By Elwynn Taylor, Department of Agronomy Corn yield has been
less variable during the past 12 years than the previous 20.
However, the yield of the past 5 years in Iowa exceeded trend.
The national yield has a run of 5 above-trend years; this is an
historical record. A run of 4 above trend years occurred in
1984-87 (with a major drought at each end). On average, a new
record corn yield is achieved every 4 or 5 years. Improved
genetics and management get the credit for the consistent
improvement, and weather is the reason that yields are somewhat
erratic over a period of years. Weather is the major
uncontrollable risk factor in agriculture. The weather is not
controllable, but the risk is manageable. Widespread drought in
the Corn Belt is occasional, the most recent being in 1988. Even
the 1988 drought did not decimate the crops of the western Corn
Belt, but it reduced yields by 30 percent over much of the
central and eastern portion. Serious drought tends to follow a
19-year cycle and the next 4 years fall in