Jasmin Miltz successfully defended her doctoral thesis on "Analysing soil organic carbon using near infrared spectroscopy in the laboratory and in the field on-line" on 9.5.2016 at the Technical University Braunschweig.
Soil organic carbon (SOC), as a key property of soil quality maintenance, varies over space and time. The assessment and monitoring of SOC is important to ensure sustainable soil management. SOC can be determined by conventional laboratory analytical techniques, but the preparation and measurement of numerous soil samples can be costly. Near infrared spectroscopy (NIRS) offers a novel, non-destructive technique allowing for rapid as wells as low-cost soil analyses and is adaptable for on-line field use.
The work for this thesis comprised two aspects of NIRS analysis: its application in the laboratory as well as in the field on-line. Although laboratory NIRS is an established method, there are no standard measurement protocols for soil analysis. Therefore, the laboratory application of NIRS was investigated with the aim to optimise soil sample preparation and measurement in order to give recommendations for a standard measurement protocol [Publication]. The on-line field application of NIRS is a relatively new method, and thus there is still a need for an evaluation of the NIR-system, manufactured by the North American company VERIS Technologies, used in this study. The field application of NIRS was examined via a comparison between horizontal measurements with a shank and vertical measurements with a probe for a two- and three-dimensional view into the soil. Further investigations were carried out to test the accuracy and reproducibility of the horizontal mapping. All measurements were used to map and characterise agricultural soils in Northern Germany, with the main focus on the calibration and prediction of SOC and total nitrogen concentrations and SOC stocks.
Generally, this work confirmed that laboratory- and field-based NIR measurements have a great potential for assessing the organic carbon and total nitrogen content in agricultural soils.