Análise da relação entre os componentes do balanço de energia e da evapotranspiração do meloeiro cultivado nas condições climáticas da região de Mossoró-RN

Abstract

The potential for irrigated orcharding and horticulture in Rio Grande do Norte state is recognized worldwide, and it is shaping as the largest melon producer (Cucumis melo L.) in Brazil. Melon production in this region is predominantly under irrigated conditions, allowing the production all year. The rapid increase in irrigation projects has led to an increase in water demand, leading to sharp downgrades of aquifers so as to generate concerns about water security in the region in periods of long droughts, fact quite common in the Brazilian semiarid region. The objective of this research was to determine the daily crop evapotranspiration (ETc) and the values of crop coefficient (Kc) for the different phenological phases melon crop in the region of Mossoró/RN, using the micrometeorological method of Bowen ratio (BERB). The study was conducted in two areas of commercial melon cultivation, located in the Rural Mossoró/RN Zone. The experiment consisted of the determination of the components of energy balance and crop evapotranspiration (ETc) using the method of Bowen ratio (BERB). The field phase was installed in two consecutive cycles of the harvest 2012. The crop coefficients (Kc) were determined by the ratio between the crop evapotranspiration by BERB method (ETBERB) and reference evapotranspiration (ETo), is being estimated from data collected in the meteorological station of INMET located in one area. The ETo was calculated using the Penman-Monteith parameterized by FAO. Performance indicators were used to compare the ETBERB with ETFAO. It was observed that the LE/Rn values were above 60%, G/Rn averaged 11% and the mean H/Rn was 21%. The ETc varied from 264.79 mm to 362.19 mm. The KC-init ial results were higher, and the Kc-middle and lower Kc-end, compared to KcFAO values of the same phenological stages, and the average differences observed were 43, 8 and 7% for stages initial, middle and final, respectively. Cultivation coefficients generated by the method BERB varied, for the initial stage of 0.27 0.32; to the middle stage of the 0.89 and 0.84 for the final stage of 0.56 0.66. The methodology of BERB enabled the obtaining of evapotranspiration and crop coefficients compatible with the traditional methodology of the FAO Manual 56 for Irrigation and Drainage. However, there was disagreement between the methods in the early stage of culture, which provided full ETBERB be up to 5% higher than the ETFAO