
%0 Journal Article
%A Degens, B. P. 
%T The contribution of carbohydrate C and earthworm activity to the water-stable aggregation of a sandy soil
%J Soil Research
%D 1997/01/08
%V 35
%N 1
%P 61-72
%K aggregate stability, earthworms, extractable carbohydrate C, organic matter decomposition, organic C.
%R https://doi.org/10.1071/S95086
%U https://www.publish.csiro.au/paper/S95086 
%X An incubation study was conducted to test the effects of decomposing clover tops (added at 0, 6&#183;2 or 12&#183;5 mg organic matter/g soil) and earthworm activity on the contribution of carbohydrate C to the stability of aggregates in a sandy soil. Soils incubated with and without earthworms were separated into surface-casts and bulk soil, and the amounts of water-stable aggregates &#62;1 mm surviving slow and rapid rewetting (when air-dry) in these soil separates were determined. Organic C and acid- and water-extractable carbohydrate C concentrations were determined in the aggregates and bulk soil. The treatments of 6&#183;2 and 12&#183;5 mg organic matter/g soil increased the &#62;1 mm aggregation of the bulk soil by more than 2&#183;2- and 2&#183;8-fold, respectively, compared with the non-amended soils. With the addition of earthworms, there were increases from 1&#183;7- to 1&#183;8-fold only in aggregates surviving slow rewetting. The acid- and water-extractable carbohydrate C contents of aggregates &#62;1 mm in the bulk and surface-cast soils were generally not greater than the carbohydrate C in the bulk soil. Generally, the carbohydrate C fractions were also not increased in the more stable aggregates (rapidly rewet) compared with the weaker aggregates (slowly rewet). Carbohydrate C in bulk soil was generally (P &#60; 0&#183;05) correlated with the amounts of aggregates surviving each rewetting treatment (r &#62; 0&#183;71, P &#60; 0&#183;01). In contrast, greater amounts of carbohydrate in aggregates surviving slow rewetting were not correlated (r &#60; -0&#183;45, P &#62; 0&#183;05), with a greater proportion of these aggregates resisting disruption when the soils were rapidly rewet (except for acid-extractable carbohydrate C; r = -0&#183;84, P &#60; 0&#183;05). These results cast doubt on the usefulness of correlations in assessing the contribution of carbohydrate C to aggregation. The amounts of carbohydrate materials in the soil appeared to have little influence on aggregation, probably because the location of bonding compounds in the soil pore matrix is more critical. 
