{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,26]],"date-time":"2026-06-26T20:12:32Z","timestamp":1782504752232,"version":"3.54.5"},"reference-count":75,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2020,1,8]],"date-time":"2020-01-08T00:00:00Z","timestamp":1578441600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Nidhi Prayas","award":["-"],"award-info":[{"award-number":["-"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Soil volumetric water content (    V W C    ) is a vital parameter to understand several ecohydrological and environmental processes. Its cost-effective measurement can potentially drive various technological tools to promote data-driven sustainable agriculture through supplemental irrigation solutions, the lack of which has contributed to severe agricultural distress, particularly for smallholder farmers. The cost of commercially available     V W C     sensors varies over four orders of magnitude. A laboratory study characterizing and testing sensors from this wide range of cost categories, which is a prerequisite to explore their applicability for irrigation management, has not been conducted. Within this context, two low-cost capacitive sensors\u2014SMEC300 and SM100\u2014manufactured by Spectrum Technologies Inc. (Aurora, IL, USA), and two very low-cost resistive sensors\u2014the Soil Hygrometer Detection Module Soil Moisture Sensor (YL100) by Electronicfans and the Generic Soil Moisture Sensor Module (YL69) by KitsGuru\u2014were tested for performance in laboratory conditions. Each sensor was calibrated in different repacked soils, and tested to evaluate accuracy, precision and sensitivity to variations in temperature and salinity. The capacitive sensors were additionally tested for their performance in liquids of known dielectric constants, and a comparative analysis of the calibration equations developed in-house and provided by the manufacturer was carried out. The value for money of the sensors is reflected in their precision performance, i.e., the precision performance largely follows sensor costs. The other aspects of sensor performance do not necessarily follow sensor costs. The low-cost capacitive sensors were more accurate than manufacturer specifications, and could match the performance of the secondary standard sensor, after soil specific calibration. SMEC300 is accurate (    M A E    ,     R M S E    , and     R A E     of 2.12%, 2.88% and 0.28 respectively), precise, and performed well considering its price as well as multi-purpose sensing capabilities. The less-expensive SM100 sensor had a better accuracy (    M A E    ,     R M S E    , and     R A E     of 1.67%, 2.36% and 0.21 respectively) but poorer precision than the SMEC300. However, it was established as a robust, field ready, low-cost sensor due to its more consistent performance in soils (particularly the field soil) and superior performance in fluids. Both the capacitive sensors responded reasonably to variations in temperature and salinity conditions. Though the resistive sensors were less accurate and precise compared to the capacitive sensors, they performed well considering their cost category. The YL100 was more accurate (    M A E    ,     R M S E    , and     R A E     of 3.51%, 5.21% and 0.37 respectively) than YL69 (    M A E    ,     R M S E    , and     R A E     of 4.13%, 5.54%, and 0.41, respectively). However, YL69 outperformed YL100 in terms of precision, and response to temperature and salinity variations, to emerge as a more robust resistive sensor. These very low-cost sensors may be used in combination with more accurate sensors to better characterize the spatiotemporal variability of field scale soil moisture. The laboratory characterization conducted in this study is a prerequisite to estimate the effect of low- and very low-cost sensor measurements on the efficiency of soil moisture based irrigation scheduling systems.