The Effect of Temperature on the Viability Of Weed Seeds in Compost

Abstract

In this study, the effect of different constant temperatures on the viability of weed seed contaminants of municipal composted waste was determined. Seeds of eight weed species were buried in moist compost in small recoverable packets. The seeds were subjected to three constant temperatures, typical of the composting process, removed after 3, 21 and 84 days and their germination and viability determined. At 55°C all of the recovered weed seeds failed to germinate and were found to be non-viable. At 35°C and 45°C an effect of incubation period was noticeable, and it was evident that there were significant differences between species in tolerance to temperature. The study showed that three days at 55°C was sufficient to destroy all the selected weed species. It was concluded that, among the species studied, seeds that survive the composting process do so as a result of localized “cool spots” caused by inefficient turning of the windrow. Alternatively wind blown species could be entering the outer parts of the windrow, immediately prior to packaging.