Assessing the Efficacy of Alternative Phosphorus Sorbing Soil Amendments

Effect of Coal Combustion By-products on Phosphorus Runoff from a Coastal Plain Soil

“…Thus, it appears as though these types of sorption studies are probably not good indicators of the potential impact of effects of CCPs treatments on P in surface runoff. Callahan et al (2002) found FGD to be more effective in promoting P sorption than ARA when mixed with acidic soils. All CCPs had low concentrations of total P and nondetectable concentrations of 2 M KCl extractable P, suggesting that their addition to soil should not substantially increase either total or readily desorbable P. Relative differences in pH of the three CCPs used (Table 1) were similar to differences in CaCO 3 equivalency values reported by Callahan et al (2002), for FBC (CaCO 3 equivalent = 57%), ARA (CaCO 3 equivalent = 21%), and FGD (CaCO 3 equivalent = 16%).…”

“…This mechanism has also been hypothesized for increased P sorption in FGD-amended soils (Stout, Sharpley, and Landa 2000). For anthracite refuse ash (ARA), mechanisms of P sorption are by both Fe and Al, either in the form of electrolytes or hydrous minerals (Callahan et al 2002).…”

“…For instance, Stout, Sharpley, and Pionke (1998) reported fluidized bed coal ash (FBC) and FGD by-product incubation (10 g kg −1 ) with soil reduced WEP by 60% and 50% respectively. Elsewhere, Callahan et al (2002) found that incubation with FBC and FGD (40 g kg −1 ) reduced WEP by at least 50%. In one of the few field studies evaluating CCPs as P-sorbing amendments, Stout, Sharpley, and Landa (2000) reported that FBC and FGD reduced dissolved P in runoff by 20% and 43%, respectively, when incorporated in the surface 5 cm of an acidic (pH = 6.0) soil at 20 g kg −1 .…”

“…In the case of FBC, high concentrations of Ca are thought to promote the formation of Ca phosphates, which are stable in neutral and alkaline soils but less so in acidic soils (Lindsay 1979). As a result of being a comparatively good liming agent (Callahan et al 2002), application of FBC to moderately acidic soil can increase soil pH sufficiently to cause possible formation of Ca phosphates. When FBC is used in acidic soils, applied Ca likely displaces exchangeable Fe and Al via mass action (Brady and Weil 1996), increasing Fe and Al in the soil solution and promoting the formation of Fe and Al phosphates, which are relatively stable in acidic soils (Lindsay 1979).…”

Characterising phosphorus transfers in rural catchments using a continuous bank-side analyser

“…In this case, mitigating against the causes of storm-induced diffuse P transfer (e.g. nutrient management plans (Tilman et al, 2002;McDowell et al, 2001); soil amendments (Callahan et al, 2002); manipulating storm flowpaths (Gburek et al, 2005)) would not necessarily be recorded as an effect at the catchment outlet when using a coarse resolution sampling regime. This has further implications for both managers and catchment stakeholders expecting to see positive improvements in water quality from diffuse transfer mitigation programmes.…”