Carlos Alberto Flores

Decision trees for digital soil mapping on subtropical basaltic steeplands

When soil surveys are not available for land use planning activities, digital soil mapping techniques can be of assistance. Soil surveyors can process spatial information faster, to assist in the execution of traditional soil survey or predict the occurrence of soil classes across landscapes. Decision tree techniques were evaluated as tools for predicting the ocurrence of soil classes in basaltic steeplands in South Brazil. Several combinations of types of decicion tree algorithms and number of elements on terminal nodes of trees were compared using soil maps with both original and simplified legends. In general, decision tree analysis was useful for predicting occurrence of soil mapping units. Decision trees with fewer elements on terminal nodes yield higher accuracies, and legend simplification (aggregation) reduced the precision of predictions. Algorithm J48 had better performance than BF Tree, RepTree, Random Tree, and Simple Chart.

Prediction of soil orders with high spatial resolution: response of different classifiers to sampling density

O objetivo deste trabalho foi avaliar a densidade de amostragem na acuracia de predicao de ordens de solos, com alta resolucao espacial, em area viticola da Serra Gaucha. Para isso, utilizou-se modelo digital de elevacao (MDE) do terreno, base cartografica, mapa convencional de solos e o programa Idrisi. Sete variaveis preditoras foram calculadas e lidas junto com as classes de solo, em pontos aleatoriamente distribuidos, nas densidades de 0,5, 1, 1,5, 2 e 4 pontos por hectare. Os dados foram usados para treinar uma arvore de decisao (Gini) e tres redes neurais artificiais: teoria da ressonância adaptativa, fuzzy ARTMap; mapa auto‑organizavel, SOM; e perceptron de multiplas camadas, MLP. Os mapas estimados foram comparados com o mapa de solos convencional para calcular erros de omissao e de inclusao, exatidao geral, e erros de quantidade e de alocacao. A arvore de decisao foi menos sensivel a densidade de amostragem e apresentou maior acuracia e consistencia. O SOM foi a rede neural com menor sensibilidade e maior consistencia. O MLP apresentou minimo critico e maior inconsistencia, enquanto fuzzy ARTMap apresentou maior sensibilidade e menor acuracia. Os resultados indicam que densidades de amostragem usadas em levantamentos convencionais podem servir de referencia para estimar ordens de solos na Serra Gaucha.

Recuperação da qualidade estrutural, pelo sistema plantio direto, de um Argissolo Vermelho

Soils with high sand content in the A horizon are prone to degradation processes, depending on management system used. This study had as objective to evaluate the degradation of a Hapludalf formed from granite, located in the Passo do Pilao watershed in Pelotas county, cultivated under conventional system, and its recovery by no-tillage system, compared to two native systems, namely grass field and forest. The experiment was setup in an agricultural area, in April of 1995, with the cultivation of Avena strigosa plus Vicia vilosa, both for conventional system and no-tillage. An area under native grasses and another with native forest were sampled for comparison. Soils samples were colleted from the layers of 0-0.05m, 0.10-0.15m and 0.20-0.25m, to determine the soil texture, porosity, densities, water retention, aggregate stability and distribution, and organic carbon content. The cultivation systems increase the soil bulk density and reduce total porosity, microporosity, water retention and availability, compared with native systems such as grass field and forest. The conventional system reduces organic carbon content and aggregate stability, whereas no-tillage, after five years, increases, somewhat, the organic carbon content in the surface layer, but increases aggregate stability to values near of those for native systems. The aggregate stability had direct relationship with organic carbon content up to an upper limit of 25g kg-1. The bulk density, macroporosity, S parameter, organic carbon content and aggregate stability are good indicators of the changes observed in the soil management systems. For the Hapludalf formed from granite, there was recovery of the properties related to soil structure stability, but in those related to soil bulk density and porosity no recovery was observed.

