Cláudia Alessandra Peixoto de Barros

Compressibilidade de um Argissolo Vermelho-Amarelo trafegado e escarificado

Farm machinery wheeling is considered a major source of soil compaction. The use of chisel plow can minimize such effects, but the chisel can cause subsurface compaction. The aim of this study was to evaluate the effect of traffic and is present below the compaction layer thought compressive parameters of soil. The treatments investigated were: no-tillage, no-tillage with additional traffic (traffic intensity of 24.67Mg km ha-1), no-tillage chiseling recent implanted, no-tillage with additional traffic and chiseling recent implanted. For the density, void ratio, preconsolidation pressure and coefficient of compressibility determination in the layers 0.0-0.10m, 0.10-0.20m, 0.20-0.30m and 0.30 to 0.40m samples were collected. The treatment no-tillage showed the lowest load support capacity and greater susceptibility to compaction. The traffic intensity of 24.67Mg km ha-1 increased bulk density and decreased void ratio until 0.30m depth. The chisel plow did not affect the preconsolidation pressure and coefficient of compressibility of soil layer below the line of action of the chisel tip.

Cultivo mínimo: efeito da compactação e deformação abaixo da atuação da ponteira do subsolador

A B ST R A C T Soil compaction at the depth of mobilization by tillage implements may occur under some soil conditions. The objective of this study was to verify the existence of compaction under the working depth and evaluate the effect of chisel plow in soil under determined levels of compaction. The treatments in study were 13 years of no-tillage and no-tillage with additional compaction. Horizontal force (F H ), Draught (F T ), vertical forces (F V ), and moment (Mo) associated the chisel tool, operation specific resistance, mobilized area, elevation area, swelling, soil penetration resistance, and physical properties of soil were determined. The additional compaction showed an increment of 18.9% in the horizontal force and draught. The greatest contribution of additional compaction was in vertical force, which provided an increment of 78.2%, showing that the load action is mainly in the vertical direction. No-tillage demonstrated smaller draught demand per mobilized soil area compared to additional compaction treatment. Instead of occurring compaction under the chisel action depth, there was soil mobilization, resulting in smaller soil mechanical penetration resistance in this layer.

Estimativa da infiltração de água no solo na escala de bacia hidrográfica

The spatial variability of soil characteristics makes the estimation of water infiltration highly dependent on the scale of analysis. Many studies require information on the dynamics of infiltration to describe the dynamics of other processes associated with water, sediment and solutes. This study aims to use two methodological strategies to estimate water infiltration at the catchment scale. The parameters of two infiltration models were fitted to a data set collected over two years of monitoring (77 rainfall-runoff events) occurring under different land use and management conditions in a rural catchment of 1.2 km2. The results of fitting to the two infiltration models at the catchment scale were compared with those obtained from two site-specific methods for estimating infiltration. With the set of monitoring data, it was possible to establish an infiltration model for the monitored catchment area. Furthermore, the results indicate that the comparison between values from the models and site-specific values are strongly dependent on the scale of analysis. That is, the site-specific measures showed mean values of high infiltration rates for this catchment, but field observations indicate low infiltration, especially in saturated areas, which affect runoff in this catchment area. This is in contrast with the results obtained by the estimation models, which present a lower order of magnitude for the estimated values of infiltration, due to the greater incorporation of factors controlling the process in their methodology, among other aspects.

Impacts of forest conversion and agriculture practices on water pathways in Southern Brazil

Division of Geography and Tourism, Department of Earth and Environmental Sciences, KU Leuven, Leuven, Belgium Department of Soil, Universidade Federal de Santa Maria, Rio Grande do Sul, Brazil Department of Agronomy, Universidade Federal do Rio Grande do Sul, Rio Grande do Sul, Brazil 4 Institute of Bio‐ and Geosciences, IBG‐3: Agrosphere, Forschungszentrum Jülich GmbH Jülich, Jülich, Germany Earth and Life Institute, Environmental Sciences, Université catholique de Louvain, Louvain, Belgium Correspondence Jérémy Robinet, Division of Geography and Tourism, Department of Earth and Environmental Sciences, KU Leuven, Leuven, Belgium. Email: jeremy.robinet@kuleuven.be

Long‐term sediment yield from a small catchment in southern Brazil affected by land use and soil management changes

Departamento de Solos, Universidade Federal de Santa Maria, Av. Roraima, 1000, Santa Maria, RS 97105‐900, Brazil Department of Civil Engineering, University of Minnesota‐Duluth, 1405 University Drive, Duluth, MN 55812, USA Faculdade de Agronomia, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 7712, Porto Alegre, RS 91540‐000, Brazil 4 Instituto de Pesquisas Hidráulicas, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9500, Porto Alegre, RS 91501‐970, Brazil Correspondence Jean P. G. Minella, Departamento de Solos, Universidade Federal de Santa Maria, Av. Roraima, 1000, Santa Maria, RS 97105‐900, Brazil. Email: jminella@gmail.com