Determination of Soil Organic Carbon Variation With on-Line VIS-NIR Sensor
Vis-NIR spectroscopy was reported by many researchers confirming the possibility of successful measurement of soil organic carbon (SOC) which was attributed to the direct spectral response of carbon in the NIR range. In this research, SOC variability was measured in two copping season with an on-line vis-NIR sensor in a field with a clay soil, 10 ha area in Karacabey Farm in Bursa, Turkey.The performance and accuracy of the SOC calibration model was evaluated in cross-validation after partial least squares regression (PLSR) and independent validation.Model performance was evaluated by means of coefficient of determination (R2), root mean square error of prediction (RMSEP) and ratio of prediction deviation (RPD). Three categories of SOC maps were developed: Three categories of maps were developed: 1) reference laboratory analyses maps based on 92 points 2) Full-data point maps based on all 6486 on-line points Vis-NIR predicted in 2013 and 3) full-data point maps based on all 2496 on-line points Vis-NIR predicted in 2015.Results show that SOC calibration model in cross-validation results is fairly accurate (R2 = 0.75, RMSEP = 0.17 % and RPD=1.81). According to the classification of RPD values, the performance of the SOC in cross-validation is classified as good. Based on 3297 points map shows the variation of the SOC at high sampling resolution. According to the SOC level of the field, 80 ton/Ha manure has been applied to the field. A year later the manure influence on SOC was measured with the on-line vis-NIR soil sensor.
Keywordsó On-line soil sensor, Proximal soil sensing, Soil organic carbon, Vis-NIR spectroscopy.