Michigan State University Extension
Michigan Soybean Information - FACT9708
11/16/00
Soybean Inoculation In Michigan
Michigan State University Extension
This research and fact sheet funded by Michigan
Soybean Promotion Committee Making Your Checkoff Pay Off
Soybean Facts Winter 1997
M. L. Vitosh
Department of Crop and Soil Sciences
Michigan State University
INTRODUCTION
Currently there is a lot of interest in soybean seed
inoculation. There are several new companies and
products that have entered the marketplace and have
created a renewed interest in seed inoculation even
on fields that have a history of soybean production.
Some of the new inoculants have claims for higher
potency, new and better strains of "Rhizobium",
higher numbers of "Rhizobium" per gram of material,
sterilized peat media, seed sticker additions and
etc. Several companies are paying more attention to
storage and handling of these materials to increase
effectiveness. There is also limited evidence that
these materials may be slightly better than the old
inoculants even when used in old soybean fields.
Urbana Laboratories have an exclusive license to
produce and sell a patented "Bradyrhizobium
japonicum" strain. In 1993, university trials in the
Midwest showed a positive response in 11 of 16 field
trials. Yield increases were small but ranged from
1-5 bushels with this new strain of inoculum when
tested on traditional soybean ground. Another reason
for renewed interest in soybean inoculants is due to
increased acreage of no-till soybeans. Concerns are
that the heavy residues, higher soil moisture
content and cooler soil temperatures may hinder
efficient soybean inoculation.
As a result of this renewed interest, Michigan State
University has conducted a number of research trials
along with replicated on-farm trials to evaluate these
products. This fact sheet presents the data and provides
guidelines for soybean growers who are interested in
soybean inoculation products.
RESULTS AND DISCUSSION
University Research Trials
Six research experiments were conducted at the Michigan
State University's research farm at East Lansing between
1993 and 1996. All of these trials were on land that had
a previous history of soybean production. The two studies
in 1996 were on land that had only grown soybeans once
prior to the study. Soybeans in this field were
inoculated for the first time in 1994. Corn was the
previous crop for all of the inoculation studies. The
yield results for each of these experiments are shown in
Table 1.
None of the inoculants studied in these trials
resulted in a significant soybean yield increase
when compared to the uninoculated control plots.
Even when experiments were combined, there were no
yield advantages due to inoculation. Soybeans
inoculated with the two Urbana treatments in the
1995 in the conventional tillage study appeared to
out-yield the uninoculated control plots but in an
adjacent no-till study soybeans treated with these
same products were no better than the control.
Replicated On-Farm Trials Twelve Michigan on-farm
trials were conducted between 1990 and 1995 across
the state. Four of these trials were in fields that
did not have a history of soybean production. Nine
trials were on ground that had a history of soybeans
but not the year before the study. Most of the
trials were conducted in a no-till production
system. All trials were planted in strips the entire
length of the field and replicated from four to six
times. The yield information for these trials is
presented in Table 2.
Three of the four fields which were new to soybeans
responded to the soybean seed inoculant treatments.
Only the Saginaw site in 1991 did not respond.
Soybeans in the control plot at this site were well
nodulated a few weeks after plant emergence which
indicates that the field contained indigenous
"Bradyrhizobium" inoculum prior to planting. This
field had a history of dry beans and sugar beets and
may have received the soybean rhizobia from other
fields due to previous flooding in the Saginaw
valley. Yield increases for the other three
locations ranged from 9 to 16 bushels per acre.
Of those fields that had a previous history of
soybean production, there was a significant yield
increase in only one trial (Sanilac 1990). All other
trials showed no significant response to seed
inoculation treatments. The average difference
between uninoculated and inoculated treatments for
these trials was 0.1 bushels per acre.
North Central On-Farm No-Till Soybean Research
Trials
Soybean inoculation trials have been conducted by
state university researchers throughout the North
Central Region for the last several years. Many of
these trials are part of a North Central No-Till
Soybean Research Project. In 1994 there were fifteen
seed inoculation comparisons made in five states.
Five of these trials were conducted in Michigan (see
Table 2). In 12 of the 15 on-farm trials,
seed inoculation failed to increase soybean yields.
Two of the three responsive sites were in Michigan.
These two sites in Ionia County did not have a
history of soybean production.
In 1995 there were 16 inoculation trials in five
states. Three of these trials were conducted in
Michigan. Seed inoculation failed to increase yields
in 13 of the 16 trials.
None of the sites in Michigan responded to the
inoculation treatments. One site at Paw Paw,
Illinois responded with a small yield increase from
three different inoculation products. At another
site near Simpson, Illinois, a significant yield
response was obtained with the Urbana USDA product
but not to other inoculants. Additional no-till
on-farm inoculation trials were conducted in 1996
but the data were not available as of this writing.
