Jarbas Honorio de Miranda

CURVAS DE DISTRIBUIÇÃO DE EFLUENTES DO ÍON NITRATO EM AMOSTRAS DE SOLO DEFORMADAS E INDEFORMADAS 1

There is a great importance to quantify the trace and the chemical elements transport in soil. This work had as objective to obtain the transport parameters of the nitrate ion in soil (pore water velocity (v), retardation factor (R), dispersivity (λ) and the dispersion coefficient (D)) in different textures soils, mainly, under different sampling forms (deformed and non deformed). The research was carried out under two samplings forms, mentioned previously, by application of 50 mg L -1 of NO3 - in two different soils profiles at a depth of 0-20 cm. The breakthrough curves was made by two forms: traditional methodology (TFSA) and the technique with non deformed sample developed during the research period. The results showed that the transport parameters fitted by the computational program CXTFIT, with deformed sampling, overestimated the parameters values, with exception of dispersivity, when compared to the non deformed sampling, for both soil types.

Estimating water application efficiency for drip irrigation emitter patterns on banana

The objective of this work was to evaluate root and water distribution in irrigated banana (Musa sp.), in order to determine the water application efficiency for different drip irrigation emitter patterns. Three drip emitter patterns were studied: two 4-L h -1 emitters per plant (T1), four 4-L h -1 emitters per plant (T2), and five 4-L h -1 emitters per plant (T3). The emitters were placed in a lateral line. In the treatment T3, the emitters formed a continuous strip. The cultivated area used was planted with banana cultivar BRS Tropical, with a 3-m spacing between rows and a 2.5-m spacing between plants. Soil moisture and root length data were collected during the first production cycle at five radial distances and depths, in a 0.20x0.20 m vertical grid. The experiment was carried out in a sandy clay loam Xanthic Hapludox. Soil moisture data were collected every 10 min for a period of five days using TDR probes. Water application efficiency was of 83, 88 and 92% for the systems with two, four and five emitters per plant, respectively. It was verified that an increase in the number of emitters in the lateral line promoted better root distribution, higher water extraction, and less deep percolation losses.

Modelo para simulação da dinâmica de nitrato em colunas verticais de solo não saturado

A agricultura intensiva esta sempre em busca de incrementos de produtividade mas, em contrapartida, pouca atencao e dedicada a possiveis impactos ambientais. Portanto, o entendimento sobre processos de transporte de solutos no solo auxilia na reducao da sua lixiviacao para as camadas subsuperficiais. Neste sentido, objetivou-se, com o presente trabalho, desenvolver e avaliar um modelo computacional aplicado para simulacao da dinâmica de solutos no solo por meio de solucoes numericas de equacoes diferenciais que descrevam esse transporte. Pelos resultados obtidos, o modelo apresentou bom ajuste das concentracoes de nitrato e dos perfis de umidade, simulados com relacao aos medidos em condicoes de laboratorio em coluna vertical de solo nao saturado.

Simulação do deslocamento de potássio em colunas verticais de solo não-saturado

Water and solute transport studies in unsaturated soil are important for both economical and environmental points of view and, in this sense, it should be emphasized the increase of agricultural use of urban and industrial residues, to the water resources and fertilizers saving. Thus, the computational modeling use is important, because it allows the monitoring of solute displacement, necessary to the environmental impacts prevention in a precise and fast way. The main objective of the present work is to simulate the displacement of potassium ion in unsaturated soil columns, using the MIDI model, as well as to present transport parameters determination of the potassium ion in a Red Yellowish Latossol, sandy phase. The obtained results allowed concluding that the model was capable to adequately simulate the potassium ion displacement.

Local head loss for uncoaxial drippers inserted in polyethylene pipes

In this paper, the results of an experimental investigation on local head losses from uncoaxial in-line emitters inserted into the pipe line are reported. Local losses corresponding to four different pipe-emitter combinations, with ten replications, were measured for a range of discharge values. For each discharge, the amount of local losses was calculated as the difference between the total measured head losses and the corresponding friction losses evaluated by the Darcy-Weisbach equation. Mathematical approaches were tested to calculate hfe based on the kinetic head coefficient (K) and constant equivalent length (Le). For the drip-line models examined, the amount of local losses, expressed as a percentage of the total losses, was found to grow with an increase in the obstruction degree. The percentage increased to 24.5% and 50.8%, respectively, for Ag/At = 0.221 and 0.429. The results of this experimental investigation indicated the practical validity of using a constant equivalent length (Le) to estimate the local head losses in a drip lateral line. The percentage variation between total head loss calculated by a step-by-step procedure and the Le approximation method was 5.5% for non-compensating pressure emitters and less than 1.7% for the pressure compensating emitters.

