Morphological and Physiological Growth of Terminalia superba Seedlings as Influenced by Different Planting Depths, Width and Urea Application

Optimum survival, growth and development of cultivated tree species are of great importance especially to timber species of high value like Terminalia superba. Poor planting technique and inadequate nutrient supply contribute to low survival and growth rate. This study examined the field response of T. superba seedlings to different planting depths, widths and urea application. Using split – plot experimental design, at 3m x 3m spacing, seedlings were subjected to Fertilizer treatments (F₀ and F₁), planting depths of 10cm, 15cm and 20cm levels (D₁, D₂ and D₃) and planting width of 10cm and 15cm (W₁ and W₂). Each treatment was replicated ten (10) times. Seedling height, collar diameter and number of leaves were assessed fortnightly for 6 months while biomass was assessed after the end of experiment. Relative Growth Rate (RGR), Absolute Growth Rate (AGR), Net Assimilation Rate (NAR), Leaf Area Ratio (LAR), Relative Water Content (RWC) and Leaf Turgidity were estimated using appropriate formula. The result showed that seedlings planted without urea,15cm width and 20cm depth planting hole (F₀W₂D₃) had the highest mean height (66.94cm), mean collar diameter (10.28mm) and number of leaves but lower values in dry matter weights and R/S ratio (0.13). Seedlings planted with fertilizer in 10cm width and 10cm depth (F₁W₁D₁) recorded the highest RWC value of 54.05%, highest positive NAR and RGR values (0.007 gcm^-2/ day^-1 and 0.305gg^-1day^-1 respectively). Therefore, seedlings subjected to zero urea application, wider and deepest holes (F₀W₂D₃) had highest values for height, collar diameter and number of leaves whereas those subjected to 5g urea application, shallow and narrow holes (F₁W₁D₁) were physiologically superior though they recorded average morphological values. The findings hereby justified the need for optimizing planting techniques and nutrient management to enhance seedling growth and also support sustainable forest management in Nigeria. It is therefore recommended that forest managers utilize wider and deeper planting holes (F₀W₂D₃) to maximize initial physical growth, while incorporating strategic urea application in standard planting holes (F1W1D1) when high physiological resilience and early assimilation rates are prioritized for T. superba establishment in Nigeria.

Keywords: Terminalia superba; Planting width; Planting techniques; Urea application; Planting width.