Assessment of seed germination and seedling growth of <i>Vachellia sieberiana</i> under different soil moisture regimes

Abstract

This study aimed at investigating causes and prescribe appropriate seed treatments of Vachellia sieberiana. Ten trees were selected in Songa pastures and surveyed for the presence of seeds and saplings under and nearby the canopy. Seeds were collected from tree floor and were treated using hot (500^oC) wire scarification, roasting for 30, 40, 50, 60 and 90 minutes and soaking in cold and hot water for 24 hours. Seed germination was tested on sound seeds from February-May, 2010 and seedlings assessed for growth and survival under different watering regimes, by applying 60ml of water/seedling daily, once or twice a week. Seedlings were raised as bare-rooted in open nursery or as potted in a greenhouse. The effect of watering regime on seedling growth and survival, height, number of leaves, leaflets and thorns, root collar diameter, root length and total biomass were observed during the experimental period. More than 50% of V. sieberiana seed on the canopy flow retained viability. Seed germination was sporadic and differed very significantly between treatments. Scarification gave the highest germination rate followed by soaking in hot and cold water. Soaking in hot water gave a more uniform germination and is thus recommended for seed treatment in this species. Growth in all traits except root length increased significantly with watering frequency. High root length was positively correlated with fine root density and may indicate ecological strategy to increase water uptake by V. sieberiana.

Keywords: Seed dormancy, survival strategy, early seedling growth, root length, fine root