Fracionamento químico e físico da matéria orgânica de um argissolo vermelho sob diferentes sistemas de uso

The objective of this study was to evaluate the total organic carbon and the physical and chemical fractions of organic matter in an Alfisol under different use systems. The land use systems evaluated was homogeneous forestry of Eucalyptus grandis, agrosilvopastoral system and native grassland, in layers from 0.000-0.025 and 0.025-0.075m depth. The coarse fraction (CFG) and the carbon associated minerals (CAM) were obtained by physical fractionation. The free light fraction (FLL), light occluded (FLO) and heavy (FP) were obtained by densimetric physical fractionation. The non-humicfractions (NH), fulvic acid (AF), humic acid (HA) and humin (HU) were obtained by chemical fractionation. The Eucalyptus grandis system promoted higher total organic carbon, CFG, FLL and FLO and AF. In the surface layer, the protective recalcitrance mechanisms by organic matter molecular and chemical stabilization are overlapping stability which result from aggregates occlusion. As is difficult to form aggregates due to sandy soil matrix, carbon youth which enter the system is decomposed by microorganisms going to a more advanced stage of decomposition, forming in this case associations with silt and clay particles. This occurs in soils where the clay percentage is low. Through the fractionation it was observed that most of the soil organic matter is stored in the form of HU.

Relações hídricas, rendimento e compostos fenólicos de uvas Cabernet Sauvignon em três tipos de solo

No presente trabalho, foi avaliada a influencia de tres tipos de solo (Argissolo Bruno-acizentado, Planossolo Haplico e Neossolo Regolitico) sobre aspectos quantitativos e qualitativos da producao de uvas destinadas a vinificacao. O experimento foi executado no ciclo 2008/2009, em vinhedo da cultivar Cabernet Sauvignon (Vitis vinifera L.), no municipio de Bento Goncalves, (RS). Avaliou-se a disponibilidade hidrica em base gravimetrica ao longo do periodo de maturacao das uvas, o potencial da agua na folha, parâmetros de crescimento vegetativo, componentes do rendimento e os compostos fenolicos no momento da colheita. Argissolos Bruno-acizentados propiciaram maior crescimento vegetativo, sobretudo em massa de ramos, comprimento de entrenos e area foliar, assim como, cachos com maior numero de bagas. Planossolos Haplicos com maior disponibilidade hidrica proporcionaram maior produtividade das videiras. Neossolos Regoliticos levaram a menor disponibilidade hidrica, o que reflete em reducao do potencial da agua na folha. Nestas condicoes de restricao hidrica, as videiras tiveram menor crescimento e rendimento, como tambem, maiores teores de taninos e indice de polifenois totais. Em geral, o Neossolo Regolitico pode ser considerado mais promissor para a obtencao de vinhos finos de qualidade.

AGREGAÇÃO E FRAÇÕES FÍSICAS DA MATÉRIA ORGÂNICA DE UM ARGISSOLO VERMELHO SOB SISTEMAS DE USO NO BIOMA PAMPA

Pasture-agroforestry systems have become an important strategy for the use of sandy soils in the Pampa Biome. The purpose of this study was to evaluate the aggregation, total organic C (TOC) and total nitrogen (TN), carbon of the physical fractions and humification degree of organic matter (OM). Evaluations were conducted in an Alfisol under homogenous eucalyptus forest (HF), between the rows of a pasture-agroforestry system (PA) and in native pasture (NP) in the layers 0.000-0.025, 0.025-0.075, 0.075-0.125, and 0.125-0.225 m. Disturbed samples were collected to evaluate water-stable aggregates (WSA %), TOC and TN. The physical (granulometrical and densimetrical) fractionation of OM was carried out, and the free light fraction (FLF) and occluded light fraction (OLF) of OM in the surface layer subjected to Fourier Transform Infrared (FTIR) and Electron Paramagnetic Resonance (EPR) analyses. The WSA and mean weight diameter in the layer 0.025-0.075 m indicated a greater degradation of the PA soil. Higher levels of TOC, TN, coarse fraction carbon (CFC), carbon associated with minerals (CAM), FLF and OLF in the surface layer were observed in HF. Between land uses, the FTIR spectra were similar. However, the FLF had more intense bands in the region of 1072 cm-1, suggesting higher amounts of polysaccharides than in the OLF. The spin densities obtained by EPR at OLF were higher than of FLF, indicating a higher humus fraction.

