Compost of municipal organic waste: Effects of different management practices on degradability and nutrient release capacity

We studied the degradability and nutrient release capacity of municipal organic waste (MOW) composts obtained with different management practices: shredding and/or mixing with wood shavings, cocomposting with biosolids, and vermicomposting. As indicators of degradability and nutrient release capacity, we measured net N and C mineralization, extractable-P release, N retained in microbial biomass, and dehydrogenase activity in 16-week laboratory incubations, using soil amended at a rate of 40 g kg−1. We also determined the extent to which these indicators were predicted from the chemical characteristics of the amendments. All products increased soil N and P availability, and the size and activity of soil microbial populations. Carbon and N mineralization, and extractable-P release were influenced by amendment chemical characteristics, especially organic matter, total N, total P, C to N ratio, extractable-P and water soluble C. Cocomposting MOW and biosolids is an important alternative for MOW management, because it was the most effective strategy at increasing product degradability and nutrient release capacity (highest net N and C mineralization, extractable-P release, and microbial biomass-N). Shredding MOW increased C mineralization, while the addition of wood shavings decreased net N mineralization, but generally did not affect C mineralization. Thus, these two practices should be used when these specific product characteristics wish to be achieved. Vermicomposting did not prove to be an efficient strategy when MOW was mixed with biosolids.