{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,1]],"date-time":"2026-04-01T09:25:11Z","timestamp":1775035511109,"version":"3.50.1"},"reference-count":25,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2013,8,8]],"date-time":"2013-08-08T00:00:00Z","timestamp":1375920000000},"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>This paper aims at exploring the potential of visible and near infrared (vis-NIR) spectroscopy for on-line measurement of soil pH, with the intention to produce variable rate lime recommendation maps. An on-line vis-NIR soil sensor set up to a frame was used in this study. Lime application maps, based on pH predicted by vis-NIR techniques, were compared with maps based on traditional lab-measured pH. The validation of the calibration model using off-line spectra provided excellent prediction accuracy of pH  (R2 = 0.85, RMSEP = 0.18 and RPD = 2.52), as compared to very good accuracy obtained with the on-line measured spectra (R2 = 0.81, RMSEP = 0.20 and RPD = 2.14). On-line predicted pH of all points (e.g., 2,160) resulted in the largest overall field virtual lime requirement (1.404 t), as compared to those obtained with 16 validation points off-line prediction (0.28 t), on-line prediction (0.14 t) and laboratory reference measurement  (0.48 t). The conclusion is that the vis-NIR spectroscopy can be successfully used for the prediction of soil pH and for deriving lime recommendations. The advantage of the on-line sensor over sampling with limited number of samples is that more detailed information about pH can be obtained, which is the reason for a higher but precise calculated lime recommendation rate.<\/jats:p>","DOI":"10.3390\/s130810177","type":"journal-article","created":{"date-parts":[[2013,8,8]],"date-time":"2013-08-08T11:41:32Z","timestamp":1375962092000},"page":"10177-10190","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":34,"title":["Potential of On-Line Visible and Near Infrared Spectroscopy  for Measurement of pH for Deriving Variable Rate  Lime Recommendations"],"prefix":"10.3390","volume":"13","author":[{"given":"Y\u00fccel","family":"Tekin","sequence":"first","affiliation":[{"name":"Vocational School of Technical Sciences, Uludag University, Bursa 16059, Turkey"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Boyan","family":"Kuang","sequence":"additional","affiliation":[{"name":"Environmental Science and Technology Department, Cranfield University, Bedfordshire,  MK43 0AL, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Abdul","family":"Mouazen","sequence":"additional","affiliation":[{"name":"Environmental Science and Technology Department, Cranfield University, Bedfordshire,  MK43 0AL, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2013,8,8]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1915","DOI":"10.1016\/S0038-0717(00)00166-8","article-title":"Soil acid and alkaline phosphatase activity as pH adjustment indicators","volume":"32","author":"Dick","year":"2000","journal-title":"Soil Biol. 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