<\/jats:p>","DOI":"10.3390\/s20020363","type":"journal-article","created":{"date-parts":[[2020,1,9]],"date-time":"2020-01-09T03:07:11Z","timestamp":1578539231000},"page":"363","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":116,"title":["Laboratory Calibration and Performance Evaluation of Low-Cost Capacitive and Very Low-Cost Resistive Soil Moisture Sensors"],"prefix":"10.3390","volume":"20","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-9351-8866","authenticated-orcid":false,"given":"Soham","family":"Adla","sequence":"first","affiliation":[{"name":"Chair of Hydrology and River Basin Management, Technical University of Munich, 80333 Munich, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Neeraj Kumar","family":"Rai","sequence":"additional","affiliation":[{"name":"Kritsnam Technologies Private Limited, Kanpur 208016, India"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sri Harsha","family":"Karumanchi","sequence":"additional","affiliation":[{"name":"Kritsnam Technologies Private Limited, Kanpur 208016, India"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5320-5072","authenticated-orcid":false,"given":"Shivam","family":"Tripathi","sequence":"additional","affiliation":[{"name":"Department of Civil Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4620-575X","authenticated-orcid":false,"given":"Markus","family":"Disse","sequence":"additional","affiliation":[{"name":"Chair of Hydrology and River Basin Management, Technical University of Munich, 80333 Munich, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Saket","family":"Pande","sequence":"additional","affiliation":[{"name":"Department of Water Management, Delft University of Technology, 2628 CN Delft, The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2020,1,8]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Klute, A. (1986). Water Content. Methods of Soil Analysis. Part 1. Physical and Mineralogical Methods, American Society of Agronomy and Soil Science Society of America. [2nd ed.].","DOI":"10.2136\/sssabookser5.1.2ed"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"632","DOI":"10.1061\/(ASCE)IR.1943-4774.0000449","article-title":"Performance analysis and calibration of a new low-cost capacitance soil moisture sensor","volume":"138","author":"Kargas","year":"2012","journal-title":"J. Irrig. Drain. Eng."},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Bogena, H.R., Huisman, J.A., Schilling, B., Weuthen, A., and Vereecken, H. (2017). Effective calibration of low-cost soil water content sensors. Sensors, 17.","DOI":"10.3390\/s17010208"},{"key":"ref_4","unstructured":"H\u00fcbner, C., Cardell-Oliver, R., Becker, R., Spohrer, K., Jotter, K., and Wagenknecht, T. (2009, January 1\u20135). Wireless soil moisture sensor networks for environmental monitoring and vineyard irrigation. Proceedings of the 8th International Conference on Electromagnetic Wave Interaction with Water and Moist Substances (ISEMA 2009), Helsinki, Finland."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1888","DOI":"10.2136\/sssaj2013.03.0093","article-title":"State of the art in large-scale soil moisture monitoring","volume":"77","author":"Ochsner","year":"2013","journal-title":"Soil Sci. Soc. Am. J."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"358","DOI":"10.2136\/vzj2007.0143","article-title":"Soil moisture measurement for ecological and hydrological watershed-scale observatories: A review","volume":"7","author":"Robinson","year":"2008","journal-title":"Vadose Zone J."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"59","DOI":"10.1016\/j.csi.2012.05.001","article-title":"A survey on wireless sensor network infrastructure for agriculture","volume":"35","author":"Yu","year":"2013","journal-title":"Comput. Stand. Inter."},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Zhang, D.J., and Zhou, G.Q. (2016). Estimation of soil moisture from optical and thermal remote sensing: A review. Sensors, 46.","DOI":"10.3390\/s16081308"},{"key":"ref_9","unstructured":"Greacen, E.L. (1981). Soil Water Assessment by the Neutron Method, Commonwealth Science Industrial Research Organization."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"574","DOI":"10.1029\/WR016i003p00574","article-title":"Electromagnetic determination of soil water content: Measurements in coaxial transmission lines","volume":"16","author":"Topp","year":"1980","journal-title":"Water Resour. Res."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"444","DOI":"10.2136\/vzj2003.4440","article-title":"A review of advances in dielectric and electrical conductivity measurements in soils using time domain reflectometry","volume":"2","author":"Robinson","year":"2003","journal-title":"Vadose Zone J."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1059","DOI":"10.2136\/vzj2004.0141","article-title":"Standardizing characterization of electromagnetic water content sensors: Part 2. Evaluation of seven sensing systems","volume":"4","author":"Blonquist","year":"2005","journal-title":"Vadose Zone J."