Abstract
The use of empirical agrometeorological models that can be adjusted to the climatic conditions of different regions has become increasingly necessary to improve water management in grain-producing municipalities. The aim of this work is to examine the correlation between various reference evapotranspiration (ETo) estimation methods and the standard FAO 56 Penman-Monteith method, as well as to determine correction factors, when necessary, for crop-producing municipalities in the northeast of Pará, during both the rainy and dry seasons. We compared simpler methods of ETo estimation to the FAO 56 Penman-Monteith method. For this purpose, meteorological data from Tracuateua, Bragança, Capitão Poço and Castanhal, provided by the National Institute of Meteorology (INMET), were used. The calibration of equations was performed through linear regression. The accuracy of different estimation methods was examined. The Turc, FAO 24 Blaney-Criddle and regression methods presented the best results for all statistical criteria; the Priestley-Taylor, Makkink and FAO 24 Radiation methods presented excellent results after calibration. The methods of Camargo and Hargreaves-Samani produced the worst results for all the criteria.
Highlights
The sowing of some crops in the North Region of Brazil is normally restricted to the first half of the year, the rainy season; if a second or third planting were adopted during the dry season, the yield could be much higher
The results clearly show the existence of two different seasons in all the municipalities: as seen, most of the rainfall and the highest measurements of air relative humidity occur from January to June, and the lowest ones occur from July to December
The Priestley-Taylor, Makkink and FAO 24 Radiation methods were significantly improved through calibration, which reduced their errors to less than 0.5 mm day-1; these methods may be used in the northeast region of Pará
Summary
The sowing of some crops in the North Region of Brazil is normally restricted to the first half of the year, the rainy season; if a second or third planting were adopted during the dry season, the yield could be much higher. This would require irrigation in order to partially or completely meet water needs, based on the rainfall regime of the region. Irrigation management, for example, requires precise information on the water consumption of the plants and on the storage of soil water, and the meteorological water balance has often been adopted as a viable alternative when limited meteorological data are available (Carvalho, Rocha, Bonomo, & Souza, 2015). The simplifications adopted in the method and the consideration of the available water capacity as invariable (Pereira, 2005) make this approach inefficient due to the substantial lack of more accurate data on crop evapotranspiration
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