{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,10]],"date-time":"2026-06-10T16:25:18Z","timestamp":1781108718011,"version":"3.54.1"},"reference-count":47,"publisher":"MDPI AG","issue":"18","license":[{"start":{"date-parts":[[2024,9,13]],"date-time":"2024-09-13T00:00:00Z","timestamp":1726185600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100005388","name":"Research and Outreach Division of the Costa Rican Institute of Technology","doi-asserted-by":"publisher","award":["1431030"],"award-info":[{"award-number":["1431030"]}],"id":[{"id":"10.13039\/501100005388","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100005388","name":"Research and Outreach Division of the Costa Rican Institute of Technology","doi-asserted-by":"publisher","award":["FI-054B-19"],"award-info":[{"award-number":["FI-054B-19"]}],"id":[{"id":"10.13039\/501100005388","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100006473","name":"Ministry of Science, Innovation, Technology, and Telecommunications MICITT","doi-asserted-by":"publisher","award":["1431030"],"award-info":[{"award-number":["1431030"]}],"id":[{"id":"10.13039\/501100006473","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100006473","name":"Ministry of Science, Innovation, Technology, and Telecommunications MICITT","doi-asserted-by":"publisher","award":["FI-054B-19"],"award-info":[{"award-number":["FI-054B-19"]}],"id":[{"id":"10.13039\/501100006473","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>With the increasing focus on irrigation management, it is crucial to consider cost-effective alternatives for soil water monitoring, such as multi-point monitoring with low-cost soil moisture sensors. This study assesses the accuracy and functionality of low-cost sensors in a sandy loam (SL) soil amended with biochar at rates of 15.6 and 31.2 tons\/ha by calibrating the sensors in the presence of two nitrogen (N) and potassium (K) commercial fertilizers at three salinity levels (non\/slightly\/moderately) and six soil water contents. Sensors were calibrated across nine SL-soil combinations with biochar and N and K fertilizers, counting for 21 treatments. The best fit for soil water content calibration was obtained using polynomial equations, demonstrating reliability with R2 values greater than 0.98 for each case. After a second calibration, low-cost soil moisture sensors provide acceptable results concerning previous calibration, especially for non- and slightly saline treatments and at soil moisture levels lower than 0.17 cm3cm\u22123. The results showed that at low frequencies, biochar and salinity increase the capacitance detected by the sensors, with calibration curves deviating up to 30% from the control sandy loam soil. Due to changes in the physical and chemical properties of soil resulting from biochar amendments and the conductive properties influenced by fertilization practices, it is required to conduct specific and continuous calibrations of soil water content sensor, leading to better agricultural management decisions.<\/jats:p>","DOI":"10.3390\/s24185958","type":"journal-article","created":{"date-parts":[[2024,9,13]],"date-time":"2024-09-13T11:29:59Z","timestamp":1726226999000},"page":"5958","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":11,"title":["Calibration of Low-Cost Moisture Sensors in a Biochar-Amended Sandy Loam Soil with Different Salinity Levels"],"prefix":"10.3390","volume":"24","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-4877-0405","authenticated-orcid":false,"given":"Mar\u00eda Jos\u00e9","family":"G\u00f3mez-Astorga","sequence":"first","affiliation":[{"name":"Agricultural Engineering, CETIA Centro de Investigaci\u00f3n y Extensi\u00f3n en Tecnolog\u00eda e Ingenier\u00eda Agr\u00edcola, Instituto Tecnol\u00f3gico de Costa Rica, Cartago P.O. Box 159-7050, Costa Rica"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2335-0615","authenticated-orcid":false,"given":"Karolina","family":"Villagra-Mendoza","sequence":"additional","affiliation":[{"name":"Agricultural Engineering, CETIA Centro de Investigaci\u00f3n y Extensi\u00f3n en Tecnolog\u00eda e Ingenier\u00eda Agr\u00edcola, Instituto Tecnol\u00f3gico de Costa Rica, Cartago P.O. Box 159-7050, Costa Rica"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1456-7190","authenticated-orcid":false,"given":"Federico","family":"Mas\u00eds-Mel\u00e9ndez","sequence":"additional","affiliation":[{"name":"Chemistry, CEQIATEC, Centro de Investigaci\u00f3n y de Servicios Qu\u00edmicos y Microbiol\u00f3gicos, Instituto Tecnol\u00f3gico de Costa Rica, Cartago P.O. Box 159-7050, Costa