Effects of compost stability on plant growth, microbiological parameters and nitrogen availability in media containing mixed garden-waste compost

Garden waste was composted over a number of weeks in a windrow, and turned regularly to maintain aerobic conditions. The physical parameters of the composting material were measured, and at 1, 2, 3 and 4 weeks of processing samples were removed and incorporated into growth media. Ryegrass was grown over 1 year and harvested regularly for measurement of dry matter and N content. In addition, compost samples were removed and the microfauna and total microbial biomass quantified. It was shown that the younger composts (1 and 2 week processing) gave higher dry matter and N yields. The young compost (1 week) contained significantly higher protozoan (especially ciliate) biomass than the older (4 week) compost, over the entire experimental period.