},{"key":"ref_13","unstructured":"Sparks, D. (2006). Advances in Crop Water Management Using Capacitive Water Sensors, Elsevier Science."},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Kojima, Y., Shigeta, R., Miyamoto, N., Shirahama, Y., Nishioka, K., Mizoguchi, M., and Kawahara, Y. (2016). Low-cost soil moisture profile probe using thin-film capacitors and a capacitive touch sensor. Sensors, 16.","DOI":"10.3390\/s16081292"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"574","DOI":"10.2136\/vzj2014.08.0114","article-title":"Calibration and evaluation of a frequency domain reflectometry sensor for real-time soil moisture monitoring","volume":"14","author":"Ojo","year":"2015","journal-title":"Vadose Zone J."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"153","DOI":"10.1006\/jaer.1996.0017","article-title":"Measurement of soil water content using a simplified impedance measuring technique","volume":"63","author":"Gaskin","year":"1996","journal-title":"J. Agric. Eng. Res."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"131","DOI":"10.1016\/0168-1699(94)90003-5","article-title":"Field measurements of soil electrical conductivity and water content by time-domain reflectometry","volume":"11","author":"Noborio","year":"1994","journal-title":"Comput. Electron. Agric."},{"key":"ref_18","first-page":"394","article-title":"Measurement of soil water content with a 50-MHz soil dielectric sensor","volume":"68","author":"Seyfried","year":"2004","journal-title":"Soil Sci. Soc. Am. J."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"67","DOI":"10.1016\/0022-1694(87)90194-6","article-title":"Soil moisture measurement by an improved capacitance technique, Part I. Sensor design and performance","volume":"93","author":"Dean","year":"1987","journal-title":"J. Hydrol."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"399","DOI":"10.2166\/wp.2003.0025","article-title":"Can development of water resources reduce poverty?","volume":"5","author":"Rijsberman","year":"2003","journal-title":"Water Policy"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"297","DOI":"10.1016\/j.jclepro.2014.04.036","article-title":"Environmental parameters monitoring in precision agriculture using wireless sensor networks","volume":"88","author":"Srbinovska","year":"2015","journal-title":"J. Clean. Prod."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"1923","DOI":"10.1002\/2015WR017841","article-title":"A socio-hydrological model for smallholder farmers in Maharashtra, India","volume":"52","author":"Pande","year":"2016","journal-title":"Water Resour. Res."},{"key":"ref_23","unstructured":"Den Besten, N. (2016). The socio-hydrology of smallholders in Marathwada, Maharashtra state (India). [Master\u2019s Thesis, Delft University of Technology]."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Matula, S., B\u00e1t\u2019kov\u00e1, K., and Legese, W.L. (2016). Laboratory performance of five selected soil moisture sensors applying factory and own calibration equations for two soil media of different bulk density and salinity levels. Sensors, 16.","DOI":"10.3390\/s16111912"},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Cosh, M.H., Ochsner, T.E., McKee, L., Dong, J.N., Basara, J.B., Evett, S.R., Hatch, C.E., Small, E.E., Steele-Dunne, S.C., and Zreda, M. (2016). The soil moisture active passive marena, oklahoma, in situ sensor testbed (smap-moisst): Testbed design and evaluation of in situ sensors. Vadose Zone J., 15.","DOI":"10.2136\/vzj2015.09.0122"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"2030","DOI":"10.1002\/2014WR016443","article-title":"An empirical vegetation correction for soil water content quantification using cosmic ray probes","volume":"51","author":"Baatz","year":"2015","journal-title":"Water Resour. Res."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"61","DOI":"10.1007\/s11430-014-4911-7","article-title":"A terrestrial observatory approach to the integrated investigation of the effects of deforestation on water, energy, and matter fluxes","volume":"58","author":"Bogena","year":"2015","journal-title":"Sci. China Earth Sci."