J. H. Zonta

Hydrological simulation using SWAT model in headwater basin in Southeast Brazil

Hydrological models are important tools that have been used in water resource planning and management. Thus, the aim of this work was to calibrate and validate in a daily time scale, the SWAT model (Soil and Water Assessment Tool) to the watershed of the Galo creek , located in Espirito Santo State. To conduct the study we used georeferenced maps of relief, soil type and use, in addition to historical daily time series of basin climate and flow. In modeling were used time series corresponding to the periods Jan 1, 1995 to Dec 31, 2000 and Jan 1, 2001 to Dec 20, 2003 for calibration and validation, respectively. Model performance evaluation was done using the Nash-Sutcliffe coefficient (ENS) and the percentage of bias (PBIAS). SWAT evaluation was also done in the simulation of the following hydrological variables: maximum and minimum annual daily flowsand minimum reference flows, Q90 and Q95, based on mean absolute error. ENS and PBIAS were, respectively, 0.65 and 7.2% and 0.70 and 14.1%, for calibration and validation, indicating a satisfactory performance for the model. SWAT adequately simulated minimum annual daily flow and the reference flows, Q90 and Q95; it was not suitable in the simulation of maximum annual daily flows.

Variabilidade espacial da fertilidade do solo em área cultivada com algodoeiro no Cerrado do Brasil

The objective of this work was to analyze the spatial variability of fertility attributes in an Oxisol under tillage to cotton cultivation in Cristalina, GO, aiming the adoption of precision agriculture in the area management. The soil was collected using a sample grid, which consisted of 90 points (80 x 80 m), distributed into 57.6 ha. Were determined contents of P, K, Ca, Mg, S, Na, Cu, Mn, B, Zn, Fe, organic matter (OM), pH, sum of bases (SB), base saturation (V), aluminum saturation (m), as well as the apparent electrical conductivity of soil (EC) measured at 30 and 90 cm depth. Classic descriptive analysis was conducted and then, semivariograms were modeled for all attributes and krigging maps. The spatial dependence of analyzed soil properties indicates that the spatial variability should be considered during the planning of soil sampling and also to soil management practices. Concerning to precision agriculture adoption and the application of inputs in variable rates, it is required to do a careful study of the soil fertility variability, creating maps based on fertility classes for each attribute, allowing to identify for which attributes this management practice should be adopted.

Tolerância de mamoneira ao herbicida pendimethalin em solos com diferentes capacidades de adsorção

The castor bean is a species of slow initial growth. The absence of registered herbicides for this crop is still a limiting factor for its expansion. The aim of this study was to evaluate the castor bean tolerance to the herbicide pendimethalin in soils with different adsorption capacities. The experiment was conducted under greenhouse conditions in a completely randomized design with five replications and consisted of a factorial combination of eight doses of the herbicide pendimethalin applied as pre-emergence (0; 187,5; 375; 750; 1500; 3000; 6000 and 12000 g ha-1 i.a.), and four types of substrate (clay loam, sandy clay loam, sandy loam and sandy soil). At 22 days after sowing the variables: plant height, leaf area, fresh and dry mass of shoots, root system volume and dry weight were determined. It was concluded that the dose of the herbicide pendimethalin tolerated by the castor bean is influenced by the adsorption capacity of the soil. The herbicide was found to be very selective to this crop, not causing significant reduction of plant growth at the doses indicated to be used for weed control.

Tolerância da mamoneira ao herbicida trifluralin em solos com diferentes texturas

The scarcity of registered herbicides for cultivation of castor beans is still a limiting factor for its expansion. Thus, the aim of this study was to evaluate the tolerance of castor bean to trifluralin herbicide in soils of different textures. The experiment was conducted in a greenhouse in a completely randomized design with five replications in a factorial with 8 doses of the trifluralin herbicide (0; 187.5; 375; 750; 1.500; 3.000; 6.000 and 12.000 g ha-1 i.a.) applied at pre-emergence and four types of substrates (washed sand; sandy loam; sandy clay loam; and clay loam soil). At 28 days after sowing, the variables plant height, leaf area, shoot dry weight, volume and dry mass of roots were measured. It was concluded that the tolerance of castor bean to trifluralin herbicide is influenced by chemical and physical characteristics of soil. In sandy and sandy loam soils, doses of trifluralin below those commonly used for weed control are sufficient to cause the decrease in the growth of castor bean plants.

