ABSTRACT In the Cerrado, the palm swamps ( veredas ) are characterized by being humid and stable environments that lead to the formation of Histosols ( Organossolos ). and soils with surface horizons of organic constitution, which are fragile and sensitive to anthropic action. This study aimed to evaluate the impact of anthropization (recurrent forest fires and livestock farming) on the chemical, physical and morphological properties of soils in two palm swamps in the Environmental Preservation Area (EPA) of Pandeiros River, Minas Gerais, namely: Água Doce, in preserved condition, and Taboa, in anthropized condition. Four soil profiles were morphologically described, two profiles in each palm swamp, with subsequent chemical and physical analyses, calculations of organic carbon stock and identification of the origin of organic matter. The results were analyzed using descriptive statistics and Pearson’s correlation coefficient. Soil morphological properties were influenced by vegetation cover, drainage and anthropization conditions. As for the physical and chemical properties, adequate values were observed in the preserved palm swamp, including lower bulk density values and higher cation contents. Anthropic actions in the anthropized palm swamp caused degradation of soils, revealed by subsidence, reduction in organic carbon content, increase in bulk density and decrease in fertility. Changes promoted in the soils of the palm swamps compromise ecosystem services, indicating that actions at either local or governmental level should be stimulated for the preservation and conservation of these environments.

ABSTRACT Bulk density (Bd) can easily be predicted from other data using pedotransfer functions (PTF). The present study developed two PTFs (PTF1 and PTF2) for Bd prediction in Brazilian organic soils and horizons and compared their performance with nine previously published equations. Samples of 280 organic soil horizons used to develop PTFs and containing at least 80 g kg-1 total carbon content (TOC) were obtained from different regions of Brazil. The multiple linear stepwise regression technique was applied to validate all the equations using an independent data set. Data were transformed using Box-Cox to meet the assumptions of the regression models. For validation of PTF1 and PTF2, the coefficient of determination (R2) was 0.47 and 0.37, mean error -0.04 and 0.10, and root mean square error 0.22 and 0.26, respectively. The best performance was obtained for the PTF1, PTF2, Hollis, and Honeysett equations. The PTF1 equation is recommended when clay content data are available, but considering that they are scarce for organic soils, the PTF2, Hollis, and Honeysett equations are the most suitable because they use TOC as a predictor variable. Considering the particular characteristics of organic soils and the environmental context in which they are formed, the equations developed showed good accuracy in predicting Bd compared with already existing equations.

RESUMO No Cerrado brasileiro têm-se observado um aumento na adoção de sistemas integrados de cultivo, como a integração lavoura-pecuária (ILP), aliada ao sistema de plantio direto (SPD), os quais vêm exercendo considerável influência nos atributos do solo. O objetivo deste estudo foi avaliar a influência do sistema de integração lavoura-pecuária (ILP) sob alguns atributos químicos, físicos e microbiológicos do solo sob Cerrado, Montividiu, Goiás. Foram avaliados a fertilidade do solo, fósforo remanescente (Prem), carbono orgânico total (COT), nitrogênio total (Nt), estabilidade de agregados (diâmetro médio geométrico - DMG), respiração microbiana (C-CO2) e a proteína do solo relacionada à glomalina - facilmente extraível (PSRG-FE). Coletaram-se amostras de solo nas profundidades de 0-5 e 5-10 cm, em três áreas: ILP (13 anos de rotação anual com Urochloa ruziziensis); pastagem de U. decumbens (15 anos de implantação); e Cerrado nativo. A área de ILP apresentou maiores valores de pH, Mg, P disponível (0-10 cm) e Prem (5-10 cm) que as demais áreas, e valores similares de COT, Nt, PSRG-FE (0-10 cm) e estabilidade de agregados (5-10 cm) à área de pastagem. A ILP não alterou as emissões de C-CO2 em relação ao Cerrado, mas reduziu essas taxas em relação à pastagem. O Pava e Prem foram indicadores sensíveis para evidenciar diferenças entre os sistemas de ILP e pastagem, com níveis mais elevados no ILP. Enquanto os indicadores COT e NT não mostraram diferenças entre estes dois sistemas. O DMG indicou maior agregação na pastagem (0-5 cm) em comparação com a ILP, enquanto a PSRG-FE não mostrou diferenças entre essas áreas. A emissão de C-CO2 indicou estabilidade nas taxas de respirometria no ILP e no Cerrado.

