COLUMBIA, Mo. -- Farmers in the Missouri Bootheel are switching from soybeans to planting rice because the weather has been too dry. Farmers in north Missouri are already thinking their water-soaked soybean fields look like rice paddies.

Bruce Beck, Extension agronomist at Poplar Bluff, Mo., said drought has delayed soybean planting. Farmers with graded and leveled land are switching to rice, which can be flood irrigated.

While drought has dominated the Delta farmland, too much rain has kept north Missouri farmers out of their fields. Many can’t plant corn or beans. Those who have planted are now seeing their crops rot in the field. Cold, wet weather promotes fungus diseases.

"Where crops were planted in central and north Missouri, there are widespread disease problems," said Laura Sweets, MU plant pathologist with the Commercial Agriculture program. "There are a lot of uneven stands, with skips and jumps.

"There are a lot of soft, slimy, watery types of rots," Sweets said.

Too much rainfall and too cool temperatures contribute to the weakened crops.

"Most of the northern half of Missouri has received 8 to 10 inches of rain since May 1," said Pat Guinan, climatologist with the Extension Commercial Agriculture program. "May is a wet month, but rainfall is running between 150 to 200 percent of normal."

Rainfall total at Chillicothe, in north central Missouri, is 12.7 inches since May 1. That compares with 2.5 inches at Malden, Mo., in the Bootheel.

The super-wet zone extends northward into Iowa, southern Minnesota and Wisconsin, and eastward into Illinois, affecting a large part of the Corn Belt.

Farmers with partial stands face tough decisions, Sweets said. Some soybean growers she has visited are thinking of over-planting, or inter-seeding, to fill in the gaps in their bean fields. Others are thinking of starting over and replanting.

But, if they do, they will be facing the same seedling diseases that wiped out the first planting.

"If they replant, they should get Phythophthora resistant varieties -- if they are available," Sweets said. "Also, seed to be replanted should be treated with a fungicide."

A poor soybean seed harvest last fall has reduced the supply of available seed.

Because of short supply, some seed suppliers are selling bags of seed with only 75 percent germination, at no reduction in price, regional Extension specialists reported on the weekly Extension teleconference crop report.

The decision to replant a sparse stand is one of the most difficult a grower will face, said Bill Wiebold, MU Extension crops specialist. It’s a calculated risk that is affected by changing environmental conditions and the new planting date.

Replant factors to take into account include stand density, condition of the stand, yield potential of the sparse stand, and estimated gross revenue at harvest.

Then, replant costs must be factored in. Those include additional herbicide or fungicide treatments, which may be needed.

The formula requires realistic and accurate estimates on expected yields -- and forecasts of prices at harvest time.

Interactive worksheets for making the calculations are available on the Internet for growers with computers. They are at: http://muextension.missouri.edu/xplor/agguides/

Formulas to calculate the replant decision are in MU Guide 4091, "Corn and Soybean Replant Decisions." Printed copies of the guide are available at Missouri county Extension centers.

The most common soybean disease Sweets sees now is Phytophthora seedling blight. Earlier Phythium attacked seeds before they could come up.

Phytophthora is a soft, watery brown rot. The seedling above the ground almost disappears. "Yesterday when checking a field, I had to get right down in the row to see where the missing plants had been," she said. "They just melt away to nothing." Under the soil line is the blackish stub of the root.

Phytophthora favors heavy, wet soils in low lying or compacted areas. This year, with excess moisture, it is more wide spread.

Sweets said she is beginning to see four leaf-spot diseases on the young soybean plants that have survived. The diseases are likely to keep coming, along with the rain.

A lot of the problems could be solved with better weather, Sweets said. "Warm sunshine with no rain for awhile would help."

Duane Dailey is a senior writer for MU Extension and Ag Information.