Soil Protection in 2007
Greg Stewart, OMAFRA
Corn Specialist
In the age of
genetic modification, value chains, and ethanol, it can be difficult for something
as mundane as soil conservation to get much attention. However, since it appears
that we are set on demanding not only food, but a host of other products from
our thin slice of top soil, the need for its attention should not be diminished.
Since I have written
relatively little about soil conservation or tillage systems in the recent past,
it is perhaps appropriate to review the basics, highlight some success, and
look to the future for increased soil conservation and cost reduction possibilities.
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Surface Residue Protection from soil erosion hinges on keeping the soil protected with residue cover. The magical number to be considered a conservation measure was generally set at 30% residue cover. 30% of the soil surface needs to be covered with some sort of plant residue to protect against the impact of rain drops and to prevent soil movement. 30% is a value that can be fairly easily obtained with a range of tillage options when following grain corn or wheat (particularly if the straw is not removed), but becomes considerably more challenging in silage corn or after soybeans. |
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Aggregate
Stability In addition to providing protection by increasing residue cover, producers can adopt practices that increase organic matter and increase the ability for the soil aggregates to remain stable in the presence of water. Reduced tillage tends to improve soil aggregate stability, along with balanced crop rotations and the use of cover crops. Long term crop rotation research at Elora (University of Guelph) has shown that lower aggregate stability generally came as a result of having more tillage and/or more soybeans in the rotation. |
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Oxford County
Example
Gordon Green and
his family farm in Oxford County on some pretty productive soils but they face
the challenge of significant slopes in some parts of their land base. Green
has adopted a practise of reduced tillage where very little tillage is done
in the fall leaving most fields easily above the 30% residue cover level. In
the spring, ahead of corn planting Green runs one of the original strip tillage
designs (Trans-till) to prepare a seedbed while leaving the inter-row areas
covered with
reside. He also
applies nitrogen (UAN) down the back of the strip tillage shank in order to
meet any of the crop’s nitrogen demands that were not covered by manure
applications. Green is pleased with the system, and likes the improved soil
stability afforded to his land by performing less tillage.
Research into spring strip tillage has shown favourable results but those growers
who have become familiar with the system realize that the seed bed can be prone
to excessive drying in some springs if the planter does not follow relatively
quickly behind the strip tillage operation.
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Figure 3: Trans-till in action. |
Developments
When one considers the range of developments over the past 30 years, it is clear
that the corn producers in Ontario have a much better equipped toolbox from
which to build their conservation cropping system than did the early innovators
in this field. Consider: improved herbicides to give burn down and residual
control, genetically modified crops that are tolerant to herbicides and protect
against European Corn Borer and Corn Root Worm, more effective insecticides
that are seed applied, better planting equipment, improved highresidue tillage
equipment, improved agronomic information regarding starter fertilizers nitrogen
use, etc.
No particular recipe will fit every corn producer’s challenges when it
comes to adopting a conservation cropping system. However, in 2007 and beyond
we should be better able than ever to create, adapt and adopt conservation systems
which protect our soils for future demands.
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Figure
4: A field of corn stalks ready for the corn planter following spring
strip tillage.
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Figure
5: The 2007 corn crop with significant residue still remaining between
the rows.
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