Voltar
THE CONTRIBUTION OF LITTER IN THE HUMIFICATION
PROCESS OF SOIL UNDER CERRADO VEGETATION, IN CORUMBATAÍ
COUNTY, SÃO PAULO STATE.
Sâmia Maria Tauk-Tornisielo, Olavo Raymundo Júnior1
1Centro de Estudos Ambientais – Universidade Estadual
Paulista – Rio Claro – SP – Brasil
--------------------------------------------------------------------------------
ABSTRACT
This study was accomplished in the area
occupied by cerrado strict sense vegetation, with the
objective of quantifying the contribution of the litter
in the humification of the soil. They were maybe distributed
to the inside vegetation, ten 1sq.m litter collectors
covered with screen of 2mm in the superior part and in
the lateral ones, until the level of the soil. This area
was denominated covered place (C). Beside each collector
was demarcated it testifies of 1m2, which usually received
litter, being the same ones designated as discovered place
(D). The litter collections were done monthly and those
from the soil on a quarterly basis, between the period
of January 94 and January 96. The soil samples were obtained
up to a depth of 10cm, for analysis of the minerals, total
carbon (TC), nitrogen, carbon/nitrogen ratio and fractions
of the humus. The humic acids fractions were obtained
after fragmenting the soil, being isolated fractions of
the light organic matter (LOM), mineral fraction (MF),
organic-mineral fraction (OMF) and colloidal fraction
(CF) (clay and siltites). The humic substances were obtained
from the colloidal fraction, according to its solubility
in different "extractants": 2N phosphoric acid
solution (free fulvic acids), 0.1M pyrophosphate (total
humus, fulvic and humic acids) and 0.1N sodium hydroxide
(total humus, fulvic and humic acids). The residual carbon,
after the extraction was considered the humine fraction.
The nutrient analyses of the litter showed seasonal variations,
related mainly to the pluviometric index. The C/N ratio
of the litter and of the soil was smaller during the rainy
months, independent of the time of the year (wet/hot or
cold/dry). The differences among the carbon level in the
soil (C) and (D) were reflected in the humic substances
obtained, mainly, in the fractions of the free fulvic
acids. The largest concentrations of carbon and of humic
acids, in the three solutions, were obtained in the place
(D). The 0.1M pyrophosphate solution was the most efficient
for to extraction of the humic fractions in both areas
(D) and (C). There was influence of the sazonality on
the humic fractions; the largest concentrations were obtained
in the dry months. The test E4/E6 applied to the humic
acids isolated with pyrophosphate and sodium hydroxide
demonstrated that in the place (C) had predominance of
the humic acids with larger molecular weight, only in
the fraction isolated with sodium hydroxide. The conclusion
was that the humification of the soil under cerrado vegetation
varies with the C/N ratio of the litter. This relation
shows a possibility of the interaction between the vegetation
and pluviometric index as far as the N input in the soil.
The high quantity of free fulvic acids in the soil D demonstrates
that they are precursors of bigger molecules, which stay
slightly, adsorbed on the soil colloids.
Key words: humic acids; fulvic acids; humification; litter;
cerrado vegetation; humine.
--------------------------------------------------------------------------------
INTRODUCTION
In different areas of tropical or temperate
climate, were made countless detailed comparisons among
soils of natural or agricultural systems and those used
for another activities. These areas are accompanied about
the evolution during the deforestation, being compared,
and several techniques of handling of soils. Balance ruptures
carted by environmental changes were observed, mainly
in the superficial horizons. The quickly important modifications
in the superficial and deep morphology of the soils were
observed (23).
The expansion of the agricultural borders
has been carting an environmental unbalance, mainly in
cerrado areas, because of the deforestation. This activity
comes carting loss of the biodiversity and of soil degradation,
for the nutrient exhaustion and erosion. The responsible
organic matter for the sustainability of those soils is
being degraded, with appreciable losses of nutrients.
This management does not have the corresponding replacement
and necessary handling to the activity maintenance and
optimization of the soils functions (14,15, 24).
Associating the subject of the cerrado
vegetation with the importance in knowing the humification
of the soil, responsible for the stock of organic carbon
and for countless tied papers the fertility. They settled
down the objectives of this study here approached.
Many studies have showed the effect of
incorporation of organic matter in the soil, such as the
vinasse (16,28,29), other effluent (6,8), and the pesticides
(12). These studies showed the demand knowledge linked
to the humification process and behavior of the humus
in the soil.
The objective went to verify the contribution
of the litter in the humification in latosol under cerrado
vegetation. In this study different extractants of humic
substances in soil colloidal fractions were used.
MATERIAL AND METHODS
The works were developed in an area of
cerrado vegetation, belonging FAPESP, located in the County
of Corumbataí, state of São Paulo (SP),
Brazil, and distant 203Km of the São Paulo City,
SP. The study area of 379,193m3 between longitudes 47o40’
and 47o45’West and latitudes 22o10’ and 22o15’South.
