{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,21]],"date-time":"2026-02-21T14:58:09Z","timestamp":1771685889857,"version":"3.50.1"},"reference-count":34,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2011,6,16]],"date-time":"2011-06-16T00:00:00Z","timestamp":1308182400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/3.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Spatially variable soil properties influence the performance of soil water content monitoring sensors. The objectives of this research were to: (i) study the spatial variability of bulk density (\u03c1b), total porosity (\u03b8t), clay content (CC), electrical conductivity (EC), and pH in the upper M\u0101kaha Valley watershed soils; (ii) explore the effect of variations in \u03c1b and \u03b8t on soil water content dynamics, and (iii) establish field calibration equations for EC-20 (Decagon Devices, Inc), ML2x (Delta-T-Devices), and SM200 (Delta-T-Devices) sensors to mitigate the effect of soil spatial variability on their performance. The studied soil properties except pH varied significantly (P &lt; 0.05) across the soil water content monitoring depths (20 and 80 cm) and six locations. There was a linear positive and a linear inverse correlation between the soil water content at sampling and \u03c1b, and between the soil water content at sampling and \u03b8t, respectively. Values of laboratory measured actual \u03b8t correlated (r = 0.75) with those estimated from the relationship \u03b8t = 1 \u2212 \u03c1b\/\u03c1s, where \u03c1s is the particle density. Variations in the studied soil properties affected the performance of the default equations of the three tested sensors; they showed substantial under-estimations of the actual water content. The individual and the watershed-scale field calibrations were more accurate than their corresponding default calibrations. In conclusion, the sensors used in this study need site-specific calibrations in order to mitigate the effects of varying properties of the highly weathered tropical soils.<\/jats:p>","DOI":"10.3390\/s110606354","type":"journal-article","created":{"date-parts":[[2011,6,17]],"date-time":"2011-06-17T13:56:03Z","timestamp":1308318963000},"page":"6354-6369","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":26,"title":["Field Calibrations of Soil Moisture Sensors in a Forested Watershed"],"prefix":"10.3390","volume":"11","author":[{"given":"Farhat","family":"Abbas","sequence":"first","affiliation":[{"name":"Natural Resources and Environmental Management Department, University of Hawaii-Manoa, Honolulu, HI 96822, USA"}]},{"given":"Ali","family":"Fares","sequence":"additional","affiliation":[{"name":"Natural Resources and Environmental Management Department, University of Hawaii-Manoa, Honolulu, HI 96822, USA"}]},{"given":"Samira","family":"Fares","sequence":"additional","affiliation":[{"name":"Natural Resources and Environmental Management Department, University of Hawaii-Manoa, Honolulu, HI 96822, USA"}]}],"member":"1968","published-online":{"date-parts":[[2011,6,16]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"179","DOI":"10.1016\/0022-1694(83)90102-6","article-title":"Surface soil moisture variation on small agricultural watersheds","volume":"62","author":"Hawley","year":"1983","journal-title":"J. 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