Necessidades hídricas da videira na região do submédio São Francisco.

Abstract

The field experiment of this study was conducted in the Bebedouro experimental basis of the (EMBRAPA/Semi-Ârido) in Petrolina-PE (Lat.:09°0'S, Long.: 40°22'W e Alt.: 365,5m), during the growing period from may to august, 1996. This study had the objective of determining the water reguirement of a five-years-old wine grape (Vitis vinifera L.) vinecrop, variety Italy, grown in a trellis system. The crop évapotranspiration (ETc), determined by the models;of soil water balance and above canopy energy balance and the reference evapotranspiration(ETo), estimated by the method of Penman were used for analyzing the behaviour of the crop coefficient (Kc = ETc/ETo) throughout the crop growing cycle. The wine grape was grown in a 4m between rows by 2m between plants spacing. The field experiment had sixteen plots of three rows of 168m2 each with a total experimental area of 2,688m2 , within a total wine grape vinecrop area of 13.000m2 It was used a trickleling irrigation system with transmitters in line spaced of 1m in the rows and a water outlet of 4 l/h. The micrometeorological parameters were monitored continuously at 1m above canopy with sensors wired in a Data Logger taking measures at each 5 seconds and storing the average of each 10 minutes. The tensiometry measures were made daily always before irrigations and the leaf area was obtained weekly. The results allowed to conclude that the soil water balance method produces values more consistent of the crop evapotranpiration that the energy balance method. It was observed a contribution of the soil water table for the roots zone in the phenological phases of fruit formation and development. The greatest portion of net radiation was used as latent heat flux while the lowest portion of Rn was used as soil sensible heat flux. It was also observed an aditional source of energy to the system by the advection of sensible heat on June, 10t h when the latent heat flux was 14.51% higher than Rn and 25.41 % higher than (Rn+G). The crop daily water use was maximum in the week period from July 1 s t to 7t h of 1996 (ETc = 4.33mm/day) and a total water consumption of 332.80mm for the whole growing observational period. The crop coefficient (Kc) values showed to be comparable to those suggested by FAO with a small difference in the phenological phases of fruits formation and development when there was a greater contribution of the soil water table to the roots zone and a resulting underestimation of the Kc valeus to be applied in the irrigation calculus. It was obtained a characteristic curve of Kc for the wine grape vegetative cycle, which allows to obtain daily values of Kc as a function of days after pruning (DAP) by the adjustment equation : Kc = - 8.10'5 (DAP)2+ 0.0091 (DAP)+ 0.4886, with r2 = 0.97.