DUNDAS (AP) — Farmers across Minnesota are rushing this week to get the last of their corn and soybeans in the ground after a cold, wet spring delayed planting past Memorial Day and into June, busting their plans and threatening to reduce growing times.

As of Sunday, 20% of the soybean crop and 8% of the corn crop in Minnesota were yet to be planted, according to the U.S. Department of Agriculture. That’s way behind the average of the last five years; statistically, Minnesota farmers two weeks ago should have been where they are now.

Harvests are sure to be reduced as a result, and so may farmers’ crop insurance coverage.

The week ending June 9 was good for farmers in other parts of the Midwest, where farmers were able to quickly make up lost ground. The corn crop in Indiana went from 31% planted to 100% planted in one week. The progress was similar in Ohio, Illinois and Michigan, where farmers had been even farther behind schedule than in Minnesota.

Just over half of the corn acreage in the 18 major corn-producing states was planted after May 25, according to the USDA, compared with the average of 16.8% from 1986 through 2018

Corn yields drop a little when the planting is delayed until mid-May. After that, yields drop dramatically.

Past studies show farmers can lose up to 24% of their harvest if they don’t plant corn until June 4, and up to 31% if they wait five days longer, according to the University of Minnesota Extension.

Soybean planting can happen later, but a June 9 planting loses farmers roughly 24% of their harvest and a June 14 planting loses them 30%.

The wet spring has also clogged shipping routes on the nation’s rivers. Hundreds of barges are held up at locks on the southern Mississippi River because of high water and fast currents, keeping supplies from farmers and limiting crops sent to market.