Growth response of Angelonia angustifolia to phosphorus fertilization

Angelonia (Angelonia angustifolia) is an annual bedding crop valued for its robust growth habit and colorful blooms. Current fertilizer recommendations are not typically specified for phosphorus (P) fertility, so this study was conducted to determine optimal P concentrations over time of two angelonia cultivars. ‘Sungelonia Blue’ and ‘Sungelonia White’ plants were grown for eight weeks with P concentrations of 0, 2.5, 5, 10, or 20 mg L^‑1. Height and diameter were measured biweekly, and dry mass was recorded at study termination. These parameters were used to calculate a growth index, and then regressed to determine optimal P concentrations over time. The final P concentrations necessary to maximize growth were 8.8 and 7.3 mg L^‑1 for ‘Sungelonia Blue’ and ‘Sungelonia White’, respectively; however, the optimal P concentration needed to maximize growth varied over time. This study provided improved P fertilization recommendations for angelonia growers.