The cerrado strict sense is tropical
vegetation with some characteristics similar to savannas
where trees are 4 to 12m high with predominance of Ocotea
pulchella (Lauraceae). The soil is medium texture red
yellow latosol with high percentage of sand, 61% to 70%,
clay, 6% to 18%, and organic matter, 35 to 48g.dm3, with
high values of nitrogen, potassium and other parameters
characterized in other study. The phosphorus contents
are very poor in soil under cerrado vegetation (28).
Inside the cerrado, specifically in an
area of 10,000m2, established previously, ten 1sq.m litter
collectors were randomly distributed in this area. In
all the collectors nylon screens were placed with opening
mesh 2 x 2mm, in the superior and lateral parts, allowing
that the same ones penetrated some centimeters in the
soil. The spaces occupied by these collectors were called
"covered area or C".
Beside each collector an area of the
same size was demarcated, which the area was considered
testify or control. This area was called "discovered
area or D".
The careful was been of digging small
channel distant 1 meter about the study areas, for the
best drainage of the rainwater. To assure the isolation
of the areas, barrages were placed with polyethylene plastic
to 5Ocm of the collection areas, seeking to avoid it drags
lateral of litter.
The soil samples were obtained each three
months among January 94 to January 96, to the whole they
were 8 samples obtained in the dimensions of 10cm3. The
collection points for soil and litter were chosen at random.
In each collection five soil composed samples were collected,
each of them made up of two sub-samples each.
The soil samples were collected with
a cup auger up to a depth of 10cm for analysis of parameters
studied. Nevertheless, the litter samples were collected
every month from the surface of collectors, and they were
quantified.
The litter was placed to evaporate in
stove to 60ºC until the obtaining of the dry weight.
The samples were crushed and stored for posterior analysis
of mineral and carbon contents. The soil went dry to the
air for posterior analyses of the organic and mineral
matter.
Fractionation of the soil.
The soil samples were sifted in sieves
of 2,000mm and dried with air flux, for the analysis of
the carbon and minerals contents. 10g of sieved, dry soil
was taken, which was placed in Erlenmeyer with distilled
water, 150mL, at 4oC, left in refrigeration for 24 hours,
to facilitate its desegregation. The divisions were accomplished
being placed three glass balls in Erlenmeyer and placed
to shake, for one hour. Each fraction was obtained sieving
the soil by sieves of 210mm and 53mm.
The fractions of 210 to 2,000mm were
obtained placing the soil in sieve of 210mm mesh and 21cm
of diameter and washed with distilled water. The plus
210mm, organic fraction (OF) and mineral fraction (MF)
were washed again with distilled water and separated.
These fractions were separated for flotation and washed
with water distilled until the transparency. These fractions
were sub-divided in MF and OF, both with 210 to 2,000mm.
The organic-mineral fraction (OMF) had 50 to 200mm and
colloidal fraction (CF) had minus 50mm.
All material that passed for the sieve
of 210mm was picked up and separated for posterior sifting
in sieve of 53mm mesh. The fractions OF and MF were placed
in stove 60oC until the obtaining of the dry weight. The
MF was observed in microscope stereoscope to guarantee
the separation of clay.
The clay attaches that persisted after
the agitation and wash were destroyed with a light friction
of the material against the sieve using a porcelain pistil,
this way it was obtained the total desegregation of the
clay.
The fraction of 53 to 210mm was obtained
the same sifting technique described previously being
proceeded, even so with sieve of 53mm mesh. The smaller
fraction than 53mm was considered as being of fine sand
and organic fraction in apprenticeship of decomposition
advanced second analysis granulometric. This fraction
was called organic-mineral fraction (OMF).
The minus 50mm fractions were obtained
with the residual liquids of the previous phases were
mixed and acidified with 2N sulfuric acid, at pH 2.0.
The mixture was let to rest for one night, 16 hours, to
obtain a precipitate or
colloidal fraction (CF). After this period,
centrifugation was accomplished to 4,000rpm. The precipitate,
after having the adjusted pH 7.0, it was placed in stove
to at 60oC until the obtaining of the dry weight. The
liquid portion was discarded. The division was considered
good when the sum of the fraction went equal to described
M, in the equation:
S = OF (210 to 2,000mm) + MF (210 to
2,000 mm) + OMF (210 to 53mm) + CF (<53mm) = M
(98.5 <S/M x 100 <100) (7).
Chemical analyzes of the organic matter.
The determination of total organic carbon
(TOC) of soil and sifted fractions were made using samples
treated with 8% potassium dichromate 5mL and sulfuric
acid 5mL in a double-boiler for one hour. To the cold
samples distilled water 50mL, phosphoric acid 5mL and
15 drops of 5% barium biphenyl amine sulfonate were added.
The titillation was made with Mohr salt (0.2N ammoniacal
ferrous sulfate).
The amount samples were for soil 350mg,
OF 40mg, OMF 400mg and humine 200mg. The EDTA 25mg and
50mg were used how carbon standard. Carbon contents were
calculated: C. fraction weight/dry sample weight (DSW).
10=mgC/g soil.
Starting from the CF the chemical division
was accomplished, of the humic acids and humine of the
soil. The humic substances were obtained in agreement
with its solubility in different extractants; being followed
the method of Dabin (7). The free fulvic acids (FFA) were
extracted with 2N phosphoric acid solution, 80mL, put
in CF, with agitation for 2 hours and centrifugation 4,000rpm
for 20 minutes. The floating liquid was separated in test
tube of 250mL.
