There's no guessing local farmers' biggest concern midway through the growing season.

Dry conditions have stressed corn and soybean fields across northwest Iowa. Though recent rainfall has helped, more precipitation is needed as crops head towards the home stretch.

"Corn has showed moisture stress for many days in a lot of fields so far this summer," said ISU Extension field agronomist Joel DeJong, who serves O'Brien County. "However, if it started raining and kept raining, the yield expectation would still be quite good."

DeJong reported that some cornfields have shown signs of leaf rolling, which occurs when the plants are not able to access the moisture they need. The curled leaves reduce daily water needs for each plant, which means it is not making as much plant food and eventually leads to lower yields.

DeJong noted soybean fields have so far faired better than corn. Still, he has seen some soybean fields with leaves turned upside-down in the afternoon, which the plant does to reduce water use.

"They are growing in most cases, but August is the critical month for them," he said.

DeJong said precipitation is desperately needed for corn as it hits tasseling season.

"The risk to the corn crop is reaching a critical time period," he said. "Water use per day as we get to the pollination stage is as high as a third of an inch per day, or a little more when it is in the 90s. If we restrict that during pollination, we could reduce the number of potential kernels we can get."

According to the latest report from the Iowa Department of Agriculture and Land Stewardship, 62 percent of the state's corn crop is rated good-to-excellent. Topsoil moisture levels rated 14 percent very short, 36 percent short, 48 percent adequate and 2 percent surplus. Subsoil moisture levels rated 18 percent very short, 45 percent short, 34 percent adequate and 3 percent surplus. Moisture levels vary widely as subsoil moisture levels in northwest Iowa rated 84 percent short-to-very short, while levels in southeast Iowa rated 84 percent adequate-to-surplus.

Thirty-nine percent of soybeans were blooming, six days ahead of the five-year average. Five percent of soybeans are setting pods, five days ahead of normal. Soybean condition was rated 59 percent good-to-excellent.