Different raw residues (meals, cakes and distillery yeasts) or composts (sewage sludge and domestic waste) were evaluated for decomposition and mineralization of N and P organic forms. The materials were incorporated to soil samples from an B horizon of an Oxisol, without acidity correction, under controlled environmental conditions. Decomposition was determined by a respirometry experiment and mineralization by incubation. For an incubation period of 30 days, raw residues produced more accumulative quantities of C-CO2 compared with composts. For an incubation period of 60 days, sewage sludge compost (4500 mg kg-1) and domestic waste (2000 mg kg-1) mineralized N, whereas meat and bone meal (385 mg kg-1) and filter cake (281 mg kg-1) immobilized it. The C/N ratio and initial N content did not explain the pathways of N mineralization. This suggested that the nature of the residues and characteristics such as fraction of easily-biodegradable C, total soluble polyphenol content and capacity to complex protein, as well as the N pools in fulvic and humic acids of the organic matter were related with N mineralization. For an incubation period of 45 days, P mineralization was positively correlated with the initial organic P content (r = 0,99**), and C/P ratio ( r = -0,88**) of the residues. Meat and bone meal showed the greatest content of mineralized P (1144 mg kg-1).
Compost of sewage sludge and domestic waste; industrial residues; soil respiration
