Letícia Sequinatto

Occurrence of agrochemicals in surface waters of shallow soils and steep slopes cropped to tobacco

Tobacco cultivation in shallow soils and steep landscape under intense use of agrochemicals contributes to environment degradation. In this study, we assessed the concentration of agrochemicals in draw wells used for human consumption and a creek in a small catchment predominantly cropped to tobacco. Chlorpyrifos, flumetralin, and iprodione were determined by gas chromatography with electron capture detection, while imidalcloprid, atrazine, simazine, and clomazone were quantified by high-performance liquid chromatography with UV detection. Considering all sampling sites, all agrochemicals were detected at least once, except for flumetralin. The occurrence of agrochemicals in tobacco crops is a consequence of their fast transfer to surface water.

Atributos físicos e químicos de um argissolo vermelho, em pomar orgânico de citros com manejo da vegetação nas entrelinhas

The management in organic citrus orchards is differentiated with respect to conventional orchards. Thus, it was aimed to evaluate some physical and chemical attributes of a typic ultisol and productivity of a mandarin orchard, cv. Montenegrin under organic production system, with different vegetation management between the lines. The treatments were: harrowing, mowing, lodging with coulter and log dragging. The evaluation of the physical attributes occurred under the canopy and in the machinery traffic area, in the depths of 0.0-0.1 and 0.1-0.2 m. The chemical fertility of the soil was determined in the layer of 0.0-0.1, 0.1-0.2 and 0.2-0.4 m, while the fruit yield was estimated from central plants of each portion. Machine traffic negatively affected the physical attributes of soil below the interface patch, although it was not restrictive to fruit yield. In all treatments there was an increase of organic matter in the topsoil, and the levels of P, K+, Ca2+ and Mg2+ in the three soil layers in relation to the adjacent area with native vegetation. The handling with harrowing showed significantly higher productivity in relation to the management with mowing.

High Nitrogen Fertilization of Tobacco Crop in Headwater Watershed Contaminates Subsurface and Well Waters with Nitrate

Our hypothesis was that subsurface and well waters in watershed with shallow, stony soils, steep landscapes, and cropped to tobacco are contaminated by nitrate. Nitrate in soil solution was monitored in (0.20 m) and below (0.5 m) root zone with tension lysimeters, in five transects. Water from two wells (beneath tobacco field and in native forest) used for human consumption was also analyzed for nitrate. Soil bulk density, porosity, and saturated hydraulic conductivity were evaluated. Soil physical and hydrological properties showed great variation at different landscape positions and soil depths. Soil coarse grain size, high porosity, and saturated hydraulic conductivity favored leaching nitrate. Nitrate in soil solution from tobacco fields was greater than in natural environment. Nitrate reached depths bellow rooting zone with values as high as 80 mg L−1 in tobacco plantation. Water well located below tobacco plantation had high nitrate concentration, sometimes above the critical limit of 10 mg L−1. Tobacco cropping causes significant water pollution by nitrate, posing risk to human health. A large amount of nitrogen fertilizers applied to tobacco and nitrate in subsurface waters demonstrate the unsustainability of tobacco production in small farming units on steeps slopes, with stony and shallow soils.

Mineralogia da argila e propriedades químicas de solos do Planalto Norte Catarinense

No Planalto Norte Catarinense sao escassas as informacoes sobre a composicao mineralogica dos solos e ha poucos perfis de solo descritos e caracterizados para a regiao. O mapa de solos de Santa Catarina indica predominância de Cambissolos, Neossolos Litolicos e Latossolos, com Gleissolos ocupando areas de varzeas. Esses solos ocorrem em relevo desde plano ate forte ondulado, onde pequenos e medios proprietarios rurais desenvolvem cultivos diversificados, com areas expressivas de reflorestamentos com pinus. Este trabalho objetivou aprofundar o conhecimento sobre a mineralogia e as propriedades quimicas de alguns desses solos, desenvolvidos de rochas sedimentares de distintas formacoes geologicas. Foram descritos e coletados cinco perfis de solo, sendo um Latossolo e quatro Cambissolos. Na fracao terra fina seca ao ar (TFSA), foram feitas analises fisicas (areia, silte, argila) e quimicas de caracterizacao basica (pH em agua, carbono orgânico, Ca2+, Mg, K, Na, Al, H + Al) e com base nesses parâmetros foi calculada a CTC efetiva, CTC pH7, Soma e Saturacao por Bases. Analises mineralogicas foram conduzidas na fracao argila do horizonte B de cada solo, utilizando-se difratometria de raios X. Todos os solos apresentaram reacao muito acida, com baixa soma e saturacao por bases e teores elevados de carbono orgânico e Al trocavel. A mineralogia da fracao argila revelou predominio de caulinitas em todos os solos, com quantidades consideraveis de illita, gibbsita e vermiculita com hidroxi-Al entrecamadas.

Qualidade de um Argissolo submetido a práticas de manejo recuperadoras de sua estrutura física

The aim of this study was to evaluate the effectiveness of alternative managements in restoring a physically degraded soil after eight years. For this, an experiment managed with direct sowing (no tillage) is being conducted since 2002, in Eldorado do Sul, RS, in an Ultisol that initially was degraded naturally with a high degree of compaction. Treatments consisted of three soil cover crops in winter (fallow, oat + vetch and forage radish), two depths (0.12 and 0.21 m) of operation of the shank of fertilizer and seed drill and three traffic conditions (tractor movements, harvester and no traffic). In summer corn and soybeans are sown in annual rotation. There was an increase in the levels of soil organic matter and of its fractions, which resulted in reduced values of density and increased macroporosity and total porosity of soil. Soil bulk density was lower in soil condition not without agricultural machinery traffic. The conversion of naturally degraded field into a system of grain production using integrated management alternatives with no tillage system restores the physical quality of soil to carry out appropriately its functions.