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.

In a 17-year Nebraska study, researchers found that conservation tillage gave higher irrigated corn yields and profits than tilled plantings. The average yield increase was 4 bushels per acre, while the three conservation tillage treatments resulted in $8 to $16 per acre less tillage costs than the conventional disc tillage treatment. The conservation tillage treatments were ridge-till, rotary-till and slot-plant, while tilled treatments consisted of chisel, disc or lister operations for the furrow-irrigated continuous corn plantings.