ISHS Acta Horticulturae 427: Strategies to Optimize Wine Grape Quality
SAP FLOW MEASUREMENTS ON GRAPEVINES |
| Authors: | J. Schmid, E.H. Rühl |
| Abstract:
The measurement of crop water consumption is in essential part for general studies on water relations, identification of stress factors, irrigation management or breeding of water plant efficient rootstocks. In field crops changes in soil water content are commonly used to estimate evapotranspiration. In vineyards this method often fails due to the extensive root systems of vines. High stone content, variable depth and composition of vineyard soils and the common use of sod cultures and cover crops; use of weighting lysimeters is too expensive and restricted to one site only. A sap flow measurement system is devised, which is based on the system of Granier. The flow meters consist of two 15-mm-long probes, placed in 2-mm aluminum cylinders. These are inserted into the trunk 10 to 15 cm above each other. Each probe consists of a syringe needle covered with a heating wire. The upper probe is heated permanently. The thermocouples of each probe are connected in a way to allow the measurement of the temperature difference between them. Increasing sap flow results in reduced temperature difference. Sap flow density is calculated from these data by the Granier formula. The calibration was performed by forced sap flow in freshly cut grapevine trunks during winter and on intact plants, growing in 10-L containers. The transpiration values obtained by the Granier system corresponded well with those determined by weight. The application of this system to physiological problems was demonstrated in a rootstock field trial in the Palatinate and a field study at Geisenheim. | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
