The soil surface roughness increases water retention and infiltration, reduces the runoff volume and speed and influences soil losses by water erosion. Similarly to other parameters, soil roughness is affected by the tillage system and rainfall volume. Based on these assumptions, the main purpose of this study was to evaluate the effect of tillage treatments on soil surface roughness (RR) and tortuosity (T) and to investigate the relationship with soil and water losses in a series of simulated rainfall events. The field study was carried out at the experimental station of EMBRAPA Southeastern Cattle Research Center in São Carlos (Fazenda Canchim), in São Paulo State, Brazil. Experimental plots of 33 m² were treated with two tillage practices in three replications, consisting of: untilled (no-tillage) soil (NTS) and conventionally tilled (plowing plus double disking) soil (CTS). Three successive simulated rain tests were applied in 24 h intervals. The three tests consisted of a first rain of 30 mm/h, a second of 30 mm/h and a third rain of 70 mm/h. Immediately after tilling and each rain simulation test, the surface roughness was measured, using a laser profile meter. The tillage treatments induced significant changes in soil surface roughness and tortuosity, demonstrating the importance of the tillage system for the physical surface conditions, favoring water retention and infiltration in the soil. The increase in surface roughness by the tillage treatments was considerably greater than its reduction by rain action. The surface roughness and tortuosity had more influence on the soil volume lost by surface runoff than in the conventional treatment. Possibly, other variables influenced soil and water losses from the no-tillage treatments, e.g., soil type, declivity, slope length, among others not analyzed in this study.

Propôs-se, neste trabalho, verificar os efeitos de manejos em Latossolo em recuperação há sete anos. Os tratamentos estudados foram: dois controles, A - Vegetação natural de Cerrado; B - Solo exposto; além dos tratamentos, C - Área apenas com espécie arbórea Gonçalo-Alves (GA) (Astronium fraxinifolium); D - Gonçalo-Alves + Nabo forrageiro (Raphanus sativus) até 2005, substituído pela crotalária (Crotalaria juncea) (GA + C); E - Gonçalo-Alves + Feijão-de-Porco (Canavalia ensiformis) (GA + FP); F - Gonçalo-Alves + Lodo de esgoto (60 t ha^-1) + Brachiaria decumbens (GA + LE +B). Não houve convergência com relação aos indicadores da qualidade do solo em recuperação há sete anos; o tratamento GA + Lodo de esgoto + Brachiaria decumbens foi o que melhor respondeu quanto ao teor de matéria orgânica do solo; os tratamentos usados para recuperação do solo tiveram comportamento semelhante relacionado ao da infiltração de água; os tratamentos com GA + Crotalária, GA + Feijão-de-Porco e GA + Lodo de esgoto + Brachiaria decumbens nas imagens tomográficas foram os que apresentaram melhores condições da estrutura do solo; a recuperação atingiu a camada do solo de 0-10 cm.

Problems involving fluid flow in porous media are of great interest in many scientific and technological areas. The development of numerical methods at the pore level allows simulating such phenomena considering characteristics and heterogeneities of the medium normally ignored in the macroscopic approach. To achieve the computational implementation of those numerical methods, it is necessary to initially define the domain (porous media) in which the simulations will be held. In this study, a simple, yet powerful methodology of representing a porous medium by means of cellular automata (CA) and microcomputed tomography is presented. Two parameters are proposed to link the tomographic images with those generated by CA. The first one considers the porosity, whereas the second one takes into account void alignment inside the image. The methodology computes the parameters in every automata image generated in a time range and compares them with the parameters of the tomographic image until certain use...

Currently, an activity that has become strategic at a national level is the cultivation of oil palm (Elaeis guineensis) in the northeast region of the Pará State, in eastern Brazilian Amazon. However, the impacts of this crop expansion on the hydro-sedimentological cycle are still unknown. Therefore, this study estimated the impacts of oil palm crop expansion on sediment production in a sub-basin under consolidated use of this crop. The Soil and Water Assessment Tool (SWAT) model was applied in the Mariquita sub-basin, calibrated by the flow regionalization technique, using data measured in the field with a current meter. Simulation results indicated an increase in sediment production between the years 2008 and 2013, which can be attributed to the large reduction of areas of secondary vegetation that were replaced by pasture, oil palm and general agriculture. Oil palm areas had a lower average monthly sediment yield in the rainiest period in all simulated years, compared with areas of general agriculture and pasture.

Os processos de mudança de uso e cobertura do solo despertam grande preocupação quanto a se compreender e melhor planejá-los a fim de evitar impactos, como perda da biodiversidade, erosão do solo e contaminação dos recursos hídricos. O trabalho propõe estimar a produção de sedimentos em cenários da microbacia hidrográfica do ribeirão das Guabirobas, localizada no município de São Carlos, SP. Para isto foi aplicado o modelo de simulação espacial CLUE-S (Conversion of Land Use and its Effects at Small Region Extent), com o objetivo de gerar cenários para o ano de 2025 da área de estudo. A posteriori, foi estimada a produção de sedimentos desses cenários com o auxílio do modelo de simulação SWAT (Soil and Water Assessment Tool). Dois cenários foram simulados: expansão da cana-de-açúcar e expansão da laranja. Por meio das diferentes demandas por áreas inseridas no CLUE-S foi possível gerar cenários da microbacia hidrográfica do ribeirão das Guabirobas para o ano de 2025 e, com o auxílio do SWAT, estimar a produção de sedimentos nos diferentes usos do solo e verificar que a cultura da cana-de-açúcar de variedades RB72-454, CTC6 e CTC11 e do híbrido entre Eucalyptus grandis e Eucalyptus urophylla foi mais significativa.