Extraction and Determination of Sulfur in Organic Horizons of Forest Soils1
- D. G. Maynard,
- Y. P. Kalra and
- F. G. Radford2
Little information exists on the accuracy, precision, and make-up of extractable S in surface organic horizons of forest soils. Eight extractants (H2O, 0.01 M CaCl2, 0.01 M KCl, 0.01 M LiCl, 0.003 M NH4OAc, 0.003 and 0.01 M NH4Cl, and 500 mg P L−1 as Ca(H2PO4)2·H2O) were evaluated for the extraction and determination of SO4-S and total extractable S in surface organic horizons of five forest soils. The analyses for SO4-S and total extractable S were performed by ion chromatography (IC) and inductively coupled plasma atomic emission spectrometry (ICP-AES), respectively. Each of the weak salt extractants removed similar amounts of SO4-S and total extractable S. Water was the least desirable extractant because it removed more organic S than the salt extractants, was the most variable for IC analysis, and produced inconsistent results. The 0.01 M NH4Cl extractant, however, was found to be the most consistent extractant. The precision ranged from 3.7 to 8.9% for the IC analyses excluding the aspen (Populus tremuloides Michx.) sample and from 1.9 to 8.4% for the ICP-AES analyses. Poor precision in the SO4-S determination of the aspen organic horizon was due to the elution of an unidentified peak adjacent to the S peak. Quantitative recoveries from 102 to 108% and from 97 to 108% were obtained in the 0.01 M NH4Cl extract by the IC and ICP-AES methods, respectively. The effect of varying solution to soil ratios was also determined for 0.01 M NH4Cl. The 10:1 solution to soil ratio was the most consistent. Ratios <10:1 had significantly lower concentrations of extractable S and SO4-S for three soils and caused logistical problems in the laboratory (i.e., slower filtering, more sample required) because of the low solutin-to-soil ratio. Storage of airdried material at room temperature (20 ± 4 °C) for 1.5 yr resultd in increased total extractable S and SO4-S concentrations.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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