Paulo César do Nascimento

Uso de regressões logísticas múltiplas para mapeamento digital de solos no Planalto Médio do RS

Logistic nominal regressions establish mathematical relations between continuous or discrete independent variables and discrete dependent variables. The prediction potential of the occurrence and distribution of soil classes in the region Ibiruba and Quinze de Novembro, RS, Brazil was evaluated. Using a digital elevation model (DEM) with 90 m resolution, were calculated several topographic characteristics (elevation, slope, and curvature) and hydrographic variables (distance to rivers, flow length, topographical wetness index, and stream power index). Multiple logistic regressions were established between the soil classes mapped on the basis of a traditional survey at a scale of 1:80.000 and the land variables calculated using the DEM. The regressions were used to calculate the probability of occurrence of each soil class. The final estimated soil map was drawn by assigning the soil class with highest probability of occurrence to each cell. The general accuracy was evaluated at 58 % and the Kappa coefficient at 38 % in a comparison of the original soil map with the map estimated at the original scale. A legend simplification had little effect to increase the general accuracy of the map (general accuracy of 61 % and Kappa coefficient of 39 %). It was concluded that multiple logistic regressions have a predictive potential as tool of supervised soil mapping.

TEORES E CARACTERÍSTICAS DA MATÉRIA ORGÂNICA DE SOLOS HIDROMÓRFICOS DO ESPÍRITO SANTO

Os teores e as caracteristicas da materia orgânica do solo (MOS) sao resultados das taxas de producao e incorporacao, decomposicao ou alteracao e mineralizacao, de acordo com as condicoes do ambiente. Nos solos hidromorficos, a dinâmica da MOS e influenciada pelo deficit de oxigenio, o que diminui a taxa de decomposicao e gera produtos diferenciados em relacao aos solos bem drenados. O presente trabalho teve por objetivo determinar os teores e caracteristicas da materia orgânica do solo em tres diferentes localidades do Estado do Espirito Santo. Foram realizadas determinacoes de C orgânico total (COT) por tres metodos, alem de fracionamento das substâncias humicas (SH), com determinacao de teores das fracoes humina (FHU), acidos humicos (FAH) e acidos fulvicos (FAF), e determinacoes de materia orgânica leve (MOL) e residuos minimos. Os resultados mostraram altos teores de C orgânico para a maioria dos horizontes superficiais dos perfis estudados, com ocorrencia de material de constituicao orgânica; altos valores na relacao SH/COT e baixos valores para EA/FHU, indicando a fracao humina como a predominante entre os compartimentos da MOS; maior mobilidade da fracao acidos fulvicos, expressa por teores relativamente maiores em subsuperficie; e altos teores de MOL, indicando incipiente humificacao, em razao do hidromorfismo.

Sistemas de manejo e a matéria orgânica de solo de várzea com cultivo de arroz

Flooded soils are important sinks of atmospheric C, hence the effect of agricultural practices on their organic matter (OM) dynamics should be better understood. This study was carried out in an 11 year experiment at IRGA (Instituto Rio Grandense do Arroz) experimental station in Cachoeirinha, Rio Grande do Sul, southern Brazil. The main objectives of this study were to evaluate the effect of no-tillage (NT) on organic C stocks, on OM lability and on the physical protection of OM in soil aggregates of a Gleysol (200 g kg-1 clay) cultivated with paddy rice (Oryza sativa L) in comparison to conventional tillage (CT). Organic C (0-20 cm) was not affected by soil management systems (38.39 Mg ha-1 in CT soil and 37.36 Mg ha-1 in NT soil) indicating that decomposition rates of OM in this anaerobic environment were not influenced by soil disturbance. The lability of OM in this flooded soil, calculated by the ratio of particulate organic C (POC)/mineral-associated organic C was higher than the values usually verified for well-drained soils of subtropical regions and, in the 0-20 cm soil layer, C was not affected by soil management systems (0.24 in CT and 0.28 in NT). The increase of the occluded light OM fraction (intra-aggregate light fraction) was only a small proportion (9%) in relation to the total organic carbon increase in NT, compared to CT, in the surface layer (0-5 cm). These data suggest that the physical protection of OM in soil aggregates was not an important mechanism of OM stabilization in this environment of restrained drainage. The reason is probably the weak soil aggregation and/or the easy access of microorganisms and their enzymes to the decomposition of the intra-aggregate OM pool due to the soil saturation by water.

