Improving Boron and Molybdenum Use Efficiencies in Contrasting Cultivars of Subirrigated Greenhouse-Grown Pot Chrysanthemums

Fertilizer boron (B) and molybdenum (Mo) were provided to contrasting cultivars of subirrigated pot chrysanthemums at approximately 6–100% of current industry standards in an otherwise balanced nutrient solution during vegetative growth, and then all nutrients were removed during reproductive growth. Two experiments were conducted for each nutrient in a naturally lit greenhouse using a randomized complete block split-plot design. Boron (0.313–5.00 µmol L(−1)) or Mo (0.031–0.500 µmol L(−1)) was the main plot, and cultivar was the sub-plot. Petal quilling was observed with leaf-B of 11.3–19.4 mg kg(−1) dry mass (DM), whereas Mo deficiency was not observed with leaf-Mo of 1.0–3.7 mg kg(−1) DM. Optimized supplies resulted in leaf tissue levels of 48.8–72.5 mg B kg(−1) DM and 1.9–4.8 mg Mo kg(−1) DM. Boron uptake efficiency was more important than B utilization efficiency in sustaining plant/inflorescence growth with decreasing B supply, whereas Mo uptake and utilization efficiencies appeared to have similar importance in sustaining plant/inflorescence growth with decreasing Mo supply. This research contributes to the development of a sustainable low-input nutrient delivery strategy for floricultural operations, wherein nutrient supply is interrupted during reproductive growth and optimized during vegetative growth.