Fertilizer Concentration and Irrigation Method Affect Growth and Fruiting of Ornamental Pepper

Abstract

To evaluate the effects of fertilizer concentration and irrigation method on growth of ornamental pepper (Capsicum annuum L. “Treasures Red”), a water-soluble fertilizer solution containing 0, 100, 200, 300, or 400 mg L⁻¹ nitrogen (N) was applied, using subirrigation and hand-watering. Fertilizer concentrations of 200–400 mg L⁻¹ N resulted in an electrical conductivity (EC) gradient from the bottom (lowest EC) to the top (highest EC) of the growing medium in subirrigated, but not in hand-watered pots. The EC in the bottom layer of the medium was affected by irrigation method only at a fertilizer concentration of 400 mg L⁻¹ N. The pH of the growing medium decreased with increasing fertilizer concentration. Shoot dry mass was highest at 200 mg L⁻¹ N in both irrigation treatments and was consistently higher with hand-watering than with subirrigation. Leaf area also was highest at 200 mg L⁻¹ N, but was not affected by irrigation method. In contrast, plant height was greater with subirrigation than with hand-watering, and also peaked at 200 mg L⁻¹ N. Hand-watering increased stem diameter compared to subirrigation and was maximal with 200–400 mg L⁻¹ N. Chlorophyll content of the leaves was much lower at 0 than at 100–400 mg L⁻¹ N, and not affected by irrigation method. Fruit fresh mass was higher with hand-watering than with subirrigation, but shoot dry mass was not affected by irrigation method. Fruiting was poor at 0 mg L⁻¹ N, but did not vary much among fertilizer concentrations ranging from 100–400 mg L⁻¹ N. Subirrigation resulted in earlier flowering and fruit ripening than hand-watering, suggesting that the production period may be a few days shorter with subirrigation. Although N, iron (Fe), and molybdenum (Mo) all increased with increasing fertilizer concentrations, N most likely limited growth at low fertilizer concentrations. In contrast to previous research, these results do not indicate that subirrigated plants should be fertilized with lower concentrations than hand-watered plants.

Keywords:

• Capsicum annuum
• Electrical conductivity
• Nitrogen
• Subirrigation
• Substrate pH

Acknowledgments

We thank Larry Freeman and Keven Calhoun for their assistance in setting up the experiments and data collection and the University of Georgia's Center for Urban Agriculture for financial support for this research.