Features Agronomy Soybeans
Compaction a pressing issue with a wet fall

"There needs to be a reason to do tillage; if you don't have a reason,
don't do it." It was 1999 that Bob Misener, a staunch no-tiller, made that
statement at a field day at the Elora Research Station. Seven years later, the
signs are in the fields: there is too much tillage being done without a viable
reason.

With winter turning to spring, many fields across southern Ontario are exhibiting
symptoms of aggressive and even routine fall tillage including rutting and standing
water. To be fair, growers who did some form of fall tillage in 2006 were confronted
with conditions that were more severe than what they had become accustomed to
as far back as 2000.

In fact, Peter Johnson believes it may have been the most challenging fall
for getting crops out of the field since 1992. "And like everything else,
it's 90 percent weather-related," says Johnson, the cereal specialist for
the Ontario Ministry of Agriculture, Food and Rural Affairs. "When you
get 12 inches of rain in October and you normally get three, I don't care how
good a manager you are, it's going to be too wet when you're in the field."

However, it is that 10 percent management component that became a stark reality
for growers late in 2006. For those who have made the adjustment with proper
inflation rates for their tires, ballasting the tractor appropriately, and doing
those extras to minimize compaction, the road to recovery for their fields might
not be as severe a challenge as those 'recreational tillers'. "They're
thinking they'll get the crop off and fix it later, but guess what? Late last
fall, they weren't able to go fix it and they can't fix it this spring, so they're
going to have a negative impact on yield in 2007, almost guaranteed," explains
Johnson. Nor will deep ripping be the one-season solution it is promoted to
be. "Long-term, you have to quit creating the problem."

Easier said than done
Of course, in a wet fall like 2006, most growers had little choice but to get
their crops off while creating compaction headaches, and more so for larger
growers. "There were farmers in 2006, as of September 30, with the combine
capacity they had, and some had three or four combines, they had 60 days of
combining to do," says Johnson, adding that the weather failed to offer
those 60 days. "And growers have run regardless, because their acreage
and their equipment-to-acreage base left them no option. Every minute they could
be in the field, they were, and the amount of damage they did in some of those
fields was extensive."

Again, Johnson points to the routine of the previous five autumn seasons, when
soybean harvests were relatively early, winter wheat planting went more according
to plan, and corn came off with little or no problems. Then came the fall of
2006.

What to look for
The signs of compaction are well known, even on the surface, continues Johnson.
As spring arrives, there will be ponding and slow drainage from areas which
are not known for such conditions. "Then when you're working the ground,
plowed fields will look dry on the surface, but if you've done something that
negatively affects the drainage, water cannot move in the soil and your evaporation
will likely be only one-tenth or less of what it should be," he says. "If
you dig down three inches and it's muck, that's another really good indication
that it's not draining the way it should be."

Part of the problem is the design of the mouldboard plow and the manner in
which it is used, year after year. According to Johnson, the plow actually creates
two smears as it turns and flips the soil. One, on the underside, is turned,
exposing it to sun, wind and the freeze-thaw, wet-dry cycles, cycles that 'fix'
the damage, thereby making it workable. But the second smear, which is the other
half of the plow smear, occurs from plow depth and about six inches deeper is
a physical barrier and something that can take years to be ameliorated. Water
can still move below that smear the first year because the plowshare only cuts
across 80 to 90 percent of the soil surface.

"The difficulty comes the following fall when I go in and plow again,"
details Johnson. "I already have one smear and three or four inches of
unsmeared, but if I smear that last portion, that's my plow-pan and that's when
I've blocked it out entirely."

That plow-pan leads to one of the key symptoms found after planting and as
the crop is developing: poor root development. Plants of varying heights will
often show a root mass that has been forced into a lateral direction by the
plow-pan.

No easy solution
For the problem of compaction and rutting there are no simple, quick-fix methods.
Its effects cannot simply be undone in one year, even with something as radical
as deep ripping.

"Some of the data from Minnesota says that without any tillage being a
factor, it can take five to eight years to actually have a significant amelioration
just by the freeze-thaw, wet-dry cycle," says Greg Stewart, corn specialist
with the Ontario Ministry of Agriculture, Food and Rural Affairs. "The
other thing is that the fields were recovered after five, six or seven years,
but when serious stress came back, whether it be a very wet year or very dry
year during the growing season, those plots took a sudden 15 percent yield hit."

For Stewart, much of the compaction that was created in the fall of 2006 was
on an individual level, almost down to a field-by-field, soil type-by-soil type
basis. "Whether you have 40 inch radials on the front of your combine or
whether you're still running 30 inch bias ply, there are quite a number of factors,"
he says, noting that for most growers, the level of compaction was greater than
they would have liked to have seen and likely worse than average. The problem,
again, is determining a course of action and not just in the here-and-now. "I'm
of the opinion that if your soil type doesn't have 'clay' in its name, and that's
a lot of acres in Ontario, going back out in the fall to try to do some tillage,
especially on soybean ground, was a complete waste of time and, in some cases,
might have done more harm than good."

On lighter soils, Stewart says the best course of action will be to give fields
more time to dry out before attempting to do some shallow to intermediate tillage
in the spring. "I'm not a fan of trying to get in there and do remedial
tillage in the early spring, especially if the ground is still tacky, so you
might be better to wait until you get a significant drying spell," says
Stewart.

"If that means you have to go with soybeans instead of corn, I don't think
it's a bad thing on two counts. One, that you have had to wait until the 20th
of May to get those fields in a situation where you can actually do some improvement
with your tillage, and two, soybeans are going to be a little more forgiving
in those compacted soils than corn will be."

Being under pressure is a good thing
Greg Stewart is a firm believer in 'research by the numbers' and where
compaction and rutting fields are concerned, he has been able to demonstrate
a clear advantage.

In 2004, Stewart took part in a demonstration at Canada's Outdoor Farm
Show near Woodstock, Ontario. The point of the display was to show the
effects of radial tires versus bias ply, and to measure the footprint
left by each. Using a Nuhn manure tanker, the experiment called for mounting
radials on one side and bias ply on the other.

"We went to the lowest warrantied inflation pressure for both tires,
so it was about 28psi or 30psi on the bias ply and 14psi or 15psi on the
radial," says Stewart, noting the latter appeared to be 'squatted
out'. The comment that many growers made was that the lower pressure radials
would be harder to pull.

Following up on those comments, a special tractor from Agriculture and
Agri-Food Canada was used in 2006 to measure the pulling power required
for both tire types. "The Michelin guys say there's less bounce,
less torque, less strain on the drawbar and sure enough, the big lower
inflation pressure radials pulled easier."

The test was done on disc ripped ground and in wheat stubble, and in
both situations, the radial came out ahead. The common response to that
finding was that the bias ply would be better on the road, the radial
on the field, but on hard ground, there would be no difference.

"But it didn't really work out that way," relates Stewart.
"With the two tires, the advantage of the radial was similar to pulling
on the no-till wheat stubble or on the ripped up or worked ground."