},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Qu, W., Bogena, H.R., Huisman, J.A., Martinez, G., Pachepsky, Y.A., and Vereecken, H. (2014). Effects of soil hydraulic properties on the spatial variability of soil water content: Evidence from sensor network data and inverse. Vadose Zone J., 13.","DOI":"10.2136\/vzj2014.07.0099"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"789","DOI":"10.1002\/2014GL062496","article-title":"Predicting subgrid variability of soil water content from basic soil information","volume":"42","author":"Qu","year":"2015","journal-title":"Geophys. Res. Lett."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"7","DOI":"10.1007\/s11119-005-0681-8","article-title":"Future directions of precision agriculture","volume":"6","author":"McBratney","year":"2005","journal-title":"Precis. Agric."},{"key":"ref_31","doi-asserted-by":"crossref","unstructured":"Martini, E., Wollschlager, U., Kogler, S., Behrens, T., Dietrich, P., Reinstorf, F., Schmidt, K., Weiler, M., Werban, U., and Zacharias, S. (2015). Spatial and temporal dynamics of hillslope-scale soil moisture patterns: Characteristic states and transition mechanisms. Vadose Zone J., 14.","DOI":"10.2136\/vzj2014.10.0150"},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Qu, W., Bogena, H.R., Huisman, J.A., and Vereecken, H. (2013). Calibration of a novel low-cost soil water content sensor based on a ring oscillator. Vadose Zone J., 12.","DOI":"10.2136\/vzj2012.0139"},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Gonz\u00e1ez-Teruel, J.D., Torres-S\u00e1nchez, R., Blaya-Ros, P.J., Toledo-Moreo, A.B., Jim\u00e9nez-Buend\u00eda, M., and Soto-Valles, F. (2019). Design and Calibration of a Low-Cost SDI-12 Soil Moisture Sensor. Sensors, 19.","DOI":"10.3390\/s19030491"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"582","DOI":"10.2136\/vzj2010.0083","article-title":"Correction of temperature and electrical conductivity effects on dielectric permittivity measurements with ECH2O sensors","volume":"10","author":"Rosenbaum","year":"2011","journal-title":"Vadose Zone J."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"1867","DOI":"10.1139\/x05-121","article-title":"Precision and accuracy of three alternative instruments for measuring soil water content in two forest soils of the Pacific Northwest","volume":"35","author":"Czarnomski","year":"2005","journal-title":"Can. J. For. Res."},{"key":"ref_36","unstructured":"Spectrum Technologies (2014). Waterscout SM100 Soil Moisture Sensor Product Manual, Spectrum Technologies, Inc.. Available online: https:\/\/www.specmeters.com\/assets\/1\/22\/6460_SM1002.pdf."},{"key":"ref_37","unstructured":"Spectrum Technologies (2015). Waterscout SMEC 300 Soil Moisture Sensor Product Manual, Spectrum Technologies, Inc.. Available online: https:\/\/www.specmeters.com\/assets\/1\/22\/6470_SMEC3004.pdf."},{"key":"ref_38","doi-asserted-by":"crossref","unstructured":"Saleh, M., Elhajj, I.H., Asmar, D., Bashour, I., and Kidess, S. (2016, January 2\u20134). Experimental evaluation of low-cost resistive soil moisture sensors. Proceedings of the 2016 IEEE International Multidisciplinary Conference on Engineering Technology (IMCET), Beirut, Lebanon.","DOI":"10.1109\/IMCET.2016.7777448"},{"key":"ref_39","doi-asserted-by":"crossref","unstructured":"Aravind, P., Gurav, M., Mehta, A., Shelar, R., John, J., Palaparthy, V.S., Singh, K.K., Sarik, S., and Baghini, M.S. (2015). A wireless multi-sensor system for soil moisture measurement. IEEE Sens., 1\u20134.","DOI":"10.1109\/ICSENS.2015.7370444"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"532","DOI":"10.1104\/pp.23.4.532","article-title":"A comparison of electric resistance units for making a continuous measurement of soil moisture under field conditions","volume":"23","author":"Bouyoucos","year":"1948","journal-title":"Plant Physiol."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"961","DOI":"10.1029\/WR016i006p00961","article-title":"Survey of methods for soil moisture determination","volume":"16","author":"Schmugge","year":"1980","journal-title":"Water Resour. Res."},{"key":"ref_42","unstructured":"Delta-T Devices Ltd (1999). ThetaProbe Soil Moisture Sensor Type ML2x User Manual ML2-UM-1, Delta-T Devices. Available online: https:\/\/www.delta-t.co.uk\/wp-content\/uploads\/2016\/11\/ML2-Thetaprobe-UM.pdf."},{"key":"ref_43","unstructured":"Miller, J.D., and Gaskin, G.J. (1998). ThetaProbe ML2x. Principles of Operation and Applications, UK Macaulay Land Use Research Institute. [2nd ed.]. Technical Note."