Ricardo Simão Diniz Dalmolin

The effect of 10% HF treatment on the resolution of CPMAS 13C NMR spectra and on the quality of organic matter in Ferralsols

The investigation of the chemical composition of soil organic matter (SOM) in Ferralsols by means of solid-state cross-polarization magic angle spinning (CPMAS) 13C nuclear magnetic resonance (NMR) spectroscopy is limited by their high iron oxide concentration and their low organic carbon content. In order to circumvent those limitations, such samples are often treated with hydrofluoric acid (HF) to remove paramagnetic material and to concentrate the amount of SOM. The main objectives of this study were to elucidate the impact of this approach on the resolution of the CPMAS 13C NMR spectra and on the chemical composition of the SOM in the A and B horizons of four Brazilian Ferralsols. Therefore, those soils were subjected to up to eight successive treatments with 10% (w/w) HF. Each of those extractions resulted in an enhancement of the C content of the samples. A relationship between mass loss caused by the treatment and texture and mineralogy was observed. However, high losses of carbon occurred during the HF treatments, particularly in the B horizons, but no consistent alterations in the distribution of carbon functional groups were determined by CPMAS 13C NMR, suggesting that preferential loss of specific carbon groups was not induced. The concentration of total and dithionite extractable Fe increased after two treatments for most of the samples. This may be best explained by the preferential dissolution of silicate leading to a selective enrichment of iron containing minerals. After four treatments, the Fe concentration declined considerably. After the second treatment, the spectral resolution improved. Considering the obtained results, it can be confirmed that the efficiency of the HF treatment is rather controlled by the number than by the duration of the extraction. We suggest that, for A horizons of Ferralsols, four repetitions of HF treatment are sufficient to yield well-defined spectra. For their B horizons, on the other hand, the CPMAS 13C NMR spectra obtained after four HF extractions were of poor quality, indicating that for these soils at least eight HF treatments have to be performed to acquire reasonable spectra.

A aptidão de uso da terra como base para o planejamento da utilização dos recursos naturais no município de São João do Polêsine - RS

The lack of knowledge on land use suitability and appropriate planning of its use have been a frequent reality causing negative impacts on the environment. In this way, the objective of this research was to determine land suitability, current land use and conflicts of use, seeking to contribute for the rational planning of the natural resources in the Sao Joao do Polesine (SJP), RS. The environmental analysis was made through the integration of different plans of information as soils, relief, hydrography, agricultural suitability, land use and areas of permanent preservation (APP). SJP presents more than 50% of its area destined to agricultural activities, 14.8% of the SJP are framed as APP, with half of that area being used inadequately. The main problems of the county are related to the inadequate use of natural resources, without considering information regarding to the environmental legislation and land suitability, in the planning process.

Relação entre os constituintes do solo e seu comportamento espectral

The spectral soil reflectance is an expression that characterizes the electromagnetic radiation reflected by soil surface. Most of the soil constituents can be identified and sometimes quantified by the spectral behavior. The main soil constituents that influence its spectral behavior are the organic matter, iron oxides, mineralogy and clay content and moisture. The use of soil reflectance allows to obtain information to quickly identify and quantify the soil characteristics, both in laboratory and orbital levels, but it has been tested and used mainly in developed countries. In Brazil, the research interest for the study of the soil spectral reflectance started in the 1980’s, being a recent research area which needs research support to achieve a better understanding of the spectral interaction among the different components of the soil.

Regressões Logísticas Múltiplas: fatores que influenciam sua aplicação na predição de classes de solos

More effective methodologies to determine the soil class distribution must be evaluated in order to meet the demand for soil maps at regional and global scales. In this study, logistic regressions were used as predictive models in an application of Digital Soil Mapping. The models were derived from an existing soil map as dependent variable and terrain attributes as independent variables. The probability of finding soil classes in the landscape at the 1st and 2nd Categorical Level of the Brazilian System of Soil Classification (SiBCS) was determined. The quality of the predicted map was tested using a contingency matrix. Approximately 85 % of the Acrisols (Argissolos) were correctly predicted, in relation to the original map. Of the hydromorphic soils, 75 % were correctly predicted. The prediction was inaccurate for classes in very similar positions in the landscape. It was also found that the non-representative soil classes of the landscape were not properly spatialized, due to sensitivity of the logistic models to the relative proportion of the samples used to adjust the models.

Matéria orgânica em Neossolo de altitude: influência do manejo da pastagem na sua composição e teor

Burning pastures after the winter is a traditional practice in highland soils, whose main purpose is the regrowth of vegetation. However, the impact of fire, as well as the influence of grazing on the organic matter of Leptosols is still unknown. The purpose of this study was to investigate the composition and content of organic matter in soil profiles from Sao Jose dos Ausentes, state of Rio Grande do Sul, and to relate the results with the occurrence of burning and grazing, in comparison with a soil under native forest. The following environments were studied: grazed native pasture (2 animals ha-1) without burning for 22 years; grazed native pasture (0.5 animals ha-1) burned every two years; and native forest adjacent to the pasture area. Composed soil samples were collected from four layers (0-5, 5-10, 10-15 and 15-30 cm) in which contents of C, of N, and of iron oxides (Fed and Feo) were determined and infrared spectroscopy and thermogravimetry analyses performed. The subsurface layers of the fire-affected environment contained greater organic matter contents, and in general, a composition with higher proportion of chemically labile structures, in comparison with the unburned pasture. In the latter environment, the lower C content than in the burned pasture was ascribed to more intensive grazing. The C distribution in the native forest environment was similar to that of the unburned pasture. Nevertheless, in the samples under forest, the proportion of organic matter of low molecular weight, extractable with 0.1 mol L-1 HCl and related mainly to microbial activity, exceeded that of the pasture environment.

