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DETACHMENT RATE, SOIL ERODIBILITY, AND SOIL STRENGTH AS INFLUENCED BY LIVING PLANT ROOTS PART I: LABORATORY STUDY

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Transactions of the ASAE. 44(5): 1167–1174. (doi: 10.13031/2013.6445) @2001
Authors:   M. Mamo, G. D. Bubenzer
Keywords:   Soil detachment, Rill erosion, Soil erodibility, Shear strength, Living roots.

The magnitude of a soils resistance to detachment depends, in part, on the physical condition of the soil. The presence of roots is believed to greatly increase soil strength and enhance its stability. Two laboratory experiments were conducted to study the influence of living roots on strength, shear detachment, and erodibility of a Plano silt loam soil (finesilty, mixed, mesic, Typic Argiudolls) using a hydraulic flume to simulate concentrated flow. Polyvinyl chloride (PVC) pipes, 102 mm in diameter and 152 mm long, were packed with soil to be used as plant pots. The pots were completely randomized; some were planted to ryegrass and some left bare for rooted and fallow treatments, respectively. Erosion tests were run at three different stages (duration) of plant growth. Following each erosion test on rooted soils, living root samples were collected and their length determined. Root length density (length of root per unit volume of soil) was related to soil erodibility and detachment rate. Root length density (RLD) increased with growth stage for the duration of the experiments. There were significant differences ( = 0.5) in average shear strength between fallow and rooted soils. Withintreatment comparison of shear strength among stages showed that the difference was more significant for rooted treatments than for fallow treatments. Mean soil detachment rate (Dr) for rooted soils was reduced by as much as 64% of that for fallow treatment. Withintreatment comparison of detachment rate among stages showed that detachment rate decreased with time for both fallow and rooted treatments. Rill erodibility (Kr) for rooted soils was also lower than for fallow soils. There was a decrease in Dr and Kr with increase in RLD. Both Dr and Kr were exponentially related to RLD. The study showed that there were no significant differences in critical shear stress (c) between fallow and rooted treatments and among their respective stages. Critical shear stress appeared to be more closely related to surface condition than to treatment.

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