
TY  - JOUR
A1  - Degens, B. P. 
T1  - The contribution of carbohydrate C and earthworm activity to the water-stable aggregation of a sandy soil
JF  - Soil Research
JO  - Soil Res.
Y1  - 1997
VL  - 35
IS  - 1
SP  - 61
EP  - 72
KW  - aggregate stability, earthworms, extractable carbohydrate C, organic matter decomposition, organic C.
UR  - https://doi.org/10.1071/S95086 
N2  - 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. 
ER  -

