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Heavy rainfall and flooding in many Midwest fields in 1993 prompted farmers and others to ask about soil compaction and the need for preplant tillage prior to planting the following year. On five Iowa farms that experienced excessive rainfall, U.S. Department of Agriculture researchers compared shallow, moderate and deep tillage and evaluated their effects on soil compaction and crop yields.
The clay loams were very productive under normal conditions. The researchers looked at bulk density (the higher it is, the more compaction), penetration resistance, soybean and corn yields and returns per acre.
While preplant tillage did lower the bulk density somewhat, it did not affect crop yields. Average per acre returns with corn were $54 less for subsoiling and $42 less for chisel plowing than for no-till corn. For soybeans, there was an average savings of $20 per acre with both no-till and shallow tillage compared to moderate or deep tillage.
The researchers concluded that soils that have been previously flooded or inundated with rainfall may have slightly higher compaction. Unless crop root functions such as nutrient and water uptake and the availability of oxygen is affected, there’s little need for preplant tillage for subsequent crops. The researchers suggested that farmers in these situations need to assess the costs and potential returns associated with tillage.
With no-till, there is limited disturbance of the top…