Cover crop debate continues
November 13, 2007
By Ralph Pearce
But fewer people seem to notice.
The sight of a bare, wheat-stubbled field basking in the August sun is a troubling
thing for some. For others it is a simple reality. It seems that in the past
three to five years, the practice of underseeding red clover to wheat, or of
planting oats or peas following the wheat harvest has fallen on a harsh reality.
Fewer growers want to go to the trouble or expense of having another crop in
the field. Some state they cannot get clover to establish, others reportedly
have difficulty with the concept of planting a crop which will not be harvested
while still others quibble with seed costs and plowdown.
Despite this trend, some growers maintain the practice of growing a cover crop
and are adamant about the benefits. Tom Hayter who farms near Dashwood, Ontario,
is one of those growers who cannot get a good 'catch of clover' and opts for
field peas. Hayter tried to get a decent crop going, using various means from
early to late planting, using a drill, but he was never happy with the consistency.
He also has grown oilseed radish, but found the large tap roots were plugging
"We always try to do a cover crop but we also have manure," explains
Hayter, who runs Hayter Turkey Farms, as well. "With our peas, we aim for
ground that may not get manure in the summer, because the peas fix their own
nitrogen, so we plant these peas immediately upon removal of the straw and they
grow really thick." So thick that Hayter had trouble with the lushness
of the pea crop with the wet fall of 2006. He could not pull his cultivator
through the mass and opted for spring discing, which he does not like to do
as a rule. However, the overall impact is that Hayter is getting bigger wheat
yields from his cover crop and manure regimen.
"The old adage used to be that you either get a wheat crop or a clover
crop, so if you get a big wheat crop, you're not going to get much clover and
I think we're getting a lot better wheat now," he says, adding that his
corn in 2007 is looking as good as it ever has. "I like the pea idea because
it's a legume, so it's better to follow with corn, which is a grass, to avoid
the allelopathic effect wheat might have; I know that the corn on the pea ground
looks a little better than our corn that didn't get peas."
The lack of cover crop is a hard thing to quantify; few statistics are kept
on the number of acres that receive any kind of cover, something that Quentin
Martin believes is part of the problem. "If there was an industry record
of red clover sales, that would be one benchmark to go by but I don't know if
anybody can generate those numbers," says Martin, who operates Cribit Seeds
and Wintermar Farms, near Elmira, Ontario. "And regardless, it's safe to
say without any statistics that there are a lot of acres that don't see a cover
crop that could."
The knock against red clover in his view, is the perception that seeding is
an added challenge, together with crop competition in years with adequate to
above adequate moisture. "With red clover, frost seeded in the spring,
it will always do well in the good areas of the field but not in the poorer
areas of the field," says Martin. He adds that he has seen sales of peas
and oats increase from his operation, particularly as a post-cereal harvest
cover. "Certainly we moved a bunch of oats and peas for cover crop in 2006,
more than ever before, but against the number of acres of wheat that were out
there, it was probably not measurable."
Gone are the days when the government paid growers to maintain some sort of
residue or cover crop, notes Martin. Under the Tillage 2000 plan initiated in
the 1980s by the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA)
and the Ontario Soil and Crop Improvement Association (OSCIA), growers could
receive as much as $10 per acre for their efforts. However, that program does
not exist anymore and any sustained research into the effects of cover crops
is sorely lacking.
Little or no research
What is also lacking is a direct correlation between cover crops and improved
yields. Dr. Dwayne Beck of South Dakota State University's Dakota Lakes Research
Farm in Pierre is a strong advocate of cover crops. At the 2007 annual meeting
of the Innovative Farmers' Association of Ontario (IFAO), he expressed his concern
at the lack of cover crops in Ontario fields. Yet, where most supporters of
cover crops recommend red clover or oats or peas, Beck believes in blending
various types of grasses or legumes, depending on the desired effect.
"If it's wheat stubble that will be seeded to corn the following year,
a common mix of ours would be a brassica, like turnip, radish canola or crambe
and that's my scavenger. It ties up the mineral nitrogen and sulphur so they
don't get lost or make the legumes 'lazy'," explains Beck. "It'll
mobilize some phosphorus and it has a big leaf that's really competitive. Then
we'll have cow pea in there which is our warm season legume and then we'll have
a cool season legume like a lentil."
The common thread with all three of these crops is that they are relatively
inexpensive. Still, there is the expectation that something has to come from
harvesting a cover crop. The hope that it will spell a better subsequent crop
to the one previously planted has never been proven. "Sometimes you may
have less yield but I can easily show you that you're putting less nitrogen
into aquifers or into surface water, and that you're adding nitrogen to the
whole system," says Beck, noting that a large part of the problem of working
with cover crops is a lack of patience. "So corn on corn and taking the
residue off and using it to make something as well, is where we're heading."
It all takes time
That is the one requirement from Beck's perspective: time to work with different
combinations to achieve the right balance. He has seen cover crops that can
help digest residue in the soil by simply helping the soil micro-fauna and macro-fauna
reach a balanced 'diet' of nitrogen and carbon. "In a tilled system, you're
basically talking about a desert, where there's very little biological activity,"
says Beck. "Essentially, you've killed everybody and you hope that the
good guys come back. Well, in good no-till, once you get the system going and
you really get the biology cranked up, you almost can't keep the residue on
Beck cites various research projects that also show everything from a reduction
in sclerotinia, take-all or rhizoctonia to enticing predators and beneficials
into a field ahead of the arrival of insect pests. The key is the time it takes
to determine how natural cycles work and many growers either believe they do
not have the time, or do not want to spend the time.
A leap of faith
Laurence Taylor agrees that growers largely lack patience and equates the mind-set
that goes with cover crops to a leap of faith, much like no-tilling; a grower
either believes in it or not. Taylor, who farms near Londesborough, Ontario,
has been an active member in the OSCIA since the 1980s and links the benefits
of cover crops to soil organic matter. "If you keep organic matter up in
the soil, and good physical properties in the soil, it weather proofs yields,"
he says. "If you have a year when weather patterns aren't good, you don't
suffer that much on yield because your soil is in good shape and part of it
is accepting this philosophy of anytime you have a chance to convert soil minerals
into organic matter, you do it."
The so-called fly in the ointment to that conventional thinking, however, is
the progress in breeding in the past decade. Researchers and breeders have been
providing growers with better wheat and improved disease resistance. "And
growers started growing it like a first class crop, so that the establishment
of clover was less certain," relates Taylor, adding that attitudes towards
tillage have shifted along with the focus away from residual nitrogen.
"You might find that growers with conventional tillage are having to replant
other crops in their rotation more often than they used to, and that's a result
of a loss of soil structure and beating it up over the years. After a wheat
crop, most guys would see the better structures and if you can add to that with
a cover crop, plus get a nitrogen crop, then wheat becomes the most profitable
crops you can have."
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