Ação dos térmitas no solo

ABSTRACT The order Isoptera is well known by its potential asa plague, although the number of species that are plagues issmall within the group. Termites are the dominant invertebratesin tropical terrestrial environments and are spread from tropicalrainforests to the savannahs, being found even in arid regions,in various habitats. These insects have a major role and arestill little studied in tropical ecosystems. Nutrient cycling,aeration, water infiltration of soil, bioturbation, aggregatesformation and organic material decomposition, are processesinfluenced by the action of termites, which , directly or indirectly,affect soil and landscape formation wherever they are. Wesuggest that a better approach must be addressed in futureresearches about these insects influence in the soil underspecified conditions of use and management, in sustainablefood production and climate changes . Key words : Isoptera, termite activity, soil biology, bioturbation,plague-termites . INTRODUCAO A importância ecologica dos isopteros emecossistemas tropicais e grande, principalmente quandoconsideradas as modificacoes que podem causar noambiente, desde alteracoes no aspecto visual dapaisagem, pela construcao de seus ninhos, alem dealteracoes da topografia, como dos microrrelevos demurundus, ate modificacoes nas propriedades fisicase quimicas do solo, efeitos no processo dedecomposicao, ciclagem de nutrientes, entre outros(HOLT & LEPAGE, 2000). Os cupins (termitas) sao amais importante fauna do solo nos tropicos quentessazonalmente secos (LOBRY DE BRUYN &CONACHER, 1990), sendo fundamentais para ofuncionamento do ecossistema, pois ocupam niveistroficos na cadeia alimentar do solo (SILVA et al., 2007).Os termitas sao reconhecidos como “engenheiros doecossistema” (DANGERFIELD et al., 1998), devido ahabilidade que possuem de modificar a estrutura do

Chemical and mineralogical changes in a Brazilian Rhodic Paleudult under different land use and managements

Changes in land use and management can affect the dynamic equilibrium of soil systems and induce chemical and mineralogical alterations. This study was based on two long-term experiments (10 and 27 years) to evaluate soil used for no-tillage maize cultivation, with and without poultry litter application (NTPL and NTM), and with grazed native pasture fertilized with cattle droppings (GrP), on the chemical and mineralogical characteristics of a Rhodic Paleudult in Southern Brazil, in comparison with the same soil under native grassland (NGr). In the four treatments, soil was sampled from the 0.0-2.5 and 2.5-5.0 cm layers. In the air-dried fine soil (ADFS) fraction (∅ < 2 mm), chemical characteristics of solid and liquid phases and the specific surface area (SSA) were evaluated. The clay fraction (∅ < 0.002 mm) in the 0.0-2.5 cm layer was analyzed by X-ray diffraction (XRD) after treatments for identification and characterization of 2:1 clay minerals. Animal waste application increased the total organic C concentration (COT) and specific surface area (SSA) in the 0.0-2.5 cm layer. In comparison to NGr, poultry litter application (NTPL) increased the concentrations of Ca and CECpH7, while cattle droppings (GrP) increased the P and K concentrations. In the soil solution, the concentration of dissolved organic C was positively related with COT levels. With regard to NGr, the soil use with crops (NTM and NTPL) had practically no effect on the chemical elements in solution. On the other hand, the concentrations of most chemical elements in solution were higher in GrP, especially of Fe, Al and Si. The Fe and Al concentrations in the soil iron oxides were lower, indicating reductive/complexive dissolution of crystalline forms. The X-ray diffraction (XRD) patterns of clay in the GrP environment showed a decrease in intensity and reflection area of the 2:1 clay minerals. This fact, along with the intensified Al and Si activity in soil solution indicate dissolution of clay minerals in soil under cattle-grazed pasture fertilized with animal droppings.

Estimativa do benefício econômico potencial de dois levantamentos de solos no Estado do Rio Grande do Sul

This study applies decision analysis techniques for the qualification of economic value of the a high intensity Soil Survey of Sentinela do Sul County, RS, Brazil (scale 1:50,000) and a soil survey of the Charcoal Basin of the Jacui River, RS, Brazil (Scale 1:100,000), using economic information related to the major regional crops and soil survey quality. The determination of the economic value is made by quantifying the increase in economic return when land use planning uses soil survey information. Results of this evaluation highlight the economic benefits generated by the use of soil survey information (R

Caracterização e classificação de solos graníticos em topossequência na região Sul do Brasil

153,15 ha-1 e R

CHARACTERIZATION AND CLASSIFICATION OF FLOODPLAIN SOILS IN THE PORTO ALEGRE METROPOLITAN REGION, RS, BRAZIL

70.15 ha-1, respectivelly for a 1:50,000 map and for a 1:100,000 map) are larger that soil survey costs (R

Atributos físicos e químicos de agregados pedogênicos e de coprólitos de minhocas em diferentes classes de solos da Paraíba

1.03 ha-1 for a 1:50,000 map and R

Razão de Perdas de Solo sob cultivo de três leguminosas

0.38 ha-1 for a 1:100,000 map).