In situ determination of electrical conductivity of potting media using time domain reflectometry

2000 ◽  
Vol 31 (15-16) ◽  
pp. 2685-2705
Author(s):  
Tom O. Owino ◽  
James M. Hamlett ◽  
E. Jay Holcomb
Keyword(s):  
Electrical Conductivity ◽  
Time Domain ◽  
Time Domain Reflectometry ◽  
Potting Media

Measuring transient solute transport through the vadoze zone using time domain reflectometry

Soil Research ◽  
2001 ◽  
Vol 39 (6) ◽  
pp. 1359 ◽  
Author(s):  
I. Vogeler ◽  
S. Green ◽  
A. Nadler ◽  
C. Duwig
Keyword(s):  
Electrical Conductivity ◽  
Solute Transport ◽  
Time Domain ◽  
Deterministic Model ◽  
Soil Surface ◽  
Time Domain Reflectometry ◽  
Richards Equation ◽  
Electrical Conductivities ◽  
Destructive Measurement

Time domain reflectometry (TDR) was used to monitor the transport of conservative tracers in the field under transient water flow in a controlled experiment under a kiwifruit vine. A mixed pulse of chloride and bromide was applied to the soil surface of a 16 m2 plot that had been isolated from the surrounding orchard soil. The movement of this solute pulse was monitored by TDR. A total of 63 TDR probes were installed into the plot for daily measurements of both the volumetric water content (θ) and the bulk soil electrical conductivity (σa). These TDR-measured σa were converted into pore water electrical conductivities (σw) and solute concentrations using various θ–σa–σw relationships that were established in the laboratory on repacked soil. The depth-wise field TDR measurements were compared with destructive measurement of the solute concentrations at the end of the experiment. These results were also compared with predictions using a deterministic model of water and solute transport based on Richards’ equation, and the convection–dispersion equation. TDR was found to give a good indication of the shape of the solute profile with depth, but the concentration of solute was under- or over-estimated by up to 50%, depending on the θ–σa–σw relationships used. Thus TDR can be used to monitor in situ transport of contaminants. However, only rough estimates of the electrical conductivity of the soil solution can so far be obtained by TDR.

In situ determination of the water desorption characteristics of peat substrates

1993 ◽  
Vol 73 (3) ◽  
pp. 329-339 ◽  
Author(s):  
J. M. Paquet ◽  
J. Caron ◽  
O. Banton
Keyword(s):  
Sample Preparation ◽  
Time Domain ◽  
Rapid Determination ◽  
Mineral Soil ◽  
Time Domain Reflectometry ◽  
Water Desorption ◽  
Alternative Method ◽  
Sample Disturbance

Knowledge of water desorption characteristics of peat substrates is of primary importance in horticulture. However, these characteristics are difficult to measure as they are influenced by sample preparation, particularly when samples are obtained from potted substrates containing growing plants. The aim of this study was to determine the effect of sample preparation on the water desorption characteristics of peat substrates and to propose an alternative method to limit sample disturbance. This study shows that water desorption characteristics of peat substrates obtained using Tempe cells differ from those obtained using pots and a tension table apparatus. However, the latter method is time and resource consuming. An alternative method for routine and rapid determination of water desorption characteristics of undisturbed samples was tested. Measurements of water potential (ψh) in pots were obtained using tensiometers. Volumetric water content (θ) was measured by time domain reflectometry (TDR), a non-destructive in situ method commonly used for mineral soil characterization. The technique measures the apparent dielectric constant of the soil (ka) and empirically relates it to θ. Empirical relationships between θ and ka were derived for three different peat substrates. Using these relationships, water desorption characteristics (θ versus ψh) were derived for three substrates in laboratory experiments and compared to water desorption characteristics obtained using a tension table to establish different ψh and a gravimetric determination of θ. The approach using TDR and tensiometers appears to be reliable, fast and to allow large number of simultaneous water characteristic determinations. Key words: Water characteristics, water release curve, time domain reflectometry, peat sustrates

scholarly journals Electrical conductivity of soil irrigated with swine wastewater estimated by time-domain reflectometry¹

2011 ◽  
Vol 35 (4) ◽  
pp. 1293-1300 ◽  
Author(s):  
Rosimaldo Soncela ◽  
Silvio Cesar Sampaio ◽  
Marcio Antonio Vilas Boas ◽  
Maria Hermínia Ferreira Tavares ◽  
Claudinei Fonseca Souza ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Soil Solution ◽  
Time Domain ◽  
Water Reuse ◽  
Soil Extract ◽  
Soil Salinization ◽  
Time Domain Reflectometry ◽  
Swine Wastewater ◽  
Indirect Determination

Wastewater application to soil is an alternative for fertilization and water reuse. However, particular care must be taken with this practice, since successive wastewater applications can cause soil salinization. Time-domain reflectometry (TDR) allows for the simultaneous and continuous monitoring of both soil water content and apparent electrical conductivity and thus for the indirect measurement of the electrical conductivity of the soil solution. This study aimed to evaluate the suitability of TDR for the indirect determination of the electrical conductivity (ECse) of the saturated soil extract by using an empirical equation for the apparatus TDR Trase 6050X1. Disturbed soil samples saturated with swine wastewater were used, at soil proportions of 0, 0.45, 0.90, 1.80, 2.70, and 3.60 m³ m-3. The probes were equipped with three handmade 0.20 cm long rods. The fit of the empirical model that associated the TDR measured values of electrical conductivity (EC TDR) to ECse was excellent, indicating this approach as suitable for the determination of electrical conductivity of the soil solution.

Improved thermo-time domain reflectometry method for continuous in-situ determination of soil bulk density

2018 ◽  
Vol 178 ◽  
pp. 118-129 ◽  
Author(s):  
Zhengchao Tian ◽  
Yili Lu ◽  
Tusheng Ren ◽  
Robert Horton ◽  
Joshua L. Heitman
Keyword(s):  
Bulk Density ◽  
Time Domain ◽  
Soil Bulk Density ◽  
Time Domain Reflectometry
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