Fractionation of Phosphorus in Sludge‐Affected Soils

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Abstract
Phosphorus accumulated in sludge‐treated soils was chemically fractionated by a sequential extraction procedure. Samples used for the study were obtained from experimental plots of a sludge land application site, where composted sludges at rates 0, 22.5, 45, and 90 t ha−1 y−1, and liquid sludges at rates of 0, 3.75, 7.5, and 15 cm/y have been applied for 5 y. There were also experimental plots whose liquid sludge treatments were terminated after 3 y. The experimental field was cropped with winter barley (Hordeum vulgare) after the sludge applications.In soils not treated with sludges, the Ca‐bound P accounted for 50–60% of the total P. An accumulation of Al‐ and Fe‐bound P occurred in all sludge‐treated soils. In the top 15 cm of surface soil, after 5 y of composted sludge treatment at a rate of 90 t ha−1 y−1 (1980), the Al‐ and Fe‐bound P was > 60% of the total P. Concentrations of water‐soluble P in sludge‐treated soils also increased. There were indications that the organically bound P in sludge‐treated soils was the most likely form to leach. Three years after the termination of sludge applications, there was little change in the distribution pattern of sludge‐borne P in the soil profile.
Funding Information
  • Regional Wastewater Solids Management Program

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