Background and aims Soil carbon sequestration can play an important role in mitigating climate change. Higher organic C inputs to agricultural soils are needed in order to increase soil organic carbon (SOC) stocks. Genotype selection and breeding towards increased root biomass may enhance root C inputs to the soil and could therefore be a promising, easy-to-implement management option for potentially increasing C sequestration. However, an increase in root C inputs may compromise yield, which is not desirable in terms of food security. Methods Data from 13 global studies with field experiments were compiled in order to estimate the potential of optimised genotype selection for enhancing root biomass without compromising the yield of winter wheat, spring wheat, silage maize, winter rapeseed and sunflower. A lack of data on the effect of variety on rhizodeposition was identified which thus had to be excluded. Results Systematic genotype selection increased mean yields by 52% and mean root biomass by 22% across all crops and sites. A median root C increase of 6.7% for spring wheat, 6.8% for winter rapeseed, 12.2% for silage maize, 21.6% for winter wheat and 26.4% for sunflower would be possible without a yield reduction. Conclusion Overall, this review demonstrates that optimised genotype selection can be a win-win option for increasing root biomass C input to soil while maintaining or even enhancing yield.

Purpose Flower strips have been shown to increase insect biodiversity and improve agricultural yields through increased pollination and pest predation. Less is known about their potential to increase soil organic carbon (SOC). We aimed to investigate the biomass production and SOC sequestration potential of flower strips as a sustainable management option of temperate agricultural soils. Methods 23 flower strips across varying soil types and climatic regions in Germany were sampled for aboveground and belowground peak biomass in order to estimate the annual carbon input to the soil. Those were used as 23 scenarios to model the potential SOC sequestration of the flower strips compared to a business-as-usual scenario for 1533 sites of the German Agricultural Soil Inventory using the RothC model. Results On average, flower strips sequestered 0.48 ± 0.36 Mg C ha−1 year−1 in the initial 20-year period after establishment. Converting 1 % of the total German cropland area into flower strips would thus lead to a mitigation of 0.24 Tg CO2 year−1, which equals 0.4 % of current agricultural greenhouse gas emissions in Germany. We found a negative correlation between C sequestration rate and the number of plant species in the flower strips, mainly related to grasses outcompeting herbaceous species. Conclusion Flower strips are one overlooked option for increasing SOC stocks of croplands that has multiple benefits for agro-ecosystems. However, within a flower strip it might not be possible to maximise both plant biodiversity and SOC sequestration.