Daniel Fonseca de Carvalho

Padrões de precipitação e índices de erosividade para as chuvas de Seropédica e Nova Friburgo, RJ

This work was carried out in order to calculate the different storm patterns, the rainfall erosivity index (EI30 and KE > 25) and adjust them with the monthly precipitation data for Seropedica and Nova Friburgo, in the State of Rio de Janeiro, Brazil. Based on the results obtained, it was concluded that the advanced pattern is the most common in these regions, corresponding to 61% in Seropedica and 58% in Nova Friburgo, of the total number of analyzed storms. The percentages of intermediate and delayed patterns were, respectively, 24 and 15%, for Seropedica and 24 and 18% for Nova Friburgo. The annual mean values of EI30 were 5,472.5 and 5,431.2 MJ mm ha-1 h-1 for Seropedica and Nova Friburgo, respectively. For the KE > 25 index, the annual mean values were 76.8 and 83.5 MJ ha-1 for Seropedica and Nova Friburgo, respectively.

Topography and spatial variability of soil physical properties

Among the soil formation factors, relief is one of the most used in soil mapping, because of its strong correlation with the spatial variability of soil attributes over a landscape. In this study the relationship between topography and the spatial variability of some soil physical properties was evaluated. The study site, a pasture with 2.84 ha, is located near Seropedica, Rio de Janeiro State, Brazil, where a regular square grid with 20 m spacing was laid out and georreferenced. In each sampling point, altitude was measured and undisturbed soil samples were collected, at 0.0-0.1, 0.1-0.2, and 0.2-0.3 m depths. Organic carbon content, soil texture, bulk density, particle density, and soil water retention at 10 (Field Capacity), 80 (limit of tensiometer reading) and 1500 kPa (Permanent Wilting Point) were determined. Descriptive statistics was used to evaluate central tendency and dispersion parameters of the data. Semivariograms and cross semivariograms were calculated to evaluate the spatial variability of elevation and soil physical attributes, as well as, the relation between elevation and soil physical attributes. Except for silt fraction content (at the three depths), bulk density (at 0.2-0.3 m) and particle density (at 0.0-0.1 m depth), all soil attributes showed a strong spatial dependence. Areas with higher elevation presented higher values of clay content, as well as soil water retention at 10, 80 and 1500 kPa. The correlation between altitude and soil physical attributes decreased as soil depth increased. The cross semivariograms demonstrated the viability in using altitude as an auxiliary variable to improve the interpolation of sand and clay contents at the depth of 0.0-0.3 m, and of water retention at 10, 80 and 1500 kPa at the depth of 0.0-0.2 m.

Intervalo hídrico ótimo em um latossolo vermelho distroférrico sob diferentes sistemas de produção

The objective of this work was to characterize the growing systems related to the structural soil quality for plants development by the Least Limiting Water Range (LLWR). The study was developed using soil samples with preserved structure of a Distroferric Red Latossol under the conventional, no tillage and integrated growing systems in de county of Dourados-MS, Brazil. In each system 28 points were sampled, in 0-0.05, 0.05-0.10 and 0.10-0.20 m deep layers, ending up with 84 samples by system which was used to adjust the water retention curve in the soil, soil resistance to penetration curve and porosity determination, all of them necessary to the LLWR determination. In the conventional and no-tillage systems the smallest restriction to de roots development was in the 0-0.05 m layer, while in the integration system the smallest limiting was in 0.10-0.20 m layer. In the conventional system, in the 0-0.05 m layer, the LLWR was equal to the available water capacity, in the direct and integrated systems the resistance to penetration was the limiting factor. The resistance to penetration was the major limiting factor in most of the studied situations.

