Impacts of zeolite, alum and polyaluminum chloride amendments mixed with agricultural wastes on soil column leachate, and CO₂ and CH₄ emissions

This study aimed to quantify leaching losses of nitrogen (N), phosphorus (P) and carbon (C), as well as carbon dioxide (CO₂) and methane (CH₄) emissions from stored slurry, and from packed soil columns surface applied with unamended and chemically amended dairy and pig slurries, and dairy soiled water (DSW). The amendments to the slurries, which were applied individually and together, were: polyaluminum chloride (PAC) and zeolite for pig and dairy slurry, and liquid aluminium sulfate (alum) and zeolite for DSW. Application of pig slurry resulted in the highest total nitrogen (TN) and nitrate-nitrogen (NO₃-N) fluxes (22 and 12 kg ha⁻¹), whereas corresponding fluxes from dairy slurries and DSW were not significantly (p < 0.05) higher than those from the control soil. There were no significant (p < 0.05) differences in leachate N losses between unamended and amended dairy slurries, unamended and amended pig slurries, and unamended and amended DSW. There were no leachate P losses measured over the experimental duration. Total cumulative organic (TOC) and inorganic C (TIC) losses in leachate were highest for unamended dairy slurry (82 and 142 kg ha⁻¹), and these were significantly (p < 0.05) reduced when amended with PAC (38 and 104 kg ha⁻¹). The highest average cumulative CO₂ emissions for all treatments were measured for pig slurries (680 kg CO₂-C ha⁻¹) followed by DSW (515 kg CO₂-C ha⁻¹) and dairy slurries (486 kg CO₂-C ha⁻¹). The results indicate that pig slurry, either in raw or chemically amended form, poses the greatest environmental threat of leaching losses and gaseous emissions of CO₂ and CH₄ and, in general, amendment of wastewater with PAC, alum or zeolite, does not mitigate the risk of these losses.