By Jeffrey Sparshott and Jesse Newman 
 

WASHINGTON--U.S. corn, soybean and wheat inventories all rose from a year earlier, according to a government report released Tuesday.

The U.S. Department of Agriculture said domestic corn stockpiles on June 1 totaled 4.447 billion bushels, up 15% from 3.852 billion bushels on the same date last year. Analysts surveyed by The Wall Street Journal had forecast 4.512 billion bushels of corn.

Soybean reserves on June 1 totaled 625 million bushels, up 54% from 405 million bushels a year earlier. Analysts had forecast 674 million bushels of soybeans.

And 753 million bushels of wheat were in storage, compared with 590 million on the same date in 2014. Analysts had forecast 713 million bushels.

Rainfall has swamped fields across the American Midwest in recent weeks, delaying soybean planting and causing concern over yield reductions in this year's corn and wheat crops.

In a separate report, the USDA said growers planted a record 85.139 million acres of soybeans, up from 83.701 million last year. Analysts had expected 85.187 million acres planted with soybeans.

"Record high planted acreage is estimated in Kentucky, Minnesota, Ohio, Pennsylvania and Wisconsin," the government agency said.

In March, the USDA estimated nationwide soybean acreage at 84.635 million.

Ahead of Tuesday's report, analysts cautioned that the USDA's outlook for soybean acreage would likely be discounted since it reflects farmers' planting intentions at the beginning of the month--before soaking rains prevented many growers from seeding their fields.

The USDA forecast corn plantings at 88.897 million acres, down from 90.597 million last year and the lowest level since 2010. Analysts had forecast 89.173 million acres.

U.S. growers are expected to plant 56.079 million acres of wheat, compared with 56.822 million in 2014. Analysts had expected 55.651 million acres.

Write to Jeffrey Sparshott at jeffrey.sparshott@wsj.com and Jesse Newman at jesse.newman@wsj.com.