Íslenskar landbúnaðarrannsóknir - 01.09.1977, Page 43

THE INOCULATION OF WHITE CLOVER 4l
TABLE 1. CHEMICAL ANALYSIS OF SOIL SAMPLES TAKEN FROM THE
EXPERIMENTAL PLOTS
Mg Ca K P pH
meq/ meq/ meq/ mg/
Treatment 100 g soil 100 g soil 100 g soil 100 g soil
Pellets................. 24.8 8.8 0.64 1.24 5.75
Highlime........ 31.2 30.1 0.76 1.49 6.85
Nolime ................. 30.8 9.5 0.64 0.99 5.85
ectiveness estimated by measuring the dry
weight of the plants.
Experiment 2.
After the preliminary laboratory study of the
effectiveness of Rhizobium strains (Expt. 1),
a field inoculation experiment was set up
to test the effectiveness of four selected
Rhizobium strains in conjunction with two
white clover varieties.
The experiment was conducted on a newly
ploughed field at Korpa near Reykjavík.
Phosphate was applied at 300 kg/ha and
potash was applied at 200 kg/ha as a basal
dressing. The plot size was lxl m and each
treatment was replicated four times in a rando-
mized block design. The following treat-
ments were used:
1. White clover varieties:
a) Aberystwyth SI84,
b) Pajbjerg smalbladet,
2. Lime treatments:
a) lime pellets,
b) lime dressing (7.5 ton/ha),
c) control, no lime,
3. Inoculation treatments:
a) strain 75 (from U. K., Rothamsted
collection),
b) strain 83 (from Sweden, 319,2009),
c) strain 33 (from Iceland),
d) strain 38 (from Iceland),
e) control, uninoculated.
The varieties, lime and inoculation treatments
were tested in all combinations. The experi-
ment was sown on the lOth of June 1976.
Inoculum was prepared by suspending the
strains of R. trifolri in skim milk. Pelleting
was carried out as described by JoNES and
Thomas (1966).
The numbers of Rhizobium bacteria on
unpelleted seeds and in the pellets were
measured with the most probable number
(M.P.N.) method (Vincent, 1970). The
mean number of bacteria on the unpelleted,
inoculated seeds at the time of sowing was
4.8xl05 per seed, wheras the mean number
in the inoculated pellets was 7.5xl04.
Soil samples for analysis were taken from
the plots at harvest time and the results are
shown in Table 1.
The experiment was harvested on the 3 lst
August, 1976. The dry weight of 15 plants
from each plot was measured and numbers of
nodules on 5 plants recorded.
RESULTS
Experiment 1.
The symbiotic characteristics of the Rhizob-
ium strains are shown in Table 2. Analysis
of variance for the shoot dry weight is summ-
arised in Table 3. There was found to be
highly significant differences between strains
(P<0.001). This was mainly due to differenc-
es within the Icelandic strains (P<0.001)