de Teixeira A.H.C.,Embrapa Semiarido |
Bastiaanssen W.G.M.,WaterWatch |
Bastiaanssen W.G.M.,Technical University of Delft
Irrigation Science | Year: 2012
Energy balance measurements were carried out in a mango orchard during two growing seasons in the semi-arid region of Brazil. The actual evapotranspiration (ET) was acquired by eddy correlation (EC) and Bowen ratio energy balance (BR) techniques. The daily energy balance closure in the EC measurements showed an average gap of 12%, with a root mean square error (RMSE) of 1.7 MJ m-2 d-1. Three different correction procedures were tested for closing the energy balance from the EC system: (1) the surface energy balance residual method (RES), (2) the Bowen ratio determined from the EC fluxes, the combination approach (EC_BR), and (3) a new regression energy balance closure technique (REG). All closing energy balance methods presented good correlation with the direct EC measurements, but the trends were not similar. The latent heat fluxes estimated by the BR method-λEBR-were higher than those from the direct EC measurements-λEEC. When using the RES method, the half-hour λEEC measurements represented around 88% of the λERES values, as the uncertainties of net radiation-Rn-and soil heat fluxes-G-are propagated into the RES method. The latent heat flux derived from the combination approach-λEEC_BR-also brings these uncertainties, being the agreements comparable with those for RES method. It was therefore concluded that a single correction method for EC measurements considering only the latent and sensible heat fluxes does not exist. A new way to solve the lack of energy balance closure from EC techniques was tested by means of a curve fitting, the REG method. Considering the REG corrections applied to the energy balance components involving all periods of the day and the average conditions of the two growing seasons, half-hour values of λEEC were overmeasured by 18%, HEC was undermeasured by 17%, and G values required a correction of 466%. The REG method appeared promising because it considers different weights for all energy balance components in the optimization process. Taking the REG results for the drier second growing season as a reference, it was concluded that seasonal ET values by the other methods in mango orchard ranged from 7 to 28% higher, showing that turbulent flux measurements lack accuracy for executing on-farm water-saving programmes and calibrating transient soil water flow models. © 2010 Springer-Verlag.
Santos C.A.F.,Embrapa Semiarido |
Boiteux L.S.,Embrapa Hortalicas
Genetics and Molecular Research | Year: 2013
One strategy to mitigate human malnutrition in semi-arid areas is to increase the protein and mineral content of cowpea cultivars. Total seed protein, potassium, calcium, iron, zinc, and sodium contents were quantifed in elite cowpea lines, with the aim to develop cultivars that had improved levels of these nutrients. Eighty-seven F6 lines derived from 6 crosses were evaluated under rain-fed conditions in Petrolina, Brazil. Seed protein and mineral content were quantifed by the micro-Kjeldhal method and in an atomic absorption spectrophotometer, respectively. Statistical analyses were estimated for all traits, including grain yield. Signifcant differences were observed for all characteristics. Seed protein content ranged from 22.5 to 34.1%, potassium levels ranged from 20,200 to 27,000 ppm, and calcium levels ranged from 410 to 6260 ppm. Iron content ranged from 36.5 to 137 ppm, while zinc content ranged from 36 to 58 ppm and sodium content ranged from 29.2 to 88 ppm. Simple correlation coeffcient values indicated that selection for high protein and mineral content does not affect grain yield. These results demonstrate that it is feasible to obtain new biofortifed cowpea cultivars by combining higher levels of protein and essential minerals. © FUNPEC-RP.
Wadt P.G.S.,Embrapa Acre |
Silva D.J.,Embrapa Semiarido
Pesquisa Agropecuaria Brasileira | Year: 2010
The objective of this work was to test the application of accuracy measures to determine the usefulness of nutritional diagnosis to compare different DRIS formulas, and to evaluate the use of these measures in the DRIS function modeling process. Three DRIS formulas were evaluated: bivariate relations (simplified); multivariate relations; and DRIS function modeling. Monitoring data from commercial mango orchards grown at São Francisco River Valley, Brazil, were used. Formula performances were evaluated based on the agreement of their diagnoses with the one provided by the sufficiency range method. Global accuracy, and the ones for insufficiency, equilibrium, excess, deficiency, sufficiency and nutritional toxicity were determined. The simplified and multivariate formulas showed similar results for insufficiency and deficiency accuracies, but they had a lower performance than the DRIS function modeling formula. This latter, for allowing of the adjustment of each DRIS function sensibility coefficient, showed to be promising in reducing the risks of false diagnosis for deficiency (as for not recommend the nutrient when it is necessary) and for insufficiency (as for recommend the nutrient when it is not necessary). However, the DRIS formula for function modeling does not show a satisfactory performance for other accuracy measures.
