Phytotoxicity of refuse compost during the process of maturation

The application of refuse compost to soil for crop cultivation has become one of the most economic ways of disposal. However, injuries to existing plants or germinating crops have been frequently reported after the application of fresh compost to agricultural land. The present investigation examined the changes of phytotoxic substances of fresh refuse compost and a fresh commercial compost during storage for 115 days. During the storage period (25 ± 5°C), a portion of each type of compost was withdrawn every 30 days for glasshouse trials on Brassica parachinensis Bailey by mixing the compost with a sandy soil (at ratios of 75, 100 and 125 tonnes ha−1). Dry weights of B. parachinensis were determined after a growing period of 26 days. It was noted that the fresh compost inhibited plant growth and that production increased gradually as the compost matured, with the highest dry weights being obtained in the final test for each type of compost. Aqueous extracts were prepared every 20 days from each type of compost. These extracts were applied to seeds of B. parachinensis, and the effects on seed germination and root length of the germinated seeds were recorded. The contents of ammonia and ethylene oxide were analysed. In general, both ammonia and ethylene oxide dropped gradually towards the end of the storage period. Their contents were inversely correlated with seed germination and root elongation of B. parachinensis. It was concluded that compost from the composting plant should be stored for at least 115 days before application to crops. Copyright © 1985 Published by Elsevier Ltd.