RESUMEN

Organic composts such as "bokashi", obtained from the fermentation of bran mixtures and inoculated with microorganisms, improve soil characteristics. In Brazil, the most widely used formulation for the production of this compost is obtained from a mixture of wheat and castor bean bran, but both have a high monetary cost. Replacing these components with regionally available sources represents the possibility of reducing costs and making more sustainable use of this waste. The aim of this study was to analyze the chemical characteristics and determine the availability of nitrogen for the plants. The study was divided into two stages, consisting of an incubation test in the laboratory and a bioassay in the greenhouse using forage sorghum as an indicator species. In the laboratory trial, the treatments consisted of two raw material sources with a low C/N ratio (castor bean bran-CAB and cottonseed bran-COB), corresponding to 40% of the mixture; three sources with a high C/N ratio (wheat bran-WHB or rice bran-RIB), gradually replaced by passion fruit peel bran-PFPB), corresponding to 60% of the mixture. The materials were mixed, moistened, inoculated with microorganisms (Embiotic®) and kept in sealed containers with a capacity of 620 cm3 for 21 days. In the greenhouse, in addition to the aforementioned treatments, seven controls were included: no addition of organic and synthetic N sources; ammonium nitrate; CAB; COB; WHB; RIB and PFPB. In the second stage, dry mass production and N content in sorghum plant tissues were determined, and the rates of N availability were estimated. It was found that the pH of the standard compost was 4.75, and in the other formulations it ranged from 4.62 to 5.3, the highest values being observed when WHB was fully replaced by RIB There was a significant difference in the EC values, but all were well below the value considered adequate. Replacing CAB with COB and WHB with RIB and PFPB resulted in a reduction in N content and an increase in the C:N ratio. Replacing WHB with PFPB led to an increase in K content and a reduction in P and Mg content. In the bioassay, the highest biomass production was in the treatments with the fermented composts, and the highest biological recovery of N was obtained in the ammonium nitrate treatment, followed by the CAB, COB and WHB treatments.

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RESUMEN

O emprego de plantas de cobertura em consórcio com bananeiras pode ser uma estratégia de manejo, possibilitando aumentos de produtividade associados à otimização de processos biológicos e maior estabilidade do sistema produtivo. Neste trabalho, objetivo-se avaliar o efeito da cobertura viva, formada por leguminosas herbáceas perenes sobre a produção de bananeira cultivar Nanicão. Os tratamentos foram: amendoim forrageiro (Arachis pintoi Krap. & Greg), cudzu tropical (Pueraria phaseoloides Benth.), siratro (Macroptilium atropurpureum Urb.), vegetação espontânea (dominada por Panicum maximum Jacq.) e vegetação espontânea + N-fertilizante. Foi avaliado o desenvolvimento vegetativo das bananeiras entre abril/1999 e julho/2000 e os atributos de produtividade. O peso do cacho e da penca foram positivamente influenciados pelo siratro e cudzu tropical empregados como coberturas vivas, quando comparados aos demais tratamentos. Todas as leguminosas proporcionaram maior crescimento das bananeiras (notadamente a partir do 6º mês), maior número de folhas emitidas e maior proporção de cachos colhidos, em relação aos tratamentos com vegetação espontânea (com e sem N-fertilizante). As leguminosas siratro e cudzu tropical promoveram condições adequadas ao desenvolvimento das bananeiras, acarretando ganhos de produtividade e eliminação da adubação nitrogenada no bananal. O potencial benéfico das leguminosas cudzu tropical e siratro como coberturas vivas capazes de proporcionar aumentos na produtividade de banana, qualifica essas espécies como alternativa promissora para a fertilidade do solo e nutrição das bananeiras.

The use of coverage plants in cover cropping with bananas can be a management strategy, increasing in productivity associated with the optimization of biological processes and greater stability of production system. The objective of this work was to evaluate the effect of live coverage by herbaceous perennial legume on the yield of banana cultivar Nanicão. The treatments were: forage groundnut (Arachis pintoi Krap. & Greg), tropical cudzu (Pueraria phaseoloides Benth.), siratro (Macroptilium atropurpureum Urb.), spontaneous vegetation (mainly Panicum maximum Jacq.) and spontaneous vegetation + N-fertilizer. Banana plant vegetative development and yield attributes between April/1999 and August/2000 were assessed. In comparison to other treatments, bunch and hand weight were more positively influenced by tropical cudzu and siratro legumes employed as live coverage. All legumes promoted higher vegetative growth for banana plants (notably from the 6th month on), a greater number of leaves, and a higher proportion of harvested bunches in relation to spontaneous vegetation (with and without N-fertilizer). Siratro and tropical cudzu legumes promoted adequate conditions for the development of the banana plants, generating yield gains, and the elimination of the need of nitrogenous fertilization in the banana plantation. The beneficial potential of tropical cudzu and siratro legumes as live coverage intercropping with banana plants qualify these species as promising alternatives for soil fertility and banana nutrition.

RESUMEN

Oribatid mite densities in the topsoil and their activity at the soil surface were monitored under three species of perennial legume cover crops namely, Arachis pintoi, Macroptilium atropupureum and Pueraria phaseoloides, grass (Panicum maximum) and bare plots on three occasions in 1998 and 1999 in a derived savanna zone in Brazil. Both densities and activity at the soil surface were higher in the early but cool dry season in April 1998 than in the early wet but warm season in November 1998 and 1999. Three taxonomic groups of macropyline oribatid mites, namely Nothrus, Archegozetes and Masthermannia as well as a brachypyline taxon, Scheloribates were suggested as possible indicators of effect of legumes on soil biota because their populations increased under the legumes and/or the irresidues. Nothrus in particular increased in abundance more than any other taxon in the presence of residues of A. pintoi. Each legume supported a unique oribatid mite community in terms of species composition and relative abundance. The large numbers of Archegozeres trapped from all the legume and grass plots in April and November 1998 were also attributed to highly conducive conditions provided by the vegetation cover and their residues. The results suggest that the oribatid mite community of the study area was numerically stable as the peak populations of different species were not synchronized. Many taxonomic groups of pycnonotic brachypyline mites were absent. Legume cover crops, especially A. pintoi, and their residues have potential in restoring oribatid mite populations to precultivation levels.

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