Macronutrient and Trace Element Leaching Following Biosolids Application on Semi-arid Rangeland Soils

Abstract

The objective of this study was to quantify the leachate concentration of macronutrients and trace elements obtained through intact soil columns containing two rangeland soils with different texture and amended with biosolids. This was done to evaluate the possibility that surface application of biosolids could adversely affect subsurface water quality via leaching. Biosolids were applied on the surface of the soil columns at 0 (control), 7, 18, 34, or 90 Mg ha⁻¹ in dry basis. Results indicated that biosolids did not increase NO₃ ⁻ − N leaching, except for the application of 90 Mg ha⁻¹ in the Stellar soil (Calciargid), the finer-textured soil. In the Armesa soil (Haplocalcid), the coarser-textured soil, all leachate NO₃ ⁻ − N concentrations were higher than the maximum contaminant limit (MCL) for drinking water established by USEPA, irrespective of biosolids treatment. Orthophosphate leaching occurred mostly in the Stellar soil and was favored by biosolids application. Of the trace elements that are regulated by USEPA, Cd, Ba, Cr, and Be were found below the MCL for drinking water irrespective of the biosolids application rate or soil type. The application of 90 Mg ha⁻¹ of biosolids represented a significantly higher potential of leaching for many elements and compounds (NO₃ ⁻ − N, SO₄ =, Cl⁻, Ca, K, Mg, Na, and Sr) than applications of 34 Mg ha⁻¹ or lower. In general, the application of biosolids up to 34 Mg ha⁻¹ did not pose potential adverse effects for subsurface water quality.

Keywords:

• desert soil
• heavy metals
• nitrogen leaching
• soil amendment
• subsurface water quality

The authors would like to acknowledge the assistance of R. E. Sosebee, D. B. Wester, R. E. Zartman, R. S. Lutz, C. Moffet, M. Benton, R. Gatewood, P. Jurado, R. Baptista, and E. Flores. The support of Merco Joint Venture, providing biosolids and funding for this study is also appreciated. This is contribution T-9-1103 of the College of Agricultural Sciences and Natural Resources, Texas Tech University, Lubbock, TX.

Notes

Different letters indicate differences (P < 0.05) between biosolids rates for a given variable. Means of variables that are not followed by letters were not significantly affected by biosolid application

^aMCL, the highest level of a contaminant that is allowed in drinking water.

^bAction level, the concentration of a contaminant, which if exceeded, triggers treatment or other requirements that a water system must follow.

^cSDWR, nonenforceable federal guidelines regarding cosmetic or aesthetic effects of drinking water.

Different letters indicate differences (P < 0.05) between biosolid rates for a given variable. Means of variables that are not followed by letters were not significantly affected by biosolid application.