Variabilidade espacial do potencial erosivo das chuvas no estado de Mato Grosso do Sul

Information about rainfall erosivity is important during soil and water conservation planning. Thus, the spatial variability of rainfall erosivity of the state Mato Grosso do Sul was analyzed using ordinary kriging interpolation. For this, three pluviograph stations were used to obtain the regression equations between the erosivity index and the rainfall coefficient EI30. The equations obtained were applied to 109 pluviometric stations, resulting in EI30 values. These values were analyzed from geostatistical technique, which can be divided into: descriptive statistics, adjust to semivariogram, cross-validation process and implementation of ordinary kriging to generate the erosivity map.Highest erosivity values were found in central and northeast regions of the State, while the lowest values were observed in the southern region. In addition, high annual precipitation values not necessarily produce higher erosivity values.

Características da chuva e perdas por erosão sob diferentes práticas de manejo do solo

This study was carried out in order to evaluate the relation between erosivity index and the rainfall pattern associated with different kinds of soil preparation and cover with erosion losses in a Red Yellow Argisol. The experiment was conducted in five soil loss experimental plots of 3.5 x 22.0 m, with the following treatments: conventional tillage (plowing plus disking) in contour lines and sowing the velvet bean (Mucuna pruriens), sun hemp (Crotalaria juncea) and corn (Zea mays L.); conventional tillage (plowing plus disking) in slope line and sowing of corn, conventional tillage (plowing plus disking) in slope line and without soil cover. The results showed that soil loss was more affected by different treatments than water loss; the treatments sun hemp and corn sowed in slope line were those that presented, respectively, the smaller and the larger soil and water losses; and the precipitation events characterized as advanced, intermediate and delayed patterns were responsible for 62.6, 11.8 and 25.6% of the water losses and for 35.1, 6.6 and 58.3% of the soil losses, respectively.

Índices e espacialização da erosividade das chuvas para o Estado do Rio de Janeiro

For improving the knowledge about rainfall erosivity in the state of Rio de Janeiro, Brazil, the present study aimed to calculate the erosivity indices EI30 and KE > 25 using two methodologies to estimate the kinetic energy, average monthly erosivity indices based on pluviometric data and to obtain the isoerosivity maps for the State. EI30 and KE > 25 were obtained using rain gauge data of 14 stations located in Rio de Janeiro. Index estimates were also obtained by using correlations with the average monthly precipitation or the rainfall coefficient and spatialization via maps generated by ArcView 3.2a software. The results permit to conclude that the erosivity indices, for the different studied places, present expressive differences among themselves; there were no significant differences between the results obtained by the equations proposed for the calculation of rain kinetic energy and the estimate of rainfall erosivity using the average monthly precipitation gave better results compared to based on rainfall coefficient.

Estimação da evapotranspiração de referência no estado do Rio de Janeiro usando redes neurais artificiais

This work was performed with the aim of proposing an artificial neural network (ANN) to estimate the reference evapotranspiration (ETo) as a function of geographic position coordinates and air temperature in the State of Rio de Janeiro. Data used for the network training were collected from 17 historical time series of climatic elements located in the State of Rio de Janeiro. The daily ETo calculated by Penman-Monteith (FAO-56) method was used as a reference for network training. ANNs of multilayer perceptron type were trained to estimate ETo as a function of latitude, longitude, altitude, mean air temperature, thermal daily amplitude and day of the year. After training with different network configurations, the one showing best performance was selected, and was composed by only one intermediary layer (with twenty neurons and sigmoid logistic activation function) and one output layer (with one neuron and linear activation function). According to the results obtained it can be concluded that, considering only geographical positioning coordinates and air temperature, it is possible to estimate daily ETo in 17 places of Rio de Janeiro State by using an ANN.

