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What is holding back soybeans?

In the early 2000s, Dr. Gary Ablett, renowned for his work as a soybean breeder,
suggested a maximum theoretical yield for soybeans at something above 150bu/ac.
He added that 150 was a conservative estimate, especially since he had known
of several years where yields topped the century mark.

Today, the number that some view as an attainable goal for consistency is 65
bu/ac, a mark that is often mentioned and seen on an individual farm basis,
but one that has yet to be reached at a county level during the current decade.

Mervyn Erb, an independent consulting agronomist from Brucefield, Ontario,
concedes the 65bu/ac level may be a lofty goal for a provincial average, but
he knows of several growers in his region of Huron, Perth and Waterloo counties
that are seeing 62bu/ac to 65bu/ac in one field, and others yielding 70 to 80
bushels in certain parts of a field. "In 2004 and 2005, we had some pretty
hot yielding soybean years and again in 2006, a lot of guys are going in the
50s," explains Erb. He notes that of all the months of the growing season,
August is the key for soybeans. "You have to have a lot of heat in August
and a lack of cool or cold evenings, too. And with a couple of good rains, you'll
have a huge set of pods at the very top of the plant, but only if you get that
rain at the right time."

Erb also believes there is a natural process of attrition in the field that
takes place during the growing season, but he cannot explain why it happens.
"Why some areas of the field seem to hold their stands better, that's a
good question," he says. "Obviously there's too much variability in
our fields, where there's a lack of topsoil in spots, some eroded knolls and
side slopes eroded, and the field consistently isn't giving us big yields."

Genetics doing its part
One aspect that stands as an advantage is the new genetics that are being developed
from year to year. Erb cites varieties like OAC Wallace, Colby and PS59s which
have performed well in the 2750CHU region in recent years, and Henry Olechowski
agrees. As research director with Hyland Seeds in Blenheim, Ontario, he has
seen some incredible advances in soybean breeding technology.

"We actually bred a true Group 000, Roundup Ready variety, one that we
can't even grow in Ontario, and we harvested about 40 miles north of Winnipeg
and it went 37.5bu/ac," says Olechowski, adding that it is close to the
latitude of James Bay in Ontario. "So in my mind, the breeders have done
a good job because I don't think it's the genetics that are holding us back."

Instead, Olechowski points to the increasingly diverse disease and pest complex.
As the soybean growing regions have expanded east and north in Ontario, so too
has the incidence of diseases and insects more commonly associated with regions
farther south and west. "With the onset of more soybeans, we have more
diseases, like white mould, the root rots, then we had cyst nematode and now
we have aphids. It's been a continuous battle for the breeders to bring tolerances
to all of these biotic factors, and that takes some energy away from just straight
high yielding traits," says Olechowski.

What lies beneath
If Erb and Olechowski are looking for support, they have it from Don McClure,
soybean breeder with Syngenta Seeds, near London, Ontario. McClure sides with
Erb on the weather issue, particularly the importance of a good August, and
he agrees with Olechowski's contention that disease and insect pressures have
confounded the potential for higher yields, as well. However, when pressed to
define the greatest impact, McClure points to soybean cyst nematode. "This
is one of the key things I point out to people who work in corn, they don't
have an equivalent of cyst nematode," he says. "There's no pest that
routinely, regularly, almost every year is taking away yield like cyst nematode
in soybeans."

What is more frustrating is that despite the efforts of provincial extension
personnel, company and consulting agronomists, researchers and breeders, the
word on SCN gets out to growers, but is often ignored. "When it first appeared
in Ontario in the Chatham area, growers didn't even want to admit they had it
because there was a real stigma attached to it, and it's taken a long time to
get over that," details McClure.

When the first cyst-resistant varieties were released, there was a yield drag
even compared to conventional varieties, which was a significant barrier to
gaining acceptance among growers. Such is not the case anymore, and it frustrates
McClure to know there is a solution, but growers are reluctant to accept that
they may have the problem. "A lot of people won't take the time to pull
up plants and look at the roots," he says. "Instead, they're going
by above-ground symptoms when it could be easily identified if they'd pull up
those roots."

McClure echoes Olechowski's statement about losing ground to breeding for resistance,
pointing to the Bt gene as the most significant development for the corn sector
in the past two decades. "Again, we don't have an equivalent in soybeans,"
he says. "We have resistance genes, but all we're doing is bringing the
yield back up to where it should be, so it's not a yield enhancement like Bt,
it's just a yield protection."

Other things to consider
Other factors that could help improve the consistency of yields include doing
more to alleviate compaction as well as suggestions that planters do more for
even emergence than no-till drills, regardless of tillage practices.

Fertility is another factor worth noting. Erb states that none of the higher
yields he sees among his clients are coming from fields with low soil tests.
In fact, the highest yielding soybeans come from livestock farms. "There
are two reasons for that: first, most dairy guys don't grow a lot of soybeans
and second, most are doing chores in the morning, so they are not out there
planting until late in the morning or after dinner when everything's warm and
perfect," he says.