Niveles de Cd, Cr, Ni y Pb extraídos mediante Mehilich-3 y DTPA en un suelo agrícola sobre sedimentos cuaternarios

The aim of this study was to determine the concentrations of extractable Cd, Cr, Ni and Pb in soils samples from a 10 ha grassland field at Castro Ribeira de Lea, Lugo (Spain). Eighty soil samples were collected at two layers of the A horizon, from 0 to 20 cm depth and from 20 cm to a variable depth defined by the boundary of the studied surface horizon, which ranged from 25 to 48 cm. Extractions of the studied elements were performed using two different solutions: Mehlich-3 and DTPA. The Mehlich-3 solution extracted higher concentrations for all the four heavy metals of interest at the two soil depths analyzed. The highest concentration recorded was for PbMehlich-3 (3.54 mg·kg-1 at 0 - 20cm and 2.67 mg·kg-1 at >20cm depths). However, mean Ni, Cr, and Cd concentrations extracted with Mehlich 3 were not higher than 0,30 mg·kg-1, while concentrations extracted with DTPA still were smaller, below 0.16 mg·kg-1- The strongest correlations between extractable concentrations of heavy metals and soil general properties were NiDTPA - pH; NiMehlich-3 - pH at >20 cm and 0-20 respectively; NiDTPA - Clay at 0-20cm, CrMehlich-3 and CdMehlich-3 - OM at 0-20 cm. Correlations with soil pH were negative, showing increasing extractability with increasing soil acidity. This notwithstanding, in our study case, the concentrations of heavy metals in the studied soil under grassland were far from levels, which are considered could be hazardous for agricultural soils. Thus, the results obtained suggest that the agricultural management (fertilizers, pesticides, etc) was appropriate in this area.El objetivo de este estudio fue determinar las concentraciones de Cd, Cr, Ni y Pb extraíbles en un suelo de pradera de 10 ha en Castro Ribeira de Lea, Lugo (España). Se recogieron 80 muestras de suelo en dos capas del horizonte A, de 0 a 20 cm de profundidad y desde 20 cm hasta el límite del horizonte estudiado; que presentó un rango de 25 a 48 cm. Las extracciones se realizaron mediante dos soluciones: Mehlich-3 y DTPA. La solución Mehlich-3 extrajo concentraciones más altas para los cuatro metales pesados en las dos profundidades del suelo muestreadas. La mayor concentración obtenida fue el PbMehlich-3 (3,54 mg·kg-1 a 0-20 cm y 2,67 mg·kg-1 a > 20 cm). Las concentraciones medias de Ni, Cr y Cd extraídas con Mehlich-3 no fueron superiores a 0,30 mg·kg-1, en tanto que las concentraciones extraídas con DTPA fueron incluso menores, siendo inferiores a 0,16 mg·kg-1. Las correlaciones más fuertes entre los metales pesados y propiedades generales del suelo fueron NiDTPA - pH; NiMehlich-3 - pH a >20 cm y 0-20 respectivamente; NiDTPA- Arcilla a 0-20 cm, CrMehlich-3 y CdMehlich-3 - MO a 0-20 cm. Las correlaciones de los metales pesados con el pH del suelo fueron negativas, obteniéndose mayores concentraciones al aumentar la acidez del suelo. Si bien, las concentraciones de metales pesados registrados en la pradera estudiada están por debajo de los niveles considerados peligrosos para suelos agrícolas. Por lo tanto, los resultados obtenidos sugieren que las actividades agrícolas (fertilización, uso de pesticidas, etc.) fueron adecuadas en este área

Mapping of some soil properties at catchment scale

[Abstract] The spatial structure of gravel content and three textural fractions (sand, silt, clay) was investigated in a 19.8 ha mixed, agricultural and forest catchment through of geostatistical techniques. Three different depths (0-15 cm, 15-30 cm and 30-45 cm) were sampled in order to describe the spatial variability from 0 to about 300 m. It was shown a spatial structure for all the studied variables, which could be described by different types of semivariograms (sphericals,exponentials an gaussians) with nugget effect component and a spatial component ranging from 3,5 to 365 m. Maps were performed using the information contained in the semivariograms by block kriging, so that contour maps were drawn for the different texture fractions and also showing the kriging errors. It was found greater spatial dependence of the studied variables in the first 15 cm than in the other depths

Spatial distribution of soil roughness in experimental microplots under different intensities of simulated rainfall