},{"key":"ref_44","unstructured":"Delta-T Devices Ltd (2017). User Manual for the ML3 ThetaProbe ML3-UM-2.1, Delta-T Devices. Available online: https:\/\/www.delta-t.co.uk\/wp-content\/uploads\/2017\/02\/ML3-user-manual-version-2.1.pdf."},{"key":"ref_45","unstructured":"Nakra, B.C., and Chaudhry, K.K. (2006). Introduction to Instruments and Their Representation. Instrumentation, Measurement and Analysis, Tata McGraw-Hill Publishing Company Limited. [2nd ed.]."},{"key":"ref_46","unstructured":"Bureau of Indian Standards (BIS) (2002). Standard Sand for Testing Cement-Specifications, IS 650:1991 (Second Revision)."},{"key":"ref_47","doi-asserted-by":"crossref","unstructured":"Adla, S., Rai, N., Harsha, K.S., Tripathi, S., Disse, M., and Pande, S. (2018, August 24). Laboratory Calibration of Soil Moisture Sensors in Porous Media (Repacked Soils). Available online: https:\/\/www.protocols.io\/view\/laboratory-calibration-of-soil-moisture-sensors-in-swnefde\/metadata.","DOI":"10.17504\/protocols.io.swnefde"},{"key":"ref_48","doi-asserted-by":"crossref","unstructured":"Rosenbaum, U., Bogena, H.R., Herbst, M., Huisman, J.A., Peterson, T.J., Weuthen, A., Western, A.W., and Vereecken, H. (2012). Seasonal and event dynamics of spatial soil moisture patterns at the small catchment scale. Water Resour. Res., 48.","DOI":"10.1029\/2011WR011518"},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"568","DOI":"10.1016\/j.agwat.2018.11.002","article-title":"Performance evaluation of a recently developed soil water content, dielectric permittivity, and bulk electrical conductivity electromagnetic sensor","volume":"213","author":"Kargas","year":"2019","journal-title":"Agric. Water Manag."},{"key":"ref_50","doi-asserted-by":"crossref","unstructured":"Dane, J.H., and Topp, G.C. (2002). Methods for measurement of soil water content: Capacitance devices. Methods of Soil Analysis: Part 4 Physical Methods, Soil Science Society of America.","DOI":"10.2136\/sssabookser5.4"},{"key":"ref_51","doi-asserted-by":"crossref","unstructured":"Morris, A.S., and Langari, R. (2012). Instrument Types and Performance Characteristics. Measurement and Instrumentation: Theory and Application, Butterworth-Heinemann.","DOI":"10.1016\/B978-0-12-381960-4.00002-4"},{"key":"ref_52","unstructured":"Carr, J.J., and Brown, J.M. (2001). Basic Theories of Measurement. Introduction to Biomedical Equipment Technology, Pearson. [4th ed.]."},{"key":"ref_53","doi-asserted-by":"crossref","unstructured":"Pearcy, R.W., Ehleringer, J.R., Mooney, H.A., and Rundel, P.W. (1989). Principles of instrumentation for physiological ecology. Plant Physiological Ecology: Field Methods and Instrumentation, Chapman and Hall. [1st ed.].","DOI":"10.1007\/978-94-009-2221-1"},{"key":"ref_54","unstructured":"McNaught, A.D., and Wilkinson, A. (1997). Compendium of Chemical Terminology, Blackwell Scientific Publications. [2nd ed.]."},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"1576","DOI":"10.2136\/sssaj1997.03615995006100060006x","article-title":"Real-time soil water dynamics using multisensor capacitance probes: Laboratory calibration","volume":"61","author":"Paltineanu","year":"1997","journal-title":"Soil Sci. Soc. Am. J."},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"269","DOI":"10.1016\/j.measurement.2019.03.062","article-title":"Investigation of temperature effects and performance evaluation of a newly developed capacitance probe","volume":"140","author":"Bello","year":"2019","journal-title":"Measurement"},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"124155","DOI":"10.1016\/j.jhydrol.2019.124155","article-title":"Impact of soil salinity, texture and measurement frequency on the relations between soil moisture and 20 MHz\u20133 GHz dielectric permittivity spectrum for soils of medium texture","volume":"579","author":"Lewandowski","year":"2019","journal-title":"J. Hydrol."},{"key":"ref_58","doi-asserted-by":"crossref","first-page":"9779","DOI":"10.3390\/s120709773","article-title":"Correcting the temperature influence on soil capacitance sensors using diurnal temperature and water content cycles","volume":"12","author":"Chanzy","year":"2012","journal-title":"Sensors"},{"key":"ref_59","doi-asserted-by":"crossref","first-page":"885","DOI":"10.13031\/2013.23153","article-title":"Model evaluation guidelines for systematic quantification of accuracy in watershed simulations","volume":"50","author":"Moriasi","year":"2007","journal-title":"Trans. ASABE."