YIELD AND QUALITY OF CARNATION (DIANTHUS-CARYOPHYLLUS L) AND GERBERA (GERBERA-JAMESONII L) IN A CLOSED NUTRIENT SYSTEM AS AFFECTED BY SODIUM-CHLORIDE

To study the consequences of NaCl-containing irrigation water in closed nutrient systems, effects of increasing NaCl concentrations up to 30 mM on yield and quality of spray carnation and gerbera were investigated. In carnation, salinity decreased peduncle length at 23 mM NaCl. In the less salinity-tolerant gerbera, number of flowers, flower weight and flower area were decreased with 8 mM NaCl. Post harvest vase-life was not affected by salinity. As a similar yield decrease occurred in a treatment which had an increased salinity using increased concentrations of major elements, it is concluded that specific ion-toxic effects of Na+ and/or Cl- were not related to the yield decrease. Chemical analysis of peduncles of carnation or gerbera flowers showed no consistent effects of NaCl on concentrations of major elements. Influx concentrations of Na+ were linearly related to the concentration in the nutrient solution. On average, influx was 2.5% and 7% of the Na+ concentration in the nutrient solution for carnation and gerbera, respectively. The consequence is that Na+ accumulates in the nutrient solution more rapidly for carnation than for gerbera. Influx concentrations of Cl- were higher, and non-linearly related to the Cl- concentration in the nutrient solution. Average electrical conductivity (EC) needed to compensate for uptake of minerals was 0.7-0.8 dS m(-2).