Edson Campanhola Bortoluzzi

Investigation of the occurrence of pesticide residues in rural wells and surface water following application to tobacco

In this work the exposure of wells and surface water to pesticides, commonly used for tobacco cropping, was assessed. Water consumption wells and surface water flows were sampled at different times. After a preconcentration step with solid phase extraction (SPE), the selected pesticides were determined by gas chromatography with electron capture detection (GC-ECD) or high performance liquid chromatography with diode array detection (HPLC-DAD). No pesticides were detected in the well water samples and surface water flow in the winter season. However, in the spring and summer higher concentrations of chlorpyrifos and imidacloprid were found in the water source samples. Atrazine, simazine and clomazone were also found. The occurrence of pesticides in collected water samples was related with the application to tobacco.

Contaminação de águas superficiais por agrotóxicos em função do uso do solo numa microbacia hidrográfica de Agudo, RS

This work was accomplished with the intention of quantifying the presence of pesticide molecules in surface waters of three landscape units (LU) with different usage configurations in the Agudo watershed of the State of Rio Grande do Sul, Brazil. Two semiautomatic water collectors were installed at the stream of each LU, from which samples were collected during rain over three stages of the tobacco growing season: seedling transplant, tobacco plants with 6-10 expanded leaves, and at harvest. Imidacloprid, atrazine, simazine, and clomazone compounds were quantified by High Performance Liquid Chromatography with Ultraviolet Detector (HPLC-UV). Chlorpyrifos, flumetralin and iprodione were analyzed by Gas Chromatography with Electron Capture Detector (GC-ECD), but these compounds were not detected in the samples. The sampling points where the LU was configured with both the presence of tobacco crops and reduced gallery forest, showed at least one pesticide compound in a sampling time. No pesticide was detected in the LU, which is completely covered with permanent vegetation or with gallery forest protecting the water courses.

Soil water dynamics related to the degree of compaction of two brazilian oxisols under no-tillage

Soil water properties are related to crop growth and environmental aspects and are influenced by the degree of soil compaction. The objective of this study was to determine the water infiltration and hydraulic conductivity of saturated soil under field conditions in terms of the compaction degree of two Oxisols under a no-tillage (NT). Two commercial fields were studied in the state of Rio Grande do Sul, Brazil: one a Haplortox after 14 years under NT; the other a Hapludox after seven years under NT. Maps (50 x 30 m) of the levels of mechanical penetration resistance (PR) were drawn based on the kriging method, differentiating three compaction degrees (CD): high, intermediate and low. In each CD area, the infiltration rate (initial and steady-state) and cumulative water infiltration were measured using concentric rings, with six replications, and the saturated hydraulic conductivity (K(θs)) was determined using the Guelph permeameter. Statistical evaluation was performed based on a randomized design, using the least significant difference (LSD) test and regression analysis. The steady-state infiltration rate was not influenced by the compaction degree, with mean values of 3 and 0.39 cm h-1 in the Haplortox and the Hapludox, respectively. In the Haplortox, saturated soil hydraulic conductivity was 26.76 cm h-1 at a low CD and 9.18 cm h-1 at a high CD, whereas in the Hapludox, this value was 5.16 cm h-1 and 1.19 cm h-1 for the low and high CD, respectively. The compaction degree did not affect the initial and steady-state water infiltration rate, nor the cumulative water infiltration for either soil type, although the values were higher for the Haplortox than the Hapludox.

Soybean root growth and crop yield in reponse to liming at the beginning of a no-tillage system

Analyzing the soil near crop roots may reveal limitations to growth and yield even in a no-tillage system. The purpose of the present study was to relate the chemical and physical properties of soil under a no-tillage system to soybean root growth and plant yield after five years of use of different types of limestone and forms of application. A clayey Oxisol received application of dolomitic and calcitic limestones and their 1:1 combination in two forms: surface application, maintained on the soil surface; and incorporated, applied on the surface and incorporated mechanically. Soil physical properties (resistance to mechanical penetration, soil bulk density and soil aggregation), soil chemical properties (pH, exchangeable cations, H+Al, and cation exchange capacity) and plant parameters (root growth system, soybean grain yield, and oat dry matter production) were evaluated five years after setting up the experiment. Incorporation of lime neutralized exchangeable Al up to a depth of 20 cm without affecting the soil physical properties. The soybean root system reached depths of 40 cm or more with incorporated limestone, increasing grain yield an average of 31 % in relation to surface application, which limited the effect of lime up to a depth of 5 cm and root growth up to 20 cm. It was concluded that incorporation of limestone at the beginning of a no-tillage system ensures a favorable environment for root growth and soybean yield, while this intervention does not show long-term effects on soil physical properties under no-tillage. This suggests that there is resilience in the physical properties evaluated.