NDVI time series for monitoring RUSLE cover management factor in a tropical watershed

Land cover, an important factor for monitoring changes in land use and erosion risk, has been widely monitored and evaluated by vegetation indices. However, a study that associates normalized difference vegetation index (NDVI) time series to climate parameters to determine soil cover has yet to be conducted in the Atlantic Rainforest of Brazil, where anthropogenic activities have been carried out for centuries. The objective of this paper is to evaluate soil cover in a Brazilian Atlantic rainforest watershed using NDVI time series from Thematic Mapper (TM) Landsat 5 imagery from 1986 to 2009, and to introduce a new method for calculating the cover management factor (C-factor) of the Revised Universal Soil Loss Equation (RUSLE) model. Twenty-two TM Landsat 5 images were corrected for atmospheric effects using the 6S model, georeferenced using control points collected in the field and imported to a GIS database. Contour lines and elevation points were extracted from a 1:50,000-scale topographic map and used to construct a digital elevation model that defined watershed boundaries. NDVI and RUSLE C-factor values derived from this model were calculated within watershed limits with 1 km buffers. Rainfall data from a local weather station were used to verify NDVI and C-factor patterns in response to seasonal rainfall variations. Our proposed method produced realistic values for RUSLE C-factor using rescaled NDVIs, which highly correlated with other methods, and were applicable to tropical areas exhibiting high rainfall intensity. C-factor values were used to classify soil cover into different classes, which varied throughout the time-series period, and indicated that values attributed to each land cover cannot be fixed. Depending on seasonal rainfall distribution, low precipitation rates in the rainy season significantly affect the C-factor in the following year. In conclusion, NDVI time series obtained from satellite images, such as from Landsat 5, are useful for estimating the cover management factor and monitoring watershed erosion. These estimates may replace table values developed for specific land covers, thereby avoiding the cumbersome field measurements of these factors. The method proposed is recommended for estimating the RUSLE C-factor in tropical areas with high rainfall intensity.

Manejo da irrigação associada a coberturas mortas vegetais no cultivo orgânico da beterraba

Praticas agricolas orgânicas, como a cobertura do solo com palha, foram testadas em area irrigada por gotejamento na Baixada Fluminense, no Estado do Rio de Janeiro. O cultivo de inverno da beterraba nesta regiao e favorecido por temperaturas mais amenas, coincidindo com a epoca de maior disponibilidade do produto no Estado. No cultivo da beterraba, foram adotados tres tipos de cobertura do solo e seis lâminas de irrigacao (0; 29; 48; 78; 100 e 148% da ETc) determinadas com base no balanco de agua no solo utilizando a tecnica da TDR. O delineamento estatistico adotado foi blocos casualizados, com seis tratamentos e quatro repeticoes. Sob cobertura morta de Pennisetum purpureum, de Gliricidia sepium e na ausencia de cobertura morta, os valores maximos relativos de EUA, no cultivo de beterraba, foram de 21,00; 32,90 e 17,90 kg m-3, respectivamente. A maior e a menor lâmina de irrigacao acumulada para cada tipo de manejo foram de 2.746 e 951 m3 ha-1 nas parcelas sem cobertura morta. Em comparacao, as parcelas com cobertura do solo reduziram em 34,5 e 10,5% as lâminas acumuladas, respectivamente. Os valores acumulados de nitrogenio nas partes das plantas foram maiores no cultivo sob cobertura morta de G. sepium, indicando vantagens desta pratica cultural associada a irrigacao por gotejamento.

Parâmetros físicos do solo e erosão hídrica sob chuva simulada, em área de integração agricultura-pecuária

This work was carried out in Dourados, Mato Grosso do Sul State, Brazil, in order to evaluate soil erosion and water loss in pasture and in no tillage agriculture in a pasture-agriculture integration system using a portable rainfall simulator. Four rainfall intensities (40, 60, 80 and 100 mm h-1) were studied, each consisting of a treatment arranged in an experimental design in randomized blocks with four replications. Accumulated average soil loss varied from 1.33 to 10.50 g m-2 and water loss varied from 1.34 x 10-3 to 34.64 x 10-3 m3 m-2. The largest soil and water losses occured in the largest rainfall intensities and the no-tillage system had the largest soil loss and the pasture the largest water loss.