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Compaction: out of sight, out of mind

Hidden from view, issue can be hard to accept.


November 13, 2007
By Ralph Pearce


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6aConsidering all that happens in a field during a year, is it possible that
compaction has become that one facet of modern agriculture that growers have
come to accept as inevitability? Newer technology, larger equipment, narrow
margins and a premium on time have created an atmosphere where more growers
seem to be willing to push the limits on overall soil health, including compaction.

The spring of 2007 was marked with what seemed to be a considerable increase
in tillage. To be fair, the weather the previous fall was anything but compliant
with wet conditions at harvest and into November forcing growers' hands and
leaving fields rutted. The obvious answer for many was to aggressively plow
under the ruts and attempt to level their fields. That was followed by multiple
passes in the spring.

The resulting compaction showed itself with the dry conditions of June 2007.
Patches of stunted and withering corn may have been indicative of compaction;
they also may have been signs of fertility problems. "These corn plants
don't have a lot of roots to them and if they have to go down looking for moisture
and hit a hard spot, you're going to see compaction showing up pretty quickly,"
says John Waters, a certified crop advisor with Lakeside Grain and Feed, near
Forest, Ontario. Despite the damage done in late 2006, he agrees most growers
had little choice. "It's not like they could have waited for the frost,
which is the conventional wisdom, because late in 2006 there was no frost. We
had snow before we got the cold weather."

More than just affecting the development of corn crops, Waters maintains it
is having a secondary effect on weeds, pointing to 'dirtier' parts of fields.
Generally, weed escapes were appearing in those sections of the field that had
been worked the most. "They were turned over and exposed to the weed seeds,
then plowed deep to get rid of ruts and not just three or four inches deep,
some were plowing 10 and 12 inches," he says. "And they were probably
turning over weed seeds that hadn't seen the light of day since they were on
a plant head five years ago."

Search for answers not a simple one
When discussing a cure for compaction, the issue of deep tillage often arises.
However, despite demonstrations and anecdotal evidence, the danger of reconsolidation
is the greatest risk. Doug Aspinall, a land resource specialist with the Ontario
Ministry of Agriculture, Food and Rural Affairs, agrees with Waters' assessment
that growers had no choice in 2006. Yet the greater need from his perspective
is not for a quick fix to compaction, but rather the changing of practices,
including flotation tires.

"I've talked to a few growers who have purchased them and they say they're
really great. Then compaction might come up in the conversation, but they like
the way they ride, too," says Aspinall. "The other thing is that with
the guidance systems that are available now with GPS and real time kinematics
(RTK) and auto steering, it means you can drive on the same patch every year."

The task of sharing information on soil interaction is not an easy one; Aspinall
has conducted many sessions from deep inside soil pits, showing growers the
plow pans that result from compaction, or macropores created by deep roots in
better case scenarios. He can talk about soil fundamentals including texture,
which cannot be altered, and structure which can. Yet without digging up the
soil or the plant, compaction is hard to quantify.

"I noticed during the last couple of weeks of June that there was corn
starting to curl up but without digging up a plant, it's hard to know,"
says Aspinall. He adds that corn with magnesium deficiency takes on a similar
yellow-green appearance as the stunted plants that may result from compaction.
"In the distance you can spot them quite easily, but that's a fertility-pH-magnesium
issue."

Problem is not on the surface
The fact that compaction is an out-of-sight, out-of-mind subject may be the
key, according to Dr. Ray McBride, a researcher with the Land Resource Science
department at the University of Guelph. In terms of soil degradation, compaction
is the unseen culprit, unlike erosion. "It's all going on underground,
you can only ever infer that compaction is a problem," he says, noting
that growers, at some level, are aware of the damage they do with tillage in
some cases. "Crop performance may decline and yields diminish, but it's
not a really good cause that farmers pick-up on."

Another concern of McBride's is the trend towards removing every last form
of crop residue and its impact on soil organic matter. "With this movement
to corn and ethanol and switch grass, and these methods that are going to convert
crops to ethanol and other fuels, that's just going to ravage the organic matter
and residues from the landscape," cautions McBride, who has been reviewing
a book by a University of Washington professor on the impacts of tillage. Entitled
Dirt: the Erosion of Civilizations, the book discusses the crisis developing
from tillage and its effect on soil and wind erosion.

As for the quick-fix mentality that has evolved in agriculture in the past
decade, McBride says there is none. Instead, there are three aspects to dealing
with compaction: prevention, mitigation and remediation. In 2007, the farm culture
is concentrating largely on remediation, with deep ripping and sub-soiling.
"Other parts of the province, where we don't think we have too much damage
yet, the emphasis should be more on the prevention and mitigation options,"
outlines McBride. "We talk a little bit about prevention and everything
from wide gantry tractors to controlled traffic to very low inflation pressure
tires on grain carts and tractors and combines."

Deep ripping, in McBride's view, has not worked to expectation in Ontario,
partly because of the reconsolidation issue but also in part because once 'repaired',
growers often return to the practices which caused the compaction in the first
place.

When in doubt, use a penetrometer
For Glen McDonald, the issue of compaction in 2007 is hard to qualify and quantify.
While he is uncertain of the extent of compaction that has occurred across Ontario,
he knows of one grower who tilled his field at least six times before planting
edible beans. As a field agronomist with Pioneer Hi-Bred, McDonald acknowledges
the allure of early planting corn that is affecting issues like compaction.

"If you can get corn in before May 10 in the London area, you have great
potential for that crop, just from an early planting standpoint," he says.
"When planters are covering larger acres, it's more difficult to avoid
compaction issues. Many fields in Ontario contain more than one type of soil;
often a grower can't wait until 100 percent of the field is ready to plant under
conventional or no-till situations."

One of the tools McDonald always carries is a penetrometer. Having it not only
confirms the existence of compaction, it can save a grower from unnecessary
investments in fertilizers. One of McDonald's growers near Mount Brydges, Ontario,
showed him a wheat field on sandy soil with significant variations in height.
McDonald took soil and tissue samples but could get the penetrometer only about
four or five inches deep.

"It wasn't a nutrient issue; that was confirmed on the soil and tissue
samples, but certainly he had compaction issues," relates McDonald. He
adds that some growers believe sand cannot be compacted. "They're very
surprised when we get out there with the penetrometer and show them where the
crops look good and where they don't."

Changing farming's standards
One of the other factors McDonald cites is the shift towards larger acreages,
which can take growers out of the fields and out of touch with the soil, a trend
that Barry Gordon also notes is taking shape. A long-time advocate of no-till,
Gordon echoes McDonald's contention that agriculture is getting bigger, with
heavier machines, larger farms and earlier planting.

The key, from his perspective, is to limit machinery weights to five tons per
axle, a figure touted by US sources in the late 1980s. Even pickup traffic across
a field should be kept to a minimum, since the ton per axle on a truck can have
a cumulative effect.

The other course of action that Gordon sees as helpful is boosting soil organic
matter through cover crops and manure applications. "Especially in those
fields that are the heavy clays with two or three percent organic matter,"
says Gordon, sales and marketing manager with C&M Seeds, near Palmerston, Ontario.
"Cover crops, incorporation of manure with straw and if we can get those
organic matters above four percent, we'll have a lot more cushion in the soil
so it doesn't compact as much."

Like McBride, Gordon advocates using controlled traffic and headlands to minimize
the impact of heavier equipment. "Even with combines, if they're nearly
full when they're near the road, empty that bin when they're there, rather than
go halfway down the field to completely fill the bin before unloading,"
he says.


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