The 1999 growing season, unlike many in recent years, has been one in which corn planting and stand establishment have proceeded with relatively few problems. We have had very few calls about poor stands, and most of the corn has emerged very well. Stands in the Urbana area are outstanding, probably the best I've seen in the past 10 years.|
Although most fields are in very good shape, there are reports that heavy rainfall after planting has caused some stand problems in several areas. Most of the damage is from flooding of low parts of the field, but soil crusting has been a problem as well. If it appears that replanting may be needed in fields where stands are poor, Table 3 can be used as a guideline for making replant decisions. This table gives percentage of maximum yield to be expected from incomplete stands, and from replanting for full stands later on.
To use this table, find the expected yield from the existing plant population and the original planting date. Then find the expected yield from a full stand if replanted on a certain date (fill in between lines if the date is between two dates listed). The difference between expected yield from replanting and that from the existing stand is the yield increase you can expect. If that more than covers the cost of replanting, then it should pay to replant. The table does not go beyond the end of May because the research was not designed to do so, but from other data we would expect a full stand planted on June 4 to yield about 75 percent of maximum, and one planted on June 10 to yield about 65 percent of maximum. Low areas that have drowned out don't need much calculation; they should be replanted as soon as they are dry enough.
Hybrids for replanting need not be changed to ones of earlier maturity if replanting is done in May unless the original hybrids were unusually full-season for the area. Corn planted late generally tends to require fewer growing degree-days to maturity, but of course they usually yield less than when planted early. Even when planting in early June, switching to earlier-maturity hybrids may not increase yield, especially since early-maturity hybrids are often not very well adapted to the area in question.--Emerson D. Nafziger