Page 44 - Volume 6, Issue 1, January 2013

© Benaki Phytopathological Institute
Travlos et al. 42
(Boyd et al., 1984) and is a deep-rooted, per-
ennial, broadleaf weed that propagates by
seed, root segments, and creeping lateral
roots (Cuthbertson et al., 1976). Moreover, S.
elaeagnifolium is now considered as a nox-
ious and invasive alien weed, against which
international measures have to be taken in
many areas (OEPP/EPPO, 2004).
Quantitative information regarding the
potential suppressive effect of alfalfa culti-
vars on weeds in current cropping systems
is rather lacking. Therefore, the objectives of
this study were to evaluate the differences
among three alfalfa cultivars (Gea, Dimitra
and Hyliki) regarding their competitiveness
against the noxious weed S. elaeagnifolium
and their productivity (forage yield) during
the first year of crop establishment.
Materials and Methods
A field experiment was conducted during
2010 (and repeated in 2011) in the exper-
imental field of Agricultural University of
Athens (37ο 59’ 12’’ N, 23ο 42’ 96’’ E, 29 m alti-
tude) in order to study the competitive abili-
ty of three alfalfa cultivars (Gea, Dimitra and
Hyliki) against silverleaf nightshade.
The soil was clay loam (Bouyoucos, 1962),
with pH 7.29 (1:1 H2O), 15 g/kg organic mat-
ter (Wakley and Black, 1934) and 160 g/kg
CaCO3. Hand-sowing took place at the rate
of 20 kg/haon 28 March, 2010 and 23 March,
2011. The field was fertilized with P2O 5 and
K 2O as recommended by soil analysis for
alfalfa (Hall, 2008). Alfalfa crop was mown
each time it reached 10% bloom. This result-
ed in four harvests each year at 65, 100, 145
and 210 days after sowing (DAS). Rhizomes
of S. elaeagnifolium (5-6 cm in length) were
uniformly planted horizontally (12-15 g/m2
in a depth of 4-5 cm), while other weed spe-
cies emerged within the experimental area
were removed by hand-hoeing.
The experimental design was a split-plot
in a randomized complete block with four
blocks (replicates). Alfalfa cultivar was the
main plot factor and the weed presence (or
absence) was the subplot factor. Main plot
and subplot sizes were 6 by 4 m and 2.5 by 4
m, respectively.
Irrigation and other common cultural
practices were conducted as needed during
the growing seasons. Mean monthly tem-
perature and rainfall data are given in Ta-
ble 1. In each cutting, forage yield was mea-
sured, while the total first-year cumulative
yield was also recorded. The dry weight of
forage was determined after oven drying at
70oC for 48 h. In the same days (65, 100, 145
and 210 DAS) measurements of the density
and biomass of silverleaf nightshade were
also taken. Visual estimation of regrowth
ability of each cultivar was also conduct-
ed 15 days after each harvest (cutting) by
means of a scale, comparing the most vig-
orous stands (high and dense, scored as 5)
with the lowest and fewer plants (scored as
1).
An analysis of variance (ANOVA) was
conducted for all data and differences be-
tween means were compared at the 5%
level of significance using the Fisher’s Pro-
tected LSD test. Linear regression was also
performed for the three cultivars relating
the forage yield and silverleaf nightshade
biomass. All statistical analyses were con-
ducted using the Statistica 9 software pack-
age (StatSoft, Inc. 2300 East 14th Street, Tul-
sa, OK 74104, USA).
Results and Discussion
The analysis of variance of our data revealed
that alfalfa forage yield and silverleaf night-
shade growth (density and biomass produc-
tion) were significantly affected by the al-
falfa cultivar and the presence or absence
of the weed. The year was also a significant
factor for the forage yield of the crop and
for the density of S. elaeagnifolium plants,
while it had no significant effect on the fresh
weight of the weed. Moreover, the interac-
tion between the above-mentioned factors
was significant for most parameters except
the biomass of silverleaf nightshade on indi-
vidual plant’s level (Table 2).
In particular, the harmful effects of silver-