It is widely recognized that vegetation plays a significant role in contrasting slope instability through the root reinforcement. The main objectives of this paper are to evaluate the root tensile of selected Pennisetum species, namely, P. pedicellatum (PPd) and P. polystachion (PPl), and to determine the soil shear strength of root-permeated soil from these species. The selected species were initially planted in the polybags using the hydroseeding technique. A mineral fertilizer of NPK ratio 10 : 8 : 10 was adopted in the hydroseeding mixture. Routine watering program was applied twice a day throughout growth observation for six months. Four replications were prepared for each species including a set of control polybags, which contained only soil for reference and comparison. The results of root tensile tests revealed the significant relationships between root diameter and tensile force. In comparison, the PPl was still indicated by higher values of root tensile force than PPd. The presence of roots clearly has contributed to the shear stress of root-permeated soils. The root density based on root biomass measurement attributed to the higher value of peak shear stress as achieved by PPl than PPd. The combined effects of root tensile and the soil shear strengths of this selected species can be used as biological materials in slope protection against erosion.

The Mission (Pennisetum polystachio) and Kyasuwa (Pennisetum pedicellatum) grasses are common perennial plants found in tropical regions that tolerates low nutrient soils, easily spread by wind and colonization of new areas. It is a great challenge for researchers to select plant species in terms of their performance for vegetation cover to minimize the sloppy soil erosion. Therefore, this study aimed to evaluate the growth performance of selected Pennisetum sp. namely P. pedicellatum (PPd) and P. polystachio (PPl) under different NPK ratio. The studied species were treated with three different treatments, F1, F2 and NF under greenhouse conditions. Hydroseeding technique was adopted for germination of the selected species in the polybags and periodically monitored for a duration of six months. Parameters measured for the growth performance of the studied species were based on plant height, total biomass and chlorophyll content. After application of the treatment F1 and F2, the soil pH changed to slightly acidic (pH 5.45) while organic content of soil was slightly increased from 3.2% to 3.9%. A similar result was also found in N and P nutrient availability of the soil. Meanwhile, available K decreased from 29.76 mg/kg to 28.41mg/kg (F1) and 23.83 mg/kg (F2) for PPl species. This trend was also observed by the PPd species. The PPd species with F1 and F2 treatments showed higher value of plant height if compared to that of PPl species. In terms of total biomass and chlorophyll content, PPl species treated with both treatments showed higher value than PPd species. Species treated with F1 showed higher value in all growth performance variables (height, dry biomass and chlorophyll content), if compared to that of F2 and NF treatments. These findings discovered Pennisetum polystatchion (PPl species) as a potential biological material that can be used as a slope vegetation cover.

Aim: In soil bio-engineering, plant has been widely adopted as important material in promoting sustainable ecological function in slope instability measures. Plant canopy provides shelter and at subsurface level, root networking attributes toward stability of soil against erosion and slope failure. To investigate the potential of selected P. polystachion as biological material in soil bio-engineering for improving the soil shear strength of sandy soil planted with P. polystachion. Methodology: The selected species was initially planted using hyroseeding technique on studied plots which facilated with and without fiber netting (made of paddy straw). A control plot was also prepared for reference of this study. The plots were routinely watered twice a day for six months before experimental program was scheduled for determining of root tensile and soil shear strength tests. Results: The root tensile strength of P. polystachion exhibited a positive significant relationship between root tensile force and root diameter. The shear strength of soil was affected by the presence of root if compared to that of soil without root (control). Biomass analysist also agree with the soil water content, ws. High biomass contributed to the increase in the values of soil shear strength parameter of cohesive, c and angle of friction, q for root-permeated soil with P. polystachion. Interpretation: This study has suggested that the potential application of this selected species for slope vegetation in improving the erosion control and slope stability in soil-bioengineering scheme.