Perda de carga localizada em gotejadores integrados em tubos de polietileno

Este trabalho foi desenvolvido para analisar as perdas de carga localizadas em gotejadores coaxiais integrados em tubos de polietileno. A perda de carga para diferentes vazoes foi determinada em quatro modelos de tubos gotejadores, com sete repeticoes. Para cada vazao, a perda de carga localizada foi calculada pela diferenca entre a perda de carga no tubo com emissor e a perda de carga continua no tubo uniforme, estimada pela equacao de Darcy-Weisbach. Aproximacoes matematicas foram sugeridas para calcular a perda de carga com base no coeficiente de carga cinetica (K) e em um valor constante de comprimento equivalente (Le). A desconsideracao da perda de carga localizada levou a superestimativa do comprimento maximo da linha lateral de ate 25,7%, para os gotejadores autocompensados, e de 9,5%, para os nao autocompensados. O calculo da perda de carga localizada, utilizando o modelo potencial para estimar o valor de K em funcao do indice de obstrucao, mostrou bons resultados, comparaveis aqueles obtidos com o valor de K ajustado pelos dados observados em laboratorio, o que resultou em pequenas variacoes na estimativa do comprimento maximo da linha lateral por esses dois procedimentos.

Temperature effect in potassium and nitrate ions in soil transport

When doing researches on solute dynamics in porous medium, the knowledge of medium characteristics and percolating liquids, as well as of external factors is very important. An important external factor is temperature and, in this sense, our purpose was determining potassium and nitrate transport parameters for different values of temperature, in miscible displacement experiments. Evaluated parameters were retardation factor (R), diffusion/dispersion coefficient (D) and dispersivity, at ambient temperature (25 up to 28 oC), 40 oC and 50 oC. Salts used were potassium nitrate and potassium chlorate, prepared in a solution made up of 5 ppm nitrate and 2.000 ppm potassium, with Red-Yellow Latosol porous medium. Temperature exhibited a positive influence upon porous medium solution and upon dispersion coefficient.

Estimation of the potential evapotranspiration by a simplified penman method

The numerous methods for calculating the potential or reference evapotranspiration (ETo or ETP) almost always do for a 24-hour period, including values of climatic parameters throughout the nocturnal period (daily averages). These results have a nil effect on transpiration, constituting the main evaporative demand process in cases of localized irrigation. The aim of the current manuscript was to come up with a model rather simplified for the calculation of diurnal daily ETo. It deals with an alternative approach based on the theoretical background of the Penman method without having to consider values of aerodynamic conductance of latent and sensible heat fluxes, as well as data of wind speed and relative humidity of the air. The comparison between the diurnal values of ETo measured in weighing lysimeters with elevated precision and estimated by either the Penman-Monteith method or the Simplified-Penman approach in study also points out a fairly consistent agreement among the potential demand calculation criteria. The Simplified-Penman approach was a feasible alternative to estimate ETo under the local meteorological conditions of two field trials. With the availability of the input data required, such a method could be employed in other climatic regions for scheduling irrigation.

Análise de métodos de estimativa de evapotranspiração na otimização de sistemas de drenagem

There are various methods to estimate the potential evapotranspiration (ETP). The simplified methods present limitations in relation to precision of the obtained results, while the more complex methods present the difficulty of availability of necessary data for calculation. In the present study the Thornthwaite and Camargo methods were compared with the Penman-Monteith method to verify the influence in obtaining daily ETP for the design of a drainage system, using the SISDRENA model. It is concluded that the differences among the methods did not affect significantly the calculation of economic drain spacing.

Water infiltration in the soil: part I cylinder infiltrometer versus sprinkler infiltrometer.

The objective of this paper was to compare values of water infiltration rate in soil, obtained with two distinct methodologies: cylinder infiltrometer and sprinkler infiltrometer. Thirty six infiltration rate curves were obtained using the cylinder infiltrometer methodology and four infiltration rate curves using a sprinkler infiltrometer. It was observed that the arithmetic mean of results from the cylinder infiltrometer methodology obtained overestimated the infiltration rate obtained with sprinkler infiltrometer and that the geometric mean and mode of the results obtained with cylinder infiltrometer approached the velocity of infiltration of water in soil obtained with the sprinkler infiltrometer.