de Freitas S.T.,Embrapa Semiarido |
Mitcham E.J.,University of California at Davis
Scientia Agricola | Year: 2013
Pitaya (Hylocereus undatus) is an exotic non-climacteric fruit that reaches its best eating quality when harvested ripe, decreasing thereafter during storage. Our objectives were to determine the best combination of storage temperature and use of perforated plastic bags to maintain the postharvest quality of the fruit. Fruits were stored at 5, 7, or 10 °C with and without a perforated plastic bag for 20 days, followed by five days at 20 °C without the bag for shelf-life determination. Storage at 5 °C, followed by 7 °C maintained better visual appearance of the pitaya fruit after 20 days, by reducing decay incidence and severity, and maintaining greener bracts compared with fruit stored at 10 °C. Pitaya fruit stored at 5 °C without a perforated plastic bag showed no decay after storage and shelf-life. In general, higher temperatures and the use of a perforated plastic bag increased decay incidence, as well as decay severity after storage and shelf-life conditions. At all temperatures, fruit stored in a perforated plastic bag had lower weight loss during storage. After shelf-life, weight loss was highest in fruit stored at higher temperatures. Storage of fruits at 5 °C resulted in minor chilling injury symptoms in the outer flesh tissue, close to the peel. Storage at 5 °C without a perforated plastic bag was the best condition to maintain the postharvest quality of the pitaya fruit.
de C. Teixeira A.H.,Embrapa Semiarido
Remote Sensing | Year: 2010
To achieve sustainable development and to ensure water availability inhydrological basins, water managers need tools to determine the actual evapotranspiration (ET) on a large scale. Field energy balances from irrigated and natural ecosystems togetherwith a net of agro-meteorological stations were used to develop two models for ETquantification at basin scale, based on the Penman-Monteith equation. The first model (PM1) uses the resistances to the latent heat fluxes estimated from satellite measurements,while the second one (PM2) is based on the ratio of ET to the reference evapotranspiration (ET0) and its relation to remote sensing parameters. The models were applied in the Low-Middle São Francisco river basin in Brazil and, after comparison against field results, showed good agreements with PM1 and PM2 explaining, respectively, 79% and 89% of the variances and mean square errors (RMSE) of 0.44 and 0.34 mm d-1. Even though the PM1 model was not chosen for ET calculations, the equation for surface resistance (rs) was applied to infer the soil moisture conditions in a simplified vegetation classification. The maximum values of rs were for natural vegetation-caatinga (average of 1,937 s m-1).Wine grape and mango orchard presented similar values around 130 s m-1, while table grape presented the lowest ones, averaging 74 s m-1. Petrolina and Juazeiro, in Pernambuco (PE) and Bahia (BA) states, respectively, were highlighted with the biggest irrigated areas. The highest increments are for vineyards and mango orchards. For the first crop the maximum increment was verified between 2003 and 2004 in Petrolina-PE, when the cultivated area increased 151%. In the case of mango orchards the most significant period was from 2005 to 2006 in Juazeiro-BA (129%). As the best performance was for PM2, it was selected and used to analyse the regional ET at daily and annual scales, making use of Landsat images and a geographic information system for different soil moisture conditions. Considering the daily rates of the regional ET, pixels with values lower than 1.0 mm d-1 occurred outside the rainy season, representing the caatinga species. Values from 1.0 to 5.0 mm d-1 during the driest conditions of the year coincided with irrigated crops, being the highest values for table grapes. The highest accumulated ET values during 2006 were for mango orchards, being around 500-1,300 mm yr-1. Vineyards presented lower values, ranging from 450-800 mm yr-1, while in caatinga they werebetween 200 and 400 mm yr-1. It could be concluded that irrigated mango orchards andvineyards in that year consumed more water than caatinga by factors of 3 and 2, respectively. The mango orchards and vineyard areas, representing 19.4 and 8.2% of the total irrigated area, respectively, resulting in a total evaporative depletion of 0.22 km3 yr-1 in the growing regions comprised of the agro-meteorological stations. © 2010 by the authors; licensee MDPI, Basel, Switzerland.