Validation of a delivery strategy for reducing nutrient inputs and improving nutrient use efficiency in greenhouse-grown sub-irrigated pot chrysanthemums

Two experiments were conducted in a naturally lit research greenhouse to validate our modified strategy for delivering nutrients to sub-irrigated chrysanthemum plants. A split-plot design was used with four blocks arranged randomly, three nutrient rates as the main plot, and two contrasting cultivars as the subplot. The entire nutrient supply was removed at bud break and markedly reduced during vegetative growth, compared to common commercial fertilizer formulations, without adversely affecting tissue nutrient levels and plant/inflorescence quality, indicating that the plants were functioning in the low nutrient sufficiency zone. Specific nutrients (Nt) were more likely to exhibit improved uptake efficiency (shoot Nt content/Nt supply) than improved utilization efficiency (inflorescence DM/shoot Nt content) with decreasing nutrient supply. Thus, the common practice of delivering superfluous nutrient levels to greenhouse-grown chrysanthemum has little scientific merit in terms of nutrient accumulation and plant longevity. Applying a low-input nutrient delivery strategy to the cultivation of indoor-grown, potted ornamental plants would improve the overall sustainability of the Canadian floricultural industry.