Preliminary soil characteristics and growth performance of selected shrub plants for bio-engineering technique

Abstract

This study presents the preliminary results of the physicochemical characteristics of the soil taken from the slope bio-engineering study. The soil would be used as a medium for the growth of selected shrub species namely Strobilanthes crispa (SC), Pseuderanthemum carruthers (PC), Tabernaemontana divaricata (TD), and Hibiscus rosa-Sinensis (HR). Soil medium was prepared in a 3:2:1 ratio (soil: organic fertilizer: sand). The plant-cutting technique was adopted and planted in polybags. The growth performance (height, number of leaves, chlorophyll, and leaf area) of these species was monitored on monthly basis up to three months. The result showed that the pH, organic matter and moisture content ranged from 4.15 to 5.23, 4.29% to 7.96% and 16.1% to 62.93%, respectively. The specific gravity and porosity of the soil ranged from 2.66 to 2.70 and 58.48% to 60.83%, respectively with clay loam and loam textures. SC and TD showed high mortality rates, with only 28% and 50% of the species still alive. However, the PC and HR had low mortality rates, with 98% and 96% of cuttings surviving, respectively. TD recorded the highest plant with 30.63 cm followed by HR (27.94 cm), PC (25.32 cm) and SC (22.36 cm). TD also recorded the highest number of leaves with 23 individuals. SC showed the highest leave area with a mean of 23.61 cm2 followed by PC (23.2 cm2), HR (14.43 cm2) and TD (13.28 cm2). HR recorded the highest chlorophyll content with a mean value of 46.62 followed by TD (45.23), SC (35.87) and PC (32.79). In conclusion, HR showed a good growth performance among the studied species. These preliminary findings suggested that all species have the potential to be used as biological material for slope erosion protection, with some soil treatment required for better growth outcomes.