Abstract:
Accelerated soil erosion and landslides is a destructive consequence of road development and
intensive agriculture in the central highlands. Therefore, cost-effective and sustainable slope
stabilization techniques have become an urgent need to solve the problem. Properly designed
vegetative covers play a significant role in slope stabilization and erosion control. However,
average plants cannot thrive on extremely degraded soils in the affected area. Therefore, the
introduction of an extremely low-demanding alien legume, Vigna marina, as a vegetation cover
was tested as an appropriate option. Protection of bare road-cuts against soil erosion was the
main focus of the study. The growth of Vigna marina under ideal to the lowest soil fertility status
was tested using five treatments - i.e. control (T1), subsoil (T2), decomposing parent material
(T3), 20% Pinus wood biochar + subsoil (T4), 20% Pinus wood biochar + decomposing parent
material (T5). Control was the ideal soil fertility status as recommended by the department of
agriculture for a similar plant (Phaseolus vulgaris L.). The highest growth in general was in T1
followed by T4 and T5. The poorest growth was recorded in T2 and T3. Nitrogen content of the
soil has been significantly increased in T2, T3, T5, T4 respectively whereas, a significant decline in soil N was recorded in T1. A significant decline in phosphorous and potassium content
in the soil was common to all. The highest Nitrogen content of root nodules was in T5 and the
lowest was in T1. The largest number and the dry weight of root nodules were observed in T4
and T5 compared to the rest. The poorest nodule activity was recorded in T1. Vigna marina has
a potential to thrive in heavily eroded land treated with Pinus wood biochar. Therefore, Vigna
marina appears to be a cost-effective sustainable slope stabilization technique for the central
highlands in Sri Lanka.
