Effect of NaCl salinity and nitrogen fertilizer formulation on yield and nutrient status of roses

Yield, quality and nutrient status of 'Bridal Pink' (on R. manetti rootstock) roses were evaluated under increasing NaCl salinity and different NO3/ NH4 ratios. Container-grown plants were irrigated over eight flushes of growth and flowering with nutrient solutions having NO3/ NH4 ratios of 100:0, 75:25 and 50:50 in combination with three NaCl concentrations. During the first four flowering flushes NaCl was supplemented at 0, 5 and 10 mM, but these concentrations were increased to 0, 15 and 30 mM during the last four flushes. Interestingly, NO3/ NH4 ratios and NaCl concentration had no main effects on any of the flower yield or quality components evaluated over the 13-month experimental period. Furthermore, visual symptoms of salt injury were observed only during the last three flowering cycles, and most heavily on the oldest foliage of plants receiving the highest salt concentration (30 mM). Leaf N and Na concentrations were not significantly affected by any of the treatments over the course of the experiment, averaging 3.34% and 45 mg . kg(-1) dry weight (DW), respectively. Leaf Cl concentrations were significantly increased by salt additions, and ranged from 0.80 to 18.9 g . kg(-1) (0.08 to 1.89% DW). Correlation analyses revealed that relative dry weight yields increased with leaf Cl concentrations up to 4.50 g . kg(-1) (0.45% DW) but were significantly depressed at higher concentrations. These results suggest that roses are more tolerant to salinity than their typical classification of sensitive. Moreover, this is the first known study to report an apparent positive effect of moderate leaf Cl concentrations on rose dry weight yields.