Luciano Gebler

Erosão hídrica associada a algumas variáveis hidrológicas em pomar de maçã submetido a diferentes manejos do solo

Soil management in perennial crops such as orchards can influence erosion. This study evaluated soil and water losses from an Oxisol under simulated rain, from August 2007 to April 2008, at the experimental station of Embrapa Uva e Vinho, in Vacaria (RS). On the 3.5 m x 11 m plots, rains of one hour were simulated at a constant intensity of 70 to 88 mm h-1. In the apple orchard, the following soil management systems were studied: i) manual weeding under apple trees and spontaneous grass and legume cover in the rest of the area (ST), ii) undesiccated oat cover, hoeing the seeds into the soil at weeding in the entire area, two months before the first rain test (NO), iii) oat cover chemically desiccated seven days before the first rain test, planted by a rotary hoe to incorporate seeds into the soil in the entire area, two months before the tests (DO); and iv) uncovered soil with removal of the previously desiccated spontaneous cover from the soil surface by weeding the entire area with a hoe, one day before each rain test (BS). The management systems related to the soil cover in the apple orchard and the rain tests influenced water erosion. Soil losses varied considerably in the treatments, more than water losses. Even with soil mobilization in the entire area for oat planting in the NO and DO treatments the control effectiveness of water erosion was equal to the ST treatment in which the soil was mobilized only under the trees. The removal of the soil cover from under apple trees greatly increased soil losses in relation to the cover maintenance, but had only little influence on water losses. The runoff duration influenced soil loss; an increase of this variable was observed with increasing runoff duration until a certain moment and, from then on, it decreased independently of the treatment; water loss increased until a certain moment and stabilized. An inverse relationship was observed between soil and water losses, independently of the soil management system under apple trees, adjusting to an exponential model.

Erosão hídrica em campo nativo sob diversos manejos: perdas de água e solo e de fósforo, potássio e amônio na água de enxurrada

Native pastures in southern Brazil are used for cattle and sheep grazing. The forage offer in the spring-summer season is greater than the animal requirement, so the forage left over is usually burned. Pasture burning mineralizes nutrients and leaves the soil bare, triggering water erosion. This study aimed to quantify total soil and water losses and P, K and NH4+ contents in the runoff water from an Oxisol with native pasture. In the treatments, the native pastures, were i) unburned and unfertilized, ii) unburned and P-fertilized, iii) burned and unfertilized, and iv) burned and P-fertilized. Rain was simulated at an intensity of 75 mm h-1 and duration of 3 h on the plots (11 m long along the slope and 3.5 m wide). Burning of the native vegetation decreased the times until runoff began and peaked and reduced soil water infiltration, but increased the maximum runoff rate, soil and water losses by water erosion and the P, K and NH4+ concentration and total losses in the runoff water, compared to no burning. The runoff sediment concentration was higher in the treatment with vegetation burning than without. The highest and lowest values of sediment concentration were detected after a shorter runoff period in the treatment with vegetation burning than in that without, which is related to the 8.9 times higher total soil loss from burnt than from unburnt grassland. The P concentration and total loss in the runoff water were higher in the treatment with than without phosphate fertilizer, in the treatment with burning as well as that without. For K and the NH4+ , the concentration and total losses were higher in the treatment with burning than in that without. Phosphorus, K and NH4+ concentration in the runoff water fit the exponential model y = ae-bx in relation to runoff duration (p < 0.01).

Adaptação metodológica no cálculo de cargas contaminantes de fósforo em bacias hidrográficas gaúchas

The excess of phosphorus in the environment can cause several negative impacts, especially with regard to water quality. Hence adequate methodologies are needed for assessing this risk at the watershed scale, emphasizing that the non-point agricultural sources impose greater estimate difficulties. The objective of this work was to propose an adapted methodology to quantify the dissolved and total reactive phosphorus movement in agricultural areas, based on the influence of agricultural crops (arboreous and herbaceous size), native pasture and its management in the State of Rio Grande do Sul (Southern Brazil). The methodology used was the study of reactive phosphorus release in plots covered by different crops and its relation to the methodology of calculation of maximum daily loads, currently accepted by the state environmental agencies for the environmental licensing of potentially polluting activities. The results show that the calculation of load of phosphorus contaminant currently in use, may be underestimating the Brazilian conditions, especially in Rio Grande do Sul, and that the new methodology allows one to include temporal variation as an element in the process of analysis, turning the licensing analysis into a dynamic and punctual process.