Rica"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1300-3887","authenticated-orcid":false,"given":"An\u00edbal","family":"Ru\u00edz-Barquero","sequence":"additional","affiliation":[{"name":"Electronic Engineering, Instituto Tecnol\u00f3gico de Costa Rica, Cartago P.O. Box 159-7050, Costa Rica"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Renato","family":"Rimolo-Donadio","sequence":"additional","affiliation":[{"name":"Electronic Engineering, Instituto Tecnol\u00f3gico de Costa Rica, Cartago P.O. Box 159-7050, Costa Rica"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2024,9,13]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2007764","DOI":"10.1002\/adma.202007764","article-title":"Smart Agriculture Systems: Soil Sensors and Plant Wearables for Smart and Precision Agriculture","volume":"33","author":"Yin","year":"2021","journal-title":"Adv. Mater."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Yadav, M., Vashisht, B.B., Jalota, S.K., Kumar, A., and Kumar, D. (2022). Sustainable Water Management Practices for Intensified Agriculture. Soil-Water, Agriculture, and Climate Change, Springer.","DOI":"10.1007\/978-3-031-12059-6_8"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"100213","DOI":"10.1016\/j.rio.2022.100213","article-title":"(INVITED) Advances in fiber optic sensors for soil moisture monitoring: A review","volume":"7","author":"Leone","year":"2022","journal-title":"Results Opt."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"100032","DOI":"10.1016\/j.atech.2021.100032","article-title":"Automation of soil moisture sensor-based basin irrigation system","volume":"2","author":"Pramanik","year":"2022","journal-title":"Smart Agric. Technol."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Hardie, M. (2020). Review of Novel and Emerging Proximal Soil Moisture Sensors for Use in Agriculture. Sensors, 20.","DOI":"10.3390\/s20236934"},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Mill\u00e1n, S., Casades\u00fas, J., Campillo, C., Mo\u00f1ino, M.J., and Prieto, M.H. (2019). Using Soil Moisture Sensors for Automated Irrigation Scheduling in a Plum Crop. Water, 11.","DOI":"10.3390\/w11102061"},{"key":"ref_7","first-page":"32","article-title":"Review of research progress on soil moisture sensor technology","volume":"14","author":"Yu","year":"2021","journal-title":"Int. J. Agric. Biol. Eng."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"108686","DOI":"10.1016\/j.compag.2024.108686","article-title":"Advancements in dielectric soil moisture sensor Calibration: A comprehensive review of methods and techniques","volume":"218","author":"Mane","year":"2024","journal-title":"Comput. Electron. Agric."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"4852","DOI":"10.1016\/j.matpr.2021.01.306","article-title":"Recalibration and performance comparison of soil moisture sensors using regression and neural network characteristic models","volume":"45","author":"Verma","year":"2021","journal-title":"Mater. Today Proc."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"75","DOI":"10.1016\/j.compstruc.2018.05.006","article-title":"Numerical model for the characterization of Maxwell-Wagner relaxation in piezoelectric and flexoelectric composite material","volume":"208","author":"Nguyen","year":"2018","journal-title":"Comput. Struct."},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Adla, S., Rai, N.K., Karumanchi, S.H., Tripathi, S., Disse, M., and Pande, S. (2020). Laboratory Calibration and Performance Evaluation of Low-Cost Capacitive and Very Low-Cost Resistive Soil Moisture Sensors. Sensors, 20.","DOI":"10.3390\/s20020363"},{"key":"ref_12","unstructured":"Muzdrikah, F.S., Nuha, M.S., and Rizqi, F.A. (2018, January 7\u20138). Calibration of Capacitive Soil Moisture Sensor (SKU:SEN0193). Proceedings of the 2018 4th International Conference on Science and Technology (ICST), IEEE, Yogyakarta, Indonesia."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Peddinti, S.R., Hopmans, J.W., Najm, M.A., and Kisekka, I. (2020). Assessing Effects of Salinity on the Performance of a Low-Cost Wireless Soil Water Sensor. Sensors, 20.","DOI":"10.3390\/s20247041"},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Stellini, J., Farrugia, L., Farhat, I., Bonello, J., Persico, R., Sacco, A., Spiteri, K., and Sammut, C.V. (2023). Broadband Measurements of Soil Complex Permittivity. Sensors, 23.","DOI":"10.3390\/s23115357"},{"key":"ref_15","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_16","unstructured":"Meta, J.H., and Hrisko, J. (2024, September 08). Capacitive Soil Moisture Sensor Theory, Calibration, and Testing. Available online: https:\/\/www.researchgate.net\/publication\/342751186_Capacitive_Soil_Moisture_Sensor_Theory_Calibration_and_Testing."