322-22 Prediction of Mineral Fines to Soil Organic Carbon Ratio with Visible Near-Infrared Spectroscopy (vis-NIRS).

Poster Number 1426

See more from this Division: SSSA Division: Soil Physics and Hydrology
See more from this Session: Soil Physics and Hydrology: II

Tuesday, November 17, 2015
Minneapolis Convention Center, Exhibit Hall BC

Cecilie Hermansen, Dept. of Agroecology, Aarhus University, Tjele, DENMARK, Maria Knadel, Department of Agroecology, Aarhus University, Tjele, Denmark, Per Moldrup, Civil Engineering, Aalborg University, Aalborg, Denmark, Mogens H. Greve, Dept. of Agroecology, Aarhus University, Tjele, Denmark, René Gislum, Dept. of Agroecology, Aarhus University, Slagelse, Denmark and Lis W. de Jonge, Agroecology, Aarhus University, Tjele, Denmark
Abstract:
The ratio of mineral fines (clay<2 µm and (clay+fine silt)<20 µm) to organic carbon (OC) is important for evaluating soil physical and chemical properties with respect to e.g. tilth conditions, clay dispersibility and PAH sorption affinities. Studies have suggested that a clay/OC ratio around 10 gives the saturation level of clay and OC complexation, with non-complexed clay being present at a ratio above 10, and non-complexed OC being present below 10. Likewise, a (clay+fine silt)/OC ratio around 20 has been suggested to indicate a shift in soil physical properties.

Visible near-infrared spectroscopy (vis-NIRS) is a fast method, with little or no -sample pre-treatment, which has shown capabilities of replacing time-consuming conventional soil analysis methods. The light absorption is measured in the visible near-infrared range from 350 to 2500 nm, where specific wavelengths are assigned to species of organic and inorganic soil components.

The ability of vis-NIRS to determine the ratio of clay/OC and (clay+fine silt)/OC was evaluated in this study. A total of 417 soil samples from seven Danish fields, with a large textural gradient (clay: 0.03-0.45 kg kg-1, organic carbon: 0.011-0.084 kg kg-1), was analysed for particle size distribution and measured with a vis-NIRS spectrophotometer in the spectral range from 400 to 2500 nm (DS2500, Foss, Hillerød, Denmark). Partial least squares (PLS) regression was used to correlate spectral data to the clay/OC ratio and (clay+fine silt)/OC ratio on a representative calibration data subset. PLS models were then tested using a validation set. Results of both the calibration and validation yielded very successful predictions of the clay/OC ratio and (clay+fine silt)/OC ratio, and thus illustrates the potential applicability of vis-NIRS as a replacement/alternative for conventional soil analysis methods.

See more from this Division: SSSA Division: Soil Physics and Hydrology
See more from this Session: Soil Physics and Hydrology: II