By Doug Cameron 

U.S. corn and soybean stockpiles continue to climb ahead of another record harvest that has sent futures prices tumbling since June, according to industry analysts.

The amount of corn in storage bins on Sept. 1 likely rose 1.5% from a year earlier to 1.757 billion bushels, according to an average of analyst estimates compiled by The Wall Street Journal. Soybean inventories are expected to have climbed almost 6% to 202 million bushels, compared with the same time last year.

The U.S. Department of Agriculture is due to release quarterly estimates for grain and oilseed stockpiles at noon EDT on Friday.

The relatively narrow band in expectations over corn stocks will likely mute the impact on futures markets, but analysts said the reaction to the soybean numbers could be larger as the band of estimates is almost 100 million bushels wide.

Some analysts are considering bumping up already high yield estimates, with the clement weather forecast over the next 10 days expected to favor harvesting beans over a still-wet corn crop in parts of the country.

The quarterly stocks reports have a limited history of surprises, but provide an important building block for industry estimates ahead of the next USDA update on global supply and demand conditions, due on Oct. 12.

The prospect of a fourth year of bumper harvests has depressed U.S. corn futures by 25% from their mid-June peak, with beans off almost 20%.

The USDA earlier this month projected farmers this fall will collect a record 15.09 billion bushels of corn and 4.2 billion bushels of soybeans.

One bright spot has been an uptick in exports. The Association of American Railroads said agricultural products shipments were 13.4% higher in the week to Sept. 24 compared with the same period last year. Activity has accelerated in recent months, with shipments now up 5.5% so far this year.

The global wheat inventory also continues to swell, with analysts forecasting U.S. stockpiles will climb 14.4% from a year earlier to 2.398 billion bushels.

The increase is in line with that experienced last year even though a multiyear low in flour prices has spurred food use, and wheat is increasingly challenging corn as an animal feed. U.S. exports remain sluggish because of the strong dollar and abundant global supplies

U.S. wheat production climbed 13.4% from a year ago to 2.326 billion bushels, slightly higher than the USDA's month-ago forecast according to analysts ahead of a separate report also due Friday.

Wheat prices have firmed in recent days as rains slowed the Australian harvest, but U.S. futures are still testing levels not seen since 2006 after a 15% decline since the start of the year.

Write to Doug Cameron at doug.cameron@wsj.com

(END) Dow Jones Newswires

September 28, 2016 17:58 ET (21:58 GMT)