ABSTRACT A significant increase in the use of integrated farming systems have been observed in the Brazilian Cerrado, such as crop-livestock integration (CLI), which combined with the no-tillage system (NTS) have shown significant influence on soil properties. Therefore, the objective of this work was to evaluate the influence of a CLI system on the chemical, physical and microbiological soil characteristics, in an area in the Cerrado biome, Montividiu, State of Goias, Brazil. The soil fertility, remaining phosphorus (Prem), total organic carbon (TOC), total nitrogen (Nt), aggregate stability (geometric mean diameter - GMD), microbial respiration (C-CO2) and easily-extractable glomalin-related soil protein (EE-GRSP) were evaluated. Soil samples were collected at depth of 0-5 and 5-10 cm in three areas with: CLI (13 years of annual rotation with Urochloa ruziziensis); Urochloa decumbens pasture (15 years of implementation); and native Cerrado vegetation. The CLI area had higher pH, Mg, P available (0-10 cm) and Prem (5-10 cm) values compared to the other areas, and equal values of TOC, Nt, EE-GRSP (0-10 cm) and aggregate stability (5-10 cm) compared to the pasture area. The CLI had no differences in C-CO2 emissions compared to the Cerrado, but had lower rates compared to the pasture. The P available and Prem were sensitive indicators to show the differences between the CLI and pasture systems, with higher contents in the CLI area. The TOC and Nt indicators had no differences between these two systems. The GMD results indicated a better aggregation in the pasture (0-5 cm) compared to the CLI area, while the EE-GRSP were similar in these areas. The total values of C-CO2 emission from the soil aggregates showed the stability of respirometry rates in the CLI and Cerrado areas.

Humic fractions of soil organic matter (SOM) and measurements of 13C and 15N isotope can be used to highlight differences between management systems with different intensities of land use. This study characterized soil fertility, quantified carbon levels in the humic fractions and evaluated the natural abundance of 13C and 15N in systems cultivated under no-tillage system (NTS) and conventional tillage system (CTS) or used with secondary forest or perennial pasture in Marmeleiro, Parana State, Southern Brazil. NTS was more efficient than the conventional tillage system (CTS) in increasing pH (0.0-0.10 m layer), Ca (0.0-0.05 m layer), P (except 0.05-0.10 m layer) and N (0.0-0.10 m) levels, total organic carbon (TOC) stocks (0.0-0.20 and 0.0-0.40 m layers); carbon of the humin fraction (C-HUM) in 0.0-0.40 m; the fulvic acid fraction (C-FAF) and humic acid (C-HAF) in 0.0-0.05 m. The use of grasses, in NTS and pasture, increased TOC stocks compared to the other soil use or management systems evaluated in the 0.0-0.40 m layer. In the topsoil layer, the anthropogenic influence of plowing and harrowing in CTS promoted greater loss of carbon in C-HUM, C-FAF and C-HAF than NTS, forest and pasture. In CTS, growing corn for 42 years after the removal of forest cover did not alter the 13C at 0.0-0.40 m. In pasture, the absence of legumes, constant deposition of cattle manure and a more stable organic matter favored high 15N levels (except at 0.0-0.05 m in CTS). The decrease in 15N values from the 0.0-0.10 to 0.10-0.20 m layer in CTS indicates that soil turnover (by plowing and harrowing) has the potential to disturb the depth-related variation in soil 15N, accelerating decomposition and compromising N transformations. Among the variables analyzed, the determination of carbon in humic fractions and 15N values were efficient in identifying soil changes produced by land use or management systems.

