Effects of Grass Transpiration on Suction Induced in Near-Saturated Soil Condition

Plant transpiration is generally known to desiccate soil and increase matric suction through root-water uptake process. Research from the agricultural discipline has identified that the root-water uptake action may be suppressed in soil which is close to saturation condition due to limited oxygen diffusion. However, grass-induced suction recovery at low suction, which may be beneficial to slope stability, is not well understood and requires further investigation. This study aimed to measure grass-induced suction influence zone both vertically and laterally in the near-saturated soil condition. Rectangular test boxes were compacted with completely decomposed saprolite (silty sand) and seeds of bermudagrass were germinated within a ring collar. The vegetated specimen was irrigated with substantial amount of water to establish the near-saturated condition and then allowed to dry for a week naturally. Variation of matric suction was measured in vegetated specimens and was compared with the bare soil as control under the same controlled atmospheric condition.