Effect of Sewage Sludge Application on the Mineralization of Nitrogen in Soils

A knowledge of the kinetics of N mineralization of sludgemay be helpful in assessing the amounts of potentially available N to crops. The present investigation was conducted to determine the effect of sludge levels on mineralization potential (N₀) and rate constant (k) in four different soils. Cumulative N mineralized increased with increasing incubation period and sludge application. The magnitude of increase in N mineralized, however, was not the same with the successive additions of sludge. It was greatest for the first increment of sludge (0.5%) and subsequently narrowed down with the further application of sludge. Maximum amounts(90 mg kg⁻¹) of mineralized N was obtained in Karnal soil (Typic Ustochrept) and lowest amounts (30 mg kg⁻¹) in Balsamand soil (Typic Ustipsamment) at 4 per cent sludge level. Both soil type and sludge level significantly affected the mineralization of sludge organic N. The values for nitrogen mineralization potential (N₀) and rate constant (k) were greater in sludge treated soils as compared to untreated soils.