Mineralogia de partículas envolvidas na formação de gradiente textural em um argissolo subtropical

Texture gradient is a prominent and ubiquitoud feature of Acrisol. The objective of this paper was to study the particle size distribution and mineralogy involved in the formation of the texture gradient of a subtropical soil in Rio Grande do Sul. Soil samples of a Red-Yellow Acrisol, formed on sedimentary parent material, were collected from trenches at two relief positions in an area of the Universidade Federal de Santa Maria, RS, Brazil. Soil samples were collected from profile 1, located on a slope and under natural pasture, in the horizons A1, A2, AB, and Bt and from profile 2, on a hilltop and under spontaneous vegetation, samples were collected in the horizons A1, A2, E, and Bt. Chemical attributes of the < 2 μm fraction were evaluated. The clay fraction (< 2 μm), after NaOH dispersion, was laser-diffracted, to discriminate the size distribution of the particles involved in the process. The < 0.2 μm fraction was separated by centrifugation, Ca2+ saturated and X ray diffracted after the following treatments: control, air-drying at room temperature (N); ethylene-glycol saturation (EG); and heating to 300 and 550 oC. The raw X ray diffractograms were modelled using DecompRX. A texture gradient was observed in both soil profiles. Clay contents in the Bt horizons of profile 1 and 2 were 2.9 and 4.4 times higher than in the surface horizons. Laser diffraction diagrams of the Bt horizon revealed an enrichment in two modal diameter sizes (0.09 and 0.2 μm). The mineralogy of Bt horizons was composed of high kaolinite-smectite (K-S) amounts in detriment of Al-hydroxy interlayered vermiculite (HIV) and illite-smectite (I-S) clay minerals. It is suggested that the textural gradient in the soil profiles was due to migration of K-S particles with a modal diameter of 0.09 im and 0.2 μm. However, there are pieces of evidence pointing out for lithological discontinuity in profile 2, indicating that particle migration was not the only process of texture gradient formation.

Efeito da calagem na relação entre solo e água

Changes in the physical properties of soil, mainly related to water retention and soil aggregation, may be linked to changes in electrochemical soil properties. The purpose of this study was to determine the effects of liming on the relationship between soil and water. In 1994, an experiment was installed in the experimental area of the Departamento de Solos da Universidade Federal de Santa Maria, in a dystrophic plinthic Gray Acrisol. Treatments consisted in surface liming and lime incorporation at 0, 2+2, 8.5, and 17 Mg ha-1. In 2006, 12 years after lime application, undisturbed soil samples were collected in triplicate from the layers 0-5 and 5-10 cm. The chemical properties of the samples were characterized. The following physical properties were evaluated i) speed of soil wettability, estimated using a capillary rise device, ii) gravimetric soil moisture, measured at the end of the capillary rise trials, iii) bulk density, estimated by the ratio between the dry mass and volume of soil clods. The wettability speed was higher in soils treated with higher limestone doses, while bulk density was not affected. There was an increase of soil water contents of around 5,1 and 6,2 mg g-1 for each tonne of lime applied. The conclusion was drawn that the lime application forms had no influence on bulk density and soil water retention; liming influences the soil - water relationship, making the soil more hydrophilic with increasing doses of lime, regardless of the form of lime application.

MANEJO DA PALHA DE AVEIA PRETA SOBRE AS PLANTAS DANINHAS E RENDIMENTO DE SOJA EM SEMEADURA DIRETA

An expressive area is cultivated during winter with black oat (Avena strigosa Schreb.) in Rio Grande do Sul State, Brazil, which provides a dense cover, affecting weed growth in soybean fields. Management systems for oat straw are variable, depending on the farmers available equipment and desired management effects. The objective of this study was to evaluate black oat straw management effects on weed suppression and soybean yield. The experiment was carried out during 1997/98 growing season, at the Federal University of Santa Maria, Santa Maria, RS, on a typic Hapludalf soil. A completely randomized block design was used in a split-plot distribution with five replications. The straw managements were assigned as main plots: (i) combine harvested; (ii) not managed, stand-up straw; (iii) rolled with a knife-roll; (iv) disked; (v) mowed; (vi) without straw and no weed control; (vii) without straw and with weed control. The split plots consisted of with and without post-emergency herbicide control of weeds . Above ground weed dry biomass, density of weeds and soybean grain yield were measured. The black oat straw management tested had no effect on total weed density and Brachiaria plantaginea (Link) Hitchc. density until 15 days after soybean seeding. Management disked and without straw and no weed control reduced total weed biomass and B. plantaginea biomass, with the option of post-emergency herbicide control. Management combine harvested, stand-up straw, mowed and without straw and weed control were efficient in weed suppression, presenting no differences for the treatments with the option of weed control in post-emergency. Management combine harvested, stand-up straw, rolled with a knife roll, disked and mowed neither affect grain moisture at harvest nor the first legume height insertion. However, grain moisture at harvest was higher in treatment without straw and no weed control and lower in treatment without straw and weed control.