El uso de lasfracciones húmicas de la materia orgánica del suelo (MOS) y las mediciones isotópicas de 13C y 15N se puede utilizar para resaltar las diferencias entre los sistemas de gestión con diferentes intensidades de uso de la tierra. El estudio caracteriza la fertilidad del suelo, cuantifica los niveles de carbono en las fracciones húmicas y evaluó la abundancia natural de 13C y 15N en el sistema de siembra directa (NTS), sistema de labranza convencional (CTS), bosque secundario y pastizales en el Sur de Brasil. NTS es más eficaz en el aumento depH (0,0 a 0,10 m), niveles de Ca (0,0 a 0,05 m), P (excepto 0,05-0,10 m) y N (0,0 a 0,10 m); los estoques de carbono orgánico total (TOC) (0,0-0,20 y 0,0 a 0,40 m), y los niveles de carbono de la fracción humina (C-HUM) en 0,0-0,40 m; carbono de la fracción de ácido fúlvico (C-FAF) y ácidos húmicos (C-HAF) en 0,0-0,05 m, que el sistema de labranza convencional (CTS). El uso de hierbas, en NTS y pastizales, aumenta las reservas de TOC en comparación con los otros sistemas de uso y manejo de suelos evaluados en 0,0-0,40 m. En la capa superior del suelo la influencia antropogénica de arar y desgarradora, en CTS promove una mayor pérdida de carbono en C-HUM, C-FAF y C-HAF en comparación con NTS, bosque y pastos. En CTS, el cultivo de maíz durante 42 años después de la eliminación de la cubierta forestal no alteró el 13C en 0,00,40 m. En pastos, la ausencia de legumbres, la deposición constante de estiércol de ganado y una materia orgánica más estable favorece a los niveles altos 15N (excepto en 0,0-0,05 m en CTS). La disminución de los valores 15N en 0,0-0,10 a 0,10-0,20 m en CTS indica que la rotación del suelo (por el arado y desgarradora) tiene el potencial para perturbar la variación relacionada con la profundidad en el suelo 15N, acelerando su descomposición y comprometiendo las transformaciones de N. Entre las variables analizadas, la determinación del carbono en fracciones húmicos y los valores de 15N son eficientes en la identificación de cambios en el suelo producidos por el uso del suelo o de los sistemas de gestión.

This study aimed to measure the concentrations of carbon (C), nitrogen (N) and the natural abundance of 13C and 15N in macro and microaggregates under systems of land use. We sampled the 0-5 and 5-10 cm layers in no-tillage system (NTS), conventional tillage system (CTS), secondary forest and pasture in southern Brazil. The largest variations of C and N concentrations were found for the 8-2 mm aggregate class, with the sequence pasture > forest = NTS > CTS, compared to the 0.25-0.105 mm class. The most negative δ13C values were found in the microaggregates and the least negative were found in the macroaggregates. Plowing and harrowing in the CTS cause the fracturing of soil aggregates, accelerating the mineralization reactions of soil organic matter (SOM) and discouraging the occlusion of SOM in the aggregates, resulting in higher δ15N values compared to the other systems evaluated. The larger variation in C and N content for the 8-2 mm class and smaller variation in the 0.25-0.150 mm class indicate that there is higher and lower sensitivity to the management system adopted in these areas and lesser and greater protection of the C and N by these aggregate classes, respectively.

