Top Crop Manager

Features Agronomy Tillage
Restorations head to the field

Moving soil and beyond.


November 13, 2007
By Top Crop Manager

Topics

16aA seldom stated but well-known theory suggests soil is permanent. It is never
actually lost, it is only moved from one location to another by way of wind,
water or tillage. Accepting that as a fact, it should be possible to replenish
or restore topsoil to levels seen on a farm many years ago.

David Lobb, a soil researcher with the University of Manitoba, has been working
on the principles of landscape restoration, the act of physically moving soil
from one area of a field to another, since the late 1980s. Although there are
some significant differences between what he sees in his current work on the
prairies and what he has encountered in eastern Canada, the message remains
the same: restore the landscape and do it before doing other soil conservation
or land improvement practices.

One of Lobb's guiding principles is that landscape restoration is the first
key step in adjusting or overhauling soil and land management practices. As
well, in his view, restoring the landscape eliminates the need for much of what
has been promoted under the banner of precision agriculture. He does not dispute
the need for the relative newcomer to farm management practices; but he believes
restoring the landscape can have that much more impact. "Tillage plays
a very important role in all of this," says Lobb. "Tillage erosion
is the largest contributor to the highly variable and degraded soils we see
in eroded landscapes."

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Before considering a move to no-till or zero-till, this problem has to be fixed.
"If your land is eroded, you have a need for restoration. If the cause
is tillage erosion, the soil isn't lost, it has just moved down to the bottom
of the hill without being washed away. The soil moved by tillage is a bulk movement,
the quality has been degraded. But what leaves by water is left as a sediment,
and it's been disaggregated and separated, and is essentially of very little
value."

The further west, the less the problem
There are spots in Ontario where this is being done and Lobb contends there
is an intensification of tillage happening in Ontario, not a reduction. And
it is going to cost growers through degraded landscapes.

For a preview of what is to come, Lobb points to the potato farming regions
of New Brunswick. Soil has been dragged down hill-slopes within fields by tillage,
and then moved from the field and further away by water erosion and potato harvesting.
"They have reached the point where their land can no longer sustain the
current forms of intensive production and can probably never be restored, certainly
not through landscape restoration," says Lobb, adding it may be a 'problem
in the making' for Ontario.

In the west, degradation is occurring, largely due to tillage erosion and,
to a lesser extent, due to wind and water erosion. In Ontario, water plays a
bigger role in soil movement, carrying soil into the streams and rivers.

Have to make a choice
No-till or reduced tillage practices tend to go hand-in-hand with restoration
measures, and Lobb acknowledges the concerns voiced by growers who insist farming
without some form of cultivation will reduce yield potential. But the choice
is less daunting than most believe, especially if a grower has these degraded
landscapes. They will worsen as tillage intensifies, once again, and if the
growers wait until the whole landscape gets degraded, the opportunity to restore
may be lost. "They have to weigh the consequences of their actions on this
issue," cautions Lobb. "Can farmers afford to have 20 to 30 percent
of the field being unprofitable, knowing that this area will increase and the
profitability will decrease?"

The perception is that economics dictate that many farmers continue traditional
practices from 20, 30 or even 50 years ago. But Lobb insists that mind-set will
serve to punish more growers as the years continue. "You can't look at
what your previous generations have done, and assume that you can use the same
practices; the crop production technologies are no longer the same, and the
land is no longer the same." says Lobb. "You can't fix the problem
without addressing the cause head on. Tillage intensity must be reduced and,
if possible, the damage repaired."

Ontario success model
Wilf Riddell became involved in what he calls remediation based on hand harvested
yields from the Tillage 2000 plots on his farm near Granton, Ontario, between
1985 and 1989. In 1985, Riddell switched to a no-till management system. Work
with provincial soil specialist Doug Aspinall and the Soil Conservation advisors
with Tillage 2000 convinced Riddell to take part in this conservation tillage
study. The work showed that the loss of topsoil from the slope positions, and
the resulting loss in soil organic matter was the primary reason for a drop
in yields. Riddell likens the organic matter in the soil to a sponge that helps
hold moisture for the plants to use and is especially important on those slope
positions.

The work with remediation, began in 1991 on three sites on his farm. On all
the sites he worked with four treatments, including manure only, manure plus
topsoil, topsoil only and a check plot (see Table 1). On Site 1, which Riddell
deemed the most-eroded of the three, the plot was tilled in the fall of 1991
after the soil and manure were applied. The two manure treatments had roughly
13.5 tonnes of manure applied per acre. Both were then incorporated using a
rotary tiller.

Table 1.

