Effect of Soil Texture on accuracy of Time Domain Reflectometry methods for Measurement of Soil Moisture Content

Document Type : Original Article

Authors

1 Msc. Student, Department of Irrigation and Reclamation, Tabriz University, Tabriz, Iran

2 Associate Professor, Department of Irrigation and Reclamation, Tabriz University, Tabriz, Iran

3 Professor, Department of Soil Science, Tabriz University, Tabriz, Iran

4 4Assistant Professor, Agricultural and Natural Resource Institute of Azarbayjane sharghi, Tabriz, Iran

Abstract

Soil moisture as an important factor in agricultural management which is measured or estimated using direct and indirect methods. Time domain reflectometry (TDR) method is One of the newest and fastest ways to measure the soil dielectric constant, indirectly which is based on the measurement of soil dielectric constant regarding the velocity of the electromagnetic waves propagation. In this paper, several experimental relations between dielectric constants and volumetric water content have been presented, but all soil properties is not considered in these methods. The main purpose of this research is the investigation of the effect of soil texture on the accuracy of volumetric water content measurement by use of TDR system. The experiments have been carried out on 5 types of texture (sandy, sandy loam, loam, sandy clay loam and clay loam) in three repetitions under quite random conditions. In addition to assessment of soil moisture using TDR, soil volumetric water content has been measured in direct (weight) method. Also, Estimated Values of soil moisture by the TDR system were compared with topp et al (1980) and mixed models. The results showed that the volumetric water content values ​​obtained from TDR system decreased with The heavier soil texture, As the percent relative error (RE) in textures sandy, sandy loam, loam, sandy clay loam and clay loam have been Respectively equal to 4.07, 8.9, 8.03, 9.13 and 11.4. comparision of estimated moisture using models showed that in all textures, topp et al (1980) models had the highest Correlation coefficient and also The accuracy of topp models is more of mixed models.  Finally, Relations have been calibrated with a high correlation (R2) between weight and TDR moisture measurements were presented.

Keywords

References

1. سالاری ا. 1387. بررسی اثر شوری بر واسنجی دستگاه TDR در مکشهای مختلف خاک. پایان‌نامه کارشناسی ارشد، دانشگاه شهید چمران اهواز، دانشکده مهندسی علوم آب، گروه آبیاری و زهکشی.
2. سلطانی محمدی، ا. 1384. تاثیر بافت خاک روی واسنجی TDR برای اندازه‌گیری رطوبت در شرایط خاک‌های خوزستان. پایان‌نامه کارشناسی ارشد، گروه آبیاری و زه‌کشی، دانشکده مهندسی علوم آب،  دانشگاه شهید چمران اهواز ، 192 ص.
3. Balanis, C.A. 1989. Advanced Engineering Electromagnetics. John Wiley & Sons, Inc., New York.
4. Chapman, d. l. 1913. Contribution to the theory of electrocapillarity, philos. Mag. 23(6):   475-  481.
5. Dobson, M.C., F.T. Ulaby, M.T. Hallikainen, and M. A. El-Rayes. 1985. Microwave dielectric behaviour of wet soil. Part II: Dielectric mixing models. Institution of Electrical and Electronic Engineers Transactions on Geosciexce and Remote Sensing. 23:35-46.
6. Gardner W. 1986. Water content methods of soil analysis. Part 1. Physical and mineralogical Methods. American Society of Agronomy, Inc., Madison, WI, Agronomy Monographs. 9:493- 544.
7. Gouy, g. 1910. Sur la constitution de la charge electrique a la surface dun electrolyte. Ann. Phys. (paris). [iv]9: 457-468.
8. Jacobsen, O. H. and Schjonning, P. 1993. A laboratory calibration of time domain reflectometry for soil water measurement including effects of bulk density and texture. Hydrology Journal. 151: 147-157.
9. Oleszczuk, R., Brandyk, T., Gnatowski, T., and Szatyowicz, J. 2004. Calibration of TDR for moisture determination in peat deposits. Int. Agrophysics. 18: 145-151.
10. Pumpanen, J. and Luvesniemi, H. 2005. Calibration of time domain reflectometry for forest soil humus layers. Boreal Environment Res. 10: 589.595.
11. Roth, K., Schulin, R., Fluhler, H. and Attinger, W. 1990. Calibration of TDR for water content measurement using a composite dielectric approach . Water Resour Res. 26(10): 2267– 2273.
12. Silberstein, R. P., Sivapalan, M. and Wyllie, A. 1999. On the validation of coupled water and energy balance model at small catchment scales. Journal of Hydrology. 220: 149 – 168.
13. Topp, G.C., Davis, J.L., and A. P.Annan. 1980. Electromagnetic determination of soil water content: Measurment in coaxial transmission lines. Water Resources Research 16:574-582.
14. Walker, J. P. 1999. Estimating soil moisture profile dynamics from near-surface soil moisture measurements and standard meteorological data. Ph.D thesis. The University of Newcastle: New South Wales, Australia.

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