Root Properties of Plants Used for Soil Erosion Control in the Usambara Mountains, Tanzania

Abstract

Plant roots may have a strong erosion-reducing effect. However, little is known about root characteristics of tropical plants used for erosion control. A study was thus conducted in the Western Usambara Mountains, Tanzania to investigate rooting characteristics of Guatemala grass (Tripsacum andersonii), Napier grass (Pennisetum purpureum) and Tithonia shrub (Tithonia diversifolia), also referred to as wild sunflower, and to evaluate their potential for erosion control. For each plant species, mean root diameter (D), root density (RD), root length density (RLD) and root area ratio (RAR) were assessed for six plants in each species and relative soil detachment rate (RSD) predicted. Mean RD values in the 0 - 0.4 m soil depth for Majulai village and Migambo village respectively were 50.9 and 58.6 kg/m3 for Guatemala grass, 30.4 and 31.3 kg/m3 for Napier grass and 22.1 and 23.0 kg/m3 for Tithonia shrub. RLD values were 35.9 and 45.0 km/m3 for Guatemala grass, 31.3 and 150.0 km/m3 for Napier grass and 10.5 and 6.4 km/m3 for Tithonia shrub. Predicted RSD values were 4.43*10-12 and 1.20*10-14 for Guatemala grass, 6.10*10-5 and 2.74*10-4 for Napier grass and 4.43*10-3 and 2.24*10-4 for Tithonia shrub in the 0 - 0.4 m soil depth. The results indicate that Guatemala grass has a higher potential to reduce soil erosion rates by concentrated flow as compared to Napier grass or Tithonia shrub in the 0 - 0.4 m soil depth. These findings have implications on the selection and use of appropriate plants for soil erosion control.