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Zemni, N., Bouksila, F., Persson, M., Slama, F., Berndtsson, R., and Bouhlila, R. (2019). Laboratory Calibration and Field Validation of Soil Water Content and Salinity Measurements Using the 5TE Sensor. Sensors, 19.","DOI":"10.3390\/s19235272"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Gonz\u00e1lez-Teruel, J.D., Jones, S.B., Soto-Valles, F., Torres-S\u00e1nchez, R., Lebron, I., Friedman, S.P., and Robinson, D.A. (2020). Dielectric Spectroscopy and Application of Mixing Models Describing Dielectric Dispersion in Clay Minerals and Clayey Soils. Sensors, 20.","DOI":"10.3390\/s20226678"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"104625","DOI":"10.1016\/j.apsoil.2022.104625","article-title":"Impacts of deficit irrigation and organic amendments on soil microbial populations and yield of processing tomatoes","volume":"180","author":"Turini","year":"2022","journal-title":"Appl. Soil Ecol."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"3","DOI":"10.1007\/s42773-019-00009-2","article-title":"Response of microbial communities to biochar-amended soils: A critical review","volume":"1","author":"Palansooriya","year":"2019","journal-title":"Biochar"},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Tsolis, V., and Barouchas, P. (2023). Biochar as Soil Amendment: The Effect of Biochar on Soil Properties Using VIS-NIR Diffuse Reflectance Spectroscopy, Biochar Aging and Soil Microbiology\u2014A Review. Land, 12.","DOI":"10.3390\/land12081580"},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Horv\u00e1th, J., K\u00e1tai, L., Szab\u00f3, I., and Korzenszky, P. (2024). An Electrical Conductivity Sensor for the Selective Determination of Soil Salinity. Sensors, 24.","DOI":"10.3390\/s24113296"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"741","DOI":"10.1016\/j.scitotenv.2019.06.244","article-title":"A quantitative understanding of the role of co-composted biochar in plant growth using meta-analysis","volume":"685","author":"Wang","year":"2019","journal-title":"Sci. Total Environ."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Villagra-Mendoza, K., Mas\u00eds-Mel\u00e9ndez, F., Quesada-Kimsey, J., Garc\u00eda-Gonz\u00e1lez, C.A., and Horn, R. (2021). Physicochemical Changes in Loam Soils Amended with Bamboo Biochar and Their Influence in Tomato Production Yield. Agronomy, 11.","DOI":"10.3390\/agronomy11102052"},{"key":"ref_25","unstructured":"Hrisko, J. (2024, September 08). Capacitive Soil Moisture Sensor Calibration with Arduino. Mark et Portal. Available online: https:\/\/makersportal.com\/blog\/2020\/5\/26\/capacitive-soil-moisture-calibration-with-arduino."},{"key":"ref_26","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_27","doi-asserted-by":"crossref","first-page":"5112","DOI":"10.1038\/s41467-019-13119-z","article-title":"Regulation of priming effect by soil organic matter stability over a broad geographic scale","volume":"10","author":"Chen","year":"2019","journal-title":"Nat. Commun."},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Schmeling, L., Elmamooz, G., Hoang, P.T., Kozar, A., Nicklas, D., S\u00fcnkel, M., Thurner, S., and Rauch, E. (2021). Training and Validating a Machine Learning Model for the Sensor-Based Monitoring of Lying Behavior in Dairy Cows on Pasture and in the Barn. Animals, 11.","DOI":"10.3390\/ani11092660"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"531","DOI":"10.1002\/sam.11583","article-title":"Optimal ratio for data splitting","volume":"15","author":"Joseph","year":"2022","journal-title":"Stat. Anal. Data Min. ASA Data Sci. J."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"012029","DOI":"10.1088\/1755-1315\/1038\/1\/012029","article-title":"Development of Low-cost Soil Moisture Monitoring System for Efficient Irrigation Water Management of Upland Crops","volume":"1038","author":"Aringo","year":"2022","journal-title":"IOP Conf. Ser. Earth Environ. Sci."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"e623","DOI":"10.7717\/peerj-cs.623","article-title":"The coefficient of determination R-squared is more informative than SMAPE, MAE, MAPE, MSE and RMSE in regression analysis evaluation","volume":"7","author":"Chicco","year":"2021","journal-title":"PeerJ Comput. Sci."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"5481","DOI":"10.5194\/gmd-15-5481-2022","article-title":"Root-mean-square error (RMSE) or mean absolute error (MAE): When to use them or not","volume":"15","author":"Hodson","year":"2022","journal-title":"Geosci. Model. Dev."