A laboratory study was designed to provide data on the decomposition o
f rape, sunflower and soyabean residues put in bags buried in soil. Th
e residue bags were removed at intervals during 1 year, analysed for r
emaining total mass, organic and water-soluble C, water-soluble sugars
, as well as for volatile acids and phenolic compounds. The decomposit
ion dynamics of total mass, total organic and water-soluble organic C,
and water-soluble sugars were reproduced satisfactorily by a double-e
xponential model of the first-order type. Generally, no large differen
ces in the rate and magnitude of decomposition among the residues were
observed; the greatest losses of both total mass and chemical compone
nts occurred in the first month of the study, during which the volatil
e acids and phenolic compounds disappeared almost completely. Of the t
hree residues, soyabean showed the lowest loss of organic carbon, losi
ng 66% of the original content over the course of the year compared wi
th 73 and 75% for sunflower and rape, respectively.