Manejo de irrigação, consumo hídrico e produtividade do coqueiro anão-verde nos tabuleiros costeiros Norte do Estado de Sergipe.

Abstract

Data of a field experiment conducted in the H. Dantas Agricultural Company located in the Irrigation District of “Platô de Neópolis”, in the North draughts-chess-board of the Sergipe State (latitude: 10ºS; longitude: 37º 35'W; altitude: 200 m), were used for determining the irrigation management, water requirements and productivity of a six years-old dwarf-green coconut orchard (Coconuts nucifera L.), irrigated by microaspersão. The water requirements of the coconuts orchard (ETc) was obtained by the Bowen ration-energy balance (BREB) and soil water balance (SWB) methods. For the application of the BREB a micrometeorological tower was mounted for installing sensors of net radiation (Rn), reflected solar radiation (Rr), dry (Td) and wet (Tw) bulbs air temperature and windspeed installed at two levels above a coconuts canopy and soil heat flux sensor (G) installed at 0,02 m soil depth. The sensors analogical signals were collected by a data acquisition system (Datalogger CR10X). In the application of the SWB method, the soil humidity was monitored by the Time Domain Reflectometry (TDR) technique, with 18 probes distributed in the experimental area with sensors located at 0,15 m; 0,30 m; 0,60 m; 0,90 m and 1,20 m soil depth. For the irrigation management, three water volume treatments were applied (50, 100 and 150 liters.plant-1.day-1), with 6 TDR probes by treatment. The data for estimating reference evapotranspiração (ETo) by the Penman-Monteith/FAO model were obtained from a automatic meteorological station installed in the experimental area. The analysis of the results showed that the ETc estimated by the BREB varied from 1.1 to 9.1 mm.day-1, with a daily average of 3.8 mm and an accumulated evapotranspiration of 1,419.6 mm for the whole observational period. The application of the SWB for the period from January to November, 2003, resulted in average daily values of ETc of 2.5, 2.9 and 3.2 mm.day-1 for the treatments of 50, 100 and 150 liter.day-1, respectively, with maximum values in the beginning and end of the year and minimum values in the middle of the observations period. The crop coefficient (Kc), obtained by the BREB varied from 0.4 to 1.2. Based upon the SWB, the average weekly values of Kc varied from 0.15 to 0.96 for the treatmentviii of 50 liter.day-1, 0.27 to 1.03 for the treatment of 100 liter.day-1 and 0.24 to 1.08 for the treatment of 150 liter.day-1. The average Kc values for the whole experimental period were 0.46, 0.57 and 0.62 for the treatments of 50, 100 and 150 liter.day-1, respectively. The obtained results allows one to reaches the following conclusions: (a) the latent heat flux can be obtained with high precision (r2 = 0.99) for low and high energy atmodpheric demand, representing a significant portion of the net radiation (70 to 90%); b) the soil heat flux represents a small portion of the net radiation; c) the annual coconuts orchard evapotranspiration obtained by the Bowen ratio-energy balance reaches 1,400.0 mm while, by the soil water5 balance it varies from 900 to 1,100.0 mm; d) Statistically, there are no significant differences in the average productivity of bunches and fruits per plant, as well as in the average volume of fruits water among the applied irrigation treatments.