Seasonal variations in forms of extractable sulfur in some New Zealand soils.
1994
Tan Z. | McLaren R.G. | Cameron K.C.
Seasonal variations in different forms of extractable S were examined in 3 New Zealand soils under permanent pasture. During the course of the year, extractable inorganic sulfate-S (I-S) levels varied substantially. Concentrations of I-S in the soils peaked in the early spring and, for 2 of the soils, remained at relatively low levels throughout the rest of the year. The third soil, however, following a decrease in concentration in late spring, showed a continuous increase in I-S during the summer and autumn period. Concentrations of extractable organic C bonded S (C-S) in soils were generally highest in the winter and declined significantly during the spring. Extractable organic HI reducible S (HI-S) concentrations fluctuated throughout the year with no clear trends. The proportions of the 3 forms of extractable S in soils also varied seasonally. The proportions of extractable organic HI-S in soils were more constant compared with the other two forms of S and generally accounted for less than 20 percent of the total extractable S. The seasonal changes in the proportions of I-S appeared to be inversely related to the changes in extractable C-S. This suggests that under the field conditions, the extractable organic C-S fraction is readily mineralized to sulfate when conditions are favourable for mineralization to take place.
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