ABSTRACT

Soil erosion is a worldwide challenge resulting to the loss oflives and properties. In Southeastern region ofNigeria, the soil is prone to movement due to its geological characteristics, heavy rainfall, and other environmental and anthropogenic factors. Vegetation is recognized as a sustainable material which can be used for stabilizing soil and reducing erosion. However, most vegetated slopes and soil also fail during heavy rainfall events. This study therefore, examines the effect ofseasonal variations on the mechanical properties ofvegetations used for sustainable erosion control. The roots oftwo different plant species Mangifera indica (tree) and Pennisetum purpureum (grass) were sampled from a field at Michael Okpara University ofAgriculture, Umudike. The mechanical properties ofthese roots were tested using the Universal Testing Machine (UTM) at National Centre for Agricultural Mechanization (NCAM). The thinner roots showed signs of gradual drying, but the' larger roots were able to retain moisture for a considerable amount oftime. This could explain why the Pennisetum purpureum which is a grass roots had more water content compared with the Mangifera indica which is a tree root. For the Pennisetum purpureum the water loss after 30 min drying range between 51% to 19%, whereas the water loss increased from 70% - 22% after 1 hour and further increased ranging from 0.79% - 30% after 24 hours drying. The tensile strength ofthe roots was-determined after different drying periods (Omins (hydrated), 30 minutes, 1 hour, 24 hours) to signify real life drying ofthe roots due to dehydration ofsoil. The mean ofthe root tensile strength ofthe Mangifera indica (17.41 MPa (hydrated), 18.93 MPa (30 mins dry), 21.84 MPa (1 . hour dry), 34.10 MPa (24 dry)) was higher greater than the Pennisetum purpureum with 5.30 MPa (hydrated roots), 12.49 MPa (roots dried for 30 mins), 17.13 MPa (roots dried for 1 hour). The result from the study show that the root tensile strength increased progressively upon root drying. Hence the study hypothesizes that as the soil get drier, there is an opportunity for the tensile strength ofthe root to increase. However, in intense rainfall, the root tensile strength reduces which makes the soil susceptible to erosion. Therefore, tensile strength ofthe hydrated roots should be used when modelling its contribution to soil strength, this is because the soil is more susceptible to fail when saturated.