Desempenho de leguminosas arbóreas no estabelecimento de um sistema agroflorestal com bananeiras

Abstract

The Agroforestry Systems (SAF) bring multiple benefits and they are an alternative to minimize environmental degradation, and to achieve a sustainable development, due to greatest diversity of species. This study evaluated the contribution of the leguminous trees, Gliricidia sepium and Acacia angustissima, grown in alley cropping of banana (Musa sp.), used as green manure in the implantation of a Agroforestry System. They were compared the production of biomass, nutrients cycling, nitrogen intake, activity and diversity of soil fauna, and banana productivity in the SAF, and with the usage of the legume Pueraria phaseoloides and nitrogen fertilization. The SAF implantation occurred in May 2004, at the Research Center of Embrapa Agrobiologia, municipality of Seropédica, Rio de Janeiro State. It was composed of açaí palm (Euterpe oleraceae) and banana tree (Musa sp.), whose seedlings were planted in October 2005. The following year it was planted the forest African mahogany specie (Kaya senegalensis), at the centre of the legumes alleys. The experimental design was of randomized blocks with five treatments and four repetitions. The treatments consisted of the leguminous trees arranged between the lines of bananas and the açaí palm, and they were: acacia angustíssima (Acacia angustissima), tropical kudzu (Pueraria phaseoloides), and gliricidia (Gliricidia sepium); besides application of nitrogen as urea and spontaneous vegetation. To quantify the production of biomass, and the release of N, P, Ca, Mg and K, the legumes branches were cut and the kudzu tropical and spontaneous vegetation were mowed, in the rainy and dry seasons. The determination of remaining dry matter, releasing of nutrients, decomposition rates, and half life time of plant residues were held to 50 grams of fresh material from litterbags, placed on the soil surface, sampled at 0, 5, 10, 15, 20, 25, 30, 40, 60 and 75 days after the installation of the experiment. Acacia angustíssima and kudzu tropical showed higher dry biomass, 9.5 and 10.8 Mg.ha-1, respectively. The gliricidia residues showed the highest decomposition rates, in the two year seasons. To assess the activity and diversity of soil fauna there were installed traps of the type pitfall and TSBF. The litter was removed and the soil blocks were divided into three layers: 0-10, 10-20 and 20-30cm. In the kudzu tropical area, it was verified the greatest number of individuals, 416 ind/arm/dia-1, followed by gliricidia, spontaneous vegetation and Acacia angustíssima, with no statistical difference between treatments. By the TSBF method, the treatments with leguminous trees, in the 0-10cm layer, showed higher numbers than the spontaneous vegetation, with more fauna groups in the layers of 0-10 and 10-20cm. Regarding the growing development of banana, at 5 months and 11 months after planting, there was difference in average height of the pseudo stem in Acácia angustíssima treatment, and in the average diameter of pseudo stem in Acácia angustíssima and gliricidia. Taken the medium length and diameter of the fruit per banana bunch, as well as the productivity and weight of the bunch, weight of hands, number of fruit per bunch and number of hands per bunch, there was no difference between treatments. The productivity of banana in the first cycle has averaged 13Mg.ha-1. It is noted that the initial banana crop production was not affected by the presence of the Acacia angustissima e Gliricidia sepium trees.