title: Potential of on-line visible and near infrared spectroscopy for measurement of pH for deriving variable rate lime recommendations.
abstract: 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.
authors: Vocational School of Technical Sciences, Uludag University, Bursa 16059, Turkey. y.tekin@uludag.edu.tr
authors: Yücel
authors: Y
authors: Tekin
authors: Boyan
authors: B
authors: Kuang
authors: Abdul M
authors: AM
authors: Mouazen
mesh_terms: D017610:Calcium Compounds / Q000032:analysis* / Q000737:chemistry*; D004784:Environmental Monitoring / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006863:Hydrogen-Ion Concentration; D010087:Oxides / Q000032:analysis* / Q000737:chemistry*; D012987:Soil / Q000737:chemistry*; D019265:Spectroscopy, Near-Infrared / Q000295:instrumentation* / Q000379:methods; D014159:Transducers
chemical_list: D017610:Calcium Compounds; D010087:Oxides; D012987:Soil; C016538:lime
references: Sensors (Basel). 2012;12(6):8338-54
references: 22969403