Measuring Soil Water Content, Electrical Conductivity, and Thermal Properties with a Thermo-Time Domain Reflectometry Probe

1999 ◽  
Vol 63 (3) ◽  
pp. 450-457 ◽  
Author(s):  
T. Ren ◽  
K. Noborio ◽  
R. Horton
Keyword(s):  
Electrical Conductivity ◽  
Thermal Properties ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Time Domain ◽  
Time Domain Reflectometry

scholarly journals CONDUTIVIDADE ELÉTRICA DA SOLUÇÃO DE SOLO EM FUNÇÃO DA CONDUTIVIDADE ELÉTRICA APARENTE E DA UMIDADE DO SOLO SOB APLICAÇÃO DE CLORETO DE POTÁSSIO COM USO DA REFLECTOMETRIA NO DOMINIO DO TEMPO

Irriga ◽  
2005 ◽  
Vol 10 (2) ◽  
pp. 174-183
Author(s):  
Tibério Santos Martins da Silva ◽  
Vital Pedro da Silva Paz ◽  
Eugênio Ferreira Coelho ◽  
Maurício Antônio Coelho Filho ◽  
Gessionei Da Silva Santana
Keyword(s):  
Electrical Conductivity ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Soil Solution ◽  
Time Domain ◽  
Linear Models ◽  
Time Domain Reflectometry ◽  
Soil Electrical Conductivity ◽  
Bulk Electrical Conductivity

CONDUTIVIDADE ELÉTRICA DA SOLUÇÃO DE SOLO EM FUNÇÃO DA CONDUTIVIDADE ELÉTRICA APARENTE E DA UMIDADE DO SOLO SOB APLICAÇÃO DE CLORETO DE POTÁSSIO COM USO DA REFLECTOMETRIA NO DOMINIO DO TEMPO  Tibério Santos Martins da Silva1; Vital Pedro da Silva Paz2; Eugênio Ferreira Coelho3; Maurício Antônio Coelho Filho3; Gessionei da Silva Santana41Universidade Federal da Bahia,  Cruz das Almas, BA, tibé[email protected] de Engenharia Agrícola, Universidade Federal da Bahia, Cruz das Almas-BA, 3Embrapa Mandioca e Fruticultura, Cruz das Almas-BA4Universidade Federal de Viçosa, Viçosa, MG,   1 RESUMO O trabalho teve como objetivo definir, em campo e em laboratório, modelos matemáticos que melhor relacionam a condutividade elétrica aparente (CEa), a umidade do solo (q) e a condutividade elétrica da solução do solo (CEw) sob aplicação de cloreto de potássio, via água de irrigação por gotejamento. O experimento consistiu de leituras de CEa e q com um analisador de umidade de reflectometria no domínio do tempo (TDR) em colunas de solo em laboratório e em várias posições de uma malha retangular de um perfil do solo, em condições de campo, seguido da extração de solução iônica nas respectivas posições. Foram ajustados modelos lineares e não lineares relacionando CEa, q e CEw. O resultados permitiram concluir que a CEw da solução do solo pode ser monitorada a partir de leituras de CEa pela TDR para fins de distribuição de solutos no solo sob fertirrigação, com uso dos modelos de Rhoades et al. (1976), Vogeler et al. (1996), Nadler et al. (1984) e empírico em condições de campo e laboratório. O modelo de Rhoades et al. (1989) e Rhoades et al. (1976) mostraram-se adequados apenas para os estudos em laboratório. UNITERMOS: fertirrigação, TDR  SILVA, T. S. M. DA; PAZ, V. P. DA S.; COELHO, E. F.; COELHO FILHO, M. A.; SANTANA, G. DA S. SOIL SOLUTION ELECTRICAL CONDUCTIVITY AS A FUNCTION OF BULK ELECTRICAL CONDUCTIVITY AND SOIL WATER CONTENT UNDER POTASSIUM CLORIDE APPLICATION USING TIME DOMAIN REFLECTOMETRY  2 ABSTRACT This study aimed to define mathematical models that suitably relate bulk electrical conductivity (CEa), soil water content (q) and soil solution electrical conductivity (CEw) under potassium chloride application by drip irrigation. The experiment consisted of readings of CEa and q using a Time Domain Reflectometry analyzer (TDR) in soil columns in laboratory and on several positions of rectangular soil profile grid under field conditions. Ionic solution was extracted in all positions of TDR readings. Linear and non-linear models relating CEa, q and CEw were adjusted to laboratory and field data. Results allowed to conclude that CEw may be monitored by readings of CEa from TDR for soil solute distribution under fertirrigation, using models of Rhoades et al. (1976), Vogeler et al. (1996), Nadler et al. (1984) and an empirical model in lab and in field. The models of de Rhoades et al. (1989) e Rhoades et al. (1976) were suitable only for laboratory studies. KEYWORDS: fertirrigation, soil electrical conductivity, TDR

scholarly journals Technical Note:Practical considerations on the use of down-sized time-domain reflectometry (TDR) probes

2002 ◽  
Vol 6 (5) ◽  
pp. 949-955 ◽  
Author(s):  
M. A. Mojid
Keyword(s):  
Electrical Conductivity ◽  
Water Content ◽  
Travel Time ◽  
Soil Water ◽  
Soil Water Content ◽  
Time Domain ◽  
Time Domain Reflectometry ◽  
Transition Time ◽  
Probe Length ◽  
Travel Path

Abstract. Nine time-domain reflectometry (TDR) probes, 2 to 10 cm long, were evaluated by comparing their measurement accuracy of TDR-pulse travel time in a sand and sandy loam soil, and electrical conductivity in NaCl solutions. TDR probes <2.5 cm in length generated trough-haped TDR waveforms with rounded corners at the points of the pulse reflection from the probe ends. The sharpness of the pulse reflection on the waveforms increased with both the increasing probe length and soil-water content. The transition time for the propagation of TDR pulse at the probe entrance increased as the soil dried up. The increased transition time caused a rightward movement of the first peak of the waveform at the probe entrance. Because of such peak movement, TDR-support software algorithm determined travel path of TDR pulse through the probe that was smaller than the actual travel path. TDR-measured pulse travel time tTDR varied erratically with the predicted pulse travel time tg (from volumetric soil-water content) for the probes <2.5 cm in length. But, for all probes ³2.5 cm in length, tTDR varied linearly with tg and followed the 1:1 line. TDR could not measure tTDR <300 ps accurately. A minimum probe length Lmin and the lowest allowable soil-water content qmin that the probe can accurately measure govern this lowest pulse travel time tmin. The mean absolute deviation between tTDR and tg was 77 ps for the 2.3 cm long probe and 1.39 ps for all probes ≥2.5 cm in length. All probes ≥2.5 cm in length measured electrical conductivity of salt solutions sTDR that compared well with the electrical conductivity measured by a conductivity meter sm. The length of the probes did not exert any noticeable influence on the accuracy of electrical conductivity measurement. Keywords: TDR probe, pulse travel time, dielectric constant, electrical conductivity

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