Bentonite has been recognized as a very good
material for the improvement of coarse textured soils. In microplot
experiment, of a sandy soil deprived of the humus layer was enriched
in 1973 with waste bentonite at the rates of 0, 3, 6 and 12 kg m
-2
.
Until 2002, the microplots were planted with different crops and
regularly enriched with mineral a
nd organic fertili
zers. Since 2003,
the microplots were left barren. In 2009, determinations of several
features of the soils (in 5-30, 30-55 and 55-80 cm layers) showed
that the historical amendment of the sandy soil with bentonite
(especially its highest dose) ensured significantly higher contents
of water, organic C, clay, silt and a sand fraction with particle
diameter <0.1 mm in 5-30 cm layer. Proportions of non-dispersible
clay in the total clay of bentonite soils in the two upper soil layers
were significantly lower than those of the control soil. A significant
increase in the penetrometer resistance was observed in 40-58 cm
layers of the control soil and the soil with 3 kg m
-2
bentonite
amendment, contrary to the soils with two highest bentonite doses