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 efficientmineral N utilization fromsludge, plantingmust 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.
