RESUMONeste trabalho objetivou-se avaliar o efeito do monocultivo e do consórcio de macaúba e pastagem sobre a qualidade química e os compartimentos de carbono em Latossolo Vermelho-Amarelo no Cerrado Maranhense. Foram estudados quatro sistemas de uso do solo: macaúba, pastagem, macaúba consorciada com pastagem e vegetação nativa de cerrado. Nesses sistemas foram coletadas amostras de solo da superfície até 60 cm, para determinação dos atributos químicos e dos teores e estoques de carbono orgânico do solo. Os maiores valores de P, K, Ca e Mg foram observados nas áreas sob pastagem. Os estoques de carbono orgânico total e os teores de carbono lábil foram maiores no solo com vegetação nativa até 60 cm de profundidade, seguida pelo sistema macaúba associada com pastagem. Maiores valores de carbono da biomassa microbiana e de quociente microbiano foram observados no solo sob pastagem em todas as camadas. A presença da pastagem é importante no consórcio com macaubeiras pois aumenta os níveis de fertilidade do solo e os estoques de carbono favorecendo a melhoria da qualidade do solo nas condições do cerrado maranhense. Palavras-chave: cerrado, oleaginosas, agrofloresta, fertilidade do solo, matéria orgânica do soloChemical quality of soil and dynamics of carbon under monoculture and intercroping of acrocomia palm and pasture ABSTRACT This study aimed to evaluate the effects of the cultivation of acrocomia palm (Acrocomia aculeata) intercropped or not with pasture on the chemical quality and carbon pools of an Oxisol of the Savanna of Maranhão state. Four land use systems were studied: acrocomia, pasture, acrocomia intercropped with pasture and savanna native vegetation. Soil samples were collected up to 60 cm depth for determination of chemical attributes and soil organic carbon contents and stocks. The highest values of P, K, Ca and Mg were observed in the soil under pasture. Total organic carbon stocks and labile carbon content were higher under native vegetation up to 60 cm followed by acrocomia intercropped with pasture system. Higher values of microbial biomass carbon and microbial quotient were verified in the soil under pasture in all depths. Pasture is important to be intercropped with acrocomia since it increases the soil fertility levels and soil carbon stocks favoring the improvement of the soil quality in the Savanna of Maranhão state.

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Cowpea (Vigna unguiculata L Walp) is a legume of great social and economic importance in tropical regions. The plant is tolerant to soil and climatic adversity, while it has high nutritional value with high protein, minerals and vitamins contents. The cowpea legume has a very high ability to fix N 2 which is important because it can reduce the costs of soluble mineral fertilizers and may contribute to sustainable agriculture, preserving the environment and natural resources. In order to observe the influence of Rhizobia the agronomic effectiveness of cowpea strains was tested in two consecutive years compared with the mineral N fertilization. The experiments were carried out in different soils of the Brazilian Northeast (semiarid and rain forest region) which measured the effectiveness of rhizobia on grain yield. The results revealed the effectiveness of strain BR 3299 in the experiment that significantly increased the grain yield (3 times when 50 kg ha -1 of N, and 2 times when 80 kg ha -1 N were used). The Rhizobia treatment promoted the grain yield (up to 1,600 kg ha -1 ), compared to application of 80 kg ha -1 of N. In general, all applied strains promoted the Brazilian Northeast average cowpea yield (300-400 kg ha -1 ).

R E S U M OObjetivou-se, neste estudo, avaliar a variabilidade espacial das frações da matéria orgânica do solo em uma área degradada em recuperação com pinhão-manso; para isto se estabeleceu, em um Argissolo Vermelho-Amarelo, uma malha de 30 por 30 m para amostragem, totalizando 55 pontos. Em cada ponto foram coletadas amostras de solo nas camadas de 0-0,05; 0,05-0,10 e 0,10-0,20 m e determinados carbono orgânico total (COT), carbono lábil (CL) e o carbono das frações ácido fúlvico (C-FAF), ácido húmico (C-FAH) e humina (C-HUM). Os maiores teores de COT foram observados na camada de 0-0,05m e variaram de 2,0 a 15,5 g kg Spatial variability of the soil organic matter fractions in degraded area under recovery A B S T R A C TThe present study aimed to evaluate the spatial variability of soil organic matter fractions in degraded area under recovery by planting Jatropha curcas. For this purpose, a grid of 30 by 30 m was established for sampling, totalizing 55 points. At each point, soil samples were collected in the 0-0.05, 0.05-0.10 and 0.10-0.20 m depths. Total organic carbon (TOC), labile carbon (LC) and fulvic acid fraction (FAF), humic acid fraction (HAF) and humin fraction (HUM) carbon were determined. The FAF at 0-0.05 and 0.10-0.20 m depths and FAH at 0.10-0.20 m depth showed coefficient of variation of 66, 74 and 77%, respectively, considered high. The other variables showed mean CV ranging from 32 to 58%. With the exception of the FAF and HUM (0-0.05 m), the other attributes showed spatial dependence classified as moderate or strong, varying from 39.6 and 410.9 m. Very low values of the total organic carbon and their fractions highlighted the soil degradation and indicate the need to increase carbon inputs using crops with high amount of residues. Palavras-chave:carbono orgânico do solo substâncias húmicas geoestatística krigagem

The silvopastoral system avoids the degradation of tropical grasslands by providing essential nutrients to the soil while improving livestock diet and farmer's income by increasing the marketable wood supply. We hypothesize that intercropping shrub‐tree legumes into signalgrass increases microbial activity and soil organic matter (SOM) quality. We investigated silvopastoral system soils over 5 yr in a subhumid climate in northeastern Brazil to determine the total C and N contents and to estimate C‐microbial biomass and respiration, microbial and metabolic quotients, humic acid (HA), and fulvic acid (FA). The experimental design evaluated (a) signalgrass intercropped with gliricidia at 0, 4, and 8 m from the center of the double legume row; (b) signalgrass intercropped with sabia at 0, 4, and 8 m from the center of the double legume row; and (c) single signalgrass. Samples were obtained after 2, 3, 4, and 5 yr from silvopastoral system implementation. The shrub‐tree legumes soils had total C (39 g kg−1) and total N (3.8 g kg−1) contents significantly higher (30 and 72%, respectively) than single signalgrass soil only on the fifth year after establishment. Microbial biomass C at 0 and 4 m from the legume's rows was 700 mg kg−1, which was 75% higher than single signalgrass soils. There was strong microbial respiration (∼50 mg C‐CO2 kg−1 d−1) in legumes soils, but the metabolic quotient did not indicate disturbance in microbial activity. The microbial quotients were significantly higher in shrub‐tree legumes soil, and the HA/FA ratio was nearly 1, demonstrating greater efficiency in SOM decomposition by microbial activity. Overall, 5 yr after establishment, the silvopastoral system has improved SOM quality and contributed to grassland sustainability.