Agroforestry systems can play a major role in the sequestration of carbon (C) because of their higher input of organic material to the soil. The importance of organic carbon to the physical, chemical, and biological aspects of soil quality is well recognized. However, total organic carbon measurements might not be sensitive indicators of changes in soil quality. Adoption of procedures that can extract the more labile fraction preferentially might be a more useful approach for the characterization of soil organic carbon resulting from different soils. This study aimed to evaluate organic carbon (C) fractions distribution in different soil layers up to 50 cm depth in two soil orders under cacao (Theobroma cacao) agroforestry systems (AFS) in Bahia, Brazil. Soil samples were collected from four depth classes (0-5, 5-10, 10-30 and 30-50 cm) under two cacao agroforestry systems (30-year-old stands of cacao with Erythrina glauca, as shade trees) in Latosol and Cambisol, in Bahia, Brazil. The determination of oxidizable carbon by a modified Walkley-Black method was done to obtain four C fractions with different labile forms of C (fraction 1: labile fraction; fraction 2: moderate labile fraction; fraction 3: low labile fraction and fraction 4: recalcitrant fraction). Overall, at two cacao AFS, the C fractions generally declined with increase in soil depth. The C fractions 1 and 2 were 50% higher on upper layers (0-5 and 5-10 cm). More than 50% of organic C was found in more labile fraction (fraction 1) in all depths for both soils. High value of C fraction 1 (more labile C)-to-total organic C ratio was obtained (around 54-59%, on Latosol and Cambisol, respectively), indicating large input of organic matter in these soils.

Aim To compare the internal balances of nutrients and the rates of nutrient cycling across nine cocoa agroforestry systems consisting of various combination of soil types (Latosols and Cambisols), production systems (cabruca and Erythrina glauca-shade) and fertilization regimes in southern Bahia, Brazil. Methods We measured nutrient stocks in litter fall production, in the accumulated litter and fruits. The internal nutrient balance for various simulations was obtained by the following expressions:(1) Balance 1=litter -fruit (seeds and husks) and (2) Balance 2=(litter+husks) -seeds. Annual litter decomposition coefficients (k) and subsequent potential of nutrient release were also investigated. The data were analyzed by principal components analysis and by Pearson correlations.

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Estudos sobre fertilização e nutrição florestal de espécies nativas e exóticas fornecem subsídios para programas de manejo para recuperação de áreas degradadas. O objetivo deste trabalho foi avaliar a produção de biomassa e a eficiência nutricional de plântulas das espécies arbóreas Swietenia macrophylla (mogno), Mimosa caesalpiniaefolia (sabiá), Cedrela fissilis (cedro-rosa) e Toona ciliata (cedroaustraliano), em resposta à fertilização fosfatada em dois níveis de calagem. Constatouse que as espécies responderam de maneira distinta à aplicação de P. O sabiá apresentou maior produção de matéria seca total e maior eficiência na utilização de P em solos com baixos teores deste elemento e foi mais responsivo à adição do fertilizante fosfatado. O mogno apresentou maior eficiência na translocação e na aquisição de P e maior relação parte aérea/raiz. As doses de P adicionadas para atingir 90% da máxima produção de matéria seca variaram de acordo com a espécie

The experiment was conducted in the municipality of Colatina-ES, Brazil, aiming at evaluating the flowering of lychee (Litchi chinensis Sonn.) in response to the girdling of branches of different diameters, located in different parts of the plant canopy and in two seasons, October 2010 and March 2011. The girdling was also carried out in October, as an attempt to extemporaneous production of litchi. As the girdling in October produced no induction of flowering, the final analysis of the experiment outlined in randomized blocks was done in 4 x 4 factorial (quadrants x branches), with four replications and one tree as experimental plot. The girdling in isolated plants consisted of: girdling branches or main branches (8.0 to 10.0 cm in diameter), girdling branches from 6.0 to 7.9 cm in diameter, girdling branches with diameters of 4.0 to 5.9 cm, and without girdling (control), located in the southeast, southwest, northeast and northwest quadrants of the plant's canopy. The amount and the length of the inflorescences and the percentage of flowering of lychee were evaluated in light of the girdling of branches and of the location of the quadrants in the canopy of the plants. It was observed that there was a difference between the amount of girdling in the variables for length and amount of inflorescences, while the girdling of branches with 8 to 10 and from 6 cm to 7.9 cm in diameter were superior to the control in girdling of branches of 4 to 5.9 cm diameter. Concerning the position of the branches in the canopy (quadrants) it was discovered that the quadrants receiving less light (southeast and southwest) had more flowers and flowering percentages, but there was no significant difference for the variable length of the inflorescence according to the quadrants. The girdling of the branches can be an alternative to the insertion of hot climates in the production of lychee.

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