Irrigação da videira europeia com base no índice de estresse hídrico da cultura.

Abstract

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.