Claudinei Fonseca Souza

Calibração da Reflectometria no Domínio do Tempo (TDR) para a estimativa da concentração da solução no solo

Time Domain Reflectometry (TDR) is a reliable method for in-situ measurements of the humidity and the solution concentration at the same soil volume. Accurate interpretation of electrical conductivity (and soil humidity) measurements may require a specific calibration curve. The primary goal of this work was to establish a calibration procedure for using TDR to estimate potassium nitrate concentrations (KNO3) in soil solution. An equation relating the electrical conductivity measured by TDR and KNO3 concentration was established enabling the use of TDR technique to estimate soil water content and nitrate concentration for efficient fertigation management.

Characterization Spatial And Temporal Patterns Of Water And Solute Distribution

The use of drip irrigation and marginal water is growing rapidly in some areas, highlighting the need to develop sound fertigation practices that combine environmental and crop production concerns. In this study, we characterize spatial and temporal water and solute distribution patterns to underpin fertigation design and management systems. Experiments were conducted in a soil box, monitoring the distribution of potassium nitrate (KNO3) and water flow from a dripper at constant flow rate of 4 L h-1, using time domain reflectometry (TDR) probes. In the interactions between the different profiles, a gradient distribution of the solution in the soil was observed, with greater storage of solution close to the dripper, which decreased gradually as it approached the wetting front. To reduce leaching of fertigated ions, the frequent application of small amounts of solution during irrigation is recommended.

NOTA TÉCNICA: CONSTRUÇÃO DE SONDAS TDR E AVALIAÇÃO EM DIFERENTES SOFTWARES DE APLICAÇÃO TÉCNICA

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.