Balanço de energia, evapotranspiração e variáveis de crescimento do algodoeiro semiperene, cultivar BRS 200.

Abstract

A field experiment was carried out at the experimental farm of the Brazilian Company of Agricultural and animal Research - Embrapa Algodao, in Barbalha-CE, (07°18'39 "S; 39°23'39 "W; 415,7 m) from of August to December of 2003.The main objective of the study was to evaluate the evapotranspiration and the energy balance components of an irrigated cotton crop cultivar BRS 200, under the soil and climate conditions of the cariri region. Inside the experimental, area a sir installing sensors to measure micrometeorological tower was mounted in the experimental area, the components the energy balance over the crop canopy. All sensors were ones were connected to an automatic system (Datalogger 2IX do Campbell Sci), programmed for readings at every 5 seconds and to extract averages at a 20 minutes interval. The growth variavles: leaf area, leaf area index and plant height were measured weekly. These variavles reached maximum values of: 1,965.7 cm2, 2.2 cm2/cm2 and 75.1 cm, respectively. The crop phenological cycle was divided into four phase, with a water consumption of 5.0 mm/day, 5.0 mm/day, 6.2 mm/day and 6.0 mm/day, in the phases I , II, III and IV, respectively. The total water required by the crop was 582.2 mm. The energy balance components were observed to be similar for net radiation, latent heat flux, soil heat flux and sensible heat flux, before, during and after irrigation. During the irrigation, all energy balance components were reduced. The behaviour of the energy balance components for days with and without cloudiness on each phenological phases were also analysed. It was observed that the maximum values occurred around mid-day and that the net radiation was higher than the other components However, in the end of the crop cycle, the values of Rn and LE were close to each other.