GIS as a Support to Soil Mapping in Southern Brazil

Traditional soil surveys follow a specific methodology to identify, characterize, and fit mapping units in a classification system and to spatialize them in order to produce soil maps. The need for observation and characterization on field, associated with the physical and chemical analyses, makes the surveys expensive and therefore scarce. The low number of surveys stimulated the development of models for digital soil mapping, whose results proved to be possible to predict and spatialize many soil characteristics. However, conventional soil surveys remain important as a basis for the development of digital soil mapping models, setting a reason to continue the development of methodologies to improve the conventional surveys. Technologies like GPS and GIS contribute to make field observation and soil sampling more objective and make the mapping process and the production of hardmaps easier and faster. The objective of this study was to develop methodologies to integrate cartographic base elements with field work, using GIS and GPS in an area corresponding to 20 topographic charts in scale 1:50,000 in the State of Rio Grande do Sul, Southern Brazil, to obtain soil mapping based on the Brazilian Soil Classification System. The result obtained was a georeferenced digitized soil map, continuous for the whole region, free of inconsistency among neighbor map sheets and with attributes associated with the mapping units. These characteristics allow the use and application of the soil map for many purposes like zoning, diagnosis, suitability analysis as well as serving as a basis to the development of models for digital soil mapping.

Caracterização de mapas legados de solos: uso de indicadores em mapas com diferetens escalas no Rio Grande do Sul

Mapas convencionais de solos tem adquirido importância crescente como entrada para diversas aplicacoes, muitas vezes sem levar em conta a sua qualidade deles. O objetivo deste estudo foi descrever e comparar mapas de solos usando indicadores quantitativos de facil determinacao. Foram utilizados nove mapas elaborados em diferentes escalas no Rio Grande do Sul e o software ArcGIS. Calcularam-se a escala efetiva, o numero de poligonos menores que a area minima mapeavel e um indice de complexidade de forma, e quantificaram-se o numero de classes taxonomicas, de tipos de solos e de unidades de mapeamento e a fracao da area com dados nao uniformes. Os resultados evidenciaram que a qualidade de mapas de solos tende a ser inferior ao presumido para sua escala de apresentacao, o que demonstra a importância e a necessidade de avaliacoes previas ao seu uso. Indicadores computados a partir dos poligonos e da legenda possibilitam avaliacao rapida e objetiva, com potencial de aplicacao na sistematizacao e documentacao de dados legados de solos no Brasil.

Mapeamento digital do solo e suas implicações na extrapolação das relações solo-paisagem em escala de detalhe

The objective of this work was to test the extrapolation of soil-landscape relationships in a reference area (RA) to a topographic map (scale 1:50,000), using digital soil mapping (DSM), and to compare these results to those obtained in similar studies previously conducted in Brazil. A soil survey in a 10 km2 RA, using conventional mapping techniques (scale 1:10,000), was made in order to map a 678 km2 physiographically similar area (scale 1:50,000) using DSM. The decision tree technique was employed to build a predictive extrapolation model based on soil classes and eight terrain attributes in the RA. The validation of DSM by application of field observation points resulted in a 66.1% global accuracy and in 0.36 kappa index. The most representative soils in the area were correctly predicted, whereas the less representative and less frequent soils in the landscape (and consequently with reduced sampling) had their prediction compromised. The RA proportion, which equals 1.5% of the total area, is a limiting factor in the formulation of soil-landscape relationships to precisely represent the mapped area by DSM.

Geotechnologies and Soil Mapping for Delimitation of Management Zones as an Approach to Precision Viticulture

Data of the physical and chemical properties of soils from three vineyards located in Vale dos Vinhedos, Bento Goncalves, Rio Grande do Sul state, in southern Brazil, were processed. Soil mapping was performed by means of four profiles and the digital elevation model in detailed scale. Then, superficial soils (0–20 cm) were sampled according to a grid pattern. Analysis of variance (ANOVA), kriging, and unsupervised classification methods were applied on physical and chemical data of superficial soils sampled according to grid pattern. This study aimed to compare both methods, the conventional soil mapping and the map produced with superficial soil sampling, about their potential for definition of the management zones, as an approach for precision agriculture. Maps elaborated by conventional soil mapping overlapped partially with the maps derived from superficial sampling, probably due to the specific methodological differences of each case. Anyway, both methods are complementary because of the focus on vertical variability and horizontal variability, respectively. In that sense, slope appears as significant edaphic parameter, due to its control on water circulation in the profile of soil.