Restricted root growth caused by traffic induced soil compaction – a field study in wheat and maize

Soil compaction has adverse impacts on key soil functions and can result in restricted root distribution. However, deep roots provide access to water and nutrient reservoirs and might enhance carbon (C) storage in subsoils. Deep rooting is thus a central element for climate-adapted plant productivity and has potential for climate mitigation. Clarity is missing, to what extent different soil traffic intensities impact root depth distribution and root-derived C inputs at field scale.

The present study was conducted to assess the impact of differing soil traffic intensities (i) on soil physical parameters related to compaction, and (ii) to what extent this affects root length density and depth distribution, as well as (iii) above ground biomass and (iV) SOC-stocks. Negative effects of increasing traffic intensities on soil physical parameters are expected to result in reduced root depth distribution and therefore reduced biomass productivity and root-induced carbon allocation.

Soil and plant biomass were sampled along increasing soil traffic intensities at three field sites in central Germany characterized as Luvisols. Penetration resistance was measured in the field, and undisturbed soil rings of top and sub soils were analyzed for bulk density and air capacity. Undisturbed soil cores were taken up to one meter depth during peak root biomass. Root biomass, depth distribution and root length density were evaluated with the core-break method using an automated root spectroscopy imaging system. Based on the results, root-derived C inputs were estimated and C/N-measurement of soil core samples was conducted.

Preliminary findings indicate higher penetration resistance and bulk density, coupled with reduced air capacity in top and subsoils on the headland, where greater traffic intensity takes place. The complete data set will be presented and discussed at the conference.

The conclusions of this study will provide a better understanding of the interactions between soil compaction, root growth and carbon storage. These findings are relevant to assess how soil management affects soil compaction and thus may hinder climate-adapted agriculture.