3.7. Phosphorus turnover
Phosphorus in organic material is released by a mineralization process involving micro-organisms. The higher initial total phosphorus (organic and inorganic) at inlet zone was due to the higher content of vegetable waste, tree leaves and cattle manure. An increase from 2.5 to 3.45 g/kg was observed at inlet zone during initial 60–70 days may be due to cattle manure, further stagnated at around 3.5 g/kg. The evaluation of total phosphorus at outlet zone shows a little increase in initial 60 days of wastes loading, an obvious recovery subsequently due to the net loss of dry mass (Huang et al., 2004). The percentage increase in total phosphorus at outlet zone was 64–75%, indicating the higher microbial activities during later stage of composting resulting more mineralization (Fig. 5). Table 4 shows the increase in final total phosphorus during maturation methods at different ambient temperatures. Results indicated that windrow and vermicomposting methods are capable enough to increase the total phosphorus but vermicomposting showed better results.