Este estudio tuvo como objetivo medir las concentraciones de carbono (C), nitrógeno (N) y la abundancia natural de 13C y 15N en macro y microagregados en los sistemas de uso de la tierra. Tomamos muestras de las capas 0-5 y 5-10 cm en el sistema de siembra directa (NTS), sistema de labranza convencional (CTS), bosque secundario y pastizales en el Sur de Brasil. Se encontró más grandes variaciones en las concentraciones de C y N para la clase agregados 8-2 mm, con la secuencia de pastos > bosque = NTS > CTS, en comparación con la clase desde 0,25 hasta 0,105 mm. Además, se encontró que los valores de 13C más negativos en los microagregados y el menos negativo se encontraron en los macroagregados. Arando y grada en el CTS causa la fractura de los agregados del suelo, lo que acelera las reacciones de mineralización de la materia orgánica del suelo (SOM) y desalentando la oclusión de SOM en los agregados, lo que resulta en valores 15N altos en comparación con los demás sistemas evaluados. Las variaciones más grandes en C y N de contenido para la clase de 8-2 mm y las variaciones más pequeñas de la clase 0,25 hasta 0,150 mm indican que hay mayor y menor sensibilidad al sistema de gestión adoptado en estas áreas y la protección menor y mayor de la C y N por estas clases de agregados, respectivamente.

Este trabalho teve como objetivo quantificar a massa da matéria orgânica leve (MOL) em água e da fração leve livre (FLL) da matéria orgânica do solo (MOS) e os respectivos teores de carbono (C), nitrogênio (N) e abundância natural de δ15N e δ13C contidos na massa da MOL, C e N na FLL em sistemas de uso do solo no Cerrado goiano (Cerradão). Foram avaliados um sistema de integração lavoura-pecuária - SILP (milho+braquiária/feijão/algodão/soja) e sistema plantio direto - SPD (girassol/milheto/soja/milho). A cobertura vegetal de Cerrado natural, adjacente ao SPD e SILP, foi considerada como condição original do solo. Coletaram-se amostras de solo nas profundidades de 0-5 e 5-10 cm, em delineamento inteiramente casualizado. O SILP apresentou maior massa e teores de C na MOL (5-10 cm) e, também maior massa e teores de C e N na FLL (0-10 cm) quando comparada com o SPD. Em relação ao Cerrado, o SILP apresentou maiores valores para N-MOL e δ15N-MOL (0-5 cm), C e N da FLL (0-5 cm). Por meio dos indicadores físicos, MOL e FLL, foi possível inferir que o SILP aumentou essas frações da MOS quando comparado ao SPD.

This study aimed to quantify the light organic matter mass (LOM) in water, free light fraction (FLF) of soil organic matter (SOM) and carbon (C), nitrogen (N) contents and natural abundance of δ13C e δ15N contained in the mass of LOM, C and N in the FLF in land use systems in the Cerrado region of Goiás State, Brazil. Were evaluated a crop-livestock integration system - CLIS (corn+brachiaria/bean/cotton/soybean) and no-tillage system - NTS (sunflower/millet/soybean/corn). The vegetal coverage of natural Cerrado, adjacent to NTS and CLIS, was considered as the original soil condition. Soil samples were collected at depths of 0.0-5.0 and 5.0-10.0 cm in full random experimental design. The CLIS showed the greatest mass and levels of C-LOM (5-10 cm), and too greatest mass and levels of C and N of FLF (0-10 cm) when compared with the NTS. Regarding the Cerrado, the CLIS showed higher values for N-LOM and 1δ15N-LOM (0-5 cm), C and N of FLF (0-5 cm). Through physical indicators LOM and FLF, it was possible to infer that the CLIS increased the SOM fractions when compared to the NTS.

