ORGANO-MINERAL FRACTIONS OF A CLIMOSEQUENCE OF SOILS IN NEW ZEALAND TUSSOCK GRASSLANDS |
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Authors: | K R TATE G J CHURCHMAN |
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Institution: | (Soil Bureau, Department of Scientific and Industrial Research, Lower Hutt, New Zealand) |
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Abstract: | The organo-mineral fractions of seven New Zealand topsoils, which are members of a climosequence, were isolated by ultrasonic dispersion in water and separated into sand-, silt- and clay-size fractions. Several soils contained stable aggregates of mainly silt-size, comprising cemented clay-size particles. The tendency of one soil (McKerrow) to form larger aggregates of sand-size was explained by its distinctive mineralogy. Total organic carbon and total nitrogen were used to indicate the amounts of organic matter in the organo-mineral fractions. The degree of humification of the organic matter was assessed by a pyrolysis-gas chromatography technique, which proved superior to the more conventional C/N method. In the sand-size fractions the climate, and especially annual precipitation, strongly influenced the amounts of organic matter, whereas in the clay- and silt-size fractions it was the composition of the organic matter that was influenced. |
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