Water use efficiency of tall fescue (Festuca arundinacea Schreb.) and
perennial ryegrass (Lolium perenne L.) under different management
intensity
Pardeller M.1,2, Schäufele R.2, Pramsohler M.1 and Peratoner G.1
1
Research Centre for Agriculture and Forestry Laimburg, I-39040 Auer, Italy.
2
Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, D-85350
Freising-Weihenstephan, Germany.
Corresponding author: [email protected]
Abstract
Drought periods have been repeatedly observed in the last decade in the southern margin of the
Alps. An adequate choice of drought-tolerant forage species and cultivars is of pivotal
importance in tackling this challenge. Tall fescue (Festuca arundinacea Schreb.) and perennial
ryegrass (Lolium perenne L.) are regarded as having contrasting levels of drought tolerance,
but less is known about their intrinsic water use efficiency (Wi). To this end, analyses of the
Carbon isotope composition of leaf material were performed on these species (one cultivar of
perennial ryegrass, and two cultivars of tall fescue differing in leaf roughness) in the course of
a field trial aiming at the optimization of seed mixtures for permanent meadows in droughtendangered areas under different management intensities and at two altitude ranges. W i was
found to be mainly affected by both genotype and altitude, with tall fescue showing higher Wi
than perennial ryegrass.
Keywords: drought, Festuca arundinacea, Lolium perenne, intrinsic water-use efficiency
Introduction
Drought periods were repeatedly observed in the last decade in the southern margin of the Alps.
The use of forage species and cultivars able to tolerate drought and efficiently use the water
available from precipitation and irrigation represents an important issue for tackling this
challenge. Perennial ryegrass (Lolium perenne L.) is considered to be well adapted to intensive
management and to produce high-quality forage, but is also known to require adequate water
availability, whereas tall fescue (Festuca arundinacea Schreb.) is regarded as a droughttolerant grass with good yield potential, but with rapidly declining forage quality (Dietl et al.,
1998). Carbon isotope discrimination and water use efficiency are highly (negatively)
correlated because both are affected by the relationship between photosynthesis and stomatal
conductance. Hence, analysis of carbon isotope composition is a suitable tool to investigate
intrinsic water use efficiency (Wi) in grassland. However, to our knowledge, no information at
a species level is known for these grasses. For this reason, specific measurements were
undertaken in the course of a field study in order to gain knowledge of Wi of tall fescue and
perennial ryegrass. Specifically, the study tested whether the known difference in drought
tolerance between the two species is related to a difference in W i and whether differences in
Wi are maintained in different environments, here at two altitudes and with different
management intensities.
Materials and methods
Leaf material of tall fescue and perennial ryegrass was obtained from a field trial established
three years before at two experimental sites (Table 1) and aiming at optimizing a seed mixture,
containing both perennial ryegrass and tall fescue, for permanent mountain meadows at
drought-endangered, non-irrigated locations. Three factors were studied in this experiment:
seed mixture (Fa40 and Fa60, containing the same species, but 40% and 60% seed weight of
tall fescue respectively), management intensity (low: 2 cuts year-1 coupled to a fertilization
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level equal to 2 livestock units ha-1; high: 3 cuts year-1 coupled to a fertilization level equal to
2.5 livestock units ha-1) and the experimental site (low altitude: San Genesio/Jenesien 835 m
a.s.l.; high altitude: Falzes/Pfalzen 1205 m a.s.l.). The experimental design is a Latin rectangle
with 3 replications and a plot size of 4 × 4 m.
Table 1. Description of the experimental sites San Genesio/Jenesien and Falzes/Pfalzen.
Experimental site
Location
Geographic coordinates
Altitude
(m a.s.l.)
Slope
(%)
Aspect
Low altitude
San Genesio/Jenesien
46° 31' 25" N 11° 20' 22" E
835
26
S
High altitude
Falzes/Pfalzen
46° 49' 18" N 11° 53' 42" E
1205
31
S
Within each plot, three genotypes were sampled: a cultivar of perennial ryegrass (Ivana), a
rough-leafed cultivar of tall fescue (Kora) and a soft-leafed cultivar of tall fescue (Barolex).