O objetivo deste trabalho foi avaliar a distribuição espacial da rugosidade do solo em microparcelas compostas por diferentes solos de Galícia (Espanha) após aplicação de distintas chuvas simuladas. Os agregados do solo, de 3-5 cm, foram coletados nos municípios de Lugo e Taboada. Em laboratório as parcelas experimentais foram construídas utilizando-se base metálica móvel de 0,86 m x 0,86 m (0,73 m2). A rugosidade do solo (dm) foi determinada com rugosímetro laser, antes e depois da aplicação de quantidades crescentes de chuva simulada (50 mm h-1 e 75 mm h-1) durante uma hora. O índice de rugosidade aleatória (RR) cresceu com o aumento do volume de chuva simulada no solo franco (Taboada). Todos os tratamentos estudados apresentaram alta razão de dependência espacial entre amostras (RD) em função do grande número de leituras fornecidas pelo rugosímetro laser, que favorece uma minimização da variabilidade ao acasoThe objective of this study was to evaluate the spatial distribution of soil roughness in microplots composed of different soils in Galicia (Spain) after application of different simulated rainfall. Clusters of 3-5 cm soil were collected in the municipalities of Lugo and Taboada. In the laboratory experimental plots were built using metallic mobile 0.86 m x 0.86 m (0.73 m2). The roughness of the soil (dm) was determined with laser reliefmeter before and after application of different amounts of rain (50 mm h-1 and 75 mm h-1) for an hour. The index of random roughness (RR) increased with increasing the volume of simulated rain in loam soil (Taboada). All treatments studied showed a high rate of spatial dependence between samples (RD), depending on the number of readings provided by laser reliefmeter, which favors a minimization of random variabilityOs autores agradecem ao Ministerio de Asuntos Exteriores y de Cooperación da Espanha (MAEC-AECID) pela concessão de bolsa de doutorado ao primeiro autor; a Fundación Carolina (Espanha) pelo apoio financeiro ao primeiro autor por meio de programa de cooperação e intercambio BrasilEspanha. Este trabalho foi financiado pelo Ministerio de Educación y Ciencia da Espanha através do projeto CGL2005-08219-C02-022 e co-financiado pela Xunta de Galicia, por meio do projeto PGIDIT06PXIC291062PN e pela European Regional Development Fund (ERDF)S

Comparing effects of tillage treatments performed with animal traction on soil physical properties and soil electrical resistivity: preliminary experimental results

Soil Compaction results from compressive forces applied to compressible soil by machinery wheels, combined with tillage operations. Draft animal‐pulled equipment may also cause soil compaction, but a huge gap exists on experimental data to adequately assess their impacts and, actually, animal traction is an option seen with increasing potential to contribute to sustainable agriculture, especially in mountain areas. This study was conducted to assess the impacts on soil compaction of tillage operations with motor tractor and draft animals. In a farm plot (Vale de Frades, NE Portugal) treatments were applied in sub‐plots (30 m x 3 m), consisting in a two way tillage with tractor (T), a pair of cows (C) and a pair of donkeys (D). Undisturbed soil samples (120) were taken before and after operations for bulk density (BD) and saturated hydraulic conductivity (Ks). The relative changes in BD observed after tillage in the 0-0.05 m soil depth increased after operations in all treatments. The increase was higher in the tractor sub-plot (15%) than in those where animal traction was used (8%). Before operation Ks class was rapid and fast in all samples, and after operation this value was reduced to 33% in T, whereas it reached 83% in C. Electrical Resistivity Tomography (ERT) was useful as a tool to identify the alterations caused by tillage operations on soil physical status. These preliminary results confirm the potential of animal traction as an option for mountain agri‐environments, yet it requires much wider research to soundly ground its assets.Authors wish to acknowledge the most relevant contribution of the farmers of Vale de Frades involved in the experiment, for their enthusiasm and refined performance in the field, accepting to freely provide their time, their work and their draft animals to carry out the required operations.info:eu-repo/semantics/publishedVersio

Comparing effects of tillage treatments performed with animal tractionon soil physical properties: preliminary experimental results

La compactación del suelo es causada por las fuerzas que compresión aplicadas al suelo mediante la maquinaria agrícola así como las operaciones de labrado, siendo particularmente preocupantes cuando el suelo está húme- do y sufre más riesgos de deformación. La tracción animal (e incluso la humana) también puede causarla, si bien no ha sido estudiada en profundidad. Hoy en día la tracción animal surge como alternativa sostenible a la meca- nizada, en especial en áreas de montaña. Este estudió se llevo a cabo para evaluar el impacto en la compacta- ción del suelo del laboreo utilizando tracción mecánica y tracción animal. La parcela estudiada está situada en Vale de Frades, NE de Portugal. En ella se aplicaron los tratamientos en sub-parcelas (30x3m), que consistían en dos pases con tractor, un par de vacas y un par de burros; siendo los aperos de volteo (arado romano) y de corte (cultivador y escarificador). Se tomaron 120 muestras de suelo antes y después de las labores para estu- diar diferentes propiedades físicas del suelo: densidad aparente, porosidad y conductividad hidráulica.Los resul- tados de este ensayo si bien parecen mostrar la tracción animal como una alternativa sostenible a la motoriza- ción, no son todavía concluyentes, haciendo necesarios estudios futuros.info:eu-repo/semantics/publishedVersio