Treatment 1992 corn 1993 soybean 1994 corn Average on two year corn Dollar increase over check Net both average per year
Corn Soybean
Site 1 (most eroded)
Check 80.6 32.2 112.9 96.8 $0.00 $0.00 $0.00
Manure only 130.7 37.8 144.3 137.5 $122.25 $38.50 $80.37
Soil only 139.5 42.0 141.9 140.7 $131.85 $67.90 $99.87
Soil + manure 150.5 48.8 141.6 146.0 $147.90 $115.50 $131.70
Average yield 125.3 40.2 135.2 130.3 $100.50 $55.47 $77.99
Note: For Site
1, manure was rotary tilled in fall 1991.
Average Site 2 and 3.
Check 116.8 54.0 137.1 126.9 $0.00 $0.00 $0.00
Manure only 103.5 55.2 132.0 117.8 -$27.52 $8.40 -$9.56
Soil only 132.4 51.9 134.9 133.7 $20.18 -$14.70 $2.74
Soil + manure 141.6 51.4 132.5 137.0 $30.30 -$18.55 $5.88
Average yield 123.5 53.1 134.1 128.8 $5.74 -$18.55 $5.88
Note: Manure applied
on surface in spring 1992 but not incorporated (average of two sites).
Average of all three
sites.
Check 116.8 54.0 129.0 122.9 $0.00 $0.00 $0.00
Manure only 103.5 55.2 136.1 119.8 -$9.23 $8.40 -$0.41
Soil only 132.4 51.9 137.3 134.9 $35.93 -$14.70 $10.61
Soil + manure 141.6 51.4 135.6 138.6 $47.10 -$18.55 $14.27
Average yield 123.5 53.1 134.5 129.0 $18.45 -$6.21 $6.12

The second and third plots showed less of the degradation than the first. As
a result, they were not rotary tilled following the topsoil and manure applications.
The following spring, planting was more difficult due to the lack of incorporation,
and slug damage on both plots was considerable, as well. "The first thing
I would say is it's a pretty good sales pitch for no-till because it's the tillage
that seems to be moving the soil," says Riddell, who has provided his findings
to groups such as the Innovative Farmers Association of Ontario. "It makes
an excellent argument to reduce tillage to a minimum."

And his results are undeniable. Assuming average corn prices of $3.00 per bushel
and soybeans at $7.00 per bushel, and 10 percent of a 100 acre farm having the
same improvement from landscape restoration as Riddell's first site, a corn-soybean
rotation could see yield increases worth $131.70 per acre. During the course
of 30 years and 10 acres per year, that would translate into $39,510 in recovered
income. "It is not like it's acres and acres, and the topsoil that came
off of those areas isn't on the other side of the field, it's in the hollow
beside those areas where it came from," says Riddell. "So it's not
like you have to move it a long way."

One note in particular: the response of crops to landscape restoration is similar
to a response curve for nitrogen in corn. Riddell's early data points to an
almost immediate jump in the first year following restoration on the most eroded
of his three sites. After that however, the yield increases level off. The yields
are still higher than with the eroded soils and by implementing a no-till system,
those yields should remain relatively stable. It should be possible to move
the soil just once, provided the grower does not return to a conventional tillage
system.

Ten years later, still positive
Adam Hayes, soil management specialist in field crops for the Ontario Ministry
of Agriculture, Food and Rural Affairs in Ridgetown, updated some of the data
sets on Riddell's farm in the fall of 2004. The work was done as a follow-up
of conditions 10 years after Riddell's initial three year comparison. "We
took some soil profiles out of there so we could see the differences in the
topsoil layer now versus the site where nothing was done," explains Hayes.
The profiles revealed that the topsoil layer is thicker and darker in colour
where the soil was added. "We also took some soil samples and analyzed
for fertility and organic matter, again fertility and organic matter levels
were higher than where no soil was added. So we were able to document the kinds
of improvements that have been made to the soil by doing that remediation. And
the no-till management has maintained the benefit."

Hayes adds his voice to that of Lobb's and Riddell's, cautioning against continued
intensive tillage practices, particularly in cases where a landscape is restored.
A return to reduced or minimum tillage can, in effect, 'damage the damage control'.
"In a lot of cases, it's the tillage that's doing the levelling and moving
the soil, so it has to be really restricted," says Hayes. "There has
to be some recognition of no-till as an important part of the solution."
-30-

The Bottom Line
During the last 10 to 15 years, growers have tried various methods
of conservation tillage. Some have stuck to these methods in recognition of
reducing erosion and others have seen unacceptable yield losses.

Our cropping practice has always been to reduce tillage wherever possible,
or no-tilling when growing soybeans and wheat. With machinery technology and
today's new seed treatments the results have been good.

Maybe with today's rising fuel costs, more growers will look at reducing tillage,
thereby benefitting the landscape. Tony Pynenburg,
Bright, Ontario
.

For those who have been doing it for years, it's no secret that buffer strips,
rock shoots, grass waterways and no-tilling reduce and/or even stop wind and
water erosion. The first step to restoration on a degraded farm is to acknowledge
the problem and take a planned approach to solving it.

The topography of the field, the direction and depth of waterways surrounding
the field and the level of damage relative to the field's productivity potential
all have to be taken into consideration. In the end, doing one or all of the
above (anything is better than nothing) should help you achieve better yields
on that farm. Leo Guilbeault, Belle River, Ontario.

 


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