ISHS Acta Horticulturae 751: IV International Symposium on Rose Research and Cultivation
MODELING MACRONUTRIENT ABSORPTION OF HYDROPONICALLY-GROWN CUT FLOWER ROSES |
| Authors: | N.S. Mattson, J. Heinrich Lieth |
| Keywords: | hydroponics, nitrogen, calcium, potassium, magnesium, Rosa × hybrida |
| Abstract:
Regulations increasingly limit the water run-off allowed from agricultural facilities. A better understanding of appropriate irrigation and fertilization regimes are needed to comply with these regulations. The objectives of this project were to determine how macronutrient absorption by roses varies in relationship to growth of new flower stems and test whether an existing mathematical model is suitable for describing nitrogen and potassium uptake across a crop cycle. Absorption of ammonium (NH4+), nitrate (NO3-), potassium (K+), calcium (Ca2+), and magnesium (Mg2+) by rose plants (Rosa × hybrida ‘Kardinal’) were measured during three crop cycles. Following a harvest, the rate of total nitrogen (N) uptake decreased to 0.15 mmol d-1 g-1 harvested dry weight (HDW) where it remained for the first five days, decreased during days 8-10, and then increased in synchrony with flower stem elongation. K+ uptake rates gradually declined for the first 12 days following a harvest cycle, then increased in synchrony with stem elongation to maximum uptake rates of 0.05 to 0.09 mmol d-1 g-1 HDW as stems reached maturity. Prior to harvest, the rate of Ca2+ uptake decreased and remained low until day 7 of the new cycle (appearance of new shoots), then increased until just prior to stem maturity. Mg2+ uptake rate increased in synchrony with stem elongation and then decreased just prior to harvest. Simulations of the N/K+ model accurately predicted the increase in N and K+ uptake rates beginning around day 10-12 and proceeding until harvest as well as the drop in N and K+ uptake occurring at harvest. The simulation does not predict the somewhat sustained uptake rates for the first 7-10 days following harvest and the decline in uptake during early stem elongation. The most likely reason for the discrepancy is that the model does not yet have mechanisms for handling redistribution of these nutrients from perennial tissues to new growing shoots or account for changes in root growth across a crop cycle. | |
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