El objetivo fue evaluar la calidad del agua de arroyos colectores de cuenca de los departamentos Federal, Federación, Feliciano y Diamante, vinculados a las represas para riego de cultivos, en situación de aguas bajas. Se muestrearon 12 ambientes de arroyos incluyendo un inventario de la vegetación. Se tomaron muestras de agua para análisis físico-químico y para la realización de dos tipos de bioensayos: Allium test y germinación de semillas de Lactuca sativa. La longitud radicular e índice de germinación, variables registradas en ambos bioensayos, se analizaron mediante la prueba Dunnet. Los arroyos del centro norte de Entre Ríos presentaron bajos valores de RAS (<10) y conductividad eléctrica (CE) menor a 750 μS cm-1. En los arroyos del departamento Diamante la CE osciló entre 910 y 1170 μS cm-1. La prueba de Allium test fue negativa al igual que el bioensayo de toxicidad en germinación de semillas de lechuga. Los análisis físicoquímicos y los bioensayos indicaron aptitud para el riego y sin toxicidad en las aguas de los arroyos del centro norte de Entre Ríos, mientras que los del departamento Diamante, si bien no presentan toxicidad, no resultarían aptos para el riego de los cultivos en época de estiaje por su alta CE.
We analyze the short term effect of the harvest residues management on the Phosphorus (P) fractions of the soil. Four trials were installed in Northeast Argentina on Vertisols (S1), Mollisols (S2) and Entisols (S3 and S4). In S1 and S2 harvest residues and forest fl oor were either (1) removed (R), (2) retained (RR), 3) burnt (BR), or (4) retained at double the normal quantity (DR). In S3 and S4 harvest residues where (1) removed (WTH), 2) retained (RR) or 3) burnt (BR). Soil samples were obtained at 0-5 cm and 5-10 cm depth layers at 18 (S1), 22(S2, S3) and 10 (S4) months after burnt treatments. P fractions were determined according to Hedley et al. (1982) methods. Soil orders showed different total P: in Mollisols P concentration (S2: 314,3 mg kg -1 ) tripled those in Entisols (S3 y S4: 118,4 mg P kg -1 ). Differences were even higher for Organic P (P o ): the highest concentration was found in Mollisols (171,4 mg P o kg -1 ) related to its higher organic matter, and the lowest concentration was in Entisols (44,0 mg Po kg -1 ). Available P was between 14 mg kg -1 and 25 mg kg -1 , enough to satisfy annual demands of forest plantations (Eucalyptus and Pinus). RR and DR did not show changes in the P fractions, although an increase in the P reserves (P o y P t ) could be expected for the middle term, due to the decomposition of the retained/added residues. R or WTH did not affect neither inorganic nor organic P fractions. The most important change was found in BR, where the available P and other mean and highly stable inorganic P fractions increased, due to the ashes; the P o was not modifi ed. The fi re was an instant mechanism to transfer the nutrients from the biomass to the soil.
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