Production and quality of Sim carnations grown hydroponically in rockwool substrate with nutrient solutions containing different levels of calcium, potassium and ammonium-nitrogen

The effects of 3 nutrient solution formulations on the production and quality of the Sim carnation varieties, Raggio d'Sole, White Sim, Manon and Doria grown in rockwool substrate were evaluated over 12 months in northern New South Wales. The solutions were: a standard (Std) formulation with a K:N ratio of 1.29:1.00, approximating that in mature carnations with N supplied as NO3-; the standard solution with 10% of the N as NH4+ (Std + NH4+); and a formulation with increased Ca and reduced K (High Ca). Production peaks occurred in March and October when the substrate was sampled for leachate nutrient composition and the flowers were assessed for quality. Total flower production from the Std + NH4+ (9.9/plant) and High Ca (9.7/plant) treatments exceeded (P0.05) (mean of 10.3/plant) from August to December. Over February-December, production from the Std + NH4+ treatment (20.8/plant) exceeded (P0.05) by nutrient solution formulation. Stem diameter, stem strength and vase life were unaffected by nutrient formulation while flowers produced in March had thinner (3.11 v. 5.24 mm diameter) and weaker (139 v. 42 mm deflection from horizontal) stems than those produced in October. The pH in rockwool slabs was stable over time and compared to the standard treatment (7.17), it was lower (P