Evapotranspiração da cultura do gergelim irrigada na região da chapada do Apodi-RN.

Abstract

The experiment was conducted in the Apodi Chapada, west of Rio Grande do Norte, in experimental station EMPARN - Agricultural Research Company of Rio Grande do Norte, Located in the municipality of Apodi -RN. The objective of the research was to determine the water requirements of irrigated sesame (Sesamum indicum L.), grow crops BRS ANAHÍ. It was conducted during the dry season 2015 year, between the months of August, September and October. A micrometeorological tower installed in the growing area housed the following instruments for the determination of the components of energy balance: a net radiometer, two pyranometer two psychrometers, two soil heat flux plates, two anemometers and one datalogger. In estimating the water requirement of the crop was used the Bowen Ratio energy balance method (BREB). The crop evapotranspiration (ETc) and the crop coefficient (Kc) were obtained for the climatic conditions of Apodi Chapada. The reference evapotranspiration (ET0) was estimated by the Penman-Monteith method using meteorological data, obtained in the weather station of INMET, in Apodi-RN. The results show that, compared to net radiation (Rn), the latent heat flux (LE), sensible heat (H), and soil heat flux (G) corresponds to 81.3%, 17.7% and 0.4%, respectively. With the evolution of the soil covered by the crop the fraction of net radiation used as latent heat flux increased, while the one used as sensible heat flux decreased. A ETc accumulated during the growing season was 566.2 mm, corresponding to an average of 6.9 mm day-1. Phase III (reproductive development of culture) showed higher water demand, with 8.0 mm day-1. The values Kc were: 0.6 at the initial stage, 0.9 in the middle stage and 0.8 in the final stage. The value of the average determined experimentally Kc It was lower than that recommended by the FAO-56 in phases: I (emergency), II (vegetative growth) and III (reproductive development) while Stage IV (fruit set and ripening) was higher.