Leaching Kinetics of Nitrate and Heavy Metals in Soils Amended with Variable Rates of Poultry Litter

Abstract

The application of poultry litter as an organic amendment enhances soil fertility but raises concerns regarding the leaching of nitrate and heavy metals into groundwater systems. This study investigates the leaching kinetics of nitrate and selected heavy metals in soils amended with variable rates of poultry litter under controlled conditions. Soil columns were treated with graded application rates of poultry litter and subjected to simulated irrigation to assess leachate composition over time. Key parameters evaluated included nitrate concentration, mobility of heavy metals such as zinc, copper, and lead, and changes in soil physicochemical properties. Results indicated that higher application rates significantly increased nitrate leaching, particularly during early stages following amendment, due to rapid mineralization and mobility of nitrogen forms. Heavy metal leaching remained relatively low compared to nitrate but showed gradual increases with higher amendment levels and prolonged leaching periods. Soil characteristics such as texture, organic matter content, and pH played a crucial role in regulating nutrient and metal mobility. Moderate application rates were found to balance nutrient availability with minimal environmental risk, reducing potential contamination of groundwater. The study highlights the importance of controlled application strategies and proper nutrient management to optimize the benefits of poultry litter while mitigating environmental impacts. While modeling approaches were used to interpret leaching dynamics, the primary focus remains on soil management and environmental sustainability. These findings provide practical guidance for farmers and land managers to improve nutrient use efficiency, safeguard soil health, and minimize the risk of nutrient and heavy metal losses in agricultural systems.