Nitrogen and Phosphorus Rates Influence Growth, Flowering, and Nutrient Uptake in Iris germanica ‘Immortality’

In this study, the influence of nitrogen (N) and phosphorus (P) rates on plant growth, flowering, anduptake of essential nutrients was evaluated in container-grown tall bearded (TB) iris (Iris germanica)‘Immortality’. Factorial combinations of three N (5, 10, or 15 mM) rates and three P (5, 10, or 15mM) rates were applied to plants via fertigation twice per week from March to September 2013. Plant height, leaf SPAD reading, and flowering data were collected during the growing season. Plants were harvested in December 2013 to measure dry weight (DW) and analyze concentrationsof essential mineral elements. Greater N rates had positive effects on plant height, leaf SPADreading, flowering performance, and uptake of several essential elements, such as potassium (K),calcium (Ca), and iron (Fe). Phosphorous rate did not significantly affect most of the growthparameters. Greater P rates increased P concentration in leaves and roots and decreased boron (B)concentration in leaves but did not significantly influence net uptake of other nutrients exceptcopper (Cu). The average N:P ratio ranged from 4.7 to 7.5, 2.4 to 4.0, and 6.0 to 8.7 in leaves, roots,and rhizomes, respectively. KCI Citation Count: 0