Root and shoot growth responses to phosphate fertilization in container-grown plants

Abstract

Areca palms [Dypsis lutescens (H. Wendl.) Beentje and J. Dransf.], spathiphyllums (Spathiphyllum Schott. 'Figaro'), ixoras (Ixora L. 'Nora Grant'), tomatoes (Lycopersicon esculentum Mill. 'Floramerica'), marigolds (Tagetes erecta L. 'Inca Gold'), bell peppers (Capsicum annuum L. 'Better Bell'), and pentas [Pentas lanceolata (Forssk.) Deflers. 'Cranberry'] were grown in a pine bark-based potting substrate and were fertilized weekly with 0, 8, 16, 32, or 64 mg (1.0 oz = 28,350 mg) of P per pot. Shoot, and to a much lesser extent, root dry weight, increased for all species as weekly P fertilization rate was increased from 0 to 8 mg/pot. As P fertilization was increased from 8 to 64 mg/pot, neither roots nor shoots of most species showed any additional growth in response to increased P. Root to shoot ratio decreased sharply as P fertilization rate was increased from 0 to 8 mg/pot, but remained relatively constant in response to further increases in P fertilization rate.