Corn Planting Date
Planting a full-season hybrid as early as possible generally helps maximize corn yield by allowing the crop to utilize more of the growing season.
For over 18 years, DuPont Pioneer has conducted planting date research at numerous locations to show how optimum planting dates vary in different parts of the Corn Belt. For instance, planting in early April provided growers in the central Corn Belt with the greatest profitability, whereas in the northern Corn Belt, planting in early May showed the greatest profitability (Figure 1).
Figure 1. Adjusted gross income responses to planting dates in the central, north-central and northern Corn Belt over 18 years.
Corn stands may be reduced when average soil temperatures are below 50 F. To help growers manage this risk, Pioneer provides stress emergence (SE) scores for its North American hybrids. Choosing hybrids with higher SE scores (and reduced genetic vulnerability) can help reduce stand loss due to cool soil temperatures.
A Pioneer study on SE showed that hybrids with higher SE had better stand establishment than those with lower SE in cold soils. (Figure 2).
Figure 2. Average stand establishment for high and low SE hybrids in 6 emergence locations. Locations are sorted from least stressful (left) to most stressful (right) based on average early stand.
Planting early to maximize yield often means planting into a stressful environment, such as cold, wet soils or planting just before a cold spell. These environments can then result in suboptimal conditions for germination.
Timing of Cold Stress
If corn is planted prior to a cold rain or snow, the seed may sit in cold, saturated soils, which imposes stress emergence and decreases stand establishment.
Pioneer research has shown that the first 24 hours after planting are critical for successful stand establishment. Cold stress within this period can greatly reduce germination, whereas cold stress that begins more than 24 hours after planting will likely be much less detrimental (Figure 3).
Figure 3. Germination of 2 hybrids with stress emergence scores of 4 (below average) and 7 (above average) following imbibitional chilling induced by melting ice. Ice was applied immediately after planting (0 hours), 24 hours later or 48 hours after pre-germination in warm conditions.