A. Saviozzi et al., PROPERTIES OF SOIL PARTICLE-SIZE SEPARATES AFTER 40 YEARS OF CONTINUOUS CORN, Communications in soil science and plant analysis, 28(6-8), 1997, pp. 427-440
Changes in chemical and mineralogical characteristics associated with
different particle size fractions in soil after 40 years of continuous
production of corn by the conventional tillage method (CC) as compare
d with those of an adjacent native grassland site (NG) are investigate
d. Results indicate that corn cropping in a soil previously supporting
native vegetation produces a decline in total and humified organic ma
tter, phenolic compounds, enzymatic activities, cation exchange capaci
ty (CEC), and hydrosoluble ions, both in the whole soil and in its par
ticle-size separates. The largest losses in organic carbon (C) and nit
rogen (N) contents of the cultivated soil were observed in the sandy f
ractions, the lowest in the silt+clay separates. The humification inde
x (HI) indicates a higher degree of humification of the organic matter
in NG than in CC samples. For both NG and GC sites the finest fractio
n (silt+clay) resulted to be enriched in organic C, total N, humus, ph
enolic compounds, enzyme activity, CEC, and hydrosoluble ions with the
only exception of mineral N forms and sulphates (SO4). Slight differe
nces were observed in the mineralogical composition of NG and CC soils
. The sandy fractions of NG showed greater amounts of phyllosilicates
while a lower content was found in the silt+clay fraction of CC as a c
onsequence of a crumbling of parent rock into small pieces induced by
repeated tillage practices.