ISHS Acta Horticulturae 792: V International Symposium on Irrigation of Horticultural Crops
TRANSPIRATION OF A KIWIFRUIT ORCHARD ESTIMATED USING THE GRANIER SAP FLOW METHOD CALIBRATED UNDER FIELD CONDITIONS |
| Authors: | R.M. Silva, T.A. Paço, M.I. Ferreira, M. Oliveira |
| Keywords: | eddy covariance, evapotranspiration, Actinidia deliciosa |
| Abstract:
The kiwifruit (Actinidia deliciosa A. Chev.) is an increasingly important crop in Northwestern Portugal. In a Mediterranean climate, characterized by dry summers, irrigation is used in order to ensure appropriate humidity either at root or shoot level. There is an insufficient knowledge to support effective irrigation management resulting in water deficits, nutrient leaching in some cases and, particularly, over-watering. The water requirements of kiwifruit vines were studied in a mature orchard (var. 'Hayward'), that was irrigated daily with micro-sprinklers and planted with a spacing of 5 × 5 m (T-bar training system) in a loamy soil. Vine transpiration (Tgr) was measured using the Granier sap flow method during the vegetative growing seasons of 2003 and 2004. For selected periods, evapotranspiration (ET) was measured using the eddy covariance method and soil evaporation plus understorey transpiration (Es) was measured using a set of eight microlysimeters. From these measurements, vine transpiration (Tec) was calculated by subtraction and compared with Tgr. This comparison provided experimental evidence of underestimation of vine transpiration from sap flow measurements using the original calibration equation. A correction allowed an adjustment of long-term sap flow measurements, obtaining Tgr data for the duration of the vegetative cycles. Maximum Tgr was 4 mm/day. During the selected summer periods (July to August), ET ranged from 2.5 to 5.5 mm/day and Es varied between 35% and 15% of ET. The crop coefficient (Kc) was 0.9-1.0 for this period. | |
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