Impact of wheat cultivar development on biomass and subsoil carbon input: a case study along an erosion-deposition gradient

Abstract. Crop biomass, especially from belowground, improves soil health and recovery. However, the effects of cultivar traits and erosion on biomass production, particularly root biomass, remain unclear. We quantified root system characteristics throughout the wheat growing season, considering different cultivars and varying soil erosion states. This data informed a model assessing cultivar performance on root biomass production under different soil water and erosion scenarios. Erosion, mainly by tillage, combined to a modern cultivar reduced total wheat biomass, leaving 3.2 t less carbon per hectare annually – of which 0.6 t come from roots in the subsoil. The modern cultivar produced 70 % more grain in depositional soils and 30 % more in highly eroded soils than older cultivars. However, this increased grain yield came with a trade-off: carbon input into soils decreased by 32 % in eroded soils and 43 % in depositional soils. Simulations reveal that modern cultivars are more sensitive to dry soil conditions. In severely eroded areas, a 12 % loss in soil water leads to a root biomass reduction of 0.05 t C ha−1 in older cultivars, whereas younger varieties exhibit a much larger decline of up to 0.2 t C ha−1.