A novel pre-treatment for rapidly separating willow roots from high clay content soil

Numerous studies have examined the root dynamics of willow biomass energy crops growing on medium to light-textured soils, using either soil coring, minirhizotron techniques, or a combination thereof. However, neither approach is well suited for studying roots in expansive high clay content soil. Our objective was to test the efficacy of a novel inexpensive root washing pre-treatment, using baking soda (NaHCO3), for facilitating the separation of willow roots from a Vertisol (70% clay). Soil cores were collected from within a willow variety trial plot of Tully Champion (Salix viminalis × Salix miyabeana) and were either conventionally washed (i.e., no pre-treatment) or washed following a pre-treatment consisting of shaking the sample for 15 min with either deionized water or 1.2 mol dm−3 NaHCO3. Measurement variables included washing duration, water usage, and recovery of fine (<2 mm) and coarse roots. The ranking of washing duration and water usage was NaHCO3 pre-treatment < deionized water pre-treatment < conventional washing. Compared to conventional washing, the NaHCO3 pre-treatment reduced the washing duration and water usage by 45 and 61%, respectively, while increasing the fine root recovery by 26%. There was no significant difference (P > 0.05) in the fine root recovery between the deionized water and NaHCO3 pre-treatments or the coarse root recovery among the three washing methods. Developing a quicker technique of separating willow roots from high clay content soil, which conserves water and increases fine root recovery, should promote further investigations of root growth dynamics within this traditionally difficult soil type.

► Separating roots from high clay content soil is notoriously difficult.
► This study examined the efficacy of a novel inexpensive soil core washing pre-treatment using baking soda (NaHCO3).
► Measurement variables included washing duration, water usage, and recovery of fine (<2 mm) and coarse roots.
► Pre-treatment shaking with NaHCO3 decreased the amount of time and water required, while increasing fine root recovery.