To the precipitate it was added 2N phosphoric
acid, 80mL, again and placed to shake for one hour, with
new centrifugation in the conditions described previously.
The procedure was repeated until the obtaining of a clear
solution all floating liquid were quantified and separated
for later carbon determination.
The extract was separated for posterior
analysis of carbon contents. The precipitate was again
submitted the solution extractant. The separation of the
fulvic and humic acids weakly adsorbed to the soil were
accomplished with solution of 0.1N sodium pyrophosphate.
The procedure went similar to the described for above.
They were separate 15mL of the floating liquid, adjusted
the pH 6.0 and, placed in stove to 60oC to concentrate
the carbon contents; the total humus or carbon was determined.
The separation of the humic and fulvic
acids were accomplished, separating 30mL of the floating
liquid, which was acidified pH 1.0 even with 2N sulfuric
acid. The samples were heated at 80oC for 15 minutes (11)
and centrifuged to 4,000rpm. The floating liquid was separated.
To the precipitate it was added 50mL of water distilled
with posterior agitation and centrifugation in the same
conditions. The precipitate or humic acids were adjusted
to pH 7.0 dried at 60oC, and separated for carbon determination.
The same process made for the sodium
pyrophosphate fraction was performed for the determination
of total humus fraction and humic acids (HAP). The fulvic
acids fractions attaché to sodium pyrophosphate
(FAP) and sodium hydroxide fractions (FAS), respectively,
were obtained through the subtraction of total carbon
values of total humus and humic acids.
The residue of centrifugation with sodium
pyrophosphate was treated with 0.1N sodium hydroxide 80mL
with agitation for two hours and centrifuged for 15 minutes
at 4,000rpm. The same process made for the sodium fractions
obtained with sodium hydroxide.
The fractions obtained with sodium hydroxide
presented strong turbid during the process of extraction
of the humic composts, to eliminate this problem it was
added 2g of sodium sulfate and, after total precipitation
of the clay it took place the centrifugation (1).
The residue obtained after the centrifugation
of the three extractants was considered as humine. The
final residue of the centrifugation was considered the
total humine (HT), the pH was adjusted with 2N sulfuric
acid, pH 7.0, and transferred for porcelain coups, placed
in stove to 60oC to evaporate the excess of water.
The relationship E4/E6 was accomplished
with the fractions of humic acids AHP and AHS (9, 30).
From each fraction obtained with different
extractants, aliquots were separated for carbon determination.
The process was the same as that used for carbon determination
in soil and sifted fractions. 10mL of dichromate 2% were
used instead of the 8% dichromate 5mL used in the other
precious analyses. The EDTA 12.5mg and 25.0mg were used
how carbon standard (F2). For the extracts, the end equation
is:
(V2) x (F2) x total volume of solution
/ initial mass of soil g x aliquot of extract (1, 7)
The carbon contents of the respective
fractions were transformed in percentage, starting from
the total carbon of the soil. It was considered great
when the total swinging of carbon presented a precision
of 90%, when the same was not obtained new analysis it
was proceeded (7). The statistical analyses methods used
were those mentioned in literature (27).
RESULTS AND DISCUSSION
The total pluviometric precipitation
obtained in the years of 1994 and 1995 was of 1,180 and
1,846mm rain, respectively. In the month of January 96,
the same index was of 351.1mm. During the same periods
the registered medium temperatures were of 22.8 and 22.2oC
in 94 and 95, respectively, including the month of January
96. The largest values of the relative
humidity of the air were obtained in
April 94, January 95, July 94 and January 96, in the two
places (C) and (D). In October 94 they happened the smallest
values in both places (D) and (C). In this month had the
highest temperatures, in places (C) and (D), the averages
of the temperatures more drops were verified in July 95.
In the study area during two years was
observed the litter humification with the parameters indicating
high value of
factor K of Olson. They results were
obtained in another studies in the same place, being with
values of the medium life of the 1.45 year-old litter
and a " turnover" of 2.09 years (25). In the
same place where the collectors of litter were installed
were obtained smaller values of K of Olson among 0.23
to 1.40 (4).
The average of the amount of litter obtained
during it study periods was of 400.26 ± 107.48.
The amount of collected material not always accomplished
the largest entrance of carbon in the soil. The CT contents
suffered influence of the sazonality, ANOVA, F=3.11*.
In the October 95 happened the largest entrance of carbon
through litter. The carbon contents in that period, differed
statistically of the others months. The opposite of this
fact, happened in January 95, in which there was the largest
entrance of litter of all the periods, even so the carbon
content was the smallest. The smallest averages in the
CT contents happened in the January 95 and January 96,
which differed of the other periods, Table 1.
Table 1. Mineral analysis of litter from a cerrado vegetation,
is located in Corumbataí county, SP.
* Characteristics of litter: g (p.s.) of litter; Corg.
% – Organic carbon (mgC/g litter); C/N ratio.
The litter is one of the most important
sources of carbon for the soil. In spite of not being
the only, they stand out other, as the suber of the roots
or same dead roots, material of microbial origin and you
encourage (13). In agreement with the vegetation type
and set each source it acquires a value in importance.