Modelagem da infiltração em solos com encrostamento superficial. Parte II: condutividade hidráulica variando no tempo

ABSTRACT The soil crust affects significantly the soil water infiltration rate. Thus, the infiltration simulation models must somehow consider the effect of crust layer to obtain good results.The objective of this work was to evaluate the performance of the Green-Ampt-Mein-Larson (GAML) model to simulate the soil water infiltration for crusting soils. The trials were carried out in a Podzol Tb distrophic Haplic Cambisol, using a rain simulator, on a bare soil. The GAML model parameters were determined , being proposed for the hydraulic conductivity of transmission zone (Kt) value the use of Kt*, which is equal to Tie x f, where Tie is stable infiltration rate and f is a decrease factor of the Tie as a function of cumulative kinetic energy of rainfall (Ec), i.e., Kt value varying over time. The GAML model with constant Kt value over time did not provide good performance, overestimating the values of infiltration rate (Ti) in most cases, where as the use of Kt* the GAML model showed good performance, being the best results obtained by combination of Kt* with matric potential (jf) values calculated by Cecilio et al. (2007) equation. The GAML model with the hydraulic conductivity in the transmission zone (Kt) value varying over time showed good results in simulation of the infiltration process in soils subjected to crusting.

Modelagem da infiltração em solos com encrostamento superficial. Parte I: modelo GAML para solos estratificados

A B ST R A C T The aim of this study was to evaluate the Green-Ampt-Mein-Larson (GAML) model and GAML model modified by Moore (1981) for layered soils, in the simulation of water infiltration process in crusting soil. The infiltration tests were performed on a Cambisol without coverage, and three successive precipitations at intervals of 24 h. For the inclusion of the soil crust layer in the input parameters of the GAML model, the value of hydraulic conductivity in the transmission zone (Kt) was equal to stable infiltration rate (Tie) obtained in bare soil, and in the GAML model for layered soils, a surface layer (crust) were proposed with a thickness of 5 mm and soil crust saturated hydraulic conductivity (Kc) determined from experimental data, and equal to 10 and 25% of the saturated hydraulic conductivity (K 0 ). In the second and third rainfall, the combinations without consideration of crust did not achieve good results and overestimated infiltration rate over time. For the model of GAML, the best results were obtained using Kt = Tie determined in bare soil, while in Model GAML for layered soils, were obtained with a value of Kc = 10 and 25% of K 0 .

Resposta do algodoeiro ao déficit hídrico em diferentes fases de crescimento.

Water deficit at certain cotton growth stages can cause severe damage to crop development, affecting physiological processes and reducing reproductive structures, with consequent yield losses. The objective of this study was to evaluate the response of cotton cultivars under water deficit applied at different stages of the crop cycle. We compared the number of bolls per meter, cotton yield, and water use efficiency for eight different cotton cultivars under a water deficit of 15 days. We selected the following growth stages: Emergence (EM), First Square (FS), First Flower (FL), Peak Bloom (PB), and First Open Boll (FOB). The control treatment was irrigated with 100% ETc. The experiment was conducted in Apodi, RN State of Brazil, semiarid region, using a sprinkler irrigation system. The number of bolls per meter, cotton yield, and water use efficiency were influenced by the interaction of cultivars x deficit periods. Lowest values were observed for water suppression in the FL and PB stages. When the water deficit was imposed in the initial stages of growth (EM to FS) or after the FOB stage, the cotton yield reduction was not significant. At the same stage and water deficit, the behavior of the different cultivars was similar. Producers are urged to take this information into account when developing irrigation schemes for cotton crops, thereby avoiding water deficits during the most critical periods of the crop cycle.

Uso da reflectometria no domínio do tempo para avaliar a distribuição de fósforo em colunas de solos fertirrigados

EnglishStudies to monitor soil solute dynamics in fertigated areas are of great importance, because they allow the adoption of measures of fertigation management, making the nutrients available in the places of greatest root density. The objective of this study was to evaluate, using the TDR technique, the phosphorus distribution in Neosol Quartizarenic (RQ) and Red Latossol (LV) soil columns fertigated with MAP. The MAP fertigations were performed in the columns; the soil water content (8) and soil bulk electric conductivity (CEs) were obtained using (with) TDR probes installed at various depths, and the nutrient concentration was estimated using mathematical models. In both soils the phosphorus was adsorbed in surface layer, not reaching 12 cm depth, regardless of the moment of the fertigation was started portuguesEstudos direcionados para o monitoramento da dinâmica de solutos no solo, sob areas fertirrigadas, sao de fundamental importância, pois permitem adotar medidas de manejo da fertirrigacao possibilitando disponibilizar o nutriente nos locais de maior densidade radicular. Objetivou-se com esse trabalho avaliar, usando a tecnica da TDR, a distribuicao de fosforo em colunas de Neossolo Quartzarenico (RQ) e Latossolo Vermelho (LV) fertirrigadas com MAP. Foram realizadas fertirrigacoes com MAP nas colunas e determinados os teores de agua (8) e condutividades eletricas do solo (CEs) com uso de sondas de TDR instaladas em varias profundidades, sendo a concentracao do nutriente estimada som uso de modelos matematicos. Em ambos os solos o fosforo ficou adsorvido a camada superficial, nao alcancado os 12 cm de profundidade, independentemente do momento da fertirrigacao