledged. The authors would like to thank the following persons for the donation of compost: Mrs Petro Nortje, Mr Ralf Hagen (Gromor National Plant Food CC), Mr Steve Ansermino and Mr Roddy Howard (Gromed Organics), Mr Charles Touzel (Chantarelle Mushrooms), and Mr Greg Caine (Allgrow Garden Products).