The scarcity of water in semiarid regions requires alternative sources for irrigation to improve agricultural production. Here, we aimed to evaluate the effects of produced water from oil exploration on the structure of soil mesofauna during the dry and rainy seasons in irrigated sunflower and castor bean fields in a Brazilian semiarid region. Three irrigation treatments were applied on plots cultivated with castor beans and sunflowers: produced water treated by filtration (filtrated) or treated by reverse osmosis (reverse osmosis) and groundwater. The mesofauna under the biofuel crops was collected and identified during the dry and rainy seasons. Although the abundance and richness of the total fauna did not differ between seasons in sunflower plots, the community was altered. In castor beans, the abundance, richness, and community of mesofauna observed in plots irrigated with produced water differed from the groundwater treatment. Irrigation with produced water promotes important changes in soil fauna community that justify their assessment for the maintenance and monitoring of agroecosystems.
As Ciências Naturais (CNs) são formadas por disciplinas de essência experimental, portanto, para que o processo de ensino e aprendizagem seja efetivo, faz-se necessário o uso de aulas práticas realizadas em laboratório. Este estudo, que tem como objetivo avaliar a utilização de laboratórios pelos/as docentes de CN do ensino fundamental – anos finais, está relacionado com a formação acadêmica, enfocando a importância da realização de aulas práticas. É uma pesquisa de abordagem qualitativa, com aplicação de um questionário contemplando, ao todo, 24 professores/as dos municípios de Abaiara, Brejo Santo e Milagres que lecionam em escolas da rede pública municipal, nos anos finais do ensino fundamental. Dessa forma, foi possível observar, entre os/as entrevistados/as, que 50% são formados nas áreas que compreendem as CNs, porém é perceptível que professores/as que não são de áreas afins às CNs ministram aulas nessa disciplina. Também foi possível observar que, na região estudada, o/a docente, mesmo formado/a dentro da área de CN, considera sua formação acadêmica insuficiente para conduzir aulas práticas de laboratório. As dificuldades encontradas pelos/as docentes perpassam sua formação e também estão atreladas à falta de estrutura física e à localização das escolas onde lecionam.
Wastewater from oil exploration may contain substances that can alter the diversity of soil organisms. This study evaluated whether produced water treated by filtration or reverse osmosis and glutaraldehyde from reverse osmosis treatments negatively affected the mesofauna in an irrigated area. In the field, irrigation with produced water treated by reverse osmosis and filtration influenced Hymenoptera and Cosmochthonius sp., while Entomobryomorpha springtails were affected only by the reverse osmosis water. In the ecotoxicological tests, reproduction in the springtail Folsomia candida was inhibited by the reverse osmosis treatment, while reproduction in the earthworm Enchytraeus crypticus was affected by both water treatments. Although glutaraldehyde did not affect the survival of F. candida, the reproduction was inhibited (EC50 = 44.4 mg/L). No adverse effect of glutaraldehyde was observed on reproduction or survival of E. crypticus. These results indicate that produced water, when used in irrigated agriculture, may affect soil functional mesofauna.
In northeast Brazil, the most part of vegetation is a deciduous seasonally dry tropical forest called of “Caatinga”. Despite the semi-arid areas correspond to most of the caatinga vegetation, there are some areas 500 m above sea level with an annual rainfall up to 1200 mm forming evergreen forest enclaves. Macroarthropod abundance and fauna composition differences in Caatinga are related to seasonal rainfall effects but, this difference is unclear in the enclaves of evergreen forests. Thus, the aim of this study was to measure the effects of rainfall on insect, arachnid, and centipede assemblages in an enclave of evergreen forest within the Caatinga vegetation. We tested the following hypotheses: 1) rainfall changes arthropod abundance and species richness; 2) predator abundance correlate with prey, and 3) abundance arthropod abundance and species richness exhibit a delayed or anticipated response to rainfall. No effects of rainfall on insects and arachnids abudance were observed. There was a significant correlation between prey and predator abundance with changes in dominant species between the rainy and dry seasons. The insects and arachnids can show some anticipated responses to rainfall. The abundance and richness of centipedes were influenced by rainfall whith a delayed response. Our findings indicate that, in evergreen forest enclaves within Caatinga vegetation, the soil arthropods show different responses compared to rainfall than the most common areas of the Caatinga domain and an increase in the detection of insects and arachnids just before the beginning of the rainy season.
The purpose of this study was to evaluate the diversity of herbaceous plants and arbuscular mycorrhizal fungi following the cultivation of sunflower (Helianthus annuus L., cv. BRS 321) irrigated with produced water. The sunflower plants were irrigated during three successive cycles with different types of water: produced water obtained through simple filtration (PWSF), and secondly, produced water treated by reverse osmosis (PWRO), and the control with groundwater from the aquifer Açu (WCA). In June 2014, five months after the final harvest, the treatments were evaluated in terms of the diversity of successor plants and their roots colonized by arbuscular mycorrhiza (AM); and samples of soil, in which the following were measured: the spore abundance of AM fungi, the levels of glomalin in easily extracted glomalin and total glomalin. Of a total of eighteen species of herbaceous plants which were identified in the experimental field, Dactyloctenium aegyptium was related with the use of PWSF, Panicum sp. and Diodella apiculata with the use of PWRO, and Trianthema portulacastrum and Eragrostis tenella with the control WCA. The diversity of AM fungi was affected by irrigation with PWSF, in which two species of Acaulospora, one species of Gigaspora and species of Paraglomus were absent, compared to the treatment with PWRO. Acaulospora sp.1 was related with the WCA control as an indicator species. The use of produced water which had undergone reverse osmosis had a shortterm effect on the content of glomalin which is easily extractable from the soil but did not change the mycorrhization rates of plants. These results enable us to infer that irrigation with produced water leads to a reduction in the diversity of herbaceous plants and of arbuscular mycorrhizal fungi in the soil, confirming the importance of monitoring agro-systems irrigated with residual water.
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