cycling In general, C-HA/C-FA ratio values were higher in the
upper
soil
layers
and
decreased
with
increasing
soil
depth.
This
behavior
may
be
associated
with
a
less
intensive
process
of
humification
in
the
deepest
soil
depths,
resulting
in
formation
of
less
condensed
organic
structures,
which
favor
predominance
of
FA
over
HA.
Higher
C-HA/C-FA
ratios
in
the
soil
surface
are
a
result
of
the
greater
influence
of
factors
which
result
in
organic
matter
transformation,
such
as
microbial
activity
and
high
levels
of
oxygen.
Our
results
showed
that
those
treatments
which
favored
input
of
organic
matter
(e.g.,
LEG,
LEG
+
m
and
HERB)
presented
greater
C-HA/C-FA
ratios,
indicating
the
predominance
of
HA
and
thereby
increasing
humus
quality.
However,
treatments
that
pro
moted
more
intense
soil
disturbance
or
removal
of
organic
residues
from
soil
surface
(e.g.,
DH,
MeM
and
MaM)
favored
reduction
of
C-HA/C-FA
ratios,
indicative
of
a
low
degree
of
humification
and
lower
humus
quality.
These
results
reinforce
that
soil
management
practices
which
contribute
to
an
increase
in
soil
organic
matter
and
an
enhancement
of
humus
quality,
such
as
LEG,
LEG
+
m
and
HERB
systems,
should
be
preferentially
adopted
in
cashew
crop
ping.
In
the
case
of
HERB
treatment,
it
is
worthwhile
to
note
that
the
cycling
of
dead
biomass
of
spontaneous
plants
left
under
the
projection
of
tree
canopy
played
an
important
ecological
role
in
the
soil
organic
matter
dynamics
and
humus
genesis;
therefore,
the
adequate
management
of
such
species
may
be
considered
a
suitable
alternative
for
soil
management
in
cashew
production
areas. The
C-HUM/C-FA
+
C-HA
ratio
(Table
7)
determines
the
struc
tural
stability
of
soil
organic
matter
(Canellas
and
Santos,
2005).
This
ratio
is
used
to
indicate
the
direction
of
the
transformation
among
humic
fractions
(Xavier
et
al.,
2009).
In
general,
in
this
study,
values
were
greater
than
one
in
all
evaluated
soil
depths,