The objectives of this study were to determine 1) the minimum controlled-release fertilizer (CRF) rate and the lowest constant medium moisture required to produce the highest quality plants and 2) if this production system affected quality of these plants under two postproduction light levels. Two New Guinea impatiens (Impatiens sp. hybrids) `Illusion' and `Blazon' (Lasting Impressions Series) differing in salt tolerance were grown for 42 days with a CRF at three rates (3.3, 6.6, or 9.9 g/pot) and two medium moisture levels (low or high) without leaching. The high moisture level (tension setpoints of 1 to 3 kPa) and 6.6 g of CRF/pot produced optimum biomass. Low medium moisture (tension setpoints of 4 to 6 kPa) reduced leaf area, leaf number, leaf N content, root, stem, and leaf dry masses as CRF rate increased from low to high for `Illusion'. Similar results in `Blazon' were observed as CRF rates increased from 3.3 to 6.6 g. Biomass decreased no further at the high rate of 9.9 g/pot. Biomass increased in both cultivars under high medium moisture when CRF rates increased from 3.3 to 6.6 g. Biomass of `Illusion' decreased at 9.9 g/pot, although no symptoms of salt sensitivity were observed (i.e., leaf tip burn). `Blazon' maintained a similar biomass when amended with 9.9 or 6.6 g CRF/pot, although electrical conductivity (EC) in the medium was 5.9 dS·m-1 in the upper half and 4.1 dS·m-1 in the lower half of the medium at the end of production. Growth of `Illusion' responded more favorably to postproduction light levels that were similar to those of production regardless of treatment imposed during production. Similar biomass responses occurred for `Blazon' regardless of the postproduction light level.
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