Time Domain Reflectometry Calibration for Typical Upland Soils in Kyushu, Japan

Miyamoto, Teruhito; Chikushi, Jiro

doi:10.6090/jarq.40.225

Cited by 10 publications

(7 citation statements)

References 19 publications

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“…These two models have been confirmed by several researchers and are widely accepted and applicable for different soils [34,52]. Previous studies [34,51] reported the decrease in Kb with decreasing BD, and hence increasing porosity, in low moisture soils. The waveforms at the dry end of the soils amended with BCP in our experiment can be explained by the decrease in BD [51], and thus low dielectric values resulting from a greater underestimation of the VSMC at the dry end.…”

Section: Evaluation Of Three Models Based On Estimated Vsmcsupporting

confidence: 66%

“…Previous studies [34,51] reported the decrease in K b with decreasing BD, and hence increasing porosity, in low moisture soils. The waveforms at the dry end of the soils amended with BC P in our experiment can be explained by the decrease in BD [51], and thus low dielectric values resulting from a greater underestimation of the VSMC at the dry end. Though soils with BC G also have lower BD, this reduction in K b might be masked by the high EC of BC G as explained above.…”

Section: Effects Of Bc On Tdr Measurementmentioning

confidence: 82%

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Effect of Biochar on TDR-Based Volumetric Soil Moisture Measurements in a Loamy Sand Podzolic Soil

et al. 2019

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Considering the increased interests in biochar (BC) as a soil amendment and a growing media substrate in agriculture, we evaluated the effect of BC incorporation on TDR (time-domain reflectometer)-based volumetric soil moisture content (VSMC) estimations in a loamy sand podzolic soil. Two commercial BC types (powdered-BC P , and granular-BC G ) were mixed in different rates (w/w) with a podzolic soil. The dielectric constants measured using a TDR cable tester (MOHR CT 100) were converted to VSMC. Three commonly used models: (i) Topp's equation, M-1; (ii) mixing model, M-2; and (iii) the forest soil model, M-3, were used. The accuracy of the estimated VSMC using these three models was statistically compared with measured VSMC. BC P at lower rates produced very similar results to the actual VSMC with M-1 and M-2 but deviated with increasing rates. The M-3 showed a non-linear relationship with measured VSMC. In BC G treatments, all models overestimated the VSMC. BC G rates higher than 15% (w/w) resulted in highly attenuated TDR waveforms and the signal was completely dissipated when rates higher than 50% (w/w) were used (typical application for field soils is less than 5% w/w). These results showed that predictions of the soil moisture content based on the soil dielectric constant might not be feasible for tested podzolic soils amended at high BC rates.

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Section: Evaluation Of Three Models Based On Estimated Vsmcsupporting

confidence: 66%

Section: Effects Of Bc On Tdr Measurementmentioning

confidence: 82%

Effect of Biochar on TDR-Based Volumetric Soil Moisture Measurements in a Loamy Sand Podzolic Soil

et al. 2019

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“…In contrast, the discrepancies between the waveforms of the soils amended with the BC (400°C) and BC (600°C) and those of the non‐amended soil may be explained by decreases in the bulk density (Miyamoto & Chikushi, ). A decrease in the bulk density results in increased air content in the soil sample.…”

Section: Resultsmentioning

confidence: 99%

Influence of biochar incorporation on TDR‐based soil water content measurements

Kameyama

Miyamoto

Shiono

2013

European J Soil Science

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Summary The incorporation of biochar (BC) into agricultural soil changes the soil's physical properties, which leads to changes in the soil's hydraulic properties, such as water retention and permeability, and alters the soil moisture environment in agricultural fields. To elucidate the effects of the incorporation of BC on the soil moisture environment, measurements of the soil water in biochar‐amended agricultural fields are needed. Time domain reflectometry (TDR) is a widely used and established technique for the continuous measurement of the soil water content (SWC) in agricultural fields. However, TDR measurements are affected by the conductivity of soils. Biochar formed at higher pyrolysis temperatures is known to be very conductive. Therefore, we investigated the influence of the incorporation of BC on TDR‐based SWC measurements. We examined calcaric dark red soil and the BC produced by pyrolysis of sugarcane bagasse at 400, 600 and 800°C. The apparent relative permittivity (εa) of the BC (800°C)‐amended soil was greater than that of the non‐amended soil at a given water content, whereas the εa values of the soils amended with the BC (400°C) and BC (600°C) were the same as that of the non‐amended soil at a given water content. We concluded that when a calibration curve obtained from a non‐amended soil is used, TDR‐based measurements tend to over‐estimate the SWC containing the BC formed at higher pyrolysis temperatures because of conductive and dielectric losses. Therefore, the use of the real component ( ε r ′ ) of the soil's complex relative permittivity instead of εa is effective when making TDR‐based water content measurements of soils that contain BC formed at higher pyrolysis temperatures.

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“…For comparison, the ε – θ relationship measured by a standard TDR probe for an Andisol in Miyazaki, Japan, as reported by Miyamoto & Chikushi (2006) is also shown in Figure 3. The ε values measured by the shaft‐mounted TDR probe were generally much lower than those measured by the standard probe.…”

Section: Resultsmentioning

confidence: 92%

“…Calibration data for an Andisol measured with the shaftmounted time domain reflectometry (TDR) probe. Dashed curve is with a conventional TDR probe(Miyamoto & Chikushi, 2006). Relationship between h values determined by the gravimetric method and by time domain reflectometry.…”

mentioning

confidence: 99%

Simultaneous measurement of soil water and soil hardness using a modified time domain reflectometry probe and a conventional cone penetrometer

Miyamoto¹,

Fukami²,

Chikushi³

2012

Soil Use and Management

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Soil strength and water content are important indices for assessing soil resistance to root growth and soil compaction both of which affect other soil properties. Therefore, simultaneous measurement of soil penetration resistance (PR) and soil water content can aid agricultural land management. We measured PR with a conventional cone penetrometer, followed immediately by determining water content using a modified TDR probe inserted into the penetrometer hole. From the results of a field feasibility test, soil water content was measured satisfactorily and correlated well with data obtained by the gravimetric method, except for those data from near the surface owing to soil disturbance when the cone penetrometer was extracted after the PR measurements. Field results demonstrate that PR and soil water content have three‐dimensional variability, with a markedly different distribution pattern between cultivated and subsoil layers at the field scale. Overall, the variability in the PR and soil water data is similar to that reported in previous studies. We conclude that our method produces results helpful to field management of soil and water because it is based on a simple and easy technique for the simultaneous measurement of soil water content and PR.

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Time Domain Reflectometry Calibration for Typical Upland Soils in Kyushu, Japan

Cited by 10 publications

References 19 publications

Effect of Biochar on TDR-Based Volumetric Soil Moisture Measurements in a Loamy Sand Podzolic Soil

Effect of Biochar on TDR-Based Volumetric Soil Moisture Measurements in a Loamy Sand Podzolic Soil

Influence of biochar incorporation on TDR‐based soil water content measurements

Simultaneous measurement of soil water and soil hardness using a modified time domain reflectometry probe and a conventional cone penetrometer

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