Qualidade de águas subterrâneas captadas em fontes em função da presença de proteção física e de sua posição na paisagem

No meio rural, a agua de consumo humano e frequentemente captada por meio de sistemas precarios. O objetivo do trabalho foi o de monitorar parâmetros fisicos, quimicos e microbiologicos da qualidade de agua subterrânea captada em fontes para uso domestico, relacionando suas posicoes na paisagem e a presenca de protecao fisica. Trinta e cinco fontes de agua subterrânea, localizadas na pequena bacia hidrografica-PBH do Arroio Lino, area rural do Municipio de Agudo - RS, foram amostradas e classificadas quanto a protecao fisica e a posicao na paisagem. Monitoraram-se, de janeiro a agosto de 2002, os seguintes parâmetros da agua: pH, cor, carbono orgânico soluvel total (COST), N-NO3, N-NH3 e fosforo total (PT), Escherichia coli e coliformes totais. Em geral, os parâmetros variaram com a epoca de coleta, ficando ora acima, ora abaixo dos Valores Maximos Permissiveis previstos pelo Ministerio da Saude do Brasil. A posicao das fontes nas cotas mais altas da paisagem da PBH mostrou-se determinante unicamente para a cor e o PT. A protecao rudimentar mostrou-se eficaz para o PT nas fontes posicionadas em cotas altas, no entanto apresentou respostas discrepantes na parte baixa da paisagem, considerando-se os parâmetros COST e N-NO3. A fonte drenada coletiva, sistema recomendado pela assistencia tecnica oficial, mostrou-se a mais eficaz em evitar a contaminacao por Escherichia coli, restringindo tambem coliformes totais, fosforo total e N-NO3 em relacao a fonte individual. A posicao das fontes na paisagem e a presenca de protecao fisica rudimentar podem ser utilizadas como criterio parcial ao uso de fontes para captacao de agua.

Porosidade e retenção de água em um argissolo sob manejos convencional e direto submetido a compressões unidimensionais

To date, little is known about the dynamics of water and air in porous spaces of soils exposed to mechanical stresses, mainly when the pressure is located on the pre-consolidation line. This study aimed to quantify the changes in the porous spaces of an Acrisol under two tillage systems, submitted to increasing one-dimensional compression, emphasizing the bulk density and water retention at two water potential levels. Undisturbed soil samples were collected under conventional tillage (CT) and no-till (NT), with three replications, from the Ap surface horizon (0-0.075 m) of an Red-Yellow Dystrophic Acrisol at the Universidade Federal de Santa Maria in Rio Grande do Sul State. The sample water content was standardized at -32 kPa in a Richards membrane-plate extractor and the samples were submitted to one-dimensional pressures of 0, 50, 100, and 200 kPa in an open-drained oedometric cell. After the trial, clods were pushed by hand and were submitted in four replications to two water potential levels (-1.600 and -100 kPa) in a Richards membrane (cell). Sample volumes as well as gravimetric water contents were determined by weighing in kerosene after oven-drying at 105 °C. ANOVA was performed as well as regression analysis, whenever necessary. The response of soil bulk density to the increasing pressure was a linear function for SPD and a square function for SPD. In both management systems the water content was exponentially related with the stress levels. Variation in water retention can be explained by 85 % by the one-dimensional compression, which was positive for CT and negative for NT. At a water potential of -100 kPa the changes in bulk density and gravimetric water content were relevant in both management systems. It was concluded thatthe soil under CT is more sensitive to mechanical stress than that under NT, as demonstrated in the magnitude of reduction of porous space and air proportion contained within.

Adsorção de fósforo em sedimentos e sua relação com a ação antrópica

The evaluation of the amount of total and soluble P in surface waters is insufficient to diagnose their pollution potential. This study aimed to evaluate the P fractions and soil properties related to P release from eroded sediments of landscape units with different pressure levels of anthropogenic activity. Water + sediments were sampled in two landscape units of a sub-watershed of the small watershed Arroio Lino, in Agudo, RS, Brazil. The following properties were evaluated: pH, sediment concentration, total organic C, sand, silt and clay fractions, iron extracted by DCB (Fed) and by oxalate (Feox), soluble P (Ps), total P (Pt), bioavailable particulate P (Ppb), potentially bioavailable particulate P (Pppb) and amount of phosphate desorbed with distilled water (Q0). It was possible to estimate the maximum capacity of phosphate adsorption (Pmax), the equilibrium concentration of phosphate (CEP) and the constant (k) related with the phosphate bond energy in the sediment. In comparison with areas with less anthropogenic activity, the sediments eroded from areas with high anthropogenic activity contained: (a) higher Pt and Pppb concentration and lower Ppb quantity; (b) higher Pmax and k values and (c) lower Q0 and CEP quantities. These results indicate the higher pollution potential of eroded sediments from areas with high anthropogenic activity, especially in stagnant water.