Increasing root-derived soil carbon input to agricultural soils by variety selection of winter wheat

Climate change mitigation and adaptation is a major challenge of modern agriculture. Increasing the incorporation of atmospheric carbon (C) as organic matter into soils through improved crop management seems to be a promising agricultural management option for supporting climate change mitigation. In order to build up soil organic C increased organic C inputs to the soil are urgently needed. In agricultural soils, crop roots are the major source of C inputs and pivotal for long-term C storage compared to aboveground biomass as their turnover is 2 to 3 times slower. This suggests, that variety selection towards increased root biomass can enhance root C inputs to the soil and could therefore increase C stocks and potentially facilitate C sequestration in soils. To quantify whether biomass allocation is affected by variety x environment interaction, we assessed root biomass, root distribution to 1 m soil depth and root: shoot ratios in a set of 10 different varieties grown at 11 experimental sites, covering a large European climatic gradient from Spain to Norway.

Preliminary results show a broad variety-specific variation in biomass production and its allocation between roots and shoots. Root biomass ranged from 1 to 3.5 Mg ha^-1 in the best variety and could be increased by 20% by selecting the best variety compared to the average root biomass without compromising yield. Root to shoot ratios varied between 0.04 and 0.58 with a mean of 0.16. Increased root biomass due to deeper roots may stabilise yields under future climate change conditions where increased frequency of drought events during vegetation periods are expected and may therefore be a climate change adaptation measure that increases the crops resilience towards changing environmental conditions. Thus, improved variety selection can help to achieve both goals of modern agriculture: climate change mitigation and adaptation.