Them source of organic matter, that is to say, the composition
of the material added to the soil contributes in a significant
way to the humus production (18). The litter is much important
in the balance of total organic carbon in the soil.
In another study involving the humification
of the soil, also in cerrado area, there was homogeneity
of the humus fractions, in the areas of native vegetation
when compared with the one of agricultural use. It was
verified that the phytomass volume added to the soil,
went more important than the composition of the same in
the formation of humidified carbon (6). To avoid their
interference linked to the variability of the vegetation,
or same, the those linked to the material volume added
to the soil, the samples were composed among two collectors,
established for I raffle.
The nutrient analyses of litter demonstrated
that the same presented medium nutrients values. If to
consider the values used to measure the fertility of the
soil, the same it was in the average of 50%, characterizing
the limit between eutrophic and dystrophic used for the
soil (2). The contribution of the nitrogen contained in
the organic matter is an important natural supply for
the plants, in soils under cerrado vegetation the same
acquires great importance due to lixiviation of the nitrate
for it leaves them deeper. The nitrogen contents of the
litter didn't present significant differences, during
the period of this study. The largest percentage of nitrogen
was obtained in January 95, 1.58%, and the smallest in
October 94, 1.21%.
If to consider that the nitrogen contents
of litter suffered little alteration during the year,
the carbon contents had fundamental importance in the
C/N ratio, which presented seasonal variations, ANOVA,
F=3.11*. In October 94 and January 95 were observed the
largest and smaller C/N ratio, respectively. he pluviometric
precipitation influenced in a significant way in this
factor, because all the quarters of smaller pluviometric
index presented the largest C/N ratio of the litter. This
factor can be linked directly with the strategies of the
vegetation, verified in another study (22).
The analysis of the other nutrients of
the litter demonstrated that they didn't present influence
of the sazonality the iron, manganese, sum of bases (SB),
Table 1. The largest nutrient contents happened in him
dry periods, October 94. It was not usually in the dry
period. Even so in the year of 1994 there was a prolongation
of the stretched and, that factor, possibly, went decisive
for the swinging of the composition of nutrients among
the dry and rainy periods. The largest pH values of the
litter presented in the months January 95 and 96, when
there were also decrease of the (H + Al) and Al+3 contents,
which have strong influence on the acidity of the soil.
It was verified that the potential acidity and the aluminum
prevail in the litter in the dry months, this behavior
was verified in the soil, so much in the areas (C) and
(D), Tables 1 and 2.
Table 2. Mineral analysis in medium texture red yellow
latosol from a cerrado region, is located in Corumbataí
County, SP, at depth of 0-10cm in covered (C) and discovered
(D) area.
In another works, accomplished in cerrado
areas the largest aluminum contents were obtained in September,
while the smallest ones happened in January and April
(3). CTC didn't present seasonal variations, even so the
quarters of little rain presented larger CTC, while in
January 95 and 96 they happen the smallest values.
Patterns similar with relationship to
the nutrients of the litter, they were also described
in another cerrado areas (3) and, in other works accomplished
in the in this same reservation of closed, correlation
are discussed among the nutrients related to the decomposition
process (4).
Soil
The nutrients analysis allowed to classify
the soil as dystrophic (V <50%) and very poor in nutrients,
with high acidity, Table 2, according to the classification
used for fertility index (19). The sazonality affected
all the nutrients and other parameters linked to the minerals
of the soil practically. For the test ANOVA, the potassium
and the boron values didn't present significant seasonal
variations. In the collection places differences significant
statistically were verified among the areas (C) and (D),
with relationship to the nutrients, magnesium, iron, manganese
and SB (sum of bases). Everybody presented the largest
concentrations in the area (D), except the iron.
Works accomplished in soils under cerrado
vegetation demonstrated that the mobility of the nitrogen
in the soil happens mainly in the vertical, but it was
not accumulated in the layers below the 60cm of depth.
In the rainy months it increases the amount of this nutrient
one considerably in the surface, due to the increase of
the microbial activity.
The results in the Table 2 suggest that
the same behavior can have been happening in the study
area, once the months of larger pluviometric index were,
also, those with the largest nitrogen contents in the
soil. As there was no difference among the nitrogen contents
among the area (C) and (D). The supply of the area (C)
it happened for other sources without being the litter.
It is possible that this stock of nitrogen originating
from of the organic matter have as source, besides the
decomposition process directly. Other possibility is the
humidity related with the matter organic. During
the occurrence of a high humidity was
observed that the acidic hydrolyze of humic acids could
isolate many aminoacids (31). It was stood out in another
work that the methods for the obtaining of an index of
readiness of nitrogen in the healthy soil in the unsatisfactory
practice (5).
In the soil the C/N ratio suffered variations
seasonal significant statistically, according to the test
ANOVA, F=14.28*, difference significant statistically
was not observed among the areas (C) and (D). In works
accomplished by other authors, in the same cerrado area,
smaller values were verified for the C/N ratio, 12 (4,
28), well below the values obtained in that study, 31
and 27, in the areas (D) and (C), respectively. The way
of collection of the soil can have been the main cause
to justify that great difference, once the litter mattress
was not despised, in the moment of the collection, standard
procedure in the samples for analysis of fertility of
the soil. (Casagrande, 1998 - personal information).
