Author(s)

Carlos Vazquez¹, Stewart T. Reed^2*, Christopher Dunn²

¹School of Science, St. Thomas University, Miami Gardens, FL, USA.
²USDA, ARS, Miami, FL, USA.

Hippeastrum (Hippeastrum hybridum), a native of Central and South America, is a bulbous ornamental flowering plant in the Amaryllidaceae family. However, the correct balance of NH₄ to NO₃-nitrogen in a fertilizer mix for Hippeastrum plants is largely unknown. Nitrogen was applied 2x weekly following irrigation at either 0.6 g (high), 0.3 g (medium) or 0.15 g (low) total N every four months. Nitrogen was supplied in different combinations of NO₃ and/or NH₄. Nitrate:NH₄-N ratios were either 100% NO₃:0% NH₄ (100NO₃), 70% NO₃:30% NH₄ (70NO₃), 50% NO₃:50% NH₄ (50NO₃) (second group only), 30%NO₃:70%NH₄ (30NO₃), or 0% NO₃/100% NH₄ (100NH₄). Growth in bulb diameter after one year of fertilizer treatments not only increased from 0.15 to 0.6 g N (low to high level), but also differed with the form of N supplied to the plant. The largest diameter bulbs were produced in the 70NO₃ and 50NO₃ high N treatments. Within any NO₃/NH₄-N ratio grouping, fertilization at the high N rate resulted in larger diameter bulbs. No significant differences existed between treatments in the number of bulbs produced. Bulb growth was greater with a portion of N supplied as NO₃ than with NH₄-N alone. These results indicate that application of N as a mixture of NH₄ and NO₃ at 0.6 g per 4 months produces the largest increase in bulb diameter.

Hippeastrum, Amaryllis, Nitrogen Fertilization, Ammonium, Nitrate

Vazquez, C. , T. Reed, S. and Dunn, C. (2015) Nitrogen Fertilization as Ammonium or Nitrate-N on Hippeastrum hybridum Bulb Growth. Agricultural Sciences, 6, 1547-1554. doi: 10.4236/as.2015.612148.