scholarly journals USE OF TIME DOMAIN REFLECTOMETRY FOR CONTINUOUS MONITORING OF NITRATE-NITROGEN IN SOIL AND WATER

2006 ◽  
Vol 22 (5) ◽  
pp. 689-700 ◽  
Author(s):  
J. O. Payero ◽  
D. D. Tarkalson ◽  
S. Irmak
Keyword(s):  
Time Domain ◽  
Continuous Monitoring ◽  
Nitrate Nitrogen ◽  
Time Domain Reflectometry ◽  
Use Of Time ◽  
Soil And Water

Use of Time-Domain Reflectometry (TDR) to measure the water-content of sandy soils

Soil Research ◽  
1995 ◽  
Vol 33 (2) ◽  
pp. 265 ◽  
Author(s):  
PJ Gregory ◽  
R Poss ◽  
J Eastham ◽  
S Micin
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Transmission Lines ◽  
Time Domain ◽  
Water Storage ◽  
Sandy Soils ◽  
Time Domain Reflectometry ◽  
Soil Water Storage ◽  
Use Of Time ◽  
Daily Evaporation

We investigated the potential sources of error when using time domain reflectometry (TDR) to measure the water content of sandy soils and evaluated the technique as a means of measuring evaporation from columns of soil and changes in soil water storage beneath crops. Inaccurate depth location of the transmission lines or the development of a hole at the tip of the transmission lines introduced an error about 10 times larger than the errors associated with hardware and software. Calibration in two sandy soils gave a curve of similar shape to that found by others except for values of dielectric constant < 6 when measured values of water content were less than those expected. Daily evaporation from soil columns measured by weighing and with TDR showed large differences between the two techniques (up to 32%) but compensating errors over time allowed cumulative evaporation to be estimated with TDR to within 6.6% of that determined by weighing over a 162 h period. Under field conditions, the agreement between TDR and neutron probe measures of changes in soil water storage in the upper 0.3 m was good and generally within 10% over both 14 day and longer periods.

scholarly journals Influência da Densidade na Estimativa da Umidade Volumétrica em um Latossolo Vermelho-Amarelo (Influence of Density in Estimation of Volumetric Moisture an Oxisol)

2013 ◽  
Vol 5 (5) ◽  
pp. 1056 ◽  
Author(s):  
Carlos Alexandre Barros de Almeida ◽  
Antonio Celso Dantas Antonino ◽  
Rejane Magalhaes de Mendonça Pimentel ◽  
Carlos Alberto Brayner de Oliveira Lira ◽  
José Romualdo de Sousa Lima
Keyword(s):  
Dielectric Constant ◽  
Soil Moisture ◽  
Bulk Density ◽  
Time Domain ◽  
Time Domain Reflectometry ◽  
Calibration Equation ◽  
Moisture Sensor ◽  
Soil Moisture Sensor ◽  
Volumetric Soil Moisture ◽  
Use Of Time

A estimativa da umidade volumétrica do solo pode ser realizada por vários métodos, entre eles destaca-se o uso da Reflectometria no Domínio do Tempo (TDR). Este tem como uso padrão, uma equação que relaciona a constante dielétrica do meio com a umidade sugerida pelo manual do fabricante. Este estudo objetivou avaliar a medição a umidade volumétrica do solo pelo sensor CS616. Na sua realização foi feita a calibração deste sensor em laboratório, para quatro camadas em um Latossolo Vermelho-Amarelo que apresentam densidades diferentes. Foram utilizados cinco métodos diferentes, três consagrados pela literatura e outros dois sugeridos por esse estudo. Os resultados permitiram concluir que nesse solo há uma grande disparidade entre os resultados encontrados durante a calibração do sensor e que a densidade do solo é um parâmetro importante nas medições de umidade do solo.Palavras-chave: reflectometria no domínio do tempo, medição direta da água no solo, equação de calibração Influence of Density in Estimation of Volumetric Moisture an Oxisol ABSTRACTThe estimation of volumetric soil moisture can be accomplished by various methods, among them stands out the use of Time Domain Reflectometry (TDR). This standard is to use an equation that relates the dielectric constant of the medium with humidity suggested by the manufacturer's manual. This study aimed to evaluate the measured volumetric soil moisture sensor for the CS616. In its realization was made to calibrate this sensor in the laboratory for four layers in an Latossolo Vermelho-Amarelo which have different densities. Was used five different methods, the literature established three and two others suggested by this study. The results showed that this soil there is great disparity between the results obtained during calibration of the sensor and the bulk density is an important parameter in measurements of soil moisture.Keywords: time domain reflectometry, direct measurement of soil water, calibration equation

Unfrozen water content in saline soils: results using time-domain reflectometry

1985 ◽  
Vol 22 (1) ◽  
pp. 95-101 ◽  
Author(s):  
D. E. Patterson ◽  
M. W. Smith
Keyword(s):  
Water Content ◽  
Time Domain ◽  
Time Domain Reflectometry ◽  
Frozen Soil ◽  
Probe Design ◽  
Unfrozen Water ◽  
Use Of Time ◽  
Unfrozen Water Content ◽  
Pore Water Salinity ◽  
Apparent Dielectric Constant

The use of time-domain reflectometry (TDR) for determining the phase composition of saline permafrost from measurement of the apparent dielectric constant, Ka, is examined.Combined TDR–dilatometry experiments were performed to assess whether the TDR method could be used on frozen soil samples with high pore water salinity. In general, unfrozen water content determinations by TDR were within ±0.025 cm3∙cm−3 of those obtained by dilatometry, with no marked influence due to salinity. A novel probe design for use on saline core samples shows promise as a means for determining unfrozen water contents in the field.

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