Íslenskar landbúnaðarrannsóknir - 01.03.1979, Qupperneq 54

52 ÍSLENZKAR LANDBÚNAÐARRANNSÓKNIR
Table 3. Nodule numbers and dry weight of lupin plants in inoculation field trials in Iceland (after 12 weeks).
Nodule numbers (mean/pl; Site ant) no ino- culation Inoculation at the time of sowing Inoculation 5 weeks after sowing Means
Icelandic inoculant 3211 Ultuna Icelandic inoculant 3211 Ultuna
Gunnarsholt . . 0.8 1.8 10.8 4.1 4.6 10.2 4.1 5.20
Skógarsandur . . 0.6 2.0 10.2 3.8 9.1 8.3 9.8 6.25
Keldnaholt . . 0.0 1.4 4.6 0.5 5.5 5.9 3.5 3.06
Means . . 0.47 1.73 8.53 2.80 6.40 8.13 5.80
D* 0.05 = 3.42 D 0.01 = 4.08
Dry weight (mg/plant)
Gunnarsholt . . 79 157 246 142 107 134 99 137
Skógarsandur . . 164 148 305 152 232 179 167 192
Keldnaholt . . 22 30 113 24 46 57 24 45
Means . . 88.3 111.7 221.3 106.0 128.3 123.3 96.7
D. 0.05 = 106.4 D 0.01 = 126.8
D* = significant differences calculated from „Q“ in the Studentized range.
There were also significant diíl'erences in
nodule numbers between sites (P<0.001)
with the mean numbers of nodules being
highest at Skógarsandur (6.2) and lowest
at Keldnaholt (3.1). The bacterial strain x
site interaction was significant (P<0.001)
mainly due to the relatively good nodul-
ation by the Icelandic inoculant and that
from Ultuna applied 5 weeks after sowing
at Skógarsandur.
The yield of lupin plants in the inocul-
ation field trials are also summarised in
Table 3. There were highly significant
differences between inoculation treat-
ments (P<0.001) with 3211 applied at the
time of sowing being most successful.
There was also a significant difference
between sites (P<0.001) with the mean
dry weight/plant being highest at Skóg-
arsandur (192 mg) and lowest at Kelna-
holt (45 mg). The bacterial x site interac-
tion was significant (P<0.05) due mainly
to the relatively good performance of all
inoculants applied at the time of sowing at
Gunnarsholt.
DISCUSSION
A soil may be lacking in effective Rhizobi-
um bacteria of the appropriate crossinoc-
ulation group for a specific legume when it
is introduced into an area for the first time.
The lack of suitable nodule bacteria is
clearly demonstroted in the present in-
vestigation where blue lupin, which has
only recently been introduced to Iceland,
shows considerable improvement in yield
and nodule number when inoculated with
an effective strain ofR. lupini. The average
yield of the lupin plants was nearly 3 times