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Most of the early-planted corn has not emerged and there are concerns and questions about what kind of stands there will be. Another issue is the possible lack of uniform emergence of the stand that causes uneven plant heights. Germination and emergence for early-planted corn requires more calendar days because soil temperatures are lower, but this has been an unusually long time period of low soil temperatures.

Field reports from crop consultants and county extension educators say that seedlings that have not emerged remain firm and healthy, suggesting that stands could be normal. With the wet and cold conditions, final stands could be lower than expected – that’s why we suggest dropping 15% more kernels than the desired final plant population with April plantings. Growers should continue to scout fields and monitor the condition of the germinating seeds.

While optimum plant populations are necessary to obtain good corn yields, the impact of lower than desired stands is usually less than the effect of later planting dates. The effect of plant population on corn grain yield is given in Table 1 and the effect of planting date is given in Table 2. For example, the yield potential of a stand of 22000 plants per acre is 88% or equal to the yield potential of a full stand of corn planted May 20. In addition, there would be replant costs, so one needs to compare yield potentials carefully before replanting corn stands that are not as good as desired.

When soil temperatures are low for a prolonged time period, corn plants are more likely to emerge over a few days rather than the desired uniformly emerging stands. In the past years with similar conditions, corn stands have had as high as 15 percent of the stand emerging 2 to 5 days later than the rest of the plants. While this is not the ideal, the effect of delayed plants on corn yield is not as dramatic as the visible effect of the shorter, later emerging plants.

The effect of late emerging plants on corn yield is shown in Figure 1 where up to 75% of the plants emerged 10 days later and 20 days later than the first emerging portion of the stand. The effect of late emergence is greater as the percent of the stand increases that is delayed and also greater as the delay becomes longer. However, with less than 25% of the stand delayed no longer than 10 days, the impact on corn yield is less than 6%.