Nutrient Competitive Effects in Chrysanthemum Amended with Flue Gas Desulfurization Gypsum

Gypsum use in agriculture has a longstanding history, yet there remains a critical need for research to understand better its impact on plant development and plant nutrient availability. This study evaluated the impact of flue gas desulfurization gypsum (FGDG) amendments on the physical and chemical properties of pine bark substrates and the growth and nutrient uptake of chrysanthemum ‘Wanda Red’. Pine bark was incorporated with controlled-release fertilizer, micronutrient fertilizer, dolomitic limestone, and varying FGDG rates (0%, 2.5%, 5%, and 10% v:v). Plant growth metrics, including dry weight, canopy volume, and foliar nutrient concentrations, were recorded at bud initiation and peak bloom. Flue gas desulfurization gypsum amendments did not significantly affect plant dry weight at bud initiation, although plants without FGDG had greater canopy volumes. By peak bloom, plants without FGDG exhibited greater dry weights, but no difference in growth indices was observed ( P = 0.8648). Although the 0% gypsum plants recorded a larger size at bud initiation, there were no differences by full bloom. Foliar nutrient analyses revealed that FGDG amendments influenced nutrient uptake, with notable reductions in nitrogen ( P = 0.0035) and potassium ( P < 0.0001) at bud initiation but no significant differences at peak bloom. Conversely, phosphorus and calcium concentrations increased with FGDG amendments, suggesting improved retention and availability. Overall, although FGDG amendments led to reduced uptake of some nutrients and minor delays in bloom, all treatments produced marketable chrysanthemums, indicating that FGDG can be integrated into production practices without compromising plant quality. Further studies are recommended to explore lower gypsum rates and their interactions with nutrient retention and crop demand.