Effect of plant spacing and harvesting age on growth, biomass and oil yield of rose-scented geranium (Pelargonium graveolens L. Herit‪)‬

In order to investigate the effect of plant spacing and harvesting age on growth, biomass and oil yield of rose-scented geranium; a study was carried out at the research field of Wondo Genet Agricultural Research Center in the 2013/14 cropping season. The study was a 4 x 5 factorial combination based on randomized complete block design (RCBD) with three replications. The experiment was consisted of four levels of plant spacing (30 x 30, 30 x 40, 30 x 50 and 30 x 60 cm, which result in 111111, 83333, 66666 and 55555 plants/ha, respectively) and five levels of harvesting age (90, 105, 120, 135 and 150 days after transplanting (DAT)). Main effects of plant spacing and harvesting age significantly influenced plant height, number of internodes, internodes length, leaf area and dry leaf weight/plant. While interaction effect of the two factors significantly influenced number of branches/plant, number of leaves/plant, leaf area index, fresh leaf weight/plant, aboveground biomass/ha, fresh leaf yield/ha, dry leaf yield/ha, dry stem yield/ha, harvest index, essential oil content and essential oil yield/ha. The finding revealed that higher number of branches and leaves were recorded at 30 x 60 cm spacing combined with 90 and 135 DAT and higher leaf area, dry leaf weight and fresh leaf weight were recorded at 30 x 60 cm along with 120, 135 and 120 DAT, respectively. At 30 x 30 cm spacing combined with 150, 120 and 150 DAT, highest plant height, leaf area index and number of internodes were obtained; while, the highest aboveground biomass, fresh leaf yield, dry stem yield and dry leaf yield were produced at 30 x 30 cm spacing with 120, 135, 150 and 135 DAT, respectively. Significantly higher essential oil content and harvest index were produced at the treatment combination of 30 x 40 cm spacing when harvested at 90 DAT. On the other hand, the essential oil yield (21.01kg/ha) at 30 x 30 cm plant spacing when harvested at 135 DAT was relatively higher than those of all treatment combinations, which, however it did not statistically different with that of 30 x 30 cm combined with 120 DAT (20.87 kg/ha). In total, it can be recommended to use 30 x 30 cm spacing level with harvesting age of 120 to 135 DAT for essential oil yield production at Wondo Genet area.