Gérson Rodrigues dos Santos

VARIABILIDADE ESPACIAL DE ATRIBUTOS FÍSICOS DE UM LATOSSOLO VERMELHO-AMARELO, SOB LAVOURA CAFEEIRA

Knowledge about the variability of soil physical properties is fundamental for the monitoring of soil quality for being directly related to the sustainability of agricultural production. This study aimed to: a) assess and identify structures of spatial dependence by the construction of semi-variograms, for a Red-Yellow Latosol (Oxisol) under coffee, b) characterize the spatial distributions of the physical properties using ordinary kriging, and c) identify the layer with greatest physical impediment. The experiment was conducted on an experimental farm of the Agricultural Research Company of Minas Gerais (Epamig), in Patrocinio, MG, on a clayey Oxisol. Samples were collected from trenches at the intersections of a rectangular 40 x 150 m grid, totaling 28 sampling points, where soil samples were collected with metal rings (2.54 cm in height and 6.30 cm in diameter), with an Uhland sampler. Each trench had three steps with a surface of 2.0 x 1.5 m, at the depth of 0.00, 0.10, and 0.25 m, from each of which seven soil samples were collected, arranged in a matrix form, totaling 588 samples. Except for total porosity, soil physical properties were spatially dependent in all layers. The ordinary kriging technique proved to be a viable alternative for the estimation of data points not sampled in the experimental area. The physical restrictions to root growth were most severe in the 0.00-0.03 m layer due to the highest soil density and lowest soil macroporosity.

Qualitative Analysis of Volunteered Geographic Information in a Spatially Enabled Society Project

The increase of data sources on the Internet and Web 2.0 advances have contributed to significant changes in the way we produce spatial information. The citizen is using collaborative environments to produce their own data, whether in the area of public security, infrastructure or for simple fun. The voluntary contribution is essential to make a spatially enabled society and help in decision-making process at all levels of a society, whether governmental, private or by the citizen. Analyzing the information gain that is recorded in collaborative Web systems is essential to know what is not being recorded in official data sources. The aim of this study is to evaluate the information gain generated by the user on a project to transform a conventional computerized municipal management for a spatially enabled society.

Pedotransfer functions to estimate bulk density from soil properties and environmental covariates: Rio Doce basin

Soil bulk density (ρb) data are needed for a wide range of environmental studies. However, ρb is rarely reported in soil surveys. An alternative to obtain ρb for data-scarce regions, such as the Rio Doce basin in southeastern Brazil, is indirect estimation from less costly covariates using pedotransfer functions (PTF). This study primarily aims to develop region-specific PTFs for ρb using multiple linear regressions (MLR) and random forests (RF). Secondly, it assessed the accuracy of PTFs for data grouped into soil horizons and soil classes. For that purpose, we compared the performance of PTFs compiled from the literature with those developed here. Two groups of data were evaluated as covariates: 1) readily available soil properties and 2) maps derived from a digital elevation model and MODIS satellite imagery, jointly with lithological and pedological maps. The MLR model was applied step-wise to select significant predictors and its accuracy assessed by means of cross-validation. The PTFs developed using all data estimated ρb from soil properties by MLR and RF, with R2 of 0.41 and 0.51, respectively. Alternatively, using environmental covariates, RF predicted ρb with R2 of 0.41. Grouping criteria did not lead to a significant increase in the estimates of ρb. The accuracy of the ‘regional’ PTFs developed for this study was greater than that found with the ‘compiled’ PTFs. The best PTF will be firstly used to assess soil carbon stocks and changes in the Rio Doce basin.

Capacidade de suporte de carga de um Latossolo Vermelho-Amarelo em uma lavoura cafeeira

O trafego intensivo de maquinas agricolas sobre solos cultivados com cafeeiros pode causar compactacao excessiva, principalmente quando realizado sob condicao inadequada de umidade, promovendo reducao da produtividade das areas sob intensa passagem de maquinas. Os objetivos deste trabalho foram: avaliar a degradacao da estrutura do solo na linha de trafego do trator (LTT) e na linha de trafego da colhedora (LTC), por meio dos atributos fisicos do solo e da capacidade de suporte de carga do solo em funcao do potencial matricial do solo; e calcular os potenciais matriciais criticos, para evitar a compactacao adicional do solo pelo uso de um trator marca Massey Ferguson, modelo 275, e de uma colhedora Jacto KTR Advance em um Latossolo Vermelho-Amarelo textura muito argilosa. O estudo foi realizado na Fazenda da EPAMIG situada no municipio de Patrocinio-MG. Para obtencao dos modelos de capacidade de suporte de carga (σp) versus potencial matricial do solo, coletaram-se amostras indeformadas na LTT e LTC, nas camadas de 0-3, 10-13 e 25-28 cm, em cinco trincheiras, as quais foram submetidas ao ensaio de compressao uniaxial, em diferentes potenciais matriciais. Alem disso, coletaram-se amostras indeformadas em seis trincheiras, para determinacao dos atributos fisicos do solo na LTT e LTC, nas camadas de 0-3, 10-13 e 25-28 cm. As operacoes realizadas com o trator degradaram mais a estrutura do solo do que as realizadas com a colhedora, pois na linha de trafego do trator (LTT) a densidade do solo, a microporosidade e a pressao de preconsolidacao foram maiores que as da linha de trafego da colhedora. O potencial matricial critico para a LTT foi de -51 kPa (0,36 m3 m-3), e para a LTC, de -291 kPa (0,30 m3 m-3).

AVALIAÇÃO DA ACURÁCIA POSICIONAL PLANIMÉTRICA EM MODELOS DIGITAIS DE SUPERFÍCIE COM O USO DE FEIÇÕES LINEARES

Atualmente, tem-se aumentado a preocupacao com a avaliacao da acuracia posicional em dados espaciais, principalmente em dados com informacoes altimetricas. Contudo, varios trabalhos avaliam apenas a componente altimetrica, desconsiderando a acuracia posicional planimetrica. Assim, este trabalho tem como objetivo avaliar a acuracia posicional planimetrica dos principais MDSs disponiveis gratuitamente para o Brasil, como os modelos SRTM (banda C e X), Aster GDEM versao 2 e TOPODATA. Para a avaliacao da acuracia posicional planimetrica dos MDSs, fez-se a extracao de feicoes caracteristicas do terreno como linhas de cumeadas e linhas de hidrografia numerica. Em seguida, de posse destas feicoes lineares, aplicou-se o metodo do Buffer Duplo para avaliar a acuracia posicional planimetrica de acordo com o padrao definido no Decreto-lei n° 89.817/ET-ADGV. Para a comparacao destes modelos, utilizou-se como referencia um MDS, na escala de 1:25.000, obtido do sensor ALOS/PRISM. Os resultados da avaliacao posicional planimetrica apresentaram Classe C na escala 1:100.000 para os MDS SRTM-X e Aster GDEM; para os MDS TOPODATA e SRTM-C, as classificacoes obtidas foram Classe B e Classe C na escala de 1:250.000, respectivamente.