Is soil texture a major controlling factor of root:shoot ratio in cereals?

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.Highlights We tested soil texture and nutrient controls on root:shoot ratios of spring barley in a pot experiment. Soil texture rather than nutrient availability was the most important factor affecting root growth The largest root:shoot ratio in the sandy soil might be related to water availability The texture effect proved to be significant in a meta-analysis of data from literature