July 25, 2005

Weather good or bad, Web site tracks crop yield trends

WEST LAFAYETTE, Ind. - Final crop yield numbers are still months away, when the last of the corn and soybeans is harvested. Between now and then, farmers can visit a Purdue University Web site for weekly updates on where yield trends are moving.

The Purdue Crop Yield Estimator, available online, provides estimates on corn and soybean crops for the United States and Indiana.

Prepared by Purdue's Department of Agricultural Economics, the yield estimator is intended to bridge the gap between monthly U.S. Department of Agriculture yield estimate reports. The yield estimator is updated by 5 p.m. every Monday, from late May through late September.

"The yield estimator is information about what the weather has done in the past week and how it might have an impact on increasing or reducing crop yields, both in the United States and Indiana," said Chris Hurt, Purdue Extension agricultural economist. "It is based on the USDA weekly Crop Progress report."

Those weekly USDA reports rank crop conditions but do not estimate yields. Official yield estimates are issued each month in the USDA's Crop Production report, beginning Aug. 12.

"For the USDA weekly Crop Progress report, USDA enumerators look at the quality of the crop," Hurt said. "Those enumerators then break the crop into five categories: very poor, poor, fair, good and excellent. Then, at the state level we have data for what percentage of the acreage of major crops, such as corn, soybeans and wheat are in each of those categories."

The Purdue yield estimator then uses crop condition data from previous years - and how those conditions affected final yields - to project current yield trends, Hurt said.

Yield estimator data indicates that national yield trends for both corn and soybeans have slipped since late May, while Indiana yields recovered slightly in the past week.

The July 17 crop estimator projected corn yields at 139.1 bushels per acre nationwide and 136.5 bushels an acre in Indiana, down about eight bushels and 14 bushels, respectively, from normal levels. National soybean yields were 1.6 bushels per acre below normal, with the Indiana crop 3.5 bushels per acre lower than normal.

"Our models have estimated that the extreme heat and dryness has taken 7-8 bushels of yield per acre out of the national corn crop," Hurt said. "We've gone from a corn crop of around 10.9 billion bushels, to a crop that's maybe 10.2 billion or 10.3 billion bushels.

"On soybeans, our numbers are suggesting about 1.5 bushel reduction per acre at this point. That's very significant - a total reduction of about 100 million bushels on this 2005 crop."

Weather will drive prices in the coming weeks, Hurt said. Should declining yield trends continue, crop prices are likely to go up.

"We're looking at a situation where if we drop yields any lower we are going to be in a short crop situation," Hurt said. "We'll need substantially higher prices to ration out a short supply of soybeans."

Hurt cautioned farmers that Crop Yield Estimator numbers are rough estimates and should not be the basis for market decisions. The Web resource has a margin of error of plus or minus 2.5 percent to 5 percent.

Writer: Steve Leer, (765) 494-8415, sleer@purdue.edu

Source: Chris Hurt, (765) 494-4273, hurtc@purdue.edu

Ag Communications: (765) 494-2722;
Beth Forbes, forbes@purdue.edu
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