A. Saviozzi et al., THE EFFECT OF 40 YEARS OF CONTINUOUS CORN CROPPING ON SOIL ORGANIC-MATTER CHARACTERISTICS, Plant and soil, 160(1), 1994, pp. 139-145
Changes in humus and some of the major extractable components of soil
organic matter were examined, following forty years of conventionally
tilled continuous corn cropping compared with those of an adjacent unt
illed native grassland soil. Results indicate that long-term continuou
s cropping caused a significant reduction in the content of alkali ext
ractable and water soluble carbon, as well as in the phenolic and chlo
roform extractable compounds, while no differences in volatile acids a
nd n-hexane extractable substances were found. On the basis of organic
C, corn cropping led to a relative enrichement of phenolic compounds,
volatile acids and substances extractable by Na4P2O7, but it did not
affect the substances extractable by water. Except for the humificatio
n ratio (HR), the humification parameters, such as humification degree
(HD), the extracted humic and fulvic acids, the C(HA)/C(FA) ratio and
the humification index (HI) revealed a higher degree of humification
of the organic matter in native grassland than in the continuous corn
cropping system. IR spectra of n-hexane, chloroform, alkaline and wate
r extracts failed to show significant differences between sites under
native grassland and sites under continuous corn.