Comparative use of cress seed germination and physiological parameters of Helianthus annuus L. to assess compost maturation

Abstract

Maturation during composting was investigated in three composts prepared from lignocellulosic wastes. We used the cress seed germination (Lepidium sativum L.) bioassay and phytotoxicity assays of Helianthus annuus plants to determine a series of physiological parameters. Germination of Lepidium sativum and leaf weight of Helianthus annuus revealed increasing maturity of all three composts during the initial period of composting, i.e. the thermophilic period. In general, the data then showed a period of transition, followed by a substage of mesophilic activity (30–60 days) when compost reached optimum ripeness, and a second mesophilic substage during the final period of composting (60–90 days). The results of cress germination tests during these periods suggest that the rate of maturation tended to stabilize, whereas some of the Helianthus annuus physiological parameters indicated a slight decrease in the quality of the matured compost. Stem length of sunflower plants was found to be too insensitive as an indicator to detect changes in the degree of maturation during composting.