Long-Term Effects of Biosolid-Amended Soils on Phosphorus, Copper, Manganese, and Zinc Uptake by Wheat

Biosolids have long been applied to agricultural land as fertilizer, and concerns exist regarding the long-term environmental impact of residual P and metals in biosolid-amended fields. Objectives of this study were to determine (i) P solubility in three soils from Maryland, Minnesota, and Illinois with histories of biosolid application and (ii) uptake of P, Cu, Mn, and Zn by wheat (Triticum aestivum L.) grown on these amended soils. In a pot study, wheat was grown on three soils that had received applications of biosolids 16 to 24 years before soil collection. Mehlich-3-extractable P increased by as much as 246%, 350%, and 274% for the amended Maryland, Minnesota, and Illinois soils, respectively, compared with control values. Mehlich-3-extractable Cu and Zn concentrations also increased with biosolid application for the three soils, whereas Mn decreased or did not change. Wheat biomass yield was reduced by 78% for the Maryland soil amended with lime-composted biosolids, accompanied by a decline of wheat tissue Mn concentration of 86%. Tissue P concentration increased by as much as 237%, 141%, and 304% for the amended Maryland, Minnesota, and Illinois soils, respectively. This study demonstrated that, regardless of soil or biosolid source, soils that had received biosolids 16 to 24 years earlier retained elevated levels of phytoavailable P and Zn, resulting in elevated levels of those elements in wheat. Although biosolids are beneficial for crop production, the risk of long-term negative effects of excess P and metal on the environment should be considered before application.