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Planting and maturation varies in soybeans

Feb. 7, 2012, Ontario – Extensive soybean breeding in Ontario is
continually leading to higher yielding soybean varieties. Unfortunately,
these higher yields are not always realized in field scale production.

One management strategy that leads to higher
yields is early planting. Another strategy is to plant longer maturing
varieties for a given growing area. With the introduction of CruiserMaxx
seed treatment, higher plant populations can often be achieved under
more stressful conditions, making it possible to plant earlier. By using
CruiserMaxx seed treatment it may be possible to combine the two
already successful management strategies of early planting and longer
maturing varieties to achieve an even higher yield potential.

A three year project was recently completed through a partnership
between Grain Farmers of Ontario, OMAFRA, the University of Guelph and
Monsanto Canada Inc. This project was conducted to determine if planting
longer maturing varieties in conjunction with earlier planting could
significantly increase yield potential. It also assessed the best
planting date for adapted varieties. The yield response to three to four
soybean varieties were measured at an early planting date (before May
15), a normal planting date (May 15-30) and a late date (after May 30)
over the three years of this study (2009 to 2011).

Varieties chosen covered a range of maturities from an adapted maturity
for a particular site to varieties up to 500 crop heat units (CHU’s)
more than adapted. The site locations for the study included Elora,
Kemptville, Seaforth, Chatham, Ridgetown,
Coteau-du-lac, St. Hugues, Ayr, Lucan, Morrisburg, St. Thomas and Bornholm.

A VARIETY OF SEASONS

The three years of the study experienced various types of growing
seasons. In 2009 the weather was largely cool and wet, and was combined
with an early killing frost in the fall. The 2010 growing season was
exceptional; the spring allowed for planting in April under good
conditions and the remainder of the season received warm weather and
timely rain. The 2011 growing season was unique; the spring was
especially wet, resulting in later than normal planting dates. Planting
was followed by dry weather in July, but the remainder of the season was
very good with hot temperatures and consistent rainfall.

MIXED RESULTS

In 2009 results were mixed. In some locations the adapted or +200 CHU
varieties yielded higher than the +400 CHU varieties, this was the
result of an early frost, which prevented the longer season varieties
from fully maturing. On average the early planting date out-yielded the
late planting date, however, in some locations there was no significance
to planting date.

In 2010 the results were very clear and consistent. There was a
significant advantage to planting earlier. Averaged across all the sites
there was a three bushels per acre advantage to early planting over a
normal planting date, and almost 10 bushels per acre compared to a late
planting. Due to the exceptional growing season, in almost all cases the
latest maturing varieties were the highest yielding.

In 2011 the results were affected by late planting conditions in the
province. Yield response to planting date varied across varieties and
site locations. Generally, the normal planting date and the early date
yielded about the same. In some cases adapted varieties that were seeded
early suffered a yield loss compared to normal planting. In some cases
late planting yielded the highest. The most likely reason for this is
the very dry July experienced in 2011, which meant that beans planted
early were trying to set pods when the stress occurred. Later planted
beans were still vegetative and so were not as adversely affected by
this stress.

On average, over the course of the study period, planting early proved
to be successful, although it did not always yield more than a normal
planting date. Seeding an adapted variety too early led to yield losses
compared to a normal planting date in some cases, but seeding a long
season variety early still provided more yield.

During the three years of this study a 0.21 percent yield reduction was
demonstrated for each day in delayed planting. For 2009-2010 the
reduction was 0.5 percent per day. This meant 5.4 bushels per acre
reduction if planting was delayed by 30 days (May 1 to May 31 for
example; see Figure 1). When the 2011 data is included, there is a
reduction of 2.5 bushels. There was no evidence that seeding in April
was too early for soybeans as long as the maturity of the bean was long
enough.

Longer maturing soybeans can be grown successfully and provide more
yield to Ontario soybean growers. For the early and normal planting
dates (before May 15 and May15 to May 30), there was a significant
advantage to using later-maturing varieties. Each +100 CHU in variety
maturity provided about a three percent yield increase. The likelihood
of reducing yields by adopting this strategy was small and the reduction
was never more than 10 percent. Choosing a variety that is +200 CHU is
an excellent strategy for fields not intended for wheat and provided 2.4
bushels per acre more yield.

Planting early is generally a good management strategy, it costs nothing
to implement and has the potential to increase soybean yields. Mother
Nature has to co-operate for this strategy to work, but when there is an
opportunity to plant soybeans early it should not be passed up. Keep in
mind a full season or a full season plus 200 CHU variety should be used
when planting early.

Growing later-maturing soybean varieties was also profitable, even if
planting was not early. However, since there is the risk that a fall
frost can reduce yield and seed quality, caution must be used in
recommending a variety that is excessively long for a given area.
Implementing a strategy of using a +200 CHU would provide 2.4 bushels
per acre more in yield with very little additional risk. However, if
planting in June, do not plant a longer maturing variety.