Sample Pretreatment and Phosphorus Speciation in Wetland Soils

Turner, Benjamin L.;Newman, Susan;Cheesman, Alex;Reddy, K. Ramesh

Abstract

We assessed the influence of sample pretreatment on the amounts and forms of P extracted in NaOH–EDTA (ethylenediamine tetraacetic acid) from a series of contrasting wetland soils from the Florida Everglades. Samples of unconsolidated benthic floc and underlying soil (0–10 cm) were extracted either fresh (overnight refrigeration only), air dried (10 d at ∼30°C), or frozen at −80°C and lyophilized (∼48 h), before extraction and solution 31P nuclear magnetic resonance (NMR) spectroscopy. Significant differences in total P extraction following pretreatment were detected for one out of four benthic floc samples and three out of four soil samples, although the changes were inconsistent: in two cases the total P extraction increased, while in two others it decreased. Assessment of the P composition by solution 31P NMR spectroscopy revealed differences among treatments, although these were mostly within the range of error associated with replicate analyses; however, DNA was not detected in a fresh sample of calcareous benthic floc, despite representing an important component of the organic P extracted from dried samples. The apparent sample-specific nature of the changes confirms the importance of carefully assessing pretreatment effects in studies of soil organic P in wetlands.

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1435-0661

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Soil Science Society of America

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10.2136/sssaj2007.0017