Mother Nature is very unpredictable, and this spring has challenged many growers at planting time. From east to west, cold temperatures, rain and even late snow in some areas caused growers to get a late start on planting. Late-planted corn can bring with it a variety of issues and challenges for growers the rest of the growing season. Many growers question how badly their potential yields may be affected if their corn was planted a bit later than usual.

Yield impacts
In general, yields decline very slowly or little at all as planting is delayed up until May 10. From May 10 to May 20, the yield declines about 1/2 bushel for each day that planting is delayed. The loss increases to about 1 bushel per day from May 20 to June 1, with greater reductions in the northern Corn Belt than in the southern Corn Belt.

University of Illinois data indicates there are no significant yield differences for the same hybrid planted in mid-April versus early May. Only slight yield advantages exist for planting in the last week of April.

"What it comes down to is how Mother Nature treats the later-planted corn," says Kelby McKinney, district agronomist, Mycogen Seeds. "Remember: Many of us had planted corn early last year-some yielded well, some did not. It's all dependent upon the timing of weather events throughout the season."

Soil compaction
Regardless of planting date, growers should always be tremendously careful not to compact the soil too intensely. Tilling or even no-tilling wet soils promote compaction, which affects the growth habits of the corn this year and causes problems with the soil structure for years to come. If you planted into soils that were too wet, watch carefully for signs of soil compaction in the growing crop.

Insect pressures increase
"Insect problems can be rampant - not so much if everybody plants at the same time, but phenomenal if a grower has the only patch of late-planted corn in an area," McKinney explains. "Expect more pressure and greater yield damage from insects such as European and southwestern corn borers, fall armyworm, corn earworm and western bean cutworm."

The importance of planting a Bt corn product, such as a hybrid with Herculex I Insect Protection becomes critical in staving off pest issues. If you didn't plant a Bt corn hybrid, you should scout your fields regularly to detect any pest issues you may be having. Then apply pesticides as directed by your agronomist.

"Drought-stressed corn has enough trouble moving water, nutrients and photosynthate products without having its internal circulatory system damaged by corn borers," McKinney says. "Pests such as corn earworm, fall armyworm and western bean cutworm can decimate yield and quality by feeding on the developing kernels."

Emergence is generally fast when corn is planted late. Why? This is due to warmer soil temperatures and longer days. There are also very few problems from soil fungi. Growth is rapid, and later-planted corn generally grows taller than early planted corn.

"Corn will mostly catch up," McKinney concludes. "Corn planted a month later than normal will generally mature within a week to 10 days of the early planting because it gets driven faster by more collective heat units."