Oscarlina Lúcia dos Santos Weber

Acetamiprid, carbendazim, diuron and thiamethoxam sorption in two Brazilian tropical soils

Sorption of acetamiprid ((E)-N1-[(6-chloro-3-pyridyl)methyl]-N2-cyano-N1-methylacetamidine), carbendazim (methyl benzimidazol-2-ylcarbamate), diuron (N-(3,4-dichlorophenyl)-N, N-dimethyl urea) and thiamethoxam (3-(2-chloro-thiazol-5-ylmethyl)-5-methyl-[1,3,5]oxadiazinan-4-ylidene-N-nitroamine) was evaluated in two Brazilian tropical soils, Oxisol and Entisol, from Primavera do Leste region, Mato Grosso State, Brazil. To describe the sorption process, batch experiments were carried out. Linear and Freundlich isotherm models were used to calculate the K d and K f coefficients from experimental data. The K d values were utilized to calculate the partition coefficient normalized to soil organic carbon (K oc ). For the pesticides acetamiprid, carbendazim, diuron and thiamenthoxan the K oc (mL g− 1) values ranged in both soils from 98 – 3235, 1024 – 2644, 145 – 2631 and 104 – 2877, respectively. From the studied pesticides, only carbendazim presented correlation (r2 = 0.82 and p < 0.01) with soil organic carbon (OC) content. Acetamiprid and thiamethoxam showed low sorption coefficients, representing a high risk of surface and ground water contamination.

Carbono orgânico nas frações granulométricas e substâncias húmicas de um Latossolo Vermelho Amarelo distrófico - LVAd sob diferentes agrossistemas

This study aimed to assess the total organic carbon content in chemical and granulometric fraction of an Oxisol from four different land use systems. The soil samples were collected in Juruena and Juara, Mato Grosso (Brazil), and prepared for the physical and chemical fractionations. The results indicated that different land use systems caused significative carbon content changing in both humic substances and granulometric fraction. It was observed from the differentiated concentration of humine and free fulvic acids for each system. The distribution of total organic carbon in the granulometric fraction 53 μm for all land use, indicating greater presence of organic material in the silt and clay.

Cargas elétricas estruturais e variáveis de solos tropicais altamente intemperizados

Highly weathered tropical soils present high amount of colloids with variable electrical charge. However, there are few references related to the quantification of such charges, mainly in soils with acric attributes, which represent one of the extremes in the weathering scale. In this study permanent and variable charges were determined in four Oxisols and compared to an Alfisol with predominantly permanent charge. Samples were investigated using the Cs+ adsorption method, which measures the structural permanent charge (so) and is based on the preference of Cs+ over Li+ in the siloxane surface sites and the lower selectivity of ionizable surface group for the cesium ion. The variable charge represented more than 50% of the total charge of the evaluated soil samples. Two of the four Oxisols with acric properties had a significant permanent structural charge, probably due to small quantities of aluminum hydroxy-interlayer vermiculite and chlorite. The amount of permanent structural charges presented by the Alfisol was five times higher as compared to the Oxisols, which may be attributed to their mineral composition differences. The cesium adsorption method was able to quantify significant amounts of structural charges even in soils with a low amount of 2:1 clay minerals.

Environmental Behavior of Chlorpyrifos and Endosulfan in a Tropical Soil in Central Brazil

The environmental behavior of chlorpyrifos and endosulfan in soil was studied in the central-western region of Brazil by means of a field experiment. Sorption was evaluated in laboratory batch experiments. Chlorpyrifos and endosulfan were applied to experimental plots on uncultivated soil and the following processes were studied: leaching, runoff, and dissipation in top soil. Field dissipation of chlorpyrifos and endosulfan was more rapid than reported in temperate climates. Despite the high Koc of the studied pesticides, the two endosulfan isomers and endosulfan sulfate as well as chlorpyrifos were detected in percolated water. In runoff water and sediment, both endosulfan isomers and endosulfan sulfate were detected throughout the period of study. Observed losses of endosulfan by leaching (below a depth of 50 cm) and runoff were 0.0013 and 1.04% of the applied amount, whereas chlorpyrifos losses were 0.003 and 0.032%, respectively. Leaching of these highly adsorbed pesticides was attributed to preferential flow.

Estoque de nutrientes sob diferentes sistemas de uso do solo de Colorado do Oeste-RO

The replacement of forest by other land use can lead to significant losses in soil organic matter, changing its dynamic and the nutrients inputs and outputs of the system. The objective of this study was to assess nutrient stocks under different land use systems in Colorado do Oeste-RO. The agroforestry (teak, and cocoa), forestry (teak with five years), teak for eight years, farming areas (teak, cocoa and pasture) and pasture were the systems evaluated and the native forest was taken as reference. In each system three small trenches were dug, in which deformed and undeformed soil samples, at depths of 0 to 5, 5 to 10, 10 to 20 and 20 to 30 cm were taken. In these samples the nutrients N, P, K, Ca and Mg, organic matter, bulk density and clay content were determined. A completely randomized design with split plots and, three replications in each system was adopted. Differences were observed in soil nutrient stocks among the usage systems and with depth. The concentration of nutrients was influenced by the system. Ca was the nutrient most stored (2912.86 to 5188.48 kg ha-1) in all systems and K was the least(17.33 to 46.22 kg ha-1). The system of teak five years is the system which is closer to the forest, for the storage of nutrients.