},{"key":"ref_60","doi-asserted-by":"crossref","unstructured":"Witten, I.H., Frank, E., and Hall, M.A. (2011). Credibility: Evaluating What\u2019s Been Learned. Data Mining: Practical Machine Learning Tools and Techniques, Elsevier. [3rd ed.].","DOI":"10.1016\/B978-0-12-374856-0.00005-5"},{"key":"ref_61","doi-asserted-by":"crossref","first-page":"72","DOI":"10.2307\/1412159","article-title":"The Proof and Measurement of Association between Two Things","volume":"15","author":"Spearman","year":"1904","journal-title":"Am. J. Psychol."},{"key":"ref_62","doi-asserted-by":"crossref","unstructured":"Armitage, P., and Colton, T. (2005). Spearman Rank Correlation. Encyclopedia of Biostatistics, John Wiley & Sons, Ltd.","DOI":"10.1002\/0470011815"},{"key":"ref_63","first-page":"69","article-title":"A guide to appropriate use of Correlation coefficient in medical research","volume":"24","author":"Mukaka","year":"2012","journal-title":"Malawi Med. J."},{"key":"ref_64","first-page":"87","article-title":"Comparison of values of Pearson\u2019s and Spearman\u2019s correlation coefficients on the same sets of data","volume":"30","author":"Hauke","year":"2011","journal-title":"Quaest. Geogr."},{"key":"ref_65","unstructured":"Jekel, C. (2019, February 12). Fitting a Piecewise Linear Function to Data. Github Repos. Available online: https:\/\/github.com\/cjekel\/piecewise_linear_fit_py."},{"key":"ref_66","doi-asserted-by":"crossref","first-page":"310","DOI":"10.1061\/(ASCE)IR.1943-4774.0000418","article-title":"Comparison of Laboratory and Field Calibration of a Soil-Moisture Capacitance Probe for Various Soils","volume":"138","author":"Kinzli","year":"2012","journal-title":"J. Irrig. Drain. Eng."},{"key":"ref_67","doi-asserted-by":"crossref","first-page":"258","DOI":"10.1016\/j.agwat.2014.10.015","article-title":"Investigating the effects of soil moisture sensors positioning and accuracy on soil moisture based drip irrigation scheduling systems","volume":"148","author":"Soulis","year":"2015","journal-title":"Agric. Water Manag."},{"key":"ref_68","doi-asserted-by":"crossref","first-page":"76","DOI":"10.1016\/j.jhydrol.2013.11.061","article-title":"On the spatio-temporal dynamics of soil moisture at the field scale","volume":"516","author":"Vereecken","year":"2014","journal-title":"J. Hydrol."},{"key":"ref_69","doi-asserted-by":"crossref","first-page":"1940","DOI":"10.2136\/sssaj2000.6461940x","article-title":"Soil Material, Temperature, and Salinity Effects on Calibration of Multisensor Capacitance Probes","volume":"64","author":"Baumhardt","year":"2000","journal-title":"Soil Sci. Soc. Am. J."},{"key":"ref_70","doi-asserted-by":"crossref","unstructured":"Sakaki, T., Limsuwat, A., Smits, K.M., and Illangasekare, T.H. (2008). Empirical two-point \u03b1-mixing model for calibrating the ECH2O EC-5 soil moisture sensor in sands. Water Resour. Res., 44.","DOI":"10.1029\/2008WR006870"},{"key":"ref_71","doi-asserted-by":"crossref","first-page":"1684","DOI":"10.2136\/sssaj2005.0023","article-title":"Improved interpretation of water content reflectometer measurements in soils","volume":"69","author":"Kelleners","year":"2005","journal-title":"Soil Sci. Soc. Am. J."},{"key":"ref_72","doi-asserted-by":"crossref","first-page":"181","DOI":"10.2136\/vzj2009.0036","article-title":"Sensor-to-sensor variability of the ECH2O EC-5, TE, and 5TE sensors in dielectric liquids","volume":"9","author":"Rosenbaum","year":"2010","journal-title":"Vadose Zone J."},{"key":"ref_73","doi-asserted-by":"crossref","unstructured":"Fares, A., Safeeq, M., Awal, R., Fares, S., and Dogan, A. (2016). Temperature and Probe-to-Probe Variability Effects on the Performance of Capacitance Soil Moisture Sensors in an Oxisol. Vadose Zone J., 15.","DOI":"10.2136\/vzj2015.07.0098"},{"key":"ref_74","doi-asserted-by":"crossref","first-page":"117","DOI":"10.13031\/aea.12908","article-title":"Time-domain and frequency-domain reflectometry type soil moisture sensor performance and soil temperature effects in fine-and coarse-textured soils","volume":"35","author":"Zhu","year":"2019","journal-title":"Appl. Eng. Agric."},{"key":"ref_75","doi-asserted-by":"crossref","first-page":"1987","DOI":"10.2136\/sssaj2012.0063n","article-title":"A novel method to determine the volume of sensitivity for soil moisture sensors","volume":"76","author":"Sun","year":"2012","journal-title":"Soil Sci. Soc. Am. 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