Two different cultivars of tall fescue with contrasting leaf roughness (and equally abundant in
the seed mixtures) were included in the study because differences in competitive ability, yield
potential and some parameters of forage quality have been previously shown to be related to
the leaf roughness of tall fescue (Peratoner et al., 2010). On 28 and 29 August 2013 samples
were taken at the high altitude and at the low altitude site, respectively. Each sample consisted
of the youngest fully expanded leaf of 10 randomly selected plants per species and plot. The
samples were oven-dried for 2 days at 60 °C and milled using a mortar mill (model RM 200,
Retch, Haan, D). The samples were subsequently dried for 24 h at 40 °C, then amounts of 0.7
± 0.05 mg were weighed into zinc cups and burned in an elemental analyzer (NA 1110, Carlo
Erba, Milan, Italy) coupled to an isotope mass spectrometer (Delta Plus, Finnigan MAT,
Bremen, D). As a control, a standard was measured with a known C/N ratio after every tenth
sample. 13C:12C ratios of samples were used to compute Wi according to Köhler et al. (2010).
Statistical data analysis was performed by means of a mixed model taking into account the
genotype, the seed mixture, the management intensity and the design factors (lines and
columns) as fixed factors. The genotype was considered to be a repeated factor with the plot as
a subject. Post hoc comparisons were performed by Sidak test. A probability of P<0.05 was
regarded as significant.
Results and discussion
Wi was found to be significantly affected by the genotype, the experimental site (both P<0.001)
and also by their interaction (P<0.01). Tall fescue was found to have higher water use
efficiency than perennial ryegrass at both sites, with the cultivar Barolex showing intermediate
values between Kora and Ivana at the low altitude site (Table 2). This confirms field
observations of better drought tolerance of tall fescue in comparison with perennial ryegrass,
and contributes to explain these different attributes 13C was consistently lower at high
altitude (i.e. carbon isotope discrimination was consistently higher at high altitude). This is in
contrast with other findings which have shown a decrease of carbon isotope discrimination
with altitude (e.g. Körner et al., 1988; Männel et al., 2007). However, these studies analysed
different species at each altitude. Here, the same plant species were sampled, and thus, the
observed change in Wi with altitude indicate the species response to a decrease in vapour
pressure deficit. The altitudinal effect on Wi was stronger in perennial ryegrass than in both tall
fescue cultivars. Again, this indicates a better adaption of tall fescue to conditions of high water
demand.
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Table 2. Intrinsic water use efficiency (μmol mol-1) depending on genotype and management intensity at two
contrasting altitudes. Means without upper case letters in common within each genotype and means without lower
case letters in common within each experimental site significantly differ from each other.
Experimental
site
Genotype
(species, cultivar)
perennial ryegrass
cv. Ivana
tall fescue
cv. Barolex
Management intensity
tall fescue
cv. Kora
low
high
Low altitude
85.6
Ab
88.6 Aab
92.4 Aa
90.3 Aa
87.4 Aa
High altitude
61.7 Bb
77.7 Ba
80.4 Ba
71.4 Ba
75.2 Ba
A further significant interaction was observed between experimental site and management
intensity (P<0.05). Nutrient supply has indeed been demonstrated to affect Wi in grassland
(Köhler et al., 2012). However, while altitude effects on Wi were consistent with those already
observed at the interaction genotype × experimental site, no significant difference depending
on management intensity could be statistically detected by the post hoc test (Table 2). Another
significant interaction was found between seed mixture and management intensity (P<0.05).
The only significant difference was found at low management intensity, with the Wi of plots
sown with Fa40 being higher than in the plots sown with Fa60 (83.4 μmol mol-1 and 78.4 μmol
mol-1 respectively). Nutrient supply and differences in species composition have indeed been
demonstrated to affect Wi in grassland (Köhler et al., 2012). However, the explanation of these
effects deserves further experimental work.
Conclusion
The present findings show that the higher drought tolerance of tall fescue relative to perennial
ryegrass is related to a higher intrinsic water use efficiency. The species differences in W i are
consistent in environments differing in vapour pressure deficit.
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