EFFECT OF PHYSICAL, CHEMICAL, AND BIOLOGICAL TREATMENT PROCESSES ON BIOSOLID NITROGEN (N) FORMS AND THEIR INFLUENCE ON SOIL N MINERALIZATION DYNAMICS AND N-ACQUIRING ENZYME ACTIVITIES IN AN ACIDIC SOIL

Abstract

Biosolids application to soils has been seen as a sustainable agricultural practice to recycle organic matter and nutrients and mitigate climate change. Four different types of biosolids were produced by treating an identical batch of raw sewage solids: N-Viro, CaO-treated, heat-dried (HDB), and composted biosolids (CB). Leached and non-leached incubation studies were conducted simultaneously for 154 days to assess N mineralization and N-acquiring enzyme activities (β-1,4-N-acetyl-glucosaminidase (NAG), leucine amino peptidase (LAP), and urease) in an acidic soil after biosolids addition. Our results showed that different biosolids treatment processes (alkaline treatment (N-Viro® Process and CaO addition), composting, and heat drying) significantly affected biosolids characteristics in terms of N forms and contents. N availability decreased in the order CaO-treated > N-Viro > HDB > CB. A first-order kinetic model fitted well to the mineralization data. N-acquiring enzyme activities all increased after biosolids addition, suggesting that soil microbial activity was stimulated.