Browsing by Author "Anderson, Martha Ann"

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    Long-term copper availability and adsorption in a sludge-amended Davidson clay loam
    Anderson, Martha Ann (Virginia Tech, 1997-04-04)
    A single application of aerobically digested sewage sludge was applied by Rappaport et al. (1988) in 1984 at rates up to 210 dry Mt ha⁻¹ on a Davidson clay loam (clayey, kaolinitic, thermic, Rhodic KandiuduIts). The heavily contaminated sludge supplied up to 760 kg Cu and 620 kg Zn ha⁻¹, which are below current cumulative limits, but above annual loading limits for these metals (USEPA, 1993). Rappaport et al. (1988) reported an increase in DTPA extractable Cu and Zn with increasing sludge rate. They observed a linear increase in com yields with an increase in sludge rate, which was attributed to high levels of available N supplied by the sludge. In the present residual study, conducted at the same research site, DTPA extractable Cu and Zn followed the trend observed by Rappaport et at. (1988). However, a linear decrease in corn and sorghum yields was observed with increasing sludge rate. The sludge-related decrease in yields was attributed to phytotoxicity (probably a combination of Al, Cu, Mn, and Zn) induced by low soil pH levels. Whole plant tissue concentrations of eu and Zn at the high sludge rates were above the normal range, however grain concentrations were within the normal range. An adsorption study was conducted, in which soils were amended with Ca(OH)₂ and Al₂(S0₄)₃, to ascertain the effect of decreased pH on Cu adsorption on the soil. Copper adsorption maxima decreased with a reduction in soil pH in all treatments. The effect of ionic strength on Cu adsorption was also investigated. Regardless of pH or ionic strength, Cu adsorption increased with an increase in sludge rate. This adsorption increase was attributed to the higher organic matter content of the sludge treatments. The organic matter at the highest sludge rate was approximately double that of the control after 11 years. The adsorption study shows that sludge amendment has long-term effects on metal retention in soils and the field study reveals that careful management of sludge-amended soils is necessary to prevent phytotoxicity.
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    Long-term effects of copper rich swine manure application on continuous corn production
    Anderson, Martha Ann (Virginia Tech, 1990-12-17)
    Three long-term field experiments were established in the spring of 1978 and continued through 1988 to evaluate corn (Zea mays L.) response to high Cu levels from Cu rich swine manure and CuS0₄ applications. The field research was conducted on soils with diverse properties, i.e., on a Bertie fine sandy loam (Aquic Hapludults), a Guernsey silt loam (Aquic Hapludalfs), and a Starr-Dyke clay loam (Fluventic DystrochreptsTypic Rhodudults). Three treatments in the long-term field experiments on the three soils were a control, annual applications of eu as eu rich swine manure, and annual applications of Cu as CuS0₄ equivalent to that in the manure. After the 11 years, 1109 mt ha⁻¹ of wet Cu rich swine manure were applied for the manure treatment. The Cu rich manure contained an average of 1316 mg Cu kg⁻¹, An average of 325 kg Cu ha⁻¹ added to the soils from the manure application over the 11 years exceeded U.S.E.P.A. guidelines for safe copper loading levels for cropland by 45 kg ha⁻¹. Copper concentrations in corn ear leaves were within the normal range of 3 to 20 mg kg⁻¹ where the 325 kg Cu ha⁻¹ were applied to the soil as either Cu rich manure or CuS0₄. Concentrations of Cu in the grain were also in the normal range of 1 to 5 mg kg⁻¹ where the high level of the two Cu sources was applied to soils. There was no decrease in corn yield on the three soils from application of either Cu source.