CT values of the soil didn't present
variations significant statistically during the collection
period. The April, July and October 94, respectively,
presented the largest averages CT values in the soil,
Table 3. In spite of, statistically, not to have happened
the influence of the sazonality and on the parameter.
In the year of 1995, when the pluviometric index was larger,
there was decrease of the carbon contents. The fraction
MOL didn't also present differences significant statistically
among the collection periods. If to consider the fractions
of the no humidify matter organic, the differences significant
statistically only happened with OMF, F = 11,21*, in that
case, there was the influence of the sazonality. In April
94 was observed the largest averages, differing of all
the periods. The smallest ones medium they were observed
in April and October 95, which differed of the other months.
Table 3. Characteristics of organic matter in medium
texture red yellow latosol from a cerrado region, is located
in Corumbataí county, SP, at depth of 0-10cm in
covered (C) and discovered (D) area.
TOC – Total organic carbon (%); LOM – Light
organic matter (%); MOF – Mineral-organic fraction
(%); FFA - Free fulvic acids (%);
FAP - Fulvic acids extracted with pyrophosphate of sodium
(%); HAP- Humic acids extracted with pyrophosphate of
sodium (%);
FAS - Fulvic acids extracted with sodium hydroxide (%);
C/N ratio; E4/E6p ratio (HAP); HAS – Humic acids
extracted with sodium hydroxide (%); TH – humine
(%); S-C/N - Ratio C/N of soil; E4/E6s ratio (HAS).
The results, obtained in the areas (C)
and (D) demonstrated that the non-humidify organic matter
fraction of the soil was accumulated in the months with
smaller pluviometric index between May and August. This
fact in itself could have been responsible for the smallest
microbial activity and consequently, smaller decomposition
speed. It is stood out that in spite of the low pluviometric
index in the stretched period, the same was not it of
smaller humidity percentage, up to ten depth centimeters.
The test ANOVA demonstrated that the sazonality influenced
in the humidity of the soil, F=14,70*. The test of Tukey
demonstrated that the months of April 94 and January 95
presented the largest percentages of humidity of the soil.
In October 94 it was obtained the smallest percentage
of that parameter. Statistically significant differences
were not verified among the place (C) and (D), demonstrating
that the litter collectors didn't interfere in the humidity
of the soil. In other work accomplished in the same area
the importance of the litter it was discussed in the accumulation
of humidity of the soil during the dry period, and its
implications on the microbial populations of filamentous
fungi and actinomycetes (21).
Several factors can have been acting
together to propitiate the high CT contents in the soil
in the dry period. The readiness of water cannot have
been the only, it was also verified in this period, accumulation
of toxicant minerals as aluminum and manganese, and increase
of the potential acidity (H+ Al). This group of factors
takes to a fall in pH value of the pH in the soil. This
way, such factors together can have been affecting the
microbial activity, provoking a fall in the rates of mineralization
of the organic matter during the dry months. Another factor
that could have contributed to the decrease of carbon
contents in the rainy period would be the loss of organic
matter for deeper layers. In the rainy months, even so
that hypothesis was disrespected, once in another works
it was not verified significant differences in the organic
matter contents below 5cm of depth (20).
The distribution of the humidify carbon
organic, extracted of CF of the soil (<53mm) it represented
65.61% ± 6.20 and 63.8% ± 6.9 in the areas
(C) and (D), respectively. In other works accomplished
in cerrado area the humidify fraction represented 96%.
In Australian soil more than 50% of the
organic carbon met in the same fraction (26). The HF values
in the area (C) and (D) were 59% ± 5,86 and 57,5%
±6,7, respectively, of the TC of the soil. Such
results were in agreement with other author, which used
the same extractants solutions of humic acids (17) and
only with 0.5N sodium hydroxide.
In the other work accomplished in cerrado
area with soil of sandy texture, it was obtained larger
amount of humic and fulvic acids and, smaller amount of
humine. The extractants utilized in this work were 0.1N
pyrophosphate solutions and 0.1N sodium hydroxide.
The difference in these results, probably,
was observed because the fraction considered in the present
study, as HT, it suffered attack for acids, HCL - HF (1:1)
to 60ºC, such procedure removed mineral Al and Faith.
This way it was possible to extract more humic and fulvic
acids associated the head office mineral of the soil.
It is possible that a treatment similar to it was described,
allow the division of the humine and the separation of
another humic and fulvic acids fractions, besides those
mentioned.
The sazonality influence on the different
fractions of humidify matter organic, the statistically
significant differences happened with AFL (F=20.08 *),
AFP (F=4.75*), AHP (F=5.63*) and AFS (F=3.69 *). There
was no influence of the sazonality on the fractions of
AHS and HT. In April 94 and January 96 these fractions
differed of the other periods with relationship to the
carbon contents of the fractions AFL and AHP. In April
94 and January 95, the AFP values differed significantly
of the other values in the other periods. In January 96,
the acid AFS differed in all the other periods of this
study. The fractions AFL, AFP and AHP are slightly adsorbed
in the soil (7), for that aspect the same ones, would
be more subject to the lixiviation and mineralization
processes.
