Mineralization of five biosolids in two tropical soils

Abstract

This work aimed to evaluate mineralization rates of the five most common biosolids (digested sludge, composted sludge, limed sludge, heat-dried sludge, and solar-irradiated sludge) when incubated to two tropical soils - a Spodosol and an Oxisol soil. Fresh sludge and stabilized biosolids were mixed with soil samples at 0.5, 1.0, 2.0, 4.0, 6.0 and 8.0 dry t biosolids/ha and incubated at 25oC in a high humidity chamber (95% air moisture), at 12 hours light/day, during 23 weeks for a non-leaching experiment. Results have showed that all the stabilization processes altered the capacity of the fresh sludge to release mineral-N. Except solar-irradiated sludge, the stabilization processes hindered the release and accumulation of mineral-N in soils. Composting and CaO-liming were the processes that most reduced the release of mineral-N. Mineralization rates and mineral-N release from biosolids were always higher in the Ferrosol compared to Spodosol soil.