Comparing Soil Tests for a Forested Acid Sandy Soil Topdressed with Sewage Effluent
1984
Fiskell, J. G. A. | Rebertus, R. | Comerford, N. B. | Pritchett, W. L.
Mobility of nutrients and heavy metals from mineralization of sewage sludge in acid soils is an environmental concern. Chemical properties of a forested acid sandy soil on flat terrain were examined at 6 and 30 months after ceasing multiple spray applications of sewage effluent. Total dry sludge applied was 5 and 26 Mg ha⁻¹ on the treated 3- by 15-m portion of 9- by 15 m plots. Less than 1.1 mg L⁻¹ of either NO⁻₃-N or PO³⁻₄-P was found at the 24- to 90-cm depth in soil solution extracted from the untreated bed adjacent to the planting area during 144 days. Treated areas were sharply defined by the growth of indigenous dog fennel (Eupatorium sp.) which was the dominant species. Mean soil pH was below 4.7 at 6 months and 5.1 at 30 months. Treated interbed Cd, Cu, and NH⁺₄-N were higher with depth at 30 months than 6 months while the reverse held for PO³⁻₄-P. Untreated bed or interbed soils had lower soil test values than corresponding treated soils. Much higher metal values were found at the 7-cm depth than deeper. Differences in metal extracted from treated and untreated soils were readily distinguished by DA (Mehlich I), DTPA-TEA, and EDTA-AA soil test methods. All three methods extracted from 25 to 75% of the metals applied in the sludge. Lack of more downward movement of N, P, and metals was attributed to slow mineralization of the sewage sludge.
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