The effect of organic management can influence positively the edaphic properties. The aim of this study was to evaluate the degree of organic carbon oxidation and the soil aggregation indexes in areas under organic management and different plant covers. The selected systems were: conventional tillage (corn - CT), no-tillage (eggplant - NT), passion fruit - Desmodium sp intercrops, fig cultivation, agroforestry system (AFS) and a secondary forest area. The soil samples were collected at 0-5 and 5-10 cm depths. The total organic carbon (TOC) was quantified and separated into four fractions (Fl, F2, F3 and F4) with decreasing degrees of oxidation, by the use of increasing quantities of sulfuric acid. Aggregate stability was determined by wet sieving, using the indices of mean weight diameter (MWD), geometric mean diameter (GMD) and sensitivity index (SI). The area under corn cultivation presented the lowest TOC concentrations and aggregation indices, in the two depths evaluated. The areas under eggplant and fig presented the highest TOC concentrations at the 0-5 cm depth, and the highest MWD at the 5-10 cm depth. There were SI values above 1 in the areas under fig and passion fruit. In general, the Fl fraction represented the largest proportion of TOC in all areas and in the two depths evaluated. The AFS presented the lowest proportions of TOC in the four fractions (0-5 cm). The area under eggplant (0-5 cm) presented the highest carbon concentrations in the Fl, F2 and F3 fractions. However, at the 5-10 cm depth, this behavior was observed in the area under corn, except for the Fl fraction. The results indicate that the management adopted in the area under corn did not favor soil aggregation and TOC. In the other areas, the SI determined indicates that the tillage practices associated to plant cover, in organic systems, preserved soil aggregation when compared to the forest area, at the 0-5 cm depth. The oxidizable carbon concentrations were influenced by the management systems adopted, with higher values in the areas where more plant residues were added to the soil.

La forma como se gestionan los recursos orgánicos aplicados al suelo puede influir las propiedades de éste. Este estudio tuvo como objetivo evaluar el grado de oxidación del carbono orgánico y las tasas de agregación del suelo en sistemas con manejo orgánico y diferentes cultivos de cobertura. Los sistemas seleccionados fueron formas de cultivo y cubierta vegetal: labranza tradicional del suelo (maíz-CT), labranza cero (berenjena-NT), consorcio maracuyá -Desmodium sp, cultivo de higos, agroforestales (AFS) y bosque secundario. Se colectaron muestras de suelo a profundidades de 0-5 y 5-10 cm en todos ellos. Se cuantificó el carbono orgánico total (TOC) y se realizó su fraccionamiento, para separar el carbono en cuatro fracciones (Fl, F2, F3 y F4), con grados decrecientes de oxidación, mediante el uso de cantidades crecientes de ácido sulfúrico. Se determinó la estabilidad de agregados en húmedo mediante peso medio de diámetro (MWD), diámetro medio geométrico (GMD) y el índice de sensibilidad (SI). El área bajo cultivo de maíz mostraron menores niveles de TOC y el índice de agregación, en las dos profundidades estudiadas. Si bien los ámbitos de la berenjena y el higo mostraron niveles más altos en el TOC de 0-5 cm de profundidad, y MWD en la profundidad de 5-10 cm. Valores de SI más de 1 se encontraron en las áreas del higo y maracuyá. En general, la fracción Fl representados la mayoría de los TOC y en todos los ámbitos, tanto en las profundidades estudiadas. El SAF tiene la proporción más baja del COT en las cuatro fracciones (0-5 cm). El área de berenjena (0-5 cm) mostraron mayores niveles de carbono en las fracciones F1, F2 y F3. Sin embargo, la profundidad de 5-10 cm, este comportamiento se observó para el área de cultivo de maíz, excepto para la fracción Fl. Los resultados indican que la dirección adoptada en el área de maíz que está desfavoreciendo la agregación de los suelos y el TOC. Al igual que en otros ámbitos, el SI encuentrado muestra que la forma de cultivo, asociadas con el tipo de cubierta vegetal, en los sistemas orgánicos, son la preservación de la agregación del suelo, en comparación con el área de bosque, en la profundidad de 0-5 cm. Los niveles de carbono oxidables fueron influenciados por los sistemas de gestión adoptados, siendo mayor en las áreas que más contribuyen a la tierra los residuos de la planta.

