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.
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. |
Figure 5: The 2007 corn crop with significant residue still remaining between the rows. |
