Growth and essential oil yield of rose‐scented geranium (Pelargonium capitatum × P. radens ‘Rose’) as affected by withholding irrigation at different times during regrowth

Abstract

Response of plant growth and essential oil yield of rose‐scented geranium (Pelargonium capitatum × P. radens ’Rose') to withholding irrigation at different times of regrowth cycles was investigated at Hatfield Experimental Farm of the University of Pretoria, South Africa, from 2004 to 2007. No‐stress (control), and 1‐month withholding irrigation periods during the 2nd, 3rd, or 4th month of regrowth were applied as treatments. Herbage yield showed a significant reduction when the water stress period was imposed during the 3rd or 4th month of regrowth. A remarkable essential oil yield loss was observed only when the plants were stressed during the 4th month of regrowth. Essential oil content (% oil on fresh herbage mass basis) apparently increased in the stressed treatments, but total oil yield dropped as a result of lower herbage mass. Essential oil composition changes in response to irrigation withholding treatments were not consistent. Water‐use efficiency was not significantly affected by withholding irrigation in the 2nd or 3rd month of regrowth. With a marginal oil yield loss, c. 330–460 m3 of water/ha per regrowth cycle could be saved by withholding irrigation during the 3rd month of the regrowth cycles. The overall results highlighted that, in water scarce regions, withholding irrigation during either the 2nd or 3rd month of regrowth could improve water productivity in rose‐scented geranium.