© Benaki Phytopathological Institute
Competitiveness of alfalfa cultivars against silverleaf nightshade
45
ability to suppress weed growth (Peters and
Linscott 1988) and appears to exert a long-
term effect on weed population dynamics
(Ominski
et al
., 1999). Several weeds are ex-
pected to be effectively suppressed by
M.
sativa
, and thus including alfalfa in crop ro-
tations regime can be part of an integrat-
ed weed management strategy for weeds
such as
Avena fatua
,
Brassica kaber
,
Cirsium
arvense, Rumex crispus
,
Amaranthus quitensis
(Ominski et al. 1999; Huarte and Benech Ar-
nold, 2003).
The inverse linear relationship (R
2
be-
tween 0.72 and 0.83) between alfalfa forage
yield and
S. elaeagnifolium
biomass found in
this study (Fig. 1) suggests that maintaining
a high crop biomass is important to avoid
the invasion of the silverleaf nightshade and
this is in full accordance with previous stud-
ies showing a similar relationship between
alfalfa and weeds (Grewal, 2010). Moreover,
it could be said that the greater suppression
of silverleaf nightshade in the case of Hyliki
was partly due to the high productivity of
this specific cultivar as previously shown in
the weed-free situation in Table 3.
In moderate to severe weed infestations,
alfalfa yield can be reduced through compe-
tition for light, water, and nutrients and the
forage quality can be lowered by decrease
Table 4.
Density of
Solanum elaeagnifolium
plants in plots of three alfalfa cultivars (Gea,
Dimitra, Hyliki) in a two-year experimental field (2010, 2011). Each number represents the
mean number of weed plants for an alfalfa cultivar per cutting or the total mean number of
weed plants for each cultivar in 2010. In parentheses the corresponding values for 2011 are
also shown.
Density of
S. elaeagnifolium
(plants/m
2
)
Cuttings
Gea
Dimitra
Hyliki
65 DAT
2.2 (3.1) a
1.2 (2.1) b
1.3 (2.1) b
100 DAT
5.3 (7.2) c
2 (3.6) d
2.2 (3.4) d
145 DAT
7.1 (7.4) e
5.2 (4.5) e
3 (3.1) f
210 DAT
3.4 (4.1) g
3.3 (5.4) g
1.2 (2.1) h
Mean
4.5 (5.45) i
2.9 (3.9) ij
1.9 (2.7) j
Means within a row followed by the same letter are not significantly different (p < 0.05) according to Fischer’s LSD
test.
Table 5.
Biomass of
Solanum elaeagnifolium
plants (fresh weight in g/plant) in plots of three
alfalfa cultivars (Gea, Dimitra, Hyliki) in a two-year experimental field (2010, 2011). Each num-
ber represents the mean fresh weight of weeds for a cultivar per cutting in both experimen-
tal years or the total mean fresh weight of weeds for each cultivar.
Fresh weight of
S. elaeagnifolium
(g/plant)
Cuttings
Gea
Dimitra
Hyliki
65 DAT
2.3 a
2.6 a
2.4 a
100 DAT
9.8 b
6.4 c
5.2 c
145 DAT
12.4 d
8.4 e
4.8 f
210 DAT
11.9 g
8.6 g
2.2 h
Mean
9.1 i
6.5 j
3.7 k
Means within a row followed by the same letter are not significantly different (
p
< 0.05) according to Fischer’s LSD
test.
1...,37,38,39,40,41,42,43,44,45,46 48,49,50,51,52