Utilização do sistema de avaliação do potencial de uso urbano das terras no diagnóstico ambiental do município de Santa Maria - RS

The accelerated urban expansion has promoted several negative impacts on the environment. The need of new methodologies that allows a more appropriate planning of the natural resources grows constantly. The objective of this research was to accomplish an environmental diagnostic in urban areas of Santa Maria - RS, Brazil, determining the land use conflicts through the Urban Land Use Potential System. Products and techniques of remote sensing and image geoprocessing were used. Improper land use is related to the fragility of the geological material and soil resources. Up to 33% of the area is used above its potential with inadequate construction and urban agriculture.

Pinus afforestation in South Brazilian highlands: soil chemical attributes and organic matter composition

In the last three decades, exotic tree species are being introduced in the natural pastures of the highlands located at the northeastern part of Rio Grande do Sul State (RS), Brazil. This alteration of land use may impart drastic changes in the soil attributes. In this context, this work aimed to evaluate the impact of Pinus taeda afforestation on soil chemical attributes and organic matter (SOM) composition in Leptosols from Campos de Cima da Serra, RS. Soil samples under eight year old (Pi8) and 30 year old (Pi30) Pinus plantations and under native pasture (NP) were studied. Contents of exchangeable cations and of micronutrients and soil pH were determined. The SOM composition was investigated by means of elemental analyses and FTIR spectroscopy. The soil under pasture had a higher content of nutrients and of SOM in comparison to Pinus soils, reflecting the higher input and decomposition rate of the below ground added residue in the grassland environment. The SOM in pasture soils showed a higher content of carbohydrate and of structures derived from microbial metabolism. Besides the depletion of nutrients and of SOM, Pinus afforestation affected the SOM quality: following afforestation, the proportion of chemically recalcitrant structures and of carboxylic groups increased, whereas N-containing groups decreased.

Extrapolação das relações solo-paisagem a partir de uma área de referência

The aim of this study was to apply an automated technique of soil mapping from predictive models developed at a reference area, into nearby areas of the same soil-landscape relationships. Generalized linear models were developed using nine terrain attributes derived from a digital elevation model as covariate predictors, with soil classes, obtained from a conventional soil survey, as dependent variables. The models were able to distinguish the three main forms of the local landscape. Soil classes with pedogenesis intimately tied to the predictive covariates obtained the best results. The soil maps generated, showed a reproducibility of 46.12% and an accuracy of 21.06%.

Morfologia dos contatos entre solo-saprolito-rocha em neossolos derivados de arenitos da formação caturrita no Rio Grande do Sul

The use of the shallow Neossolos (Leptosols and Regosols) is limited in view of the small depth and rock fragments on the surface. There is a lack of information about the definition of the contacts between soil, saprolite and rock in this soil class, as well as tools that would facilitate the morphologic field identification. The objectives of this research were an evaluation of the morphology of the contact between soil, saprolite and rock in the Neossolos derived from the sandstones of the Caturrita Formation, in the central area of Rio Grande do Sul State; to test and to adapt the weathering classes of Pedron et al. (2009) to the conditions of sedimentary rock; and to verify the correlation of the weathering classes with penetration resistance. It was stated that the morphology of the saprolithic layers of the Neossolos Litolicos (Leptosols) and Neossolos Regoliticos (Regosols) derived from sandstone are similar to the same soil classes derived from volcanic rocks in the State, allowing the adaptation of the same weathering classes proposed by Pedron et al. (2009). The tests with the impact penetrometer showed high correlation with the weathering classes adapted in this study. The following contacts were identified in the studied profiles: lithic contact, lithic fragmentary contact, and saprolithic fragmentary contact. The authors suggest, considering its importance, the inclusion of this latter in the Brazilian soil classification system.

Carbono orgânico, óxidos de ferro e distribuição de agregados em dois solos derivados de basalto no Rio Grande do Sul - Brasil

Several factors can affect the behavior of soil structure. Amongst them, the organic carbon (OC) content and the content and type of iron oxides present in the soil have been related as the most important. This work is aimed at evaluating soil aggregate behavior regarding to the role of organic carbon, and forms of iron oxides in two soils developed from basalt in subtropical Brazil. Aggregates with size less than 8 mm of an Udorthents and a Paleudult under forest, pasture and conventional tillage of the steep backslope of Sul Riograndense plateau were shaked in water during 0, 30, 60 and 90 minutes. The aggregate distribution in three size classes was measured as well as the content of OC, iron extractable with ditionite-citrate-bicarbonate (Fed) and ammonium oxalate (Feo) in the aggregates. The Udorthents showed greater content of soil OC than Paleodult and the forest soil showed greater content of soil OC than pasture and conventional tillage. The content of Fed and Feo were similar between both soils and uses. The studied soils showed a differentiated degree of aggregate hierarchy (AH). The most stable aggregates (90min of shaking) presented a trend to possess greater content of OC than the less stable ones (0min of shaking). Amongst the variables considered in this study, the content of OC was the attribute that more affects the expression of AH and the action of iron oxides in the aggregation not only depends on its type and amount, but also of the content of soil OC. It was also observed that the most stable aggregates (90min of shaking) tended to present greater content of Fed and smaller content of Feo.