O objetivo deste estudo foi avaliar o efeito da calagem nos atributos químicos do solo, na produção de matéria seca e no acúmulo de N, P e K na cultura do feijoeiro, conduzido em casa-de-vegetação. Foram utilizadas amostras de terra da camada de 0-20 cm de um Organossolo da região de Santa Cruz, RJ. O delineamento experimental foi o inteiramente casualizado, com seis tratamentos e cinco repetições. Os tratamentos constituíram-se em cinco níveis de saturação por bases (V%): 30; 45; 60; 75 e 100% e o controle, com saturação natural do solo. Ao final do ciclo da cultura, foi coletada a parte aérea das plantas, que foi seca em estufa a 65 ºC até peso constante. Em seguida, determinou-se a produção de matéria seca e o acúmulo de N, P e K. Após a coleta, foram retiradas amostras de terra dos vasos nas quais foram determinados os valores de pH (em H2O), Ca, Mg, Na, H+Al, Al, P e K. Foi verificado que, na saturação por bases de 43%, o Al foi totalmente neutralizado e houve aumento do pH do solo e dos teores de Ca, sem apresentar diminuição dos teores de P disponível. A produção de matéria seca e o acúmulo de nutrientes ajustaram-se a um modelo quadrático em função do aumento da saturação por bases. Houve aumento significativo na produção de matéria seca e na extração de N, P e K pelo feijoeiro a partir da menor dose de calcário aplicada, sendo decrescentes os incrementos com a aplicação de doses maiores de calcário.

The objective of this study was to evaluate the liming effect on the soil chemical attributes, biomass production and N, P and K content in a bean crop, in a greenhouse experiment. Were used soil samples collected from 0-20 cm layer of a Histosol in the region of Santa Cruz, Rio de Janeiro State, Brazil. The experimental design was randomized, with six treatments and five replications. The treatments consisted of five base saturation (V) values: 30; 45; 60; 75; 100%, and a control with natural soil saturation. At the end of the cycle, the biomass was collected and dried in an oven at 65 ºC for 48 hours. After drying, were determined the weight of dry matter and N, P and K content. After plant collection, soil samples were collected from the pot, and pH, Ca, Mg, Na, H+Al, Al, P and K were determined. It was verified that the saturation to 43% the Al was completely neutralized and a significant increase in Ca, without reduced available P in the soil. The biomass production and nutrient accumulation described a quadratic model as a function of bases saturation increasing. There was a significant increase in dry matter production and N, P and K extraction by bean from the lowest liming rate, and decreasing the increments with the higher doses of lime application.

O objetivo deste estudo foi verificar a influência do manejo agroecológico na distribuição dos agregados estáveis em água e no teor de carbono orgânico dos agregados em diferentes coberturas vegetais. Foram selecionadas cinco áreas, a saber: sistema agroflorestal; cultivo de figo (Ficus carica L.); consórcio maracujá (Passiflora edulis S.)-Desmodium sp.; cultivo de feijão (Phaseolus vulgaris L.), em manejo convencional, e cultivo de milho (Zea mays L. ), em plantio direto. Em cada área, foram coletadas amostras de terra indeformadas, nas profundidades de 0 - 5 e 5 - 10 cm, e avaliada a estabilidade dos agregados e o teor de carbono orgânico nos agregados (COAGR). A maior massa de agregados encontra-se na classe de 2,00 mm, em ambas as profundidades, com exceção do cultivo de feijão. Nas duas profundidades, a classe de 2,00 mm apresentou os maiores valores de COAGR para a área do consórcio macaracujá - Desmodium sp.

The objective of this study was to verify the influence of agroecological handling in the distribution of stable aggregates in water and in the levels of aggregate organic carbon under different vegetable covers. Five areas were selected: agroflorestal system; fig cultivation (Ficus carica L.); passion fruit (Passiflora edulis S.) and Desmodium sp. consortium; bean cultivation (Phaseolus vulgaris L.), under conventional system; and corn (Zea mays), in no-tillage system. In each area, undisturbed samples were collected, in 0-5 and 5-10 cm depths, and water aggregate distribution and organic carbon of aggregate (OCAGR) were quantified. The highest aggregate mass was observed in the 2.00 mm aggregate class, in both depths, except for the bean cultivation area. In both depths, the class with greater diameter showed the highest OCAGR values for the area of passion fruit - Desmodium sp. consortium.

