Microbiological soil attributes of a pasture area with surplus irrigation of wastewater effluent / Atributos microbiológicos do solo em área de pastagem irrigada com lâminas excedentes de efluente de esgoto tratado

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

Crop irrigation with treated sewage effluent (STE) is an interesting and attractive practice, when applied in a controlled manner, as well as it makes possible the release of water of better quality for other human activities and serves as a way to polish the STE through the "biological filter" comprising the soil-plant system. However, wastewater irrigation is a recent practice in Brazil and little is known about its effects on the quality of tropical soils. The aim of this work was to evaluate the effects of surplus irrigation with STE of a pasture area cultivated with BermudagrassTifton 85 for 18 months, on the microbial activity, functional groups of microorganisms, on the community-level physiological profile and on the community structure of ammonia oxidizing bacteria. The experiment was carried out at the municipal district of Lins, São Paulo State, close to the sewage treatment plant (STP), operated by Sabesp (Companhia de saneamento básico do Estado de São Paulo), cultivated with bermuda grass Tifton 85 (Cynodon dactylon Pers. X C. niemfuensis Vanderyst). The treatments were based on the amount of irrigation required for the adequate water amount necessity for this pasture grass, and other 3 surplus irrigation treatments, as follow: 0% of excess (control), 25%, 50% and 100% of excess of STE irrigation. Surplus STE pasture irrigation for 18 months changed soil chemical and microbiological parameters. The evaluation of surplus STE irrigation and also the precipitation effects decreased the soil pH and exchangeable magnesium and potassium, while it increased the exchangeable calcium and sodium. The root colonization of Bermudagrass by arbucular mycorrhizal fungi was not affected by surplus STE irrigation, after 18 months. The principal response curve analysis demonstrated that the functional groups of microorganisms: ammonifiers and denitrifiers, were the most affected by surplus STE irrigation. The treatment with 25% of surplus irrigation caused only minor variation on the functional groups of microorganisms, compared to the control irrigation. The soil microorganisms metabolic potential, evaluated by the kinetic of carbon substrates consumption, using Biolog Ecoplates, was stimulated by STE irrigation. Even 100% surplus STE irrigation did not cause a significant modification of the the microbial communities metabolic potential, when compared to the control STE irrigation. STE irrigated pasture areas presented dominance of the genus Nitrosospira, among ammonium oxidizing bacteria.

ASSUNTO(S)

bermudagrass wastewater irrigação irrigation microbiologia do solo pasture. análise multivariada capim tifton multivariate analisys pastagens. Águas residuárias soil microbiology

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