BalanÃo hÃdrico e de energia em solo cultivado e sem vegetaÃÃo, para as condiÃÃes do brejo paraibano / Water and energy balance in the cultivated and bare soil in a montane area in paraiba, Brazil

AUTOR(ES)

Josà Romualdo de Souza Lima

DATA DE PUBLICAÇÃO

2004

RESUMO

In the areas of rainfed agriculture it is very important to quantify losses of water by evapotranspiration and soil evaporation. The methods used for measuring evapotranspiration and/or evaporation varies from direct measurements techniques, using lysimeters, to measurements of the water and energy balances. The precision lysimeters have high cost, being only used for research purposes. The water and energy balances methods have been very used due the simplicity, robustness and lower cost. Therefore, the objective of this study was to assess the water and energy balance components in the soil cultivated with cowpea (Vigna unguiculata (L) Walp) and without vegetation, besides comparing the methods used to determine the cowpea evapotranspiration. Two experiments (2002 and 2003) were performed in the 4 ha area of the Centro de CiÃncias AgrÃrias, UFPB, municipality of Areia, Paraiba State (6o 58â S, 35o 41â W). To determine the energy balance, the area was instrumented with a rain gauge, a pyranometer, a net radiometer, and sensors for measuring air temperature and humidity, and wind speed in two levels. Two locals, in the soil, were instrumented with two temperature sensors located at 2.0 cm and 8.0 cm below soil surface and one heat flux plate placed at 5.0 cm below soil surface. The measurements were recorded every 30 minutes on a datalogger. To determine the water balance, three plots were installed, composed one-meter access tube for neutron probe measurements, and 8 tensiometers. The results show very good correlation between the aerodynamic method and the Bowen ratio energy balance method, for all atmospherics and soil water conditions. For the two years, in average 72% of the net radiation was used by crop evapotranspiration. The energy and water balance can be used to determine the crop evapotranspiration and soil evaporation, and regardless of the method used, the major water use by crop occurred in the reproductive stage. In the year of 2002, the average values for actual evapotranspiration obtained by using the water balance and energy balance, were 4.33 and 3.98 mm. day-1 respectively. In the year of 2003, were respectively 4.2 and 4.1 mm. day-1. Also, it was verified that the crop did not suffer water stress in the two-year period of study

ASSUNTO(S)

balanÃo hÃdrico engenharia nuclear solo cultivado solo sem vegetaÃÃo brejo paraibano

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