Measuring and simulating leaching of nutrients from a calcareous soil amended with sewage sludge and poultry manure

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.