One route of an annual U.S. crop tour on Wednesday saw a corn crop in Illinois suffering from dryness and hail damage and soybeans that looked somewhat similar to last year.

Scouts on the route of the Pro Farmer Midwest Crop Tour estimated an average corn yield of 147.3 bushels an acre after surveying three fields in a district in central Illinois that included Woodford and Marshall counties. Last year, the tour estimated an average yield of 180.7 bushels an acre for the same district based on surveys of 35 fields.

The scouts estimated an average of 1,209.5 soybean pods per three-foot-by-three-foot square in the district. That was down slightly from the tour's 2010 average of 1,241.9 soybean pods for the district.

The crops "had too much heat and not enough rain," said Mark Bernard, an independent agronomist on the tour.

Grain users and traders are paying close attention to the forecasts because supplies of corn and soybeans are estimated to be historically low. Strong global demand for the crops, particularly from China, has drained inventories and pushed prices to lofty levels.

Intense heat and dryness in July hurt the crops across the Midwest. The weather was especially harmful for the corn crop, as it was in a key period of development during the stressful conditions.

The heat sped up development of the corn crop, with one field near Manlius, Ill. seen to be almost mature. Farmers will start harvesting in the next few weeks.

Corn and soybean fields in Marshall County near Lacon, Ill., showed signs of hail damage. Hail can reduce output if it harms crops by disrupting the flow of nutrients from the roots.

Crop conditions were "extremely variable," Bernard said. There were big differences in crop quality and output potential within fields and from field to field.

The scouts in Illinois were on the eastern portion of the four-day tour, which began Monday. Several groups departed from Bloomington, Ill., Wednesday morning to survey different routes and will meet up in Iowa City, Iowa, Wednesday night to compare their results.

There is a western portion of the tour that departed Wednesday from Nebraska City, Neb., and will meet up in Spencer, Iowa, Wednesday night.

Scouts from the eastern and western groups will converge in Austin, Minn., Thursday. Pro Farmer, an agricultural advisory firm, is slated to issue corn and soybean crop estimates Friday based partly on results from the tours.