Advancing farm technology hasn’t freed no-tillers from the whims of Mother Nature. Rainfall remains an especially critical factor beyond the control of growers. What science has done, however, is look to the past and find weather patterns that can be useful in choosing management practices for the coming season.

“It’s written in the trees,” according to Elwynn Taylor, an Iowa State University climatologist and host of a popular Midwest radio weather program heard on WOI-AM 640 and on the Web at www.woi.org. He notes that scientists have examined yearly rainfalls by looking at the rings of trees as much as 4,000 years old. The researchers also have studied weather records dating back centuries.

Patterns Emerge

What they’ve found, Taylor says, is both a 19-year cycle and a 90-year cycle for rainfall and widespread droughts that are tied directly to declines in national crop yields. Seventeen times in the past 100 years, droughts have dropped yields more than 10 percent below the yield trends of the previous 30 years. A closer look at those 100 years reveals that the droughts have been cyclical.

“In every 19 years, we usually have three droughts, two of them serious” Taylor says. “It may vary by a year or two, but the drought cycle averages out to 18.6 years.” Because the last nationwide drought occurred in 1988, the U.S. is due for another drought-prone period, he adds.

“As we go from 2005 to 2010, we will be in the 6 risky years, when we will…