Journal of the Japanese Society of Soil Physics
Online ISSN : 2435-2497
Print ISSN : 0387-6012
Soil salinity assessment in a field covered with seawater using the 5TE sensor
Teruhito MIYAMOTOKoji KAMEYAMAYukiyoshi IWATATakahiro SHIONO
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JOURNAL FREE ACCESS

2015 Volume 131 Pages 15-22

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Abstract

It is essential to simultaneously monitor soil water content (θ) and bulk electrical conductivity (ECa) in field soils for soil salinity assessment. A low-cost ca-pacitance sensor, 5TE (Decagon Devices), can be used to study temporal variations in θ and ECa. Laboratory and field experiments were conducted to investigate the appli-cability of the 5TE sensor to monitor the salinity in the fields damaged with seawater at the time of the 2011 of the Pacific coast of Tohoku earthquake. The dependency of calibration curves on salinity for estimating θ was eval-uated. The salinity effects could be neglected when the so-lution EC (ECw) was lower than 7 dS m−1. The Rhoades model was found to be reasonably accurate to describe the ECa–ECw–θ relationships. Moreover, ECw obtained by the 5TE sensor, combined with the Rhoades model, was positively correlated with EC1:5 (EC of 1 : 5 soil:water ex-tracts). These results suggested that EC1:5 can be estimated from the θ and ECa measurements using the 5TE sensor. Field monitoring using the 5TE sensors revealed that salts in the root zone were sufficiently removed by rainwater during the summer after the damage; thus, EC1:5 values at 0.15 and 0.3 m depths became adequately lower by the end of July. In the following months, EC1:5 values at 0 and 0.3 m depths remained lower than 0.2 dS m−1 during the cultivation period for strawberries from October to April whereas EC1:5 values at 0.45 m depth fluctuated between 0.4 and 0.8 dS m−1. Simultaneous monitoring of θ and ECa, by using the 5TE sensors, can provide highly detailed information concerning temporal variations in soil salinity.

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© 2015 Japanese Society of Soil Physics
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