Measuring and simulating leaching of nutrients from a calcareous soil
amended with sewage sludge and poultry manure
Abstract
Leaching of nutrients due to the application of sewage sludge and
poultry manure is a major problem in intensive farming. Simulating helps
assess the nutrient loss and establish better methods for fertilization.
This study was conducted to investigate the leaching of nutrients
(NH4-N, NO3-N, Na, K, Ca, and Mg) from soils amended with different
rates (1%, 3%, and 5%) of sewage sludge and poultry manure. The
breakthrough curves of cations were also simulated by the PHREEQC
program. The addition of sewage sludge and poultry manure to the soil
columns increased the leaching of nutrients compared to the control
soil. For all soil columns, the highest concentrations of leached
nutrients were observed in the first leachate and decreased
exponentially over time. Regardless of the amount of amendments applied,
the percentage (the proportion of cumulative nutrient leached relative
to the exchangeable one) of cumulative leaching losses of NO3-N, Na, K,
Ca and Mg were significantly higher, while NH4-N was lower from
poultry-amended soils than sewage sludge-amended soils. Based on the
results, more attention should be paid to the potential risk of soil
nutrient leaching especially NH4-N, K and NO3-N posed after applying
sewage sludge and poultry manure, respectively. The simulation results
indicated that predicting breakthrough curves of NH4-N, K, and Ca (mean
NRMSE < 1) by the PHREEQC program was better than Mg and Na
(mean NRMSE > 1) and cation exchange was the main mechanism
to control the concentrations of cations in the leachates.