CHANGES IN SOIL ORGANIC SULPHUR FRACTIONS DUE TO THE LONG TERM CULTIVATION OF SOILS |
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| Authors: | R G MCLAREN R S SWIFT |
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| Institution: | Edinburgh School of Agriculture, West Mains Road, Edinburgh |
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| Abstract: | The amount and chemical nature of soil organic sulphur was determined in several pairs of soils taken from long-term pasture and adjacent, continuously cultivated sites. Similar determinations were also carried out on organic matter extracts obtained from the soils. The lower levels of sulphur in the arable soils compared with pasture soils were assumed to have resulted from the mineralisation of organic matter brought about by cultivation. Losses of sulphur caused by this mineralisation were found to occur in all three organic fractions examined. A high proportion (75%) of the sulphur lost consisted of carbon-bonded sulphur with only 25% derived from HI-reducible forms. Despite this, it is suggested that, of the two forms, HI-reducible sulphur has a more transitory nature and is possibly of greater importance in the short-term mineralisation of sulphur whereas carbon-bonded sulphur passes through an HI-reducible form prior to release as inorganic sulphur. It is suggested that the sulphur present in the fulvic acid pool could, likewise, be most important for short-term mineralisation. |
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