Fósforo reativo: Arraste superficial sob chuvas simuladas para diferentes coberturas vegetais

O fosforo e um elemento quimico chave para a qualidade da agua, agindo principalmente como gatilho desencadeador das floracoes algais. A principal fonte de fosforo nas pequenas bacias rurais advem da agricultura feita nas encostas das bacias, podendo chegar de varias formas ao corpo d’agua, porem as formas mais impactantes sao o fosforo reativo total e o dissolvido. A forma dissolvida e a que apresenta maiores riscos pois pode percorrer distâncias comparativamente maiores do que o fosforo reativo nos sedimentos em suspensao que podem acabar depositados ao longo do caminho. Portanto, este trabalho visa avaliar se diferentes coberturas do solo por culturas anuais podem interferir no arraste destas formas de fosforo, afetando o risco da degradacao dos recursos hidricos das pequenas bacias rurais. Apesar de nao ter havido diferenca significativa entre os tratamentos, verificou-se sazonalidade ao longo do experimento representando uma estacao de cultivo. Isto significa que houve variacao do nivel de risco, uma vez que, no terco inicial das primeiras chuvas, o risco de arraste de fosforo na enxurrada foi mais elevado em relacao a periodos chuvosos mais distantes da epoca de plantio/fertilizacao, tornando-se possivel avaliar o risco a bacia de forma sazonal e nao anual.

Transferência superficial de fósforo reativo potencialmente contaminante por chuvas simuladas intensas

Phosphorus is naturally present or added to the soil and, depending on the mix of factors, may trigger a high environmental risk to water resources in river basins. The aim of this study was to quantify the transfer for soil surface of some forms of reactive phosphorus originating from phosphorus fertilization on bare soil, carried by the runoff. The experiment was carried out in Lages, SC, Brazil, with two replications in the field under intense simulated rainfall (64 mm h−1 for 50 minutes). The results indicate that phosphorus may represent a serious environmental risk to water resources of basins at different scales in time and space, through the reactive forms of phosphorus and their different ways of transportation.

Analytical method validation to evaluate dithiocarbamates degradation in biobeds in South of Brazil

In order to evaluate the efficiency of biobeds on DTC degradation, the aim of this study was to apply, optimize and validate a method to determine dithiocarbamate (mancozeb) in biobeds using gas chromatography-tandem mass spectrometry (GC-MS). The DTC pesticide mancozeb was hydrolysed in a tin (II) chloride solution at 1.5% in HCl (4 mol L-1), during 1 h in a water bath at 80 °C, and the CS2 formed was extracted in isooctane. After cooling, 1 mL of the organic layer was transferred to an auto sampler vial and analyzed by GC-MS. A complete validation study was performed and the following parameters were assessed: linearity of the analytical curve (r2), estimated method and instrument limits of detection and limits of quantification (LODm, LODi, LOQm and LOQi, respectively), accuracy (recovery%), precision (RSD%) and matrix effects. Recovery experiments were carried out with a standard spiking solution of the DTC pesticide thiram. Blank biobed (biomixture) samples were spiked at the three levels corresponding to the CS2 concentrations of 1, 3 and 5 mg kg-1, with seven replicates each (n = 7). The method presented satisfactory accuracy, with recoveries within the range of 89-96% and RSD ≤ 11%. The analytical curves were linear in the concentration range of 0.05-10 µg CS2 mL-1 (r2 > 0.9946). LODm and LOQm were 0.1 and 0.5 mg CS2 kg-1, respectively, and the calculated matrix effects were not significant (≤ 20%). The validated method was applied to 80 samples (biomixture), from sixteen different biobeds (collected at five sampling times) during fourteen months. Ten percent of samples presented CS2 concentration below the LOD (0.1 mg CS2 kg-1) and 49% of them showed results below the LOQ (0.5 mg CS2 kg-1), which demonstrates the biobeds capability to degrade DTC.

Pontos de abastecimento de pulverizadores agrícolas: uma revisão comparando os modelos em uso

Pontos de abastecimento de pulverizadores sao locais destinados ao preparo das caldas agroquimicas e carregamento de equipamentos de pulverizacao agricola, classificados pela legislacao ambiental e trabalhista como equipamento de seguranca ambiental. Ha suficiente bibliografia tecnica que recomenda e descreve os processos construtivos e de manejo de tais locais, mas ha pouca clareza sobre como se chegou a esta forma consensual, aliado ao pouco embasamento cientifico de seus beneficios e riscos agregados. Alguns aspectos como impermeabilizacao, constituicao do material, manejo do piso e dos residuos de agroquimicos, interferem na capacidade de evitar que os possiveis contaminantes atinjam o solo e as aguas, interferindo no descarte final. Aspectos funcionais ainda carecem de respostas, como a possibilidade do piso reter e armazenar o contaminante e se tornar um emissor a longo prazo, a definicao do tempo de vida util do equipamento, dentre outros. Recentemente houve avancos na filosofia construtiva dos pontos de abastecimento de pulverizadores, com a introducao da remediacao de residuos in situ, atraves da biodegradacao, ganhando denominacoes, como biobeds, dentre outras. O objetivo desta revisao e discutir as diferentes formas de pisos e manejo nestes locais, seus riscos e a possibilidade de se tornarem um passivo ambiental.