Spatial variability of the physical and mineralogical properties of the soil from the areas with variation in landscape shapes

Este trabalho teve como objetivo avaliar a influência das formas do relevo na variabilidade espacial de atributos físicos e suas relações com a mineralogia da argila de um Latossolo Vermelho eutroférrico, utilizando a técnica da geoestatística. Os solos foram amostrados nos pontos de cruzamento de uma malha, com intervalos regulares de 10 m, nas profundidades de 0,0-0,2 m, 0,2-0,4 m e 0,4-0,6 m para os atributos físicos e 0,6-0,8 m para os atributos mineralógicos. Os valores médios para a densidade do solo e resistência do solo à penetração são maiores no compartimento I onde a relação Ct/Ct+Gb é relativamente maior, indicando a presença de maior teor de caulinita. No compartimento II a condutividade hidráulica e a macroporsidade são maiores, influenciados provavelmente pelo predomínio da gibbsita. Portanto, conclui-se que a identificação das pedoformas é muito eficiente para compreender a variabilidade espacial de propriedades do solo. Sendo que, as variações na forma da paisagem promovem variabilidade espacial diferenciada das propriedades físicas e mineralógicas do solo.

An appropriate data set size for digital soil mapping in Erechim, Rio Grande do Sul, Brazil

Digital information generates the possibility of a high degree of redundancy in the data available for fitting predictive models used for Digital Soil Mapping (DSM). Among these models, the Decision Tree (DT) technique has been increasingly applied due to its capacity of dealing with large datasets. The purpose of this study was to evaluate the impact of the data volume used to generate the DT models on the quality of soil maps. An area of 889.33 km² was chosen in the Northern region of the State of Rio Grande do Sul. The soil-landscape relationship was obtained from reambulation of the studied area and the alignment of the units in the 1:50,000 scale topographic mapping. Six predictive covariates linked to the factors soil formation, relief and organisms, together with data sets of 1, 3, 5, 10, 15, 20 and 25 % of the total data volume, were used to generate the predictive DT models in the data mining program Waikato Environment for Knowledge Analysis (WEKA). In this study, sample densities below 5 % resulted in models with lower power of capturing the complexity of the spatial distribution of the soil in the study area. The relation between the data volume to be handled and the predictive capacity of the models was best for samples between 5 and 15 %. For the models based on these sample densities, the collected field data indicated an accuracy of predictive mapping close to 70 %.

Comparison between detailed digital and conventional soil maps of an area with complex geology

Since different pedologists will draw different soil maps of a same area, it is important to compare the differences between mapping by specialists and mapping techniques, as for example currently intensively discussed Digital Soil Mapping. Four detailed soil maps (scale 1:10.000) of a 182-ha sugarcane farm in the county of Rafard, São Paulo State, Brazil, were compared. The area has a large variation of soil formation factors. The maps were drawn independently by four soil scientists and compared with a fifth map obtained by a digital soil mapping technique. All pedologists were given the same set of information. As many field expeditions and soil pits as required by each surveyor were provided to define the mapping units (MUs). For the Digital Soil Map (DSM), spectral data were extracted from Landsat 5 Thematic Mapper (TM) imagery as well as six terrain attributes from the topographic map of the area. These data were summarized by principal component analysis to generate the map designs of groups through Fuzzy K-means clustering. Field observations were made to identify the soils in the MUs and classify them according to the Brazilian Soil Classification System (BSCS). To compare the conventional and digital (DSM) soil maps, they were crossed pairwise to generate confusion matrices that were mapped. The categorical analysis at each classification level of the BSCS showed that the agreement between the maps decreased towards the lower levels of classification and the great influence of the surveyor on both the mapping and definition of MUs in the soil map. The average correspondence between the conventional and DSM maps was similar. Therefore, the method used to obtain the DSM yielded similar results to those obtained by the conventional technique, while providing additional information about the landscape of each soil, useful for applications in future surveys of similar areas.

