Rose-scented geranium (Pelargonium capitatum Â P. radens) growth and essential
oil yield response to different soil water depletion regimes
B.K. Eiasu, J.M. Steyn
, P. Soundy
Department of Plant Production and Soil Science, University of Pretoria, Pretoria 0002, South Africa
Irrigation is a major contributor to agricultural productivity.
Irrigation increases land productivity by about 127%, and is
expected to supply half of the world’s food demand by the year
2025 (Fereres and Cen
a, 1998; Qadir and Oster, 2004). Variable soil
water status results in variable production, depending on the
duration of the water stress and the plant growth stage (Pandey
et al., 2000).
South Africa is a drought prone (mostly semi-arid) country
with variable climate (Shand and Basson, 2003). Most of the
fresh water resources of the country (about 60%) are used for
irrigation (Conley, 1997; Enright, 2003). Since irrigation
productivity is relatively low, it is suggested that part of the
water used in agriculture be transferred to other non-agricul-
tural economic sectors to maximize water productivity (Nieu-
woudt et al., 2003). Such a shift in the allocation of water
resources may impose further restrictions on agricultural
business, unless innovative irrigation management for each
and every crop is introduced.
Rose-scented geranium (Pelargonium species) is a perennial
herb that belongs to the Geraniaceae family. The plant is cultivated
for its high value essential oil, which is used for production of high-
grade perfumery, cosmetic products and for aromatherapy
(Rajeswara Rao et al., 1996). Worldwide, annual geranium oil
production is estimated to be worth about 12.5 million US dollars
(Williams and Harborne, 2002). Trade in essential oils is expected
to increase in the future as a result of the growing number and
preferences of consumers, and the continuously widening uses of
essential oil constituents (Sangwan et al., 2001).
Studies on response of rose-scented geranium essential oils to
soil water have come up with different results. Rajeswara Rao et al.
(1996) reported that moist seasons resulted in higher essential oil
yield. A report by Singh (1999) indicated that a soil water regime of
0.6 IW to CPE (irrigation water to cumulative pan evaporation)
ratio gave higher essential oil yield without a signiﬁcant change in
oil composition. Weiss (1997), on the other hand, reported that
water stressed conditions resulted in a mild increase in oil yield.
Results obtained from greenhouse pot experiments by Eiasu et al.
(2008) also showed that high irrigation frequency plus a one-week
withholding of irrigation prior to harvesting increased essential oil
In South Africa, rose-scented geranium is produced in the
Mpumalanga Lowveld, KwaZulu-Natal, Western Cape and Lim-
Agricultural Water Management 96 (2009) 991–1000
Received 25 May 2008
Accepted 22 January 2009
Available online 23 February 2009
Essential oil composition
Fresh herbage mass
Maximum allowable depletion level
Plant available soil water
Effective irrigation management in arid and semi-arid regions, like South Africa, could increase crop
yield and thereby improve productivity of scarce fresh water resources. Experiments were conducted at
the Hatﬁeld Experimental Farm of the University of Pretoria, South Africa, from 2004 to 2006, to
investigate the effect of soil water depletion regimes on rose-scented geranium (Pelargonium
capitatum Â P. radens cv. Rose) essential oil yield, essential oil composition and water-use efﬁciency
in an open ﬁeld and a rain shelter. Four maximum allowable soil water depletion levels (MAD), 20, 40, 60
and 80% of the plant available soil water (ASW) in the top 0.8 m root zone, were applied as treatments.
Plant roots extracted most soil water from the top 0.4 m soil layer. Increasing the soil water depletion
level to 60% and higher resulted in a signiﬁcant reduction in herbage mass and essential oil yield. Water
stress apparently increased the essential oil concentration (percentage oil on fresh herbage mass basis),
but its contribution to total essential oil yield (kg/ha oil) was limited. Irrigation treatments did not affect
essential oil composition. An increase in maximum allowable depletion level generally resulted in a
decrease in leaf area and an increase in leaf to stem fresh mass ratio. Up to 28% of irrigation water could
be saved by increasing maximum allowable depletion level of ASW from 20 to 40%, without a signiﬁcant
reduction in essential oil yield.
ß 2009 Elsevier B.V. All rights reserved.
* Corresponding author. Tel.: +27 124203880; fax: +27 124204120.
E-mail address: firstname.lastname@example.org (J.M. Steyn).
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