When wet weather delays planting, corn growers deliberate on whether to switch to an alternative crop or continue planting corn. In many instances, farmers have forward contracted corn and need to deliver a crop. Farmers may also consider switching to earlier maturing hybrids and generally want to know how much yield they will lose if planting gets delayed into May.
In the Mid-South for instance, nearly 90% yield potential can be achieved for corn planted as late as May 9. For areas with more Midwestern growing conditions, greater than 90% yield potential can be maintained through mid-May. Mid- to late-April is typically considered a normal corn planting window in Virginia; however, equal to slightly higher corn yields have been reported with May plantings (Figure 1). Based on a six-year study in Kentucky, yields from early- to mid-May plantings were only 8% lower than those achieved with April plantings (Figure 2).
Averaged over all hybrids, locations and years, 244 fewer GDUs were required when planting was delayed from late-April or early-May to early- or mid-June (approximately 40 days). This is an average reduction in hybrid GDU requirement of about six GDUs per day of planting delay.
Research conducted in Ark. demonstrated that corn reduces the number of days from planting to silking when planted late (Figure 3). Days from planting to silking were 74, 74, and 79 for commonly planted hybrids with 111, 114, and 116 CRM. In contrast, days from planting to silking ranged from 47 to 51 for the same hybrids planted in mid-May.