Terrain forms and spatial variability of soil properties in an area cultivatedwith citrus

The technique of precision agriculture and soil-landscape allows delimiting areas for localized management, allowing a localized application of agricultural inputs and thereby may contribute to preservation of natural resources. Therefore, the objective of this work was to characterize the spatial variability of chemical properties and clay content in the context of soil-landscape relationship in a Latosol (Oxisol) under cultivation of citrus. Soil samples were collected at a depth of 0.0-0.2 m in an area of 83.5 ha planted with citrus, as a 50-m intervals grid, with 129 points in concave terrain and 206 points in flat terrain, totaling 335 points. Values for the variables that express the chemical characteristics and clay content of soil properties were analyzed with descriptive statistics and geostatistical modeling of semivariograms for making maps of kriging. The values of range and kriging maps indicated higher variability in the shape of concave topography (top segment) compared with the shape of flat topography (slope and hillside segments below). The identification of different forms of terrain proved to be efficient in understanding the spatial variability of chemical properties and clay content of soil under cultivation of citrus.

Terrain forms and spatial variability of soil properties in an area cultivatedwith citrus

A técnica de agricultura de precisão e a relação solo-paisagem permitem delimitar áreas para o manejo localizado, o que permite a aplicação localizada de insumos agrícolas e, consequentemente, pode contribuir para a preservação de recursos naturais. Portanto, o objetivo deste trabalho foi caracterizar a variabilidade espacial das propriedades químicas e do teor de argila, no contexto da relação solo-paisagem, em um Latossolo sob cultivo de citros. Amostras de solo foram coletadas na profundidade de 0,0-0,2 m, em uma área de 83,5 ha cultivada com citros, na forma de malha, com intervalos regulares de 50 m, com 129 pontos na forma de relevo côncava e 206 pontos na forma plana, totalizando 335 pontos. Os valores obtidos para as variáveis que expressam as propriedades químicas e para o teor de argila do solo foram submetidos à análise estatística descritiva e geoestatística com a modelagem de semivariogramas para a confecção de mapas de krigagem. Os valores de alcance e mapas de krigagem indicaram maiores variabilidades na forma de relevo côncava (segmento topo), quando comparada com a forma plana (segmentos meia encosta e encosta inferior). A identificação de diferentes formas de relevo mostrou-se eficiente no entendimento da variabilidade espacial das propriedades químicas e do teor de argila do solo sob cultivo de citros.

Delineation of specific management areas for coffee cultivation based on the soil-relief relationship and numerical classification

Predicting and mapping productivity areas allows crop producers to improve their planning of agricultural activities. The primary aims of this work were the identification and mapping of specific management areas allowing coffee bean quality to be predicted from soil attributes and their relationships to relief. The study area was located in the Southeast of the Minas Gerais state, Brazil. A grid containing a total of 145 uniformly spaced nodes 50 m apart was established over an area of 31. 7 ha from which samples were collected at depths of 0. 00-0. 20 m in order to determine physical and chemical attributes of the soil. These data were analysed in conjunction with plant attributes including production, proportion of beans retained by different sieves and drink quality. The results of principal component analysis (PCA) in combination with geostatistical data showed the attributes clay content and available iron to be the best choices for identifying four crop production environments. Environment A, which exhibited high clay and available iron contents, and low pH and base saturation, was that providing the highest yield (30. 4l ha-1) and best coffee beverage quality (61 sacks ha-1). Based on the results, we believe that multivariate analysis, geostatistics and the soil-relief relationships contained in the digital elevation model (DEM) can be effectively used in combination for the hybrid mapping of areas of varying suitability for coffee production. © 2012 Springer Science+Business Media New York.

