Implication of sludge stabilization process and polymeric material addition on nitrogen and carbon mineralization

Abstract

Soil fertility deterioration has been a challenge limiting crop productivity. Recycling municipal sludge in agroecosystems proved to be an effective soil nutrient source. However, due to varied nutrient content emanating from wastewater sources and treatment processes, sludges require application rate optimization for sustainable reuse. A laboratory incubation study was conducted over 90 days to quantify carbon (C) and nitrogen (N) mineralization rate from sludge amended soils. Aerobic (AeD) sludge, anaerobic digested sludges without polymer (AnDP0) and with polymer (AnDP1) treatments were applied at 10 tons ha-1. N fractions and other parameters varied significantly with sludge treatment. AeD had significantly higher total N than AnD sludges. AeD sludge mineralized significantly higher cumulative CO2 – C than AnD. AnD sludges had higher final N mineralization rates of 43% (AnDP0) and 54% (AnDP1) against 41% from AeD sludge. Polymeric material addition increased net N mineralization rate by 10%. Cumulative mineralized N showed to be driven by the size of applied organic N pool. Applied organic N was higher in AeD relative to AnD sludges, leading to higher net N mineralized. N mineralization was faster within first 30 days of sludge application, suggesting that, for efficient mineral N utilization from sludge, planting must be planned to synchronize crop N needs with this high biosolids N release period. The study showed the importance of basing sludge application rates on N content and mineralization rate rather than a single and generalized recommendation rate; a strategy that limits excess nutrient application and reducing pollution whilst enriching agroecosystems.

Keywords

• Municipal wastewater sludge
• Net N mineralization
• Carbon evolution
• Aerobic sludge
• Anaerobic sludge
• Polymer