The Soil-Root Strength Performance of Alternanthera Ficoidea and Zoysia Japonica as Green Roof Vegetation

¹ Research Centre for Soft Soil (RECESS), Universiti Tun Hussein Onn Malaysia, 86400 Parit Raja, Batu Pahat, Johor, Malaysia
² Micropollutant Research Centre (MPRC), Faculty of Civil and Environmental Engineering, Universiti Tun Hussein Onn Malaysia, 86400 Parit Raja, Batu Pahat, Johor, Malaysia
³ Horticulture Research Centre, MARDI Headquarters, Serdang, P.O. Box 12301, 50774 Kuala Lumpur

^* Corresponding author: hartini@uthm.edu.my

Abstract

The rise of awareness on environmentalism has demanded that all parties involved in built environment to implement green technology in their construction projects. Great care must be taken when designing a green roof system including the selection of plants and appropriate substrates. This study was performed to investigate the soil-root composite strength of two types of green roof vegetation (A. Ficoidea and Z. Japonica) at different growth periods for up to 6 months. Both plants were planted in six plastic plots (45 cm × 29 cm × 13 cm) containing a mixture of perlite, vermiculite and organic soil. Every two months, a series of direct shear tests were conducted on a sample from each species to determine the root-soil shear strength. The tests continued until the 6^th month. The average results showed that Z. Japonica had higher soil-root shear strength (49.1 kPa) compared to A. Ficoidea after two months of growth. In the 4^th month however, A. Ficoidea managed to surpass Z. Japonica (28.7 kPa versus 18.5 kPa) in terms of shear strength. However, their average peak shear strength decreased sharply compared to the previous month. Lastly, in six months, A. Ficoidea sustained a higher average peak soil shear strength (56.5 kPa) compared to Z. Japonica (14.3 kPa). Therefore, it can be concluded that A. Ficoidea may offer a better soil reinforcement than Z. japonica and thus it could potentially be a good choice of green roof vegetation.