Spatial variability of physical attributes of an alfisol under different hillslope curvatures

The influence of relief forms has been studied by several authors and explains the variability in the soil attributes of a landscape. Soil physical attributes depend on relief forms, and their assessment is important in mechanized agricultural systems, such as of sugarcane. This study aimed to characterize the spatial variability in the physical soil attributes and their relationship to the hillslope curvatures in an Alfisol developed from sandstone and growing sugarcane. Grids of 100 x 100 m were delimited in a convex and a concave area. The grids had a regular spacing of 10 x 10 m, and the crossing points of this spacing determined a total of 121 georeferenced sampling points. Samples were collected to determine the physical attributes related to soil aggregates, porosity, bulk density, resistance to penetration and moisture within the 0-0.2 and 0.2-0.4 m depth. Statistical analyses, geostatistics and Student's t-tests were performed with the means of the areas. All attributes, except aggregates > 2 mm in the 0-0.2 m depth and macroporosity at both depths, showed significant differences between the hillslope curvatures. The convex area showed the highest values of the mean weighted diameter, mean geometric diameter, aggregates > 2 mm, 1-2 mm aggregates, total porosity and moisture and lower values of bulk density and resistance to penetration in both depth compared to the concave area. The number of soil attributes with greater spatial variability was higher in the concave area.

Spatial variability of physical attributes of an alfisol under different hillslope curvatures

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Influência do relevo e erosão na variabilidade espacial de um Latossolo em Jaboticabal (SP)

Com o objetivo de avaliar as relações entre formas de paisagem e erosão em um Latossolo Vermelho eutroférrico (LVef) por meio de técnicas geoestatísticas na Fazenda Santa Isabel, município de Jaboticabal (SP), identificaram-se modelos de paisagem côncavo e linear. Coletaram-se amostras de solo em ambas as formas de paisagem em uma malha regular espaçada de 50 x 50 m em sete transeções na profundidade de 0,00-0,20 m, totalizando 412 pontos em 93 ha. Determinou-se a erodibilidade dos solos pelo método indireto, granulometria, bem como o carbono orgânico para cada ponto da malha, sendo esses valores usados na estimativa do potencial natural de erosão (pne). Os dados obtidos das propriedades de solo, erodibilidade e potencial natural de erosão foram analisados por meio de estatística descritiva e geoestatística com a modelagem de semivariogramas, sendo este utilizado para a confecção de mapas de krigagem. Segundo os resultados, as propriedades do solo e do pne apresentaram maior variabilidade espacial na pedoforma côncava, apesar de esta forma de paisagem apresentar menores perdas de solo por erosão e menor variabilidade espacial da erodibilidade. Deste modo, conclui-se que a erosão não adicionou variabilidade espacial para as propriedades do solo na mesma magnitude do relevo.

Avaliação de características morfométricas na relação solo-superfície da Bacia Hidrográfica do Córrego Rico, Jaboticabal (SP)

Com a análise das características morfométricas procura-se entender a relação solo-superfície, em decorrência dos processos erosivos sobre estruturas e litologias variadas. Neste trabalho, objetivou-se avaliar as características morfométricas do padrão de drenagem e do relevo em microbacias hidrográficas de 2ª ordem de magnitude, em Latossolo Vermelho-Escuro e Argissolo Vermelho-Amarelo, com vistas ao planejamento agroambiental da Bacia Hidrográfica do Córrego Rico, município de Jaboticabal, SP. O estudo foi baseado em fotografias aéreas, pancromáticas, verticais na escala 1:35.000 da região administrativa de Ribeirão Preto. Com técnicas de fotointerpretação, foram traçadas a rede de drenagem e respectivas microbacias hidrográficas, onde as variáveis selecionadas foram determinadas. As classes de risco de degradação, resultando no uso potencial do solo, foram determinadas de acordo com o coeficiente de rugosidade. As características do padrão de drenagem e do relevo repercutiram no comportamento hidrológico e litológico das microbacias hidrográficas, possibilitando a diferenciação entre as unidades de solos. A densidade de drenagem e a amplitude altimétrica foram as características que mais contribuíram para o poder discriminatório na relação solo-superfície. Na análise conjunta do potencial de uso do solo, verificou-se, principalmente, adequação para agricultura nos Latossolos e pecuária e, ou, reflorestamento nos Argissolos.

