ABSTRACT. The use of organic wastes in agricultural soils is one of the possible ways to employ these materials. The aims of this study were to evaluate the effectiveness of organic wastes and Fermented Bokashi Compost (FBC), to establish the most efficient use of organic wastes for a soil, changing the net nitrogen mineralization and soil chemical properties. The experimental design was completely randomized in a 6 x 2 x 5 factorial, being five organic wastes plus an control (soil without waste), with or without FBC, evaluated at 0, 7, 42, 70 and 91 days of incubation, with three replicates, under laboratory conditions. The organic wastes enhanced the soil chemical properties and increased nitrogen concentration in soil. However, the net nitrogen mineralization was affected by C/N ratio of wastes and incubation time. The FBC mixed with the wastes accelerated and enhanced organic matter degradation, resulting in quickly available quantity of net nitrogen. The wastes can be considered potentially useful as organic fertilizer but their usefulness appears to depend on knowing the C/N ratio of each one. The FBC can be used when one wants a more accelerated degradation, resulting in a quicker quantity of available nutrients to the plants.Keywords: efficacy of microorganisms, sewage sludge, degradation, fertility.Mineralização líquida de nitrogênio e mudanças químicas no solo com a aplicação de resíduos orgânicos com 'Composto Fermentado Bokashi' RESUMO. O uso de resíduos orgânicos nos solos é uma das maneiras possíveis para empregar estes materiais. Os objetivos deste estudo foram avaliar a eficácia de resíduos orgânicos e do composto fermentado Bokashi (FBC) e estabelecer o uso mais eficiente dos resíduos, alterando a mineralização líquida de nitrogênio e as propriedades químicas do solo. O delineamento experimental foi inteiramente casualizado, em fatorial 6 x 2 x 5, sendo cinco resíduos mais um controle (solo sem resíduo), com ou sem FBC, avaliados aos 0, 7, 42, 70 e 91 dias de incubação, com três repetições, em condições de laboratório. Os resíduos orgânicos melhoraram as propriedades químicas e aumentaram a concentração de nitrogênio no solo. No entanto, a mineralização líquida do nitrogênio foi afetada pela relação C/N dos resíduos e o tempo de incubação. A mistura do FBC com os resíduos acelera e melhora a degradação da matéria orgânica, resultando em uma quantidade de nitrogênio líquido rapidamente disponível. Os resíduos estudados podem ser considerados potenciais adubos orgânicos, contudo sua utilidade parece depender do conhecimento da relação C/N de cada um. O FBC pode ser usado quando se deseja uma degradação mais acelerada, resultando em rápida quantidade de nutrientes disponíveis para as plantas.Palavras-chave: eficácia dos microorganismos, lodo de esgoto, degradação, fertilidade.
In recent years, the number of cases of heavy metal contamination has increased worldwide, leading to reports on environmental pollution and human health problems. Phytoremediation can be potentially used to remove heavy metal from contaminated sites. This study determined heavy metal concentrations in the biomass of plant species growing on a multi-metal-contaminated site. Seven plant species and associated rhizospheric soil were collected and analyzed for heavy metal concentrations. While plant Cu, Zn, Cd, Ni, Pb, As, and Ba concentrations ranged from 8.8 to 21.1, 56.4 to 514.3, 0.24 to 2.14, 1.56 to 2.76, 67.8 to 188.2, 0.06 to 1.21, and 0.05 to 0.62 mg kg(-1), respectively, none of the plants was identified as hyperaccumulators. Those in the rhizospheric soil ranged from 10.5 to 49.1, 86.2 to 590.9, 0.32 to 2.0, 3.6 to 8.2, 19.1 to 232.5, 2.0 to 35.6, and 85.8 to 170.3 mg kg(-1), respectively. However, Zn, Cd, Pb, and As concentrations in the soil outside the rhizosphere zone were 499.0, 2.0, 631.0, and 48.0 mg kg(-1), respectively. Senecio brasiliensis was most effective in translocating Cu, Cd, and Ba. The most effective plant for translocating Zn and Pb was Baccharis trimera and, for element As, Dicranopteris nervosa and Hyptis brevipes. Heavy metal and metalloid levels in spontaneous plants greatly exceeded the upper limits for terrestrial plants growing in uncontaminated soil, demonstrating the higher uptake of heavy metal from soil by these plants. It is concluded that naturally occurring species have a potential for phytoremediation programs.
SUMMARYMicrobial processes have been used as indicators of soil quality, due to the high sensitivity to small changes in management to evaluate, e.g., the impact of applying organic residues to the soil. In an experiment in a completely randomized factorial design 6 x 13 + 4, (pot without soil and residue or absolute control) the effect of following organic wastes was evaluated: pulp mill sludge, petrochemical complex sludge, municipal sewage sludge, dairy factory sewage sludge, waste from pulp industry and control (soil without organic waste) after 2, 4, 6, 12, 14, 20, 28, 36, 44, 60, 74, 86, and 98 days of incubation on some soil microbial properties, with four replications. The soil microbial activity was highly sensitive to the carbon/nitrogen ratio of the organic wastes. The amount of mineralized carbon was proportional to the quantity of soil-applied carbon. The average carbon dioxide emanating from the soil with pulp mill sludge, corresponding to soil basal respiration, was 0.141 mg C-CO 2 100 g -1 soil h -1 . This value is 6.4 times higher than in the control, resulting in a significant increase in the metabolic quotient from 0.005 in the control to 0.025 mg C-CO 2 g -1 C mic h -1 in the soil with pulp mill sludge. The metabolic quotient in the other treatments did not differ from the control (p < 0.01), demonstrating that these organic wastes cause no disturbance in the microbial community.Index terms: microbial respiration, microbial carbon, microbial nitrogen, metabolic quotient, organic sludge.(1) Part of the dissertation of the first author, for a post-graduate degree in Agricultural Sciences, 2, 4, 6, 12, 14, 20, 28, 36, 44, 60, 74, 86
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