Sewage Biosolids Cumulative Effects on Extractable‐Soil and Grain Elemental Concentrations

Abstract

AbstractWhile land application of sewage biosolids is the most expedient method of recycling plant nutrients, concern over trace element additions resulted in U.S. Environmental Protection Agency (USEPA) beneficial‐use regulations. We studied 11‐yr biosolids addition effects on ammonium bicarbonate diethylenetriaminepentaacetic acid (AB‐DTPA) and 4 M HNO3 extractable levels of soil Cd, Cu, Mo, Ni, P, Pb, and Zn, and the relationship between the soil‐extractable concentrations and grain concentrations. The soils at our four dryland wheat (Triticum aestivum L.) sites were Aridic Paleustolls (Weld and Platner loam). For each application, we used four rates of biosolids (0, 7, 14, and 28 Mg ha−1) from the Littleton/Englewood, CO Wastewater Treatment Plant. We tested linear, quadratic, and either exponential‐rise (plateau) or exponential‐decay models for AB‐DTPA‐ and 4 M HNO3‐extractable concentrations compared with the cumulative quantity of biosolids‐borne element added and with elemental grain concentrations. Models for AB‐DTPA‐extractable Cu, P, Pb, and Zn and 4 M HNO3‐extractable Cu and P vs. the cumulative quantity added produced R2 values ≥ 0.46. For grain concentrations, only the models for AB‐DTPA vs. grain Zn produced an R2 ≥ 0.50. For monitoring soil levels of Cd, Cu, Mo, Ni, P, Pb, and Zn in Paleustolls (common soils in the western Great Plains dryland wheat areas) that continuously receive biosolids, we recommend AB‐DTPA over 4 M HNO3 soil extractions. The AB‐DTPA extractions also provide soil fertility information (NO3‐N and plant available P, K, and micronutrients).