Statistically significant differences
among the places C and D happened with relationship to
CT of the soil. The CT medium values in the place (C)
were of 24.95 %o ± 2.96, and in the place (D) was
of 31.3%o ± 3.5. The same happened with the fraction
of MOL. Statistically significant differences were not
verified in OMF. CT of the soil reflects the non humidify
and humidify organic matter so much, it is observed that
the stock of non-humidify carbon was just affected in
the fraction MOL and not in the fraction FOM. As the humidify
fractions the differences among the places C and D happened
with most of the fractions, except in the fraction AFS.
Those results demonstrate that the blockade of the litter
entrance had strong influence in the humification process,
demonstrating that the formation of the humic substances
is a dynamic process in the tropical soils. Such results
agree with the that obtained in another areas, where it
was evident that the phytomass accumulation
in the soil, independent of its composition it is of fundamental
importance for the formation of the humus (5). Even so,
in another work the importance of the litter composition
was highlighted, mainly originating from of leguminous
that nodular, and of fast growth to accelerate the vegetable
succession in areas degrade (10).
The statistically significant correlation
were obtained among the fractions AHS and HT in both places
C and D, being (r=0.78) and (r=0.71), respectively. The
fraction HT was correlated positively with CT of the soil
in the respective ones local C (r=0.78) and D (r=0.70).
Those results demonstrate the importance of the carbon
more strongly
adsorbed to the organic-mineral complex
of the soil, generating other fractions of humidify organic
matter possibly and influencing positively in the stock
of total carbon of the soil. Other statistically significant
correlation happened in the place (C), CT was correlated
positively with the fractions MOL (r = 0.71); AHS (r=1.0)
with the fractions MOL x AFL (r = 0.74); MOL with AHS
(r=0.73). In the place (D) was observed the correlation
CT with AHS (r=1.0).
The fractions AHP and AHS were submitted
to the test E4/E6, through which was possible to verify
statistically significant differences related with the
sazonality, being F=4.69 and F=5.21, respectively. The
sazonality influence had already been verified in another
work in the same study area, as the relationship E4/E6
(20).
Statistically significant differences
were obtained among the places (C) and (D) in the fraction
AHS (F =13.46*). The largest values of the extinction
coefficient were obtained in the area (D), Table 3, evidencing
the prevalence of
molecules of smaller molecular weight.
The same results were cited in literature (9). The statistically
significant differences didn't happen among the collection
places with the fraction AHP. Possibly in the place (C),
due to interruption of the litter entrance him fraction
AHS, was altered, taking the largest concentration of
humic acids with larger molecular weight. This alteration
becomes important, if we consider that the amount of carbon
didn't differ among the collection places, that is to
say it was only affected the characteristics of the humic
acids, Table 3.
The seasonal variations in the values
of the relationship E4/E6 also demonstrate the dynamism
of the substance in soil under cerrado vegetation. The
knowledge of the swinging among the molecules of high
and low molecular weight in tropical soils, besides the
factors that influence in that aspect can help in the
adapted handling of these soil, seeking to preserve and
or same to increase the humidify matter organic contents.
It was observed that in soil with little vegetation (discovered)
for ten years that the percentage of aromatic carbon and
aromatic were larger. It already had the possibility of
incorporation of carbon and nitrogen to the humic compound
residents in the soil, what would propitiate an increase
in the stock of humidify carbon. Thwarting the fact that
the humic acids, due to the high time of residence in
the soil would not suffer abrupt modifications in a small
period of time (7).
CONCLUSION
The interruption of one of the important
sources of carbon for the soil, the litter, caused changes
in some nutrients of the soil (magnesium, iron, sum of
bases). There was decrease of the TC of the soil. The
sazonality affected most of the fractions of the humidify
matter organic, less AHS and HT. Among the collection
places there only was not statistically significant difference
with the fraction AFS. The relationship E4/E6 was affected
in the fraction AHS. The humic acids of place (D) presented
smaller values, indicating prevalence of humic acids with
larger molecular weight. It is possible that the interruption
of the entrance of carbon in the soil, don't cause the
immediate exhaustion of the stock of carbon, even so the
resident organic matter will suffer change in its molecular
structure, prevailing the composed high weight molecular,
more adsorbed to the loamy micelles.
--------------------------------------------------------------------------------
RESUMO
Contribuição da serapilheira
no processo de humificação do solo sob vegetação
de cerrado sob processo de humificação do
solo sob vegetação de cerrado, município
de Corumbataí, SP. O estudo foi realizado em área
ocupada por vegetação de cerrado, com o
objetivo de quantificar a contribuição da
serapilheira no processo de humificação
do solo. Foram distribuídos ao acaso no interior
da vegetação, dez coletores de serapilheira
com 1m2, revestidos com tela de 2mm na parte superior
e nas laterais, até o nível do solo. Ao
lado de cada coletor foi demarcada um área testemunha
de 1m2, a qual recebeu normalmente serapilheira, sendo
as mesmas designadas como: local coberto (C) e descoberto
(D). As coletas de serapilheira foram mensais e as de
solo trimestrais, no período de Jan/94 a Jan/96.
