Redox Status, Poultry Litter, and Phosphorus Solubility in Atlantic Coastal Plain Soils
- P. A. Vadas and
- J. Thomas Sims
Artificially drained, agricultural soils in Delaware's Inland Bays watershed are high in P from poultry litter and fertilizer applications. The potential loss of P from these soils to drainage waters during soil reduction and reoxidation was investigated. Soil from three artificially drained, cultivated fileds and two wooded areas was collected and characterized as Fallsington sandy loam (fine-loamy, mixed, mesic Typic Ochraquult), Pocomoke loamy sand (coarse-loamy, siliceous, thermic Typic Umbraquult), and Osier loamy sand (siliceous, thermic Typic Psammaquent). Topsoils, unamended and amended with poultry litter (PL), and subsoils were reduced for 28 d and reoxidized for 14 d at 25 and 35°C. The soils were analyzed for pH, redox potential (Eh), soluble P and Fe2+, and P fractions (unoccluded Fe-P and Al-P, occluded Fe-P and Al-P, and Ca-P) under oxidized, reduced, and reoxidized conditions. Reduction decreased Eh to moderately reduced (200–350 mV) and reduced (−100 to 100 mV) values, and increased pH (0.8 ± 0.1) and soluble Fe2+ (44 ± 24 mg/kg). Reoxidation returned Eh, pH, and Fe2+ to near initial values. Reduction increased soluble P in unamended cultivated topsoils (0.69 ± 0.42 mg/kg), decreased soluble P in amended cultivated topsoils (1.42 ± 1.31 mg/kg), but had little effect in subsoils or wooded soils. Reoxidation decreased soluble P in cultivated topsoils, but increased soluble P in subsoils and wooded soils. Reduction increased the extractability of all P fractions in cultivated topsoils (20 ± 12 mg/kg), but increased only Ca-P extractability in subsoils and wooded soils (9 ± 3 mg/kg). Reoxidation decreased the extractability of these fractions to near initial values.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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