May 23, 2008

Cool wet weather continues to plague portions of the central Corn Belt, resulting in significant planting and emergence delays for this year's crop. Producers across north central and east central Iowa, some of the top yielding acreage in the state, had to mud-in their crop prior to May 15. After the driest week since November 6-12, 2007, producers were able to sow one-third of their corn crop. Iowa saw an increase from 46% planted on May 11 to 78% planted on May 18.

Iowa isn't the only state experiencing delays. Portions of Minnesota, Wisconsin, Illinois, Missouri, Indiana, and Ohio also had delayed planting. In addition, recent heavy rains of 3 to 8 inches have producers from southern Missouri through southern Ohio facing the possibility that corn will need to be replanted. On top of the moisture, below normal temperatures have delayed corn emergence.

How significant are corn emergence concerns? As of May 18, several states were still at low levels for this time of year - Minnesota (3%), Wisconsin (7%) and Iowa (18%), significantly below their normal levels - Iowa (57%), Minneosta (46%) and Wisconsin (27%). On the bright side, four of the top 10 corn-producing states had seen at least 25% of their corn emerge by May 18, including Nebraska (25%), Illinois (34%), Indiana (35%), and Ohio (28%).

The warm temperatures experienced across the central Plains during the past week are projected to spread eastward over the next week, bringing an end to below normal temperatures for the eastern Corn Belt. Corn that has been in the ground for several weeks and not emerged due to cold soil temperatures will likely emerge at the same time as recently planted seed. It is entirely possible that 50-75% of the crop will emerge within a one-week window, increasing the risk of stress/drought damage if appropriate conditions materialize.

By May 25, nearly 50% of Iowa's corn crop should have emerged. If we use last growing season's temperatures, which were slightly above normal, and project them on this production season, at least 50% of Iowa's corn crop will not reach the tassel stage until July 18 or later. Corn silking will not occur until July 25 for at least 50% of the crop. Climatological temperature statistics indicate, that on average, the hottest seven-day period across the central U.S. is centered on July 21.

Thankfully, Nebraska producers are not as vulnerable as their eastern counterparts. At present, the corn crop is about seven days behind the five-year average. If we have normal temperatures, tassel and silking are projected to occur in the first two weeks of July. These projections would be pushed into the second half of July if temperatures during the next 45 days average at least 2°F below normal.

Weather models indicate that much of the central Plains will see two-week average temperatures close to normal. During the next 7-10 days, above normal precipitation should return to the region, with several significant rounds of severe weather possible. Precipitation projections for May 22-30 indicate 1-2 inches across the western third of the state and 2-4 inches across the eastern two-thirds.

Al Dutcher
State Climatologist