TDR PROBES CONSTRUCTION AND EVALUATION FOR ESTIMATING SAP FLOW IN WOODY PLANTS

Abstract

The efficient water application in agriculture involves modern equipment and appropriate management of this resource. The water amount absorbed for crop can be determined by measuring xylem sap flow and, Time Domain Reflectometry (TDR) technique has potential to be accurate and virtually free of interference. Thus, the objective of this study was TDR probes construction and evaluation of different sizes that could be read in three different software for purpose of measuring sap flow in woody plants. The experiment was conducted at the Agricultural Sciences Center at UFSCar. Probes of six sizes (200, 150, 100, 70, 50 and 20 mm) were constructed and evaluated in distilled water at 20º C for three software applications of the technique, PCTDR at Campebell Scientific, WinTDR at Utah State University e o TDR-Lab at CSIC. The software demonstrates difficulties in automatic reading, WinTDR and PCTDR being more limited as the manual reading and PCTDR failed to perform readings in probes of 1.6 mm rod diameter. In conclusion, the TDRLab software is promising to analyze smaller sizes probes, but further studies are needed of the probes physical constitution, especially in epoxy for greater precision in the readings.