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"20","DOI":"10.3390\/hydrology1010020","article-title":"Evaluating Three Hydrological Distributed Watershed Models: MIKE-SHE, APEX, SWAT","volume":"1","author":"Golmohammadi","year":"2014","journal-title":"Hydrology"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"135","DOI":"10.1061\/(ASCE)1084-0699(1999)4:2(135)","article-title":"Status of Automatic Calibration for Hydrologic Models: Comparison with Multilevel Expert Calibration","volume":"4","author":"Gupta","year":"1999","journal-title":"J. Hydrol. Eng."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"45","DOI":"10.5194\/gi-12-45-2023","article-title":"Calculation of soil water content using dielectric-permittivity-based sensors\u2014Benefits of soil-specific calibration","volume":"12","author":"Zawilski","year":"2023","journal-title":"Geosci. Instrum. Methods Data Syst."},{"key":"ref_36","doi-asserted-by":"crossref","unstructured":"Sarathbavan, M., Kumar, G.J., Udhayakumar, S., and Kamala Bharathi, K. (2022). Maxwell-Wagner Dielectric Relaxation Induced Superior Dielectric Properties and Phase Transitions in Na0.5bi0.5tio3 Nanorods. SSRN Electron. J.","DOI":"10.2139\/ssrn.4118371"},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Abdulraheem, M.I., Chen, H., Li, L., Moshood, A.Y., Zhang, W., Xiong, Y., Zhang, Y., Taiwo, L.B., Farooque, A.A., and Hu, J. (2024). Recent Advances in Dielectric Properties-Based Soil Water Content Measurements. Remote Sens., 16.","DOI":"10.3390\/rs16081328"},{"key":"ref_38","doi-asserted-by":"crossref","unstructured":"Rasheed, M.W., Tang, J., Sarwar, A., Shah, S., Saddique, N., Khan, M.U., Imran Khan, M., Nawaz, S., Shamshiri, R.R., and Aziz, M. (2022). Soil Moisture Measuring Techniques and Factors Affecting the Moisture Dynamics: A Comprehensive Review. Sustainability, 14.","DOI":"10.3390\/su141811538"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"373","DOI":"10.1515\/intag-2017-0025","article-title":"Effect of biochar on the unsaturated hydraulic conductivity of two amended soils","volume":"32","author":"Horn","year":"2018","journal-title":"Int. Agrophys"},{"key":"ref_40","unstructured":"Cihlor, J., and Ulaby, F. (2024, July 27). Dielectric Properties of Soils as a Function of Moisture Content. Lawrence, Kansas, 1974. Available online: https:\/\/www.semanticscholar.org\/paper\/Dielectric-properties-of-soils-as-a-function-of-Cihlar-Ulaby\/603de3b8e665b0e66ced05ea26f3d5d5811bb65c."},{"key":"ref_41","first-page":"1","article-title":"Performance of the capacitive moisture sensor under different saline conditions","volume":"53","author":"Santos","year":"2022","journal-title":"Rev. Ci\u00eancia Agron\u00f4mica"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"13","DOI":"10.1186\/s40486-023-00178-7","article-title":"Designing wearable capacitive pressure sensors with arrangement of porous pyramidal microstructures","volume":"11","author":"Javidi","year":"2023","journal-title":"Micro Nano Syst. Lett."},{"key":"ref_43","doi-asserted-by":"crossref","unstructured":"Bertocco, M., Parrino, S., Peruzzi, G., and Pozzebon, A. (2023). Estimating Volumetric Water Content in Soil for IoUT Contexts by Exploiting RSSI-Based Augmented Sensors via Machine Learning. Sensors, 23.","DOI":"10.3390\/s23042033"},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"109289","DOI":"10.1016\/j.compag.2024.109289","article-title":"Review of low-cost, off-grid, biodegradable in situ autonomous soil moisture sensing systems: Is there a perfect solution?","volume":"225","author":"Meshram","year":"2024","journal-title":"Comput. Electron. Agric."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"823","DOI":"10.3390\/agriengineering6010047","article-title":"An Effective and Affordable Internet of Things (IoT) Scale System to Measure Crop Water Use","volume":"6","author":"Payero","year":"2024","journal-title":"AgriEngineering"},{"key":"ref_46","doi-asserted-by":"crossref","unstructured":"Dafalla, M. (2024). Using 5TE Sensors for Monitoring Moisture Conditions in Green Parks. Sensors, 24.","DOI":"10.3390\/s24113479"},{"key":"ref_47","doi-asserted-by":"crossref","unstructured":"Zhang, Y., Hou, J., and Huang, C. (2023). Basin Scale Soil Moisture Estimation with Grid SWAT and LESTKF Based on WSN. Sensors, 24.","DOI":"10.3390\/s24010035"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/24\/18\/5958\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T15:55:56Z","timestamp":1760111756000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/24\/18\/5958"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2024,9,13]]},"references-count":47,"journal-issue":{"issue":"18","published-online":{"date-parts":[[2024,9]]}},"alternative-id":["s24185958"],"URL":"https:\/\/doi.org\/10.3390\/s24185958","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2024,9,13]]}}}