Newly Introduced Creeper Legume Vigna marina as a Solution for Protection of Road Cuts in Sri Lanka

Abstract

Acelerated soil erosion and landslides are destructive degradation consequences in the central highlands, Sri Lanka. Therefore, cost-effective and sustainable slope stabilization techniques have become an urgent need to solve the problem. Properly designed vegetation covers play a significant role in erosion control. However, average plants cannot thrive on extremely degraded soils in the affected area. Therefore, the introduction of a low-demanding legume, Vigna marina (Burm.) Merr., as a vegetation cover was tested against soil erosion. Protection of bare road-cuts against soil erosion was the main focus of the study. The growth of V. marina was tested using five treatments - i.e. control (T1), subsoil (T2), decomposing parent material (T3), 20% Pinus wood biochar+subsoil (T4), and 20% Pinus wood biochar+decomposing parent material (T5). Control treatment was established as recommended by the Department of Agriculture for a similar plant (Phaseolus vulgaris L.). The highest growth was recorded in T1 followed by T4 and T5. The poorest growth was recorded in T2 and T3. Nitrogen (N) content of the soil has been significantly increased in T2, T3, T5 and T4 respectively whereas, a significant decline in soil N was recorded in T1. A significant decline in phosphorous (P) and potassium (K) content in the soil was common to all. The highest Nitrogen content of root nodules was in T5 and the lowest 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. Therefore, V. marina appears to be a cost-effective sustainable slope stabilization technique for protection of road cuts.