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Recent findings from a Manitoba study stress
the importance of successful nodulation of soybeans with Rhizobium
bacteria on virgin ground (i.e. never having grown soybeans
before). Soybeans and their rhizobium are not native to North
America, and rhizobium inoculant must be used when soybeans are
introduced.
Dr. Dave McAndrew, Agriculture and Agri-Food
Canada Morden, conducted studies of inoculant performance and seed
treatment compatibility between 1998 and 2000 at 2 sites per year.
Three varieties, Korada, Pioneer 9004 and Glacier were evaluated.
The major findings were:
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At 2 sites there was no advantage to
inoculation, since soybeans nodulated even in the check plots.
Inoculated soybeans had been sown in the same plots some 15 and 29
years previously. It is apparent that once introduced, rhizobium
inoculant does survive under Manitoba conditions for extended
periods of time.
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On virgin fields, yields were maximized through
use of granular inoculant.
|
Inoculant Type |
Rate |
Nodules/
Plant |
Yield bu/ac |
Protein % |
|
Nitragin Soil Implant
(granular) |
24 kg/ha |
62 a* |
39 a* |
39.9 a* |
|
Nitragin Cell-tech
2000 (liquid) |
75 ml/27 kg seed |
29 b |
31 c |
36.2 c |
|
MicroBio RhizoGen
Adhere (peat based) |
400g/150 kg seed |
18 c |
31 c |
35.6 d |
|
HiStick MicroBio
(peat based) |
400 g/125 kg seed |
27 b |
34 b |
37.1 b |
|
none |
|
5 d |
26 d |
33.9 e |
* means in the column followed
by the same letter are not significantly different.
Well nodulated plants also tended to be taller and had larger seed
size. Less nodulated plants ripened prematurely.
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Seed
treatments containing insecticides reduced nodulation when peat
inoculant was used.
|
Inoculant Type |
Emergence/m2 |
Nodules/plant |
Yield bu/ac |
Protein % |
|
Nitragin Soil Implant
(granular)
Nitragin cell-tech
2000 (liquid) |
|
93 a*
59 b |
45 a*
39 b |
40.6 a*
37.8 b |
|
Seed treatment
combination |
|
|
|
|
|
Vitaflo (carbathiin
and thiram)
Apron (metalaxyl)
Agrox B-3 (captan,
diazinon and lindane)
none |
33 b
34 a
33 ab
30 c |
71 b
78 ab
68 b
88 a |
41 b
43 a
40 c
43 a |
38.8 c
39.5 b
38.7 c
39.8 a |
* means
in the column followed by the same letter are not significantly
different.
All fungicide seed treatments increased stands
slightly. However, Agrox B-3 seed treatment also contains diazinon
and lindane for control of seedcorn maggot and wireworm,
respectively, and this treatment tended to reduce nodulation with
the peat inoculant. The granular inoculant performed well
regardless of seed treatments. Should either of these insect pests
have been problems, this treatment may well have produced superior
stands and yield.
Summary:
Nodulation of soybeans with rhizobium bacteria is
critical on virgin soybean ground. The most reliable, highest
yielding treatment has been granular inoculant. This treatment also
avoids any toxicity when seed treatments are used.
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