MONOSACCHARIDES IN HYDROLYSATES OF WATER-STABLE AGGREGATES AFTER 67 YEARS OF CROPPING TO SPRING WHEAT AS DETERMINED BY CAPILLARY GAS CHROMATOGRAPHY

Abstract

Two non-replicated, unfertilized, dryland grain rotations—continuous wheat and wheat-fallow — were established in 1912 on a Dark Brown Chernozemic soil in southern Alberta. The effect of long-term cropping on the monosaccharide distribution in the hydrolysates of the water-stable aggregates was assessed. Although all the hydrolysates of the aggregates had the same suite of monosaccharides, the relative proportions changed with cultivation. The eight monosaccharides identified represented between 92 and 96% of the total GC detector response. The monosaccharide C of aggregate organic C for the native prairie varied from 6.9 to 7.6%, while for the continuous wheat and the wheat and fallow of the wheat-fallow rotation it varied from 3.6 to 5.5%, from 1.8 to 5.1%, and from 1.6 to 6.7%, respectively; the higher percentages were associated with the larger aggregate fractions. Except for galactose, the average relative proportions of the monosaccharides identified in the hydrolysates of the water-stable aggregates were not much different from those reported in the literature for the hydrolysates of whole soils. Key words: Monosaccharides, aggregate fractions, water-stable aggregates, capillary gas chromatography, long-term rotation