Íslenskar landbúnaðarrannsóknir - 01.03.1979, Page 52

50 ÍSLENZKAR LANDBÚNAÐARRANNSÓKNIR
rogen fertilizers is to use legumes, which
have the ability to fix nitrogen biologic-
ally.
Blue lupin (Lupinus nootkatensis Donn.),
introduced to Iceland from Alaska in 1945
has limited distribution in Iceland. Its
dispersal seems to be limited by lack of
suitable Rhizobium bacteria in the soil,
since sowing seeds without inoculation
rarely produces mature plants. On the
other hand, this species can easily be
grown where it has been introduced by
planting whole plants already nodulated.
Where lupin has established in Iceland it
seems to tolerate the cold environmental
conditions and produces ripe seeds. It se-
ems not to be very demanding in terms of
soil conditions, being able to establish in
gravel, sand or other soils. It might there-
fore be of potential value as a pioneer crop
in reclamation. With this in view, the
present investigation was initiated to
evaluate the effect ofinoculation ofLupinus
nootkatensis with Rhizobium lupini under
field conditions in Iceland.
MATERIALS AND METHODS
Symbiotic characteristics of three strains of R.
lupini
Symbiotic properties of three R. lupini st-
rains (3211 and 3210 from the Rotham-
sted Collection of Rhizobium and 90 from
Iceland) were tested in symbiosis with Ic-
elandic population of Lupinus nootkatensis.
The éxperiment was conducted in ster-
ile sand, the chemical composition of
which was: pH: 7.0; phosphorus: 4 mg/1;
potassium: 7 mg/1; magnesium: 9 mg/1
and nitrate nitrogen: 3 mg/1. Pregermin-
ated seedlings, grown from surface steril-
ized seeds of Lupinus nootkatensis were
transplanted singly into 14 cm pots. Each
treatment was replicated 20 times and all
the pots randomised. At the time of
planting each pot was inoculated with 10
ml of appropriate bacterial solution con-
taining ca. 5 X 107 bacteria/ml. Quarter
strength Jensen’s solution (JENSEN, 1942)
containing trace elements (Gibson, 1963)
was added to the saucer of each pot and
from time to time during the experiment,
the level of this solution was maintained
by further addition of this solution with-
out any bacteria. The experiment was car-
ried out at 12°C in a controlled environ-
mental room at Aberystwyth giving 16
hours a day. It was harvested after 12
weeks when the numbers of nodules on the
roots were counted and scored for size
(Table 1) and the yield measured by
weighing the air dried plants.
Table 1.
Nodule assessment key.
Score Nodule size (mm)
5 >10
4 8-10
3 05 1 00
2 4- 6
1 2- 4
0 < 2
Inoculation field trials in Iceland
The experiments were conducted in the
following localities in Iceland: Keldna-
holt, Gunnarsholt, Skógarsandur, Búrfell
and Sigalda. To facilitate this study 7 in-
oculation treatments were used:
A) Uninoculated control,
B) Inoculant applied at the time of
sowing: