Sâmia Maria Tauk-Tornisielo, Olavo Raymundo Júnior1

1Centro de Estudos Ambientais – Universidade Estadual Paulista – Rio Claro – SP – Brasil



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.



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.


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).





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).



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).


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.






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.



This research benefited from the help of FAPESP, CNPq to financial support and grant.






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.