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da Silva V.P.R.,Federal University of Campina Grande | Pereira E.R.R.,Federal University of Campina Grande | de Azevedo P.V.,Federal University of Campina Grande | de Sousa F.A.S.,Federal University of Campina Grande | de Sousa I.F.,DEA UFS
Revista Brasileira de Engenharia Agricola e Ambiental | Year: 2011

Rainfall daily data of 600 meteorological stations were analyzed to assess the changes in precipitation in northeastern Brazil. Maps of rainy day numbers and the coefficient of variation (CV) for rainfall and rainy days are presented. Autocorrelation function was obtained for the annual rainfall in northeastern Brazil. Results showed that the semiarid regions have a high coefficient of variation for both rainfall and rainy days than those located in northeastern coast and 'agreste' of Brazil. The highest values of coefficient of variation are associated to the lowest values of rainfall and rainy days. The rainfall change in northeastern Brazil is smaller in rainy regions than in dry regions. The high changes in rainfall and rainy days are limiting features to the rainfed agriculture in semiarid environments. The correlograms of rainfall indicated significant trend for the limits of 95% confidence levels on some stations. Source


Sousa I.F.,DEA UFS | Netto A.O.A.,DEA UFS | Campeche L.F.M.S.,Federal University of Sao Paulo | Barros A.C.,UFAL | And 2 more authors.
Revista Brasileira de Engenharia Agricola e Ambiental | Year: 2011

This paper, as Part II of a research carried out in Sergipe state, aims to determine evapotranspiration and crop coefficient of dwarf-green coconut (Cocos nucifera L.) based on lysimeter measurements and Bowen ratio-energy balance method. The reference evapotranspiration was obtained by the Penman-Monteith approach on daily-scale during the experimental period. The data acquisition system was used to obtain all data from the sensors necessary to determine the energy balance components. The water requirements of coconut palm during the phenological growth stage is 1263.30 mm, with daily average of 3.90 mm d-1. The crop coefficient during this phenological growth stage varies between 0.50 and 1.80, with daily mean of 0.96. Source


de S. Campeche L.F.M.,Federal University of Sao Paulo | Netto A.O.A.,DEA UFS | Sousa I.F.,DEA UFS | Faccioli G.G.,DEA UFS | And 2 more authors.
Revista Brasileira de Engenharia Agricola e Ambiental | Year: 2011

The objectives of present study were to develop and to calibrate a large-scale weighing lysimeter in order to estimate evapotranspiration of fruit plants. The equipment consisted of a metallic bucket (steel carbon) of circular design with total area of 5.72 m 2 and total mass of 10.5 t. A seedling of dwarf-green coconut palm was transplanted in lysimeter and maintained under same fertilization conditions of experimental field. For automation of the process, a mechanism of load relief based on systems of levers and counterbalances was used, leaning in a load cell with capacity of 200 kg and precision of 0.02% of its capacity. The output data of load cell were stored in an automatic data acquisition system. The relationship between mass variation (mm) and voltage (mV) of the load-cell lysimeter described a linear model with minimum hysterisis. Also, it can be concluded that the methodology used for the calibration of the weighing lysimeter was appropriate, showing a coefficient of determination of 0.99 for the calibration equation. Results also indicated that the large-scale weighing lysimeter can be used with success in the determination of evapotranspiration of fruit plants. Source


Guimaraes D.V.,Federal University of Lavras | Gonzaga M.I.S.,DEA UFS | Melo Neto J.O.,Federal University of Lavras
Revista Brasileira de Engenharia Agricola e Ambiental | Year: 2014

The main objective of this study was to investigate changes in carbon dynamics and stocks in agricultural soils. Soil samples were collected at 0-10 cm and 10-30 cm depths in two agricultural areas (cultivated with banana (Musa spp.), and cultivated with citrus (Citrus sinensis). A native forest soil was used as a reference and to determine the carbon pool management index. Organic matter was physically fractionated into particulate organic matter (> 53 μm) and complexed organic matter (< 53 μm). Analysis of total organic carbon was run to characterize soil organic matter. Comparing to the native forest soil, the banana cultivation increased the total soil organic carbon content (TOC) in approximately 14% while citrus cultivation reduced the TOC content in about 38%. The cultivated soils reduced the particulate organic matter fraction in more than 50%, showing a higher decomposition rate of the organic residues. The Carbon Management Index values were lower than 1 in all treatments, however the best results were observed for the citrus orchard (116.5). Overall, the change in land use from native forest to fruit crops reduced soil organic matter content, especially its labile fraction, and reduced soil quality. Source

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