Effect of tillage method on early root growth of Miscanthus

Fulfilling climate change mitigation goals will require increased planting of bioenergy crops. Miscanthus is a versatile biomass crop suitable for bioenergy production and bio-products and is expected to form a large part of the bioenergy mix. Reduced impact field preparation and crop establishment are needed to align with sustainable agricultural policies and preserve soil carbon stocks. However, the impact of conservation tillage methods on the root growth of Miscanthus, with implications for establishment, plant resilience and carbon cycling, is currently unknown. Therefore, in this study, we use in-situ minirhizotrons to capture root growth and turnover (root increase/decrease) during the establishment period for field-grown Miscanthus planted with minimum and no-tillage methods (Min Till and No Till, respectively). It was found that the No Till method resulted in higher root length density (Min Till 0.56 vs. No Till 1.39 [cm cm⁻²] at 30–50 cm soil depth, for 2-year-old plants in October) and thinner roots in the subsoil (Min Till 14% vs. No Till 60%, roots in the 0–0.4 mm diameter class, 30–50 cm soil depth, for 1 year-old plants in October) providing potential for improved resource acquisition and soil carbon sequestration. Rapid root growth provided a substantial root base in both treatments (Min Till 1195 and No Till 1442 [g dry matter m⁻²], 0–50 cm soil depth, for 1-year-old plants in October) before resources were allocated to developing rhizomes and above-ground growth. For new planting of Miscanthus on former (marginal) grassland, our results demonstrate that using conservation tillage methods is viable in terms of root growth and plant resilience. Additionally, the observed early years root turnover provides insight into carbon inputs to the soil, important for the modelling of early establishment carbon dynamics.