O relevo na interpretação da variabilidade espacial dos teores de nutrientes em folha de citros

Foliar diagnosis is a method for assessing the nutritional status of agricultural crops, which helps in the understanding of soil fertility and rationalized application of fertilizers taking into account economic and environmental criteria. The study aimed to use the landrelief as criteria to assist in interpreting the spatial variability of nutrient content of the citrus leaf. The leaves were collected at regular intervals of 50 m, totaling 332 sampling points. Data were analyzed by descriptive statistics, geostatistics and induction of decision tree. With the aid of digital elevation model (MDE) and the profile planaltimetric, the area was divided into three different landrelief and sub-strands. The highest values for nutrients from the leaves of citrus were observed at the top (concave area) segments on a half-slope and lower slope. The nutrients from the citrus leaves showed high values of correlation (above 0.5) with the altitude of the study area. The technique of geostatistics and the induction of decision tree show that the relief is the variable with the greatest potential to interpret the maps of spatial variability of nutrients from the citrus leaves.

Variabilidade espacial da estabilidade de agregados e matéria orgânica em solos de relevos diferentes

Soils submitted to the same management system in places with small relief variation manifest different spatial variability on their attributes. The objective of this work was to evaluate the spatial variability of the geometric medium diameter, aggregates in the >2 mm class, aggregates in the 2-1 mm class and organic matter of an Oxisol under culture of the sugarcane. Samplings of the soil in regular intervals of 10 m, in grid form, totaling 100 points, collected in the depths of 0.0-0.2 m and 0.2-0.4 m were made. Data were submitted to descriptive statistics, geostatistics and in sequence to kriging analyzes. Values of the variation coefficient were low for organic matter in the depth of 0.0-0.2 m, mean in the depth of 0.2-0.4 m, high for geometric medium diameter and mean for aggregates in the >2 mm class, aggregates in the 2-1 mm class in all studied depths. The occurrence of space dependence was observed for all the variables, and the largest ones were observed in the depth of 0.0-0.2 m. Small variations in the forms of the relief condition spatial variability differentiated for organic matter and stability of aggregates in the studied depths.

Influência das superfícies geomórficas na distribuição espacial dos atributos do solo em área sob cultivo de cana-de-açúcar

Variations in soil attributes occur based on relief forms and parent material. The objective of this research was to study the influences of geomorphic surfaces on the spatial distribution of soil attributes in a sugarcane cultivation area. First, 530,67 hectares were mapped by using a Global Positioning System. Then, a Digital Elevation Model was developed and geomorphic surfaces were identified and delimited, according to topographic and stratigraphic criteria based on detailed field investigations. Soil samples were collected every 7 ha, at 0.0-0.25 m and 0.80-1.00 m depths, totalizing 134 samples. Texture, Ca, K, Mg, SB, CEC, V%, pH, and OMS analyses were carried out as well as descriptive statistics and geostatistics analysis. It was concluded that the geostatistic techniques and digital elevation model helped to notice that soil attributes presented limits close to the geomorphic surfaces ones.

Mapeamento de atributos e planejamento amostral para latossolos utilizando suscetibilidade magnética, cor e relação solo-paisagem

Pós-graduação em Agronomia (Produção Vegetal) - FCAV

Disaggregation of polygons of surficial geology and soil maps using spatial modelling and legacy data

Examples from the Murray-Darling basin in Australia are used to illustrate different methods of disaggregation of reconnaissance-scale maps. One approach for disaggregation revolves around the de-convolution of the soil-landscape paradigm elaborated during a soil survey. The descriptions of soil ma units and block diagrams in a soil survey report detail soil-landscape relationships or soil toposequences that can be used to disaggregate map units into component landscape elements. Toposequences can be visualised on a computer by combining soil maps with digital elevation data. Expert knowledge or statistics can be used to implement the disaggregation. Use of a restructuring element and k-means clustering are illustrated. Another approach to disaggregation uses training areas to develop rules to extrapolate detailed mapping into other, larger areas where detailed mapping is unavailable. A two-level decision tree example is presented. At one level, the decision tree method is used to capture mapping rules from the training area; at another level, it is used to define the domain over which those rules can be extrapolated. (C) 2001 Elsevier Science B.V. All rights reserved.