Maria Cândida Moitinho Nunes

Theoretical Definition of Formation Damage Zone With Applications to Well Stimulation

Flow of particulate suspension in porous media with particle retention and consequent permeability reduction is discussed. Using analytical model for suspension injection via single well, the permeability damage zone size was defined and expressed by transcendental equation. Analysis of field data shows that usually the size of damaged zone does not extend more than 1 m beyond the injector. The definition of damage zone size is used for design of well stimulation via deposition removal. DOI: 10.1115/1.4001800

Estimativa da erodibilidade em entressulcos de latossolos do Rio Grande do Sul

Models of soil water erosion prediction and estimation are generally based on a series of parameters, normally determined by applying simulated rainfall in the field or laboratory. The use of simpler, faster and cheaper parameters such as texture, content and oxide type and aggregate water stability may contribute to facilitate the estimation of the factor interrill soil erodibility (Ki). The purpose of this study was: i) to determine the interrill soil erodibility of three Brazilian Oxisols; ii) evaluate the use of soil sand and clay contents in the prediction of interrill soil erodibility, as in the WEPP model; iii) verify the correlation among some soil properties and the interrill soil erodibility factor. The interrill soil erosion rates were determined in laboratory, using three Oxisols with different clay content of the State of Rio Grande do Sul, Brazil, under a mean intensity of simulated rainfall of 88 mm h-1, applied during 180 min on bare soil, using experimental interrill plots of 0.36 m2 at a slope of 0.09 m m-1 and an initial water tension of 6 kPa. The susceptibility of soils with high clay and Fe oxide contents and higher water aggregate stability to interrill erosion was lower. The experimentally determined values of interrill soil erodibility (Ki factor) varied from 0.76 x 106 kg s m-4 to 1.48 x106 kg s m-4 for the studied Oxisols. The aggregate water stability index was highly correlated with the interrill soil erodibility factor (r= -0.90**). The use of soil sand and clay contents, as suggested by the WEPP model, did not prove adequate to estimate the interrill soil erodibility (Ki factor). The variation in clay and Fe oxide contents explained 97 % (p<0.01) of the interrill soil erodibility variation.

Produção de sedimentos pela erosão em entressulcos em três Latossolos do Rio Grande do Sul

The sediment particle size distribution depends on soil type and texture. This study had the objective to evaluate the sediment yield by interrill soil erosion in three Oxisols of Rio Grande do Sul state, Brazil: Rhodic Hapludox (LVaf and LVdf) and a Typic Hapludox (LVd), of different textural classes, by simulated rainfall events in laboratory. Experimental plot with test area of 0.36 m2 and 0.09 m m-1 slope was used. Simulated rainfall with mean intensity of 88 mm h-1 and duration of 90 min was applied in three replications on three oxisols. Sediment particles leaving the experimental plots were collected in a set of sieves. The distribution of sediment diameter varied as the soil texture. The sediment yielded by interrill soil erosion had individual particles and aggregates smaller than those in the original soil. Most of the sediment yielded by interrill soil erosion at LVdf soil was in the class diameter from 9.51 to 4.76 mm whereas in LVaf was from 4.76 to 2.00 mm and in LVd was from 1.00 to 0.25 mm. The original LVdf and LVaf soils present higher clay, organic carbon and iron oxides contents and greater aggregate water stability than the LVd soil, and this probably explains the differences among size classes of sediment yielded by interrill soil erosion.

EFICIÊNCIA DE TELAS TERMOREFLETORAS E DE SOMBREAMENTO EM AMBIENTE PROTEGIDO TIPO TELADO SOB TEMPERATURAS ELEVADAS - DOI: 10.13083/1414-3984.v22n01a04

Cultivation in protected environments allows for crop production in seasons that normally would not be suitable for open field production. This study sought to evaluate the variations in luminosity, air and soil temperature and relative humidity of the air in different environmental conditions during the winter and summer, in Caceres-MT, using screens with mesh of 30, 40 and 50% shading, thermo-reflective screens with 30, 40 and 50% shading and an open field. The experimental design utilized consisted of randomized blocks with 10 replications, represented by 10 days of collection. It was observed that the screened environments reduced the minimum, average and maximum values of the luminosity and air temperature attributes, and resulted in an increase in relative humidity compared to the open field environment. The black screens with 40% and 50% shading and the 50% thermo-reflective screen presented greatest efficiency to reduce luminosity and air temperature. The screen with 50% shading was that which resulted in the greatest indices of relative humidity of the air among the treatments.