Actual Field Data Feeds into August Crop Estimate

Uncertainty reigns over this year's crop. Tom J. Bechman

Published on: Aug 4, 2006

Arlan Suderman, Farm Progress marketing analyst for Farm Futures and Farm Futures Daily, an e-mail subscription service, can't wait until next week's crop report comes out. You might say he's like a kid at Christmas. Part of the reason for his excitement this year is because conditions are so varied around the Corn Belt that he's wondering if the enumerators wrapping up field visits now found what most people thought they would find in the field.

The July estimate is based largely upon acreage and trend yield for each crop. The August estimate is the first one that relies upon any input from enumerators who have actually been in fields. And while they sample only a minute portion of Corn Belt fields, the estimate carries clout and is usually closer than many might think because the entire process involves sites picked at random by computerized programs to represent larger acreage.

"The August estimate is really our first baseline estimate of what we can expect this year, based upon what's really in the field," Suderman says.

The August estimate dips below trend more times than it projects a yield above trend, based upon the past 11 years. However, an overall look at data from those years indicates that what happens from July to August in estimates is not very useful in predicting what will happen when the September report is issued.

However, going beyond August is a different story, Suderman notes. Final yield has ended up higher than August yield estimates in 8 of the past 10 years, including the past 5 years in a row. In fact the average increase from the August estimate to final yield is 6.2 bushels per acre, figured over the past five years.

For years Jim Newman, ag climatologist, closely examined how weather patterns during critical parts of the growing season tend to impact estimates. He found that USDA numbers tend to rise from August forward in years with cool, wet summers, but fall in drier, warmer years. The critical period for the prognostication for soybeans is mid-August into September.

However, last year Suderman's reliance on which way USDA yields had trended from August forward proved more reliable than guess based upon Newman's theory.

Part of the problem, which exists again this year, is that weather is so variable from state to state, and even within states inside the Corn Belt. If you planted corn in April in Indiana this year, for example, you probably think that the yield estimate should be moving upward. But if you replanted in late May or early June, as many did, and your corn is just now tasseling or hasn't reached that stage yet, you might think the yield trend should be below normal.

Here's an important piece of advice as you sort out information from upcoming USDA reports- just remember that looking out your back door over your back 40 is a pretty lousy indication of what the whole Midwest might be like, and of which way yield trends might be headed.