As amostras de solos foram obtidas até 10cm de
profundidade para análise dos minerais, teores
de carbono total (CT), nitrogênio, relaçãoC/N
e frações do húmus. As frações
dos ácidos húmicos foram obtidas após
fracionamento do solo, isolando-se frações
da matéria orgânica leve (MOL), fração
mineral (FM), fração organo-mineral (FOM)
e fração coloidal (FC) (argilas e siltitos).
As substâncias húmicas foram obtidas a partir
da fração coloidal, segundo sua solubilidade
em diferentes extratantes: solução de ácido
fosfórico 2N (ácidos fúlvicos livres),
pirofosfato 0,1M (húmus total, ácidos fúlvicos
e ácidos húmicos) e hidróxido de
sódio 0,1N (húmus
total, ácidos fúlvicos
e ácidos húmicos). O carbono residual, após
as extrações, foi considerado a fração
humina. As análises de nutrientes demonstraram
que a composição química da serapilheira
apresentou variações sazonais, relacionadas
principalmente ao índice pluviométrico.
A relação C/N da serapilheira e do solo
foi menor nos meses chuvosos, independente da época
do ano (verão ou inverno). A diferença entre
os teores de carbono dos locais (C) e (D), refletiram-se
nas substâncias húmicas obtidas, principalmente,
nas frações dos ácidos fúlvicos
livres . As maiores concentrações de carbono
e de ácidos húmicos, nas três soluções,
foram obtidas no solo descoberto. A solução
de pirofosfato 0,1M foi mais eficiente para a extração
das frações húmicas em ambas as áreas
descoberta e coberta. Houve influência da sazonalidade
sobre as frações húmicas, as maiores
concentrações foram obtidas nos meses secos
. O teste E4/E6 aplicado aos ácidos húmicos
isolados com pirofosfato e soda, demonstrou que no local
coberto predominaram os ácidos húmicos de
maior peso molecular, somente na fração
isolada com soda.
Palavras chaves: ácidos húmicos; ácidos
fúlvicos; humificação; vegetação
de cerrado; humina.
--------------------------------------------------------------------------------
ACKNOWLEDGMENTS
This research benefited from the help of FAPESP, CNPq
to financial support and grant.
REFERENCES
Alves, B.J.R, Santos, J.C.F dos, Urquiaga,
S., Boddey, R. M. Análise do carbono nos estudos
da matéria orgânica do solo. Hungria, M,
Araújo, S. R (eds.). In : Manual de Métodos
Empregados em Estudosesta munusl Hsvp;sz/rl; de Microbiologia
Agrícola., EMBRAPA Planaltina, 1995. p.513 - 525.
Adámoli, J, Macêdo, J., Azevedo, L.G.de,
Netto, J.M. Caracterização da região
dos Cerrados. In: Solos dos Cerrados, Tecnologia e estratégias
de manejo. 1986. p.167 – 174.
Araújo, G.M. Comparação do estado
nutricional de dois cerradões em solos distróficos
e mesotróficos no planalto central do Brasil. Instituto
de Biociências, Universidade de Brasília,
DF. 1884, 130p. (Dissertação de Mestrado).
Attili, D.A. Sucessão fúngica e decomposição
da fração foliar da serapilheira de cerrado
no município de Corumbataí, SP, Rio Claro,
SP. Instituto de Biociências, Rio Claro, UNESP.
1989, 183p. (Dissertação de Mestrado).
Ceretta, C.A. Fracionamento de N orgânico, substâncias
húmicas e caracterização de ácidos
húmicos de solo em sistemas de cultura sob plantio
direto. Universidade Federal do Rio Grande do Sul, Faculdade
de Agronomia. Porto Alegre. 1995, 127p. (Tese de Doutorado).
Ceretta, C.A., Tisott, A.R., Barcellos, L.A.R., Gomes,
V.S.da. Aproveitamento de esterco líquido de suínos
em pastagem de campo nativo na região da depressão
central do Rio Grande do Sul. 2° Encontro Brasileiro
Sobre Substâncias Húmicas, EMBRAPA, São
Carlos. 1997, p135.
Cerri, C.C., Feigl, B., Piccolo, M.C.
Manual de aula prática. CENA, Piracicaba. 1990,
78 p.
Cintra, A.A.D., Melo, W.J., Chelli, R.A., Leite, S.A.S.
Influência de tipos de materiais orgânicos
e um produto a base de alga calcária (Lithothamninum
calcareum) no fracionamento de matéria orgânica
de um Latossolo vermelho-amarelo cultivado com alface
(Lactuca sativa). 2O Encontro Brasileiro Sobre Substâncias
Húmicas, EMBRAPA, São Carlos. 1997. p.141.
Chen, Y, Senesi, N., Schnitzer, M. Information provided
on humic substances by E4/E6 ratios. Soil Sci. Am. J.,
41:352-358. 1977.
