Nitrogen mineralization of thermally-dried sewage sludge

Abstract

Results of a trial of nitrogen mineralization are presented in order to evaluate the mineralization of thermally dried sewage sludge applied to soil. A laboratory incubation was conducted during 52 weeks with three different soils (S1, S2, S3) and thermally dried sewage sludge applied in rates of 0, 15, 30 and 601 ha-1. The results showed that the cumulative nitrogen mineralized (N-NH4 + + N-NO3 - ) for S1 (acid) was 364.60 mg N kg-1 soil, 292.19 mg N kg-1 soil for S2 (basic) and 221.85 mg N kg-1 soil for S3 (sand). The response of each variable (N-NH4 + + N-NO3 -, N-NH4 +, N-NO3 -) and each soil (S1, S2, S3) ammended with different application rates was evaluated by regression analyses and the results showed differences between all soils and rates. For N-NO3 - the results showed differences between soils at the beginning of nitrification. These results are important because they allow to synchronize the application of sludge ammendments to the soils with the N-demand of the crops and thereby optimize productivity avoiding environmental pollution.