Field Establishment of Chrysophyllum albidum G. Don Seedlings through Planting Depth, Hole Width and Nitrogen Fertilizer Application

Abstract

The successful establishment of indigenous fruit tree species is fundamental to sustainable forest management, biodiversity conservation, and the domestication of economically important non-timber forest products. Chrysophyllum albidum G. Don (African star apple) is a valuable indigenous multipurpose tree species in West Africa whose large-scale cultivation is constrained by inadequate information on appropriate field establishment techniques. This study evaluated the effects of planting depth, planting-hole width and nitrogen fertilization on the early growth, biomass accumulation and physiological performance of C. albidum seedlings under field conditions at the Forestry Research Institute of Nigeria (FRIN), Ibadan. A split-split plot experiment arranged in a Randomized Complete Block Design (RCBD) was established using 120 seedlings. Treatments consisted of three planting depths (10, 15 and 20 cm), two planting-hole widths (10 and 15 cm), and two fertilizer levels (0 and 5 g urea seedling⁻¹), resulting in twelve treatment combinations replicated ten times. Morphological parameters were monitored fortnightly for six months, while biomass and physiological growth indices were determined at the end of the experiment. Analysis of variance revealed that fertilizer application and planting depth did not significantly (P > 0.05) influence seedling height, collar diameter or leaf production. Planting-hole width significantly affected leaf production (P < 0.05), indicating that adequate root-zone preparation enhanced canopy development during the establishment phase. Although biomass accumulation and physiological parameters varied among treatment combinations, interaction effects among the silvicultural treatments were not statistically significant. The findings demonstrate that C. albidum seedlings exhibit considerable adaptability to moderate variations in planting depth and fertilizer application during early establishment, while appropriate planting-hole width improves early canopy development. These results provide valuable silvicultural information for plantation establishment, restoration programmes, and the domestication of African star apple in tropical forest ecosystems.

Keywords: African star apple; indigenous fruit tree; field establishment; planting depth; nitrogen fertilization; silviculture