Franco, A.A., Campello, F.C. Importância da qualidade
da serapilheira na sucessão vegetal em áreas
de recuperação na amazônia. 2°
Encontro Brasileiro Sobre Substâncias Húmicas,
EMBRAPA, São Carlos. 1997, p.53-59.
Koltzclow, K.M., Sposito, G. Analytical properties of
the soluble, metal-complexing fractions in sludge-soil
mixture. IV Determination of carboxyl groups in fulvic
acid. Soil Sci. Am. J., 43: 318 – 323. 1979.
Lavorenti, A. Identificação de perigos de
resíduos ligados de pesticidas em substâncias
húmicas. 2O Encontro Brasileiro Sobre Substâncias
Húmicas, EMBRAPA, São Carlos, 1997, p.66
-71.
Lynch, J.M. Soil biotechnology. Microbiological factors
in crop productivity. London. Blackwell Scientific Pub,
1983. 191 p.
Nascimento,V.M., Melo, W.. J.de, Neptune, A.M.L. Efeitos
da rotação de culturas sobre frações
da matéria orgânica de um Latossolo sob vegetação
de cerrado. Científica, UNESP, 16: 13-19. 1988.
Nascimento, V.M., Almendros, G., Fernandes, F.M. Soil
humus characteristics in virgin and cleared areas of the
Paraná river basin in Brazil. Geoderma, 54: 137-150.
1992.
Palma, M.S., Tauk, S.M., Raymundo, O. Jr. Aspectos da
humificação em Latossolo vermelho-amarelo
textura média, tratado com vinhaça, sob
cultura de milho. Ciência e Cultura, São
Paulo, 41: 1125 – 1128. 1989.
Pallo, Fj.P. Evolution of organic matter in some soils
under shifting cultivation practices in Burkina Faso.
Mulongoy, K., Merckx, R. (eds.). Soil Organic Matter Dynamics
and Sustainability of Tropical Agriculture. A Wiley-Sayce
Co-Publication, 1993, p.109 -120.
Primavesi, A. A agricultura em regiões
tropicais: manejo ecológico do solo. 9. ed., Livraria
Nobel, São Paulo. 1986. 549 p.
Raij,V.B., Cantarella, H., Quaggio, J.A.,
Furlani, A.M.M. Boletim técnico 100. Recomendações
de adubação e calagem para o Estado de São
Paulo. Instituto Agronômico, Fundação
IAC, Campinas, SP.1996.
Raymundo, O. Jr. Fungos filamentosos, actinomicetos e
ácidos húmicos, em diferentes profundidades
de Latossolo vermelho amarelo textura média em
área de cerrado, no município de Corumbataí,
SP., Rio Claro. Instituto de Biociências, Rio Claro,
UNESP, 1992.149p. (Dissertação de mestrado)
Raymundo, O. Jr. Occurrence of hyphomycetes and actinomycetes
in red-yellow latosol from a cerrado region in Brasil.
Revista de Microbiologia, 28: 197-203. 1997.
Ribeiro, J.F. Comparação da concentração
de nutrientes na vegetação arbórea
e nos solos de um cerrado e um cerradão no Distrito
Federal, Brasil. Brasília, Instituto de Ciências
Biológicas, Universidade de Brasília, DF.,
1983. 86p. (Dissertação de Mestrado).
Ruellan, A. Pedologia e desenvolvimento: a ciência
do solo ao serviço do desenvolvimento. XXI Congresso
Brasileiro de Ciência do Solo, 69-74. 1988.
Silva, J.E.da; Resck, D.V.S. 1997. Matéria orgânica
do solo. Vargas, M.A.T., Hungria, M. In: Biologia Dos
Solos Dos Cerrados. 1a Ed. Planaltina, EMBRAPA- CPAC.
1997. 524 p.
Santos, P.F., Rodrigues, G. S. Avaliação
de métodos para a estimativa da decomposição
do folhedo em ecossistema de cerrado (Corumbataí-SP).
34a.Reunião Anual da SBPC, Campinas, 1982, p.559.
Skjemstad, J.O, Clarke, P., Taylor, J.A., Oades, J.M.,
Mcclure, S.G. The chemistry and nature of protected carbon
in soil. Aust. J. Soil Res., 34: 251- 271. 1996.
Sokal, R.R., Rohlf, F.S. Biometry: the principles and
practice of statistics in biological research. San Francisco,
Freeman and Company. 1969.
Tauk, S.M. Efeito de doses cumulativas de vinhaça
em algumas propriedades do solo sob cerrado e do solo
de culturas de milho e cana-de-açúcar nos
municípios de Corumbataí e de Rio Claro,
SP, Rio Claro. Instituto de Biociências, Rio Claro,
UNESP, 1987. 349p. (Tese de Livre Docência).
Tauk, S.M. Substâncias húmicas e atividade
microbianas no solo. 2° Encontro Brasileiro Sobre
Substâncias Húmicas, EMBRAPA, São
Carlos, . 1997. p. 208.
Trubetskoj, O.A., Trubetskaya, O.E., Markova, L.F., Muranova,
T. A. Comparison of amino-acid compositions and E4/E6
ratios of soil and water humic substances fractions obtained
by polyacrylamide gel electrophoresis. Environment International,
20: 387 – 390. 1994.
.
