Effects of Spacing and Post-Pinching Regrowth on Biomass Allocation, Root–Shoot Ratio, and Canopy Development of Moringa Species in Semi-Arid Northern Nigeria

Post-pinching regrowth and plant spacing are key determinants of vegetative performance, biomass allocation, and canopy development in Moringa species under semi-arid conditions. A factorial experiment was conducted in a Randomized Complete Block Design with three replicates to evaluate the effects of four spacing treatments (15×15, 15×20, 20×20, 20×30 cm) on the growth performance, root–shoot ratio, and leaf area index (LAI) of Moringa peregrina, M. oleifera, M. stenopetala, and M. oleifera ‘PKM 1’. Seedlings were pinched at 4 weeks after emergence to stimulate branching, and growth parameters were measured over 8 weeks. Post-pinching regrowth significantly influenced the number of leaves (NL) and branches (NB), with M. oleifera ‘PKM 1’ showing superior performance (NL = 261 ± 10.5; NB = 18 ± 1.5). Closer spacing enhanced NL, NB, and plant height, whereas wider spacing promoted root allocation and structural development. Root–shoot ratio decreased with increasing spacing, indicating adaptive biomass partitioning to optimize resource acquisition, while LAI varied among species, reflecting differences in canopy architecture and light interception efficiency. Regression analyses revealed strong positive relationships between root and shoot biomass (R² = 0.85–0.94) and negative correlations between R/S ratio and spacing (R² = 0.80–0.89), demonstrating species-specific plasticity in growth strategies. These findings highlight the importance of optimizing spacing and post-pinching management to enhance leaf yield, biomass allocation, and productivity in Moringa agroforestry systems, providing actionable insights for sustainable and resilient cultivation in semi-arid environments.