Effect of Poultry Litter and Biochar Application Methods on Nutrient Loss

Abstract

High levels of phosphorus (P) and trace metals, such as copper (Cu) and zinc (Zn), can cause significant water quality issues when delivered to water bodies. This study investigated the impact of different poultry litter application methods on P and metals leaching in pastures using rainfall simulation on soils containing macropores. The major objectives of this study were to examine the effectiveness of different application methods (surface vs subsurface) of poultry litter and pine wood pristine biochar on the leaching of dissolved reactive phosphorus (DRP) and trace metals via preferential flows. Intact undisturbed soil cores were used for column-based successive rainfall simulation experiments. Treatments were surface-applied poultry litter, subsurface-banded poultry litter, surface-applied poultry litter + biochar, subsurface-banded poultry litter + biochar, and control (no biochar and nor poultry litter). Results showed that treated columns leached significantly greater amounts of dissolved reactive phosphorus (DRP) than control columns. However, DRP leaching decreased with successive rainfall events. Subsurface application proved to be more effective than surface broadcasting in controlling DRP losses. Additionally, the pristine biochar used in this study did not help reduce DRP leaching. Further, treated columns leached significantly higher amounts of copper and zinc than controls columns, likely due to the presence of metals in the soluble fraction in poultry litter and changes in soil conditions such as pH and dissolved organic matter. There was no significant difference in the leaching of aluminum and iron between treated and control columns, as most aluminum and iron were not present in the mobile fraction in both poultry litter and soil. With successive simulations, the leaching of copper, zinc, and aluminum decreased, while the subsurface leaching of iron increased in columns treated with poultry litter, likely due to reducing conditions and the flow interruption technique. Incorporating pristine biochar with poultry litter reduced the leaching of iron and aluminum more effectively than copper and zinc. This study provides an overview of the effectiveness of manure and biochar application on the leaching and deposition of P and metals in soil columns and prompts further in-depth research on nutrient and metal management in agricultural ecosystems.