SOUSA, J. S.; http://lattes.cnpq.br/5496506276973041; SOUSA, Josadark Soares de.
Résumé:
Data from a field experiment conducted in the experimental area of the EMBRAPA
SEMI - ARIDO in Petrolina - PE (Latitude: 09°09'S; Longitude: 40°22'W and Altitude:
365,5m) in the period from april, 24 to august, 1 t h of 1996, with a four-years-old wine
grape (vitis vinifera L.) vine crop, grown in a trellis system and submitted to two
irrigation treatments were used for detecting the possibility of monitoring the crop
water stress by the infrared thermometry technique. The crop canopy temperature
(Tc ) was monitored with an infrared thermometer while the canopy stomatal
resistance (rc ) was obtained in a basis on porometric measurements of leaf stomatal
resistance (rs|). The soil humidity was monitored also by the use of tensiometers in
soil installed in the profundity of 20, 40, 60, 80 and 100cm. Measurings of the air
temperature (Ta), net radiation (Sr), winds peed (u), vapor pressure deficit (DPV) and
the phisiological parameters (stomatal resistance and transpiration) were made
regularly at 10:00 and 14:00 o'clock and in weekly daytime cycles between 7:00h and
17:00h at each 60 minutes interval. The stress degree day (SDD), crop water stress
indices CWSIj and CWSIj were determined. For the CWSIj the low and upper
baselines were obtained, while the CWSIj was estimated from the crop canopy
resistance under conditions of potential transpiration (rc p ) using porometric
measurements. The values of the SDD index for the TNI treatment were high than
those of the Tl treatment. The values of the CWSIj showed a large variability during
the growing season due to variations in the global solar radiation. The values of the
CWSIj showed also a high variability from one day to another, due to variations in the
global solar radiation and wind speed. From the discussion of the crop water stress
indexes presented above it was observed an high variability thoughout the
observation period, difficulting the determination of a critical value that could
characterizes irrigation scheduling. Even so, it was suggested that, in the
experimental climatic and soil conditions, the crop must be irrigated every time the
CWSIj reaches the value of 0.4. It was concluded that, despite the stress index has
not being pronounced, the fruits production was larger in the irrigated treatement. In
the non irrigated treatement, it was observed alterations in the plant morfological
development and fruits production.