Incubation kinetics reflected the existence of two pools of carbohydrate metabolites. One pool was characterized by its lability with a mean residence time of about two weeks, whereas the second was preserved from biodegradation. The yield of sugar production by soil micro-organisms was poorly affected by the quality of the substrates glucose, cellulose and glycine, and very similar distributions of individual sugars were observed (Glc > Gal = Man = Rham > Xyl = Ara = Fuc). Soil type affected sugar biosyntheses slightly more, reflecting some diversity of either microbial communities or ecophysiology among soils. These results provided important indications to further calibrate a comprehensive model of carbohydrate dynamics in soils.