O aporte de matéria orgânica ao solo via leguminosas em sistemas de aleias pode ser uma alternativa para o uso sustentável do trópico úmido. O objetivo deste trabalho foi comparar o aporte de matéria orgânica facilmente oxidável proveniente da combinação de resíduos de diferentes leguminosas utilizadas em sistemas de condução de culturas em aleias sob Argissolo Vermelho-Amarelo. Foram avaliadas duas espécies de leguminosas de alta qualidade de resíduos - leucena (Leucaena leucocephala) e guandu (Cajanus cajan), e duas espécies de baixa qualidade de resíduos - sombreiro (Clitoria fairchildiana) e acácia (Acacia mangium), combinadas entre si, nos seguintes tratamentos: sombreiro + guandu; leucena + guandu; acácia + guandu; sombreiro + leucena; leucena + acácia e testemunha sem leguminosa. As amostras de solo foram coletadas nas profundidades de 0-5 e 5-10 cm, nas entrelinhas. Foi quantificado e fracionado o C orgânico total (COT), estratificado em quatro frações (F1, F2, F3 e F4) com graus decrescentes de oxidação. As áreas com sombreiro/leucena, acácia/leucena e acácia/guandu apresentaram os maiores teores de COT (0-5 cm), e a área testemunha, os menores (5-10 cm). A maior proporção do COT estava nas frações F1+F2; a área testemunha teve os menores teores de C nessas frações. O tratamento acácia/guandu apresentou maiores teores de C na fração F1 nas duas profundidades. O tratamento leucena/guandu apresentou as maiores proporções do COT nas frações F3 + F4. Os resultados indicam que, no cultivo em sistema de aleias, a combinação de leguminosas de alta e baixa qualidade de resíduos (acácia/guandu) favorece o aumento de matéria orgânica facilmente decomponível, enquanto o uso de leguminosas de alta qualidade de resíduos favorece maiores proporções de C somente nas frações mais resistentes (F3 + F4).

The input of organic matter to the soil by legumes in alley cropping systems may be an alternative for a sustainable soil use in the humid tropics. The objective of this study was to compare the input of oxidizable organic matter in a combination of residues from different legumes in alley cropping systems on an Ultisol. Two legume species were evaluated: leucena (Leucaena leucocephala) and pigeon pea (Cajanus cajan), which have high-quality residues, and Philippine pigeonwings (Clitoria fairchildiana) and acacia (Acacia mangium), with low-quality residues. The residues were combined in the following treatments: Philippine pigeonwings + pigeon pea; leucena + pigeon pea; acacia + pigeon pea; Philippine pigeonwings + leucena; leucena + acacia; an area without legumes was used as control. Soil samples were taken from the layers 0-5 and 5-10 cm in the crop inter-row. Total organic carbon (TOC) was quantified and divided into four fractions (F1, F2, F3 and F4) with decreasing oxidation degrees. In the areas with Philippine pigeonwings/leucena, acacia/leucena and acacia/pigeon pea the TOC content was higher at the depth of 0-5 cm. In the area without legumes the TOC content was the lowest at the depth of 5-10 cm. The highest TOC proportion was observed in the F1+F2 fractions, and the carbon contents for these fractions were lower in the area without legumes. In the acacia/pigeon pea treatment the C content was higher in the F1 fraction at both depths, while the TOC proportions were greater in the treatment leucaena/pigeon pea in the fractions F3 + F4. The results indicate that the combination of high and low quality residues (acacia/pigeon pea) favors the increase of easily decomposable organic matter, while the use of high-quality residues resulted in higher carbon proportions in the more resistant fractions (F3 + F4).