Msc Chris Henke1, Dr Julien Guigue1, Dr Eleanor Hobley1, Pr, Dr Ingrid Kögel-Knabner1
1Technical University of Munich, Freising, Germany
Significant amounts of water and nutrients are stored in deep soil horizons and subsoil management is being considered as an option to sustain high demand in crop productivity. At the same time, subsoils contain a large proportion of total soil organic carbon (SOC) and the dynamics of SOC in subsoils are now receiving more attention, especially given the link of SOC with climate processes. However, subsoils are highly heterogeneous, subsoil SOC contents are low and have longer turnover times, so that detecting SOC changes in subsoils is difficult using classic soil analyses based on sample homogenisation by depth increments.
We analysed soil cores from a field experiment with deep ploughing treatments, with and without compost incorporation, using hyperspectral Vis-NIR imaging spectroscopy. The C distribution within the soil was modelled at a very high spatial resolution (53×53 µm) using random forest and artificial neural network algorithms. The SOC mapping revealed an increase in SOC stocks resulting from deep ploughing (12% relative increase). We hypothesize that, in addition to the added SOC, an increase in rooting densities resulting from lowered bulk density and enhanced nutrient availability in the subsoil are the driving factors for this C accumulation.
Hyperspectral imaging of soil cores is a promising tool for the quantification of SOC stocks and changes in deeper horizons, and allows visualisation of the spatial heterogeneity of soil organic carbon.
Julien Guigue is a Post-Doctoral scientist at Technical University of Munich. He is doing research on soil organic matter dynamics in agricultural ecosystems, more specifically on the effect of agricultural management of subsoils on SOM distribution and stocks.