Fundamentally Speaking
Joel Karlin DTN Contributing Analyst

Wednesday 10/31/12

Corn & Soybean Yields Year Following Drought Episodes

For the Eastern U.S, the remnants of Hurricane Sandy, which is now pummeling much of the Atlantic Seaboard and closed trading in New York, will continue to add to moisture reserves in the Delta and Eastern Corn Belt that had become quite depleted over the past year.

For much of the Western Corn Belt and Central and Southern Plains however, beneficial moisture remains sparse.

In light of recent graphics showing that the most severe drought plagued regions of the U.S. needing anywhere from 12-20 inches of rain to bring subsoil moisture levels back to normal, we were curious what U.S. corn and soybean yields were the year after a drought.

First, we looked at those years where the average July-August Palmer drought reading was -2.00 or lower.

Recall that a reading of -2.00 to -3.00 indicates a moderate drought and since 1950 there have been 11 such July-August periods including 1954, 1955, 1956, 1963, 1966, 1988, 2000, 2001, 2002, 2006, and 2012.

We then looked at final yields of both the U.S. corn and soybean crops using a rather long 63-year trend measurement.

The average of the 10 years after these drought periods show corn yields the following year averaging 2.8% below trend and soybeans 2% below trend.

Note that are two periods of extended drought of 1954-1956 where corn yields averaged 10.7% below trend and soybeans 1.2% above trend and 2000 to 2002 where corn yields averaged -1.6% below trend and soybeans were down 3.7% from trend.

The point here is that while this summer’s drought caused corn and soybean yields to fall 24.2% and 13.8% respectively below their 20-year trend, a continuation of this drought which is not unprecedented could result in yet a fourth year in a row of below trend U.S. row crop yields.

This would not be a help in boosting world grain and oilseed supplies especially with early season optimism about huge South American corn and soybean production tempered by excess rains which have delayed timely plantings.


Posted at 8:54AM CDT 10/31/12
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