Effect of soil sodicity on growth, yield, essential oil composition, and cation accumulation in rose-scented geranium

The effect of soil sodicity exchangeable sodium percentage (ESP) on the growth, yield, essential oil composition, and cation accumulation of two cultivars (Bourbon and Cimpawan) of geranium (Pelargonium graveolens) were studied in a pot experiment. Irrespective of soil sodicity, two cultivars of geranium differed significantly in their plant height and herb and oil yield. Plant height was not significantly affected with increases in soil ESP from 0.7 (control) to 20.0 and 7.0, respectively, for cultivars (cv) Bourbon and Cimpawan, but further increase in soil ESP decreased the plant height. The herb yield of cv Bourbon significantly increased with increasing soil ESP to 16.0, and the oil yield increased with increasing ESP to 7.0. Further increase in soil ESP decreased the yield. The increase in yield of cv Bourbon was 13.1 and 15.1% in the herb and 40.0 and 15.2% in the oil over the control (ESP 0.7) at soil ESP of 7.0 and 16.0, respectively. Decreases in yield were 3.5, 4.9, 53.3, and 59.3% in the herb yield and 3.8, 5.7, 53.3, and 80.0% in the oil over control (ESP 0.7) at soil ESP of 20.0, 24.0, 28.0, and 30.0, respectively. The herb and oil yield of cv Cimpawan significantly decreased with increase in soil ESP. The decease in yield was 17.7, 20.2, 40.7, 53.1, 70.7, and 72.6% in the herb and 4.0, 6.8, 30.9, 45.4, 83.2, and 84.0% in the oil over control (soil ESP 0.7) at the soil ESP 7.0, 16.0, 20.0, 24.0, 28.0, and 30.0, respectively. The concentration of isomenthone, linalool, citronellyl formate, and geranyl formate in the essential oil increased at low levels of soil ESP (between 16.0 to 24.0) but decreased at high soil ESP (>28). The concentration of l-citronellol, nerol, and geraniol gradually increased with increase in soil ESP. The increase in the soil ESP enhanced the concentration of sodium (Na) and decreased that of potassium (K) in shoot and root tissues of geranium as compared to control. The concentration of Ca in shoot tissues of cv Bourbon significantly decreased with increase in soil ESP, but in the cv Cimpawan, the Ca concentration was not significantly affected with increase in soil ESP from 0.7 to 16.0, and thereafter the Ca concentration significantly decreased with further increase in soil ESP. The concentration of Na, K, and Ca were relatively higher in shoot than in root tissues. The K/Na and Ca/Na ratios in shoot tissues of both cultivars of geranium decreased with increase in soil ESP. The K/Na and Ca/Na ratios in shoot were not found to be related to the differences in sodicity tolerance of the cultivars of geranium tested in this experiment. The concentration of zinc (Zn) in shoot tissues decreased with increase in soil ESP. The cv Bourbon maintained a higher concentration of Zn in shoot tissues at high sodicity than that of cv Cimpawan. The results suggest that the geranium is slightly to moderately tolerant of soil sodicity stress.