SUMMARY AND CONCLUSIONS
These data suggest that soybean seed inoculation
with "Bradyrhizablum" is only beneficial when
soybeans are planted on new soybean ground (ground
that has never grown soybeans). When native soil
"Bradyrhizobium" inoculum was present, soybeans did
not significantly respond to seed treatment with
"Bradyrhizobium". We have evaluated Hi-Stick,
Nitragin, Urbana and Sow-Fast inoculants for the
last six years at Michigan State University. Most of
our trials have been on land that has had a previous
history of soybean production (two or three years
away from the previous soybean crop). In these
trials we did not get a yield increase due to
soybean seed inoculation or liquid in-furrow
treatments. Several possible explanations may exist
to explain these results; 1) soybean fields supplied
plenty of mineralized nitrogen, 2) indigenous
rhizobia out compete the inoculant rhizobia or 3)
the inoculant rhizobia are no more effective in
fixing nitrogen than indigenous rhizobia.
The decision on whether or not to inoculate soybeans
is still dependent on whether the site has a recent
history of healthy-looking soybeans. The practice of
inoculating fields that have been out of soybeans
for more than three or four years may still be a
good insurance practice due to the inexpensive
nature of the products. Seed treatment still seems
to be as good as other types of treatment. The
concern about poor inoculation in no-till production
systems seems to be unwarranted. Heavy residues with
cooler soil temperatures still seem to produce good
soybean root nodulation. The fact that more
attention is being paid to new "Rhizabium" strains,
new methods of preparation and application
techniques with better product storage and handling
is a positive attraction for all growers who choose
to inoculate.
Table 1. University soybean inoculation trials
conducted in a corn-soybean rotation at the Michigan
State University Research Farm at East Lansing.
1993-1996.
Part I
Inoclant
Type and ---------------Yield (bu/acre)------------
Product 1993 1994 1995 1995 1996 1996
Name conv. conv. conv. no-till conv. no-till
----------------------------------------------------
Uninocu-
lated 61 44 53 54 57 42
control
----------------------------------------------------
Sterile Peat
HiStick 60 47 53 54 - -
1x
HiStick 57 42 - - - -
2x
Sow-Fast - 45 50 53 55 45
1x
Sow-Fast - 41 - - - -
2x
----------------------------------------------------
Non Sterile Peat
Nitragin 59 - - - 56 39
1x
Nitragin 60 - - - - -
2x
Nitragin
Pro- - - - - 56 42
Treat
Urbana - - 56 54 55 43
Regular
Urbana - - 56 53 55 45
USDA
----------------------------------------------------
Liquids
Urbana - - 56 52 - -
USDA
Urbana
Frozen - - - - 54 45
Prep
Nitragin
Cell- - - - - 53 42
Tech S
Nitragin - - - - 57 42
Lift
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Part II
Inoculant ------------Mean of . . . ------------
Type and 93-95 94-96 95 96 95-96
Product Name 4 expt 5 expt 2 expt 2 expt 4 expt
----------------------------------------------------
Uninoculated 53 50 54 50 52
control
----------------------------------------------------
Sterile Peat
HiStick 1x 54 54
Sow-Fast 1x 50 52 50 51
----------------------------------------------------
Non Sterile Peat
Nitragin 1x 48
Nitragin Pro-Treat 49
Urbana Regular 55 48 52
Urbana USDA 55 50 52
----------------------------------------------------
Liquids
Urbana USDA -
Urbana Frozen Prep 50
Nitragin Cell-Tech S 48
Nitragin Lift 50
====================================================
Table 2. Michigan on-farm soybean inoculation
trials. 1990-1995
Soy- -Yield (bu/acre)-
bean Uninoc-
His- County ulated Inocu-
tory Year Location Tillage Control lated
----------------------------------------------------
No 1990 Huron Conventional 25b * 34a
1991 Saginaw Conventional 52a 53a
1994 Ionia Conventional 30b 46a
1994 Ionia No-till 32b 46a
------Average (4 trials)------ 35b 45a
----------------------------------------------------
Yes 1990 Sanilac Conventional 45b 47a
1991 Bay Conventional 52a 52a
1994 Macomb No-till 33a 35a
1994 Lapeer No-till 42a 41a
1994 Gratiot No-till 53a 51a
1995 Saginaw No-till 53a 53a
1995 Clinton No-till 49a 49a
1995 Clinton No-till 47a 48a
1996 Saginaw No-till 41a 42a
------Average (9 trials)------ 46a 46a
----------------------------------------------------
* Numbers followed by different letters within a row
are significantly different at the 90 percent
probability level.
Copies of the Soybean Research Fact Sheet are available
from:
Michigan Soybean Promotion Committee
http://www.michigansoybean.org
MSUE County Office
http://www.msue.msu.edu/msue/ctyentpg/
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