Plant Density Manipulation on the Growth of Tephrosia bracteolata Guill. & Perr. and Associated Weed Species

Abstract

This study investigated the influence of plant density manipulation on dry matter accumulation and weed-suppressing ability of Tephrosia bracteolata. The seeds of Tephrosia bracteolata were sown on a field with 0.2 m inter-row spacing while intra-row spacing was varied from 0.1 m – 1.6 m. The plant densities were D0 = 0 Plants/m2, D1 = 50 Plants/m2, D2 = 25 Plants/m2, D3 = 12.5 Plants/m2, D4 = 6.25 Plants/m2 and D5 = 3.125 Plants/m2. The experiment was conducted in a Randomised Complete Block Design with three replications. Data were collected 16 weeks after sowing on Plant Height, Number of Leaves, Stem Diameter, Shoot Dry Weight, and Weed Dry Weight. Weed species were enumerated using 0.5 m by 0.5 m quadrats to calculate species relative importance value, Shannon-Wiener index, dominance index, and equitability index. The results showed that plant density on plant height and stem diameter were not significantly different α0.05, while number of leaves, shoot dry weight, and weed dry weight observed at 12.5 Plants/m2 were significantly different at α0.05 compared to other plant densities. Twenty-eight weed species and one woody tree species were enumerated. Desmodium scorpiurus, Diodra sarmentosa, and Tridax procumbens were the most important species, while species dominance was low across plant densities. Shannon-Wiener index was highest in 6.25 Plants/m2 (2.425) and lowest in 50 Plants/m2 (1.911). The equitability index was lowest in 50 Plants/m2 (0.745) and highest in 0 Plants/m2. These results suggest that Tephrosia bracteolata sown at 12.5 Plants/m2 positively influenced dry matter accumulation and weed suppression.