Estimation of inputs of belowground carbon constitutes a major uncertainty in carbon (C) balance models. Fixed allocation coefficients are widely used although root:shoot ratio is known to respond to abiotic stressors. This
pot experiment investigated the C allocation response of spring barley (Hordeum vulgare, L.) to soil texture and nutrient availability. Differences in nutrient availability, induced by a long-term history of contrasting N and PK
fertilizer application to the soil, did not affect root:shoot ratio. Soil texture had a significant effect; the smallest root:shoot ratio (0.10) occurred in a clay loam soil and the largest (0.22) was in a sandy soil. We hypothesized
that this relation was related to hydraulic properties of the root–soil contact zone and were able to confirm this relation with existing datasets from the literature. The results obtained in this study could be useful for future
estimates of root-derived C inputs, for example in carbon turnover models, but thorough in situ validation with different plant species is required.
