Consumo hídrico, produtividade e qualidade do fruto da goiabeira irrigada na região do submédio São Francisco.

Abstract

This work aimed to determine water needs of a guava orchard, Paluma variety, five-yearold ín 6 m x 6 m grid spacing and irrigated by micro sprinkler, in a producer area located at the sub-medium river São Francisco, on the basis of the determination of evapotranspiration of the culture (ETc) using the Bowen ratio energy balance (BERB) and the soil water balance (BHS) methods. In order to determine the ETcBERB it was installed a micrometeorological tower into the orchard, with sensors of net radiation, global solar radiation, reflected solar radiation, dry and wet temperature and wind speed, these last ones in two leveis above the plant canopy; on the ground, under the plant canopy, it was installed a flux plate to measure the soil heat flux. For the determination of the ETCBHS, were installed a rain gauge, a panei electronic to monitor the irrigation and tensiometersand profíle probe of soil moisture. The ETc was related to reference evapotranspiration (ETo), obtained according to the FAO-Penman-Monteith, to determine the crop coefficient (Kc) of the guava orchard. Furthermore, it was carried experiments on phenology and productivity of the culture. The experimental area was composed of two treatments of irrigation: 1) PR - area of producer and 2) PE - area of the research. In treatment PR, a water application test was carried in compliance with the indications contained in the irrigation project; no longer treatment PE, the blade of irrigation was gotten in function of the crop coefficient (Kc) determined in a previous stage (Stage 1), of the efticiency of application of water (Ea) determined in field and of the reference evapotranspiration (ETo) determined in a conventional agrometeorological station. The results indicated that the productive cycle lasted 179 days, divided in 7 phenological phases. The curve of fruit growth presented a double sigmoid behavior, with crop harvest concentrated around 135 days after the flowering. The index of fruit-loosening was bigger in the plants of treatment PR (38,3%) rather than in the plants of the PE (19,7%), resulting in bigger productivity with that one treatment. The net radiation (Rn) represented 65% of the solar global radiation (Rg) and can be assessed by means of the following equation: Rn = 0,6803.Rg 8,4489, R2 = 0,9939. The average albedo of the orchard during the productive cycle was equal to 17,2%. The latent heat flux (LE) represented 90.7% of Rn, while the sensible heat flux and soil heat flux had represented 12,3 e 3,63% of Rn, respectively. The average value of ETcBERB for the productive cycle of guava was 5,3 mm day-1, conditioning the attainment of a value of KcBERB 1,1, revealing sufficiently superior to that value determined in Stage 1 (equal to 0,77). This variation was attributed to the increase of the foliar area and age of the orchard. The average values of the ETc gotten by means of the soil water balance for treatments of the producer (ETcBHSPR) and the research (ETcBHSPE) had been equal the 6.3 mm day"1 e 5.6 mm day"1, respectively. The amount of water applied in the two treatments did not present great difference in the productivity and quality of fruits; however, the efficient water use (EUA) was bigger in treatment PE (2.91 kg mm"1) in comparison with the treatment PR (2.66 kg mm-1).