Distribuição espacial da granulometria, cor e carbono orgânico do solo ao longo de um transecto em microbacias na Amazônia meridional

The study was conducted in forested headwater catchments near Juruena, Mato Grosso with the objective of determining the spatial distribution of soil physical characteristics including clay content, redness ratio, and soil organic carbon along a transect that encompassed distinct soil classes. Soil samples from 0-20 cm and 40-60 cm depths were collected from 34 points. Variables were analyzed using descriptive statistics and geostatistics. The parameters analyzed by ordinary kriging demonstrated that the highest spatial variability occurred within the soil class Typic Kandiustox. In the study area, Plinthustults and Ultisols (with plinthic characteristics) were only found to occur in landscape positions less than 280 m above sea level; Oxisols were found exclusively above 280 m.a.s.l. The redness ratio and clay content were the soil parameters with the highest spatial variability across the transect. Poorly drained areas (demonstrated by lower values of redness ratio) demonstrated the lowest degree of spatial variability, and correspondingly, the highest consistency of color within the diagnostic horizons.

CRESCIMENTO E TEOR DE MICRONUTRIENTES EM PLANTAS DE MILHO SOB DOSES DE NÍQUEL E CALAGEM

The experiment was conducted in a greenhouse located at the Federal University of Mato Grosso, Cuiaba-MT, from March to May 2012. The objective was to assess the effects of different rates of nickel application with and without liming on maize growth and micronutrient levels. The study was a randomized block design in a 2 x 5 factorial arrangement with four replicates, for a total of 40 plots, including with and without liming and five rates of nickel application, on a clayey Red Yellow Latosol (Oxisol, USDA classification and Ferralsol, FAO classification). Both lime and nickel applications influenced plant growth, reducing plant development with increased nickel application without liming. It was also observed that both lime and nickel applications altered micronutrient levels in the maize plants, independent of which part of the plant was evaluated. Nickel played an antagonistic role with manganese and zinc and a synergistic role with copper and iron.

Oxidizable fraction of organic carbon in an Argisol under different land use systems

The objective of this study was to evaluate carbon input in labile and stable fractions in an ARGISOL of northwestern Brazil under different land use systems. Use systems being evaluated include: forest - MA (reference), agrosilvopasture - TCP (teak, cocoa and pasture); agroforest - TC (teak and cocoa); teak forest at 8 and 5 years - T8 and T5, and pasture - PA. In each system three furrows were made at depths of 0-5 cm, 5-10 cm and 10-20 cm. An area consisting of native vegetation (forest) adjacent to the experiment was sampled and used as control treatment. The use systems MA, T8 and T5 had higher levels of total organic carbon (COT) and the MA system had higher levels of labile carbon (CL) than the other systems, with the exception of TC at a depth of 10-20 cm. In the MA system, COT levels were higher in comparison to use systems TCP, TC and PA while CL levels were higher than the levels observed in use systems TCP and TC. In most cases being analyzed, CL levels were lower than COT levels, therefore this trait can be used as an indicator to assess anthropogenic changes relating to the maintenance or condition of soil organic matter.

Sorção do inseticida tiametoxam nas frações orgânica e mineral de um latossolo amarelo

The sorption of thiamethoxam in a Brazilian Oxisol was determined in soil samples with and without organic matter for two different dephs (0-0.1 and 0.4-0.7 m). The results indicated a predominant sorption of thiamethoxam on soil without organic matter. The following Kd values of 4.25 mL g-1 (0-0.1 m, r2 = 0.8534) and 5.30 mL g-1 (0.4-0.7 m, r2 = 0.9884) and Kf values, 7.65 mL g-1 (0-0.1 m, r2 = 0.9623) and 7.72 mL g-1 (0.4-0.7 m, r2 = 0.9775) were obtained. Those sorption coefficient values indicated a small interaction between thiamethoxam for both original soil and soil without organic matter.

MÉTODO DA ADSORÇÃO DE CÉSIO PARA DETERMINAÇÃO DA CARGA ES- TRUTURAL EM SOLOS ALTAMENTE INTEMPERIZADOS (1)

The knowledge of permanent and variable charge is of high importance to a better understanding of the fate of chemical elements in soil. Four Brazilian Oxisols presenting acric character were investigated by an ion adsorption method that measures the structural charge density (sO) and were compared to an Alfisol (NV), which had predominantly permanent charge. The method is based on the preference of siloxane surface sites for cesium over lithium and on the lower selectivity of ionizable surface group for the ion cesium. In the Acrudoxes, the permanent charge decreased as the weathering index (Ki) decreased. The cesium adsorption method quantified significant amounts of structural charge, even in highly weathered soils.