{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,2]],"date-time":"2026-04-02T04:21:57Z","timestamp":1775103717343,"version":"3.50.1"},"reference-count":46,"publisher":"MDPI AG","issue":"17","license":[{"start":{"date-parts":[[2023,8,23]],"date-time":"2023-08-23T00:00:00Z","timestamp":1692748800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>In this study, a novel chromotropic acid-based color development method was proposed for quick estimation of soil nitrate (NO3\u2212). The method utilized a 3D printed device integrated with the rear-end camera of a smartphone and a stand-alone application called SMART NP. By analyzing the mean Value (V) component of the sample\u2019s image, the SMART NP provides instant predictions of soil NO3\u2212 levels. The limit of detection was calculated as 0.1 mg L\u22121 with a sensitivity of 0.26 mg L\u22121. The device showed a % bias of 0.9% and a precision of 1.95%, indicating its reliability. Additionally, the device-predicted soil NO3\u2212 data, combined with kriging interpolation, showcased spatial variability in soil NO3\u2212 levels at the regional level. The study employed a Gaussian model of variogram for kriging, and the high Nugget\/Sill ratio indicated low spatial autocorrelation, emphasizing the impact of management factors on the spatial distribution of soil NO3\u2212 content in the study area. Overall, the imaging device, along with geostatistical interpolation, provided a comprehensive solution for the rapid assessment of spatial variability in soil NO3\u2212content.<\/jats:p>","DOI":"10.3390\/s23177345","type":"journal-article","created":{"date-parts":[[2023,8,23]],"date-time":"2023-08-23T08:20:30Z","timestamp":1692778830000},"page":"7345","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":10,"title":["A Smartphone-Enabled Imaging Device for Chromotropic Acid-Based Measurement of Nitrate in Soil Samples"],"prefix":"10.3390","volume":"23","author":[{"ORCID":"https:\/\/orcid.org\/0009-0001-1544-3854","authenticated-orcid":false,"given":"Veerabhadrappa","family":"Lavanya","sequence":"first","affiliation":[{"name":"Agricultural and Food Engineering Department, Indian Institute of Technology, Kharagpur 721302, India"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3147-1828","authenticated-orcid":false,"given":"Anshuman","family":"Nayak","sequence":"additional","affiliation":[{"name":"Agricultural and Food Engineering Department, Indian Institute of Technology, Kharagpur 721302, India"}]},{"given":"Partha","family":"Deb Roy","sequence":"additional","affiliation":[{"name":"Agricultural and Food Engineering Department, Indian Institute of Technology, Kharagpur 721302, India"},{"name":"ICAR-Indian Institute of Water Management, Bhubaneswar 751023, India"}]},{"given":"Shubhadip","family":"Dasgupta","sequence":"additional","affiliation":[{"name":"Agricultural and Food Engineering Department, Indian Institute of Technology, Kharagpur 721302, India"},{"name":"Department of Agricultural Chemistry and Soil Science, Bidhan Chandra Krishi Viswavidyalaya, Mohanpur 741252, India"}]},{"given":"Subhadip","family":"Dey","sequence":"additional","affiliation":[{"name":"Agricultural and Food Engineering Department, Indian Institute of Technology, Kharagpur 721302, India"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0831-092X","authenticated-orcid":false,"given":"Bin","family":"Li","sequence":"additional","affiliation":[{"name":"Department of Experimental Statistics, Louisiana State University, Baton Rouge, LA 70803, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3814-825X","authenticated-orcid":false,"given":"David C.","family":"Weindorf","sequence":"additional","affiliation":[{"name":"Department of Earth and Atmospheric Sciences, Central Michigan University, Mount Pleasant, MI 48859, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1913-3973","authenticated-orcid":false,"given":"Somsubhra","family":"Chakraborty","sequence":"additional","affiliation":[{"name":"Agricultural and Food Engineering Department, Indian Institute of Technology, Kharagpur 721302, India"}]}],"member":"1968","published-online":{"date-parts":[[2023,8,23]]},"reference":[{"key":"ref_1","first-page":"255","article-title":"Uncertainty analysis in environmental modelling under a change of spatial scale","volume":"Volume 80","author":"Finke","year":"1998","journal-title":"Soil and Water Quality at Different Scales, Developments in Plant and Soil Sciences"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"444","DOI":"10.1016\/j.jhydrol.2011.08.041","article-title":"Assessing impacts of alternative land use and agricultural practices on nitrate pollution at the catchment scale","volume":"409","author":"Laurent","year":"2011","journal-title":"J. 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