Atributos físicos do solo, adubado com lodo de esgoto e silicato de cálcio e magnésio

Este trabalho teve como objetivo avaliar o efeito da aplicação de lodo de esgoto e de silicato de cálcio e magnésio sobre os atributos físicos de um Cambissolo Háplico, cultivado com girassol. Os tratamentos foram distribuídos em esquema fatorial (4 x 2) + 1, correspondendo a quatro doses de lodo de esgoto desidratado (0; 6,25; 12,5 e 18,5 t ha-1), duas doses de silicato de cálcio e magnésio (0 e 240 g m-1) e um tratamento adicional com adubação mineral. O delineamento utilizado foi em blocos casualizados, com três repetições. Após 150 dias da adubação, coletaram-se amostras de solos, nas camadas de 0-20 e 20-40 cm, para avaliação da densidade aparente, densidade de partícula, porosidade total, grau de dispersão, grau de floculação, índice de estabilidade de agregados, diâmetro médio ponderado, diâmetro médio geométrico e resistência do solo à penetração. O tratamento adicional, correspondente à adubação mineral, não diferiu dos tratamentos correspondentes às adubações com lodo de esgoto e silicato de cálcio e magnésio, em relação aos atributos físicos do solo. Para o silicato de cálcio e magnésio, também não se constataram diferenças nos atributos físicos do solo, entre a dose zero e 240 g m-1. Por outro lado, a aplicação de lodo de esgoto diminuiu o grau de dispersão de argila e aumentou a porosidade total do solo, o grau de floculação de argilas e o índice de estabilidade de agregados a úmido, não tendo, porém, influenciado os demais atributos físicos

Biomarkers indicate mixture toxicities of fluorene and phenanthrene with endosulfan toward earthworm (Eisenia fetida)

alpha-Endosulfan and some polycyclic aromatic compounds (PAHs) are persistent in the environment and can reach crop products via contaminated agricultural soils. They may even be present as mixtures in the soil and induce mixture toxicity in soil organisms such as earthworms. In this study, the combined toxicities of PAHs with alpha-endosulfan were determined in Eisenia fetida adults using an artificial soil system. alpha-Endosulfan and five PAHs were tested for their acute toxicity toward E. fetida in artificial soils. Only alpha-endosulfan, fluorene, and phenanthrene showed acute toxicities, with LC50 values of 9.7, 133.2, and 86.2 mg kg(-1), respectively. A mixture toxicity assay was conducted using alpha-endosulfan at LC10 and fluorene or phenanthrene at LC50 in the artificial soils. Upon exposure to the mixture of fluorene and alpha-endosulfan, earthworms were killed in increasing numbers owing to their synergistic effects, while no other mixture showed any additional toxicity toward the earthworms. Along with the acute toxicity results, the biochemical and molecular changes in the fluorene- and phenanthrene-treated earthworms with or without alpha-endosulfan treatment demonstrated that enhancement of glutathione S-transferase activity was dependent on the addition of PAH chemicals, and the HSP70 gene expression increased with the addition of alpha-endosulfan. Taken together, these findings contribute toward understanding the adverse effects of pollutants when present separately or in combination with other types of chemicals.ope

Effect of organic amendment on soil fertility and plant nutrients in a post-fire Mediterranean ecosystem

International audienceBackgrounds and aims In Mediterranean frequentlyburnt areas, the decrease of soil fertility leads to regressivevegetation dynamics. Organic amendments couldhelp to accelerate post-fire ecosystem resilience, byimproving soil properties and plant nutrition. This studywas conducted to assess the potential of a compostedbiosolid to restore an early post-fire shrubland.Methods About 50Mg.ha−1 of fresh co-composted sewagesludge and green wastes were surface applied7 months after fire on a silty-clayey soil. We monitoredover a 2-year period organic matter and nutrient transfersto soil, nutrient responses of dominant plant species,and ecosystem contamination by potentially toxic traceelements.Results Over the experimental survey, compost rapidlyand durably improved soil P2O5,MgO and K2O content,and temporarily increased N-(NO3− + NO2−) content.Plant nutrition was improved more or less durably dependingspecies. The most positive compost effect wason plant and soil phosphorus content. Plant nutrientstorage was not improved 2 years after amendment,suggesting luxury consumption. No contamination bytrace elements was detected in soil and plant.Conclusions The use of compost after fire could helpfor rapidly restoring soil fertility and improving plantnutrition. The increase of soil nutrient pools afteramendment emphazised the diversity of plant nutritionaltraits. Eutrophication risk could occur from high compostand soil P2O5 content