The composition of soil organic matter (SOM) is influenced by land use and
fertilization. We studied changes in the SOM in a long-term field experimen
t on a sandy Podzoluvisol. The control plot and four combinations of manuri
al treatments of the experiment were selected: one with mineral fertilizer
only and three combinations of organic manure with mineral fertilizer: catt
le manure +NPK, cattle manure +PK and straw + NPK. The SOM was extracted by
sodium pyrophosphate solution (pH = 10) and hot water (100 degrees C). The
extracts were analysed by Fourier-Transform Infrared (FT-IR) spectroscopy
and gel permeation chromatography (GPC). The FT-IR spectra from sodium pyro
phosphate extracts indicate that composition of SOM is indeed influenced by
different fertilization. The C=O band at 1710 cm(-1) in the samples of the
plots fertilized with cattle manure has the highest absorption intensity,
whereas the material from the plot fertilized with straw + NPK has the leas
t intense. The GPC analyses of the extracts showed that adding cattle manur
e +NPK increased the molecular size of SOM in comparison with the control p
lot. The analysis of hot-water extracts with FT-IR showed no significant di
fferences in functional groups, but GPC chromatograms distinguished feature
s in molecular size distribution. Fertilization with cattle manure increase
d the molecular size of the SOM in comparison with the control, but the dif
ferences in content of carboxylic groups and molecular weight were detected
in sodium pyrophosphate extracts only.