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Planning your soybean planting date

There has been much debate over the last few years on when to plant soybeans


November 12, 2007
By Eric Bosveld

8aThere has been much debate over the last few years on when to plant soybeans.
In 2004, many soybeans were planted in 'tough' conditions, at dates well past
the optimum, in the southwestern part of Ontario. High yields require a full
canopy by the time the days get shorter after June 21st. This is difficult under
normal conditions with late May, early June plantings.

Who knows what the spring of 2005 will bring? Nevertheless, if conditions permit,
will you start to plant on May 1st, or before? Or, will you wait until after
the 10th to start? Presuming you have the choice, under what circumstances will
you deviate from your plan? If you start early, will you continue planting until
you are finished? Or, will you save some planting for the mid-May period regardless
of the conditions? What seeding rate should you use and what adjustments should
you make under optimal or sub-optimal conditions? Should you plan to treat?
These are questions that require some thought and are worthy of some pre-season
planning.

Ontario certified crop adviser, Graham Hutton, manager at Belmont Farm Supply,
believes soybean growers in his area have benefitted from very early May plantings
more years than they have been penalized. "The last two years, growers
that planted earlier in May have had higher yields and better IP seed quality
and size," explains Hutton. "Attaining high yields of high quality
product is critical to our long-term IP business from both our customers' and
the IP market's perspective."

With the improved vigour of today's varieties, higher seed quality standards
and new seed treatments, the old 'norms' may no longer apply. It is generally
agreed that soybeans need soil temperatures of 12 to 15 degrees C (55 to 60
degrees F) and to absorb 1.5 times their weight in moisture to germinate. According
to Don McClure, soybean breeder at Syngenta Seeds (NK Brand), many newer varieties
can germinate at the lower end of the range without much impact on the stand
and its variability.

Still, planting too early into dry, cold soil or under sub-optimal conditions
may do more harm than good. The risk that the germinated seeds and/or seedlings
are exposed to inclement weather and unfavourable soil conditions increases
with earlier plantings. So how much risk should one take? The goal is still
to get a full crop up and out of the ground, no matter what the date. Waiting
until later in May does not necessarily guarantee that conditions will be better.

Most experts agree that whatever your risk profile, not all your soybeans should
be planted early, even if conditions permit. Using treated seed helps reduce
the risk of many seed rots and seedling diseases, such as pythium and fusarium
that will thin the stand and reduce seedling vigour. It may make the difference
between a solid stand and a replant requirement.

Belmont Farm Supply, Lakeside Grain and Feed and Setteringtons Fertilizer Service
are three Ontario companies that believe seed treatment is at least part of
the answer. All three have invested heavily in seed treating equipment to better
serve their customers that want to plant earlier. "Our customers have recognized
the need to make seed treatment decisions based on the planting conditions at
the time," explains Ian Shipley, manager at Lakeside Grain and Feed.

Some feel that seed treatment should be planned for all early planting, regardless
of the conditions, and thereby used as insurance. "Compared to the cost
of a weak stand or replanting, seed treatment is normally a good decision for
our customers, particularly for earlier planted soybeans," says certified
crop adviser Brian Taylor, who is manager at Setteringtons Fertilizer Service.
"Under our conditions in Essex County, we can get away with planting treated
seed in late April if the soil conditions are right and we have a good forecast
ahead of us."

Hutton agrees that there is a need to be flexible and plant treated seed when
conditions warrant, regardless of the planting date, however, all early- planted
soybeans should be treated.

8bOf course, seeding rate needs to be considered as well. Besides considering
all the normal factors like seed size, row spacing and so on, some believe rates
should be adjusted according to the conditions at planting. Several US extension
services, such as those in Ohio and Minnesota recommend adjusting the rate upwards
by five to 10 percent if soil temperatures are low (12 to 15 degrees C), or
when planting early.

In conclusion, for most of Ontario, many experts agree that treating seed for
early plantings is normally cost-effective. Growers also need to be prepared
to treat if conditions warrant, regardless of the date, and many believe it
should be a normal practice. There is usually little advantage of planting in
April (with the possible exception of the most southwestern part of Ontario)
and substantial risk that the stand will be insufficient for high yields, even
with higher seeding rates and seed treatment.

Soil temperature can vary widely across a field and needs to be measured to
ensure it averages 12 degrees C or warmer at planting. You should expect that
areas in the field that are below 12 degrees or are a little wet will benefit
from seed treatment to protect them from their extended period in the soil prior
to emergence. Seed must be placed into moisture in order to get a decent stand,
regardless of the date. If conditions are marginal, adjusting the seeding rate
up slightly (by as much as 10 percent) has produced positive results in other
regions. -30-

*Eric Bosveld is a Certified Crop Adviser in Ontario and works as a development
manager with The Agromart Group in Belton, Ontario.