Estimativa das necessidade hídricas na mangueira.

Abstract

In the last years, the mango orchard cropping activities has increased in the submedium São Francisco region as a consequence of the favorable soil and climate conditions to fruit crops irrigation and the great acceptance of the mango fruits in the internal and external markets. The field experiments of this study were carried out in the irrigated areas of the EMBRAPA Experimental Station of Bebedouro, Petrolina, PE, during the 1998 and 1999 productive cycle of a 9,880m2 six years old mango orchard, 'Tommy Atkins' variety, in a spacement of 8m between trees rows by 5m between trees and drip irrigated. During both experiments, a micrometeorological tower was mounted between two mango trees with sensors of net radiation, global radiation, dry and wet bulbs temperature and windspeed installed at 1.40m apart two levels above canopy. Soil heat flux plates were installed in the .05m soil depth under trees canopy while tensiometers sets were positioned at each .20m from the surface down to 2.20m soil depth. The analogical signs were collected by a Datalogger (model 21X of the Campbell Scientific) and the 10 minutes averages storaged data of net radiation, dry and wet bulbs temperature gradient, windspeed gradient and soil heat flux were used for determining the energy balance components while the soil water content was monitored by the tensiometers data. The Bowen ratio-energy balance and soil water balance methods were applied to estimate the mango orchard évapotranspiration while the Penmam-Monteith/FAO model was used in the determination of the reference évapotranspiration. The error analysis showed that the soil water balance, based upon week periods, is more appropriate than the above canopy energy balance for estimating mango orchard evapotranspiração. For the climatic conditions of the experimental area, the mango orchard crop coefficient (K\-) showed to be variable throughout the productive cycle as a function of the number of days after flowering (DAF) according to the equation: Kc = 0.36 + 0.009 (DAF) - 4.0 X 10"5 (DAF)2 and r2 = 0.78. The energy balance results also indicated that for low cloudiness conditions, the latent heat flux (LE) can be obtained with reasonable precision as a function of the net radiation R„: LE = -18.772 - 0.766 R„, and r2 = 0.99. The soil water balance method is only efficient for estimating mango orchard évapotranspiration when the term regarding to deep drainage is considered and should not be applied for periods of time longer than a week in the soil and climate conditions of the submedium São Franscisco region.