Nitrogen-Yield Relationships in Greenhouse Roses

Abstract

The establishment of critical tissue N (Ncrit) for greenhouse rose production has been primarily based on visual symptoms of N deficiency, with relatively less consideration to yield parameters. This work examined the relationship between rose leaf N concentration and flower yield and quality. Microlysimeter-grown `Royalty' rose plants were irrigated with complete nutrient solutions containing N concentrations of 30, 60, 90, 120, 150, and 220 mg·liter–1. Results after 1 year indicated no significant differences in total dry weight, number of flowers, and stem length for plants irrigated with 90 to 220 mg·liter–1 N. Tissue N concentrations were significantly lower for plants that received 30 or 60 mg N/liter. Estimated Ncrit for yield parameters were ≈2.7% of leaf dry weight. Chlorophyll content and color leaf attributes (hue, chroma, and value) were correlated with tissue N concentration. The results suggest that the rate of N application typically recommended for greenhouse roses is considerably higher than necessary.