Pelletized paper mill waste promotes nutrient input and N mineralization in a degraded Alfisol

Pulp and paper mill waste, such as biomass fly ash and sewage sludge, is commonly disposed of in landfills. This waste can be valuable as nutrients and C sources for degraded soils. Ash and sludge samples were chemically characterized before ash/sludge pellets were experimentally manufactured for use as soil amendment. An incubation experiment was carried out with controlled moisture and temperature; nutrient input and N mineralization were evaluated at 0, 15, 30, 45, and 60 d intervals using three pellet types with different proportions of ash, sludge, and gypsum (as a binder) and applied at four doses equivalent to 0, 10, 20, and 40 Mg ha^-1. Results indicated that the Alfisol that was amended with pelletized residues increased P Olsen and exchangeable K and Ca contents, as well as soil pH (p < 0.05) in direct response to the applied doses. Organic matter decreased during incubation at all the doses and pellet types (p < 0.05); however, N mineralization did not show a clear pattern during incubation. Nitrogen mineralization potential (N₀) was different depending on pellet types and application rates; Pellet 2 (10% sludge) exhibited the highest N₀ values, while Pellet 3 (20% sludge) had lower N₀ than the control. Pulp and paper mill waste can be used to amend degraded soils by creating sustainable use through pelletizing because it facilitates transport and can evenly distribute sludge and ash on soils in a single application.

Keywords
Nitrogen modeling; pulp and paper mill waste; pelletized waste; pelletized ash/sludge; soil incubation.