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Agronomic Crops Network

Ohio State University Extension


Date of Planting

The recommended time for planting corn in northern Ohio is April 15 to May 10 and in southern Ohio, April 10 to May 10. Approximately 100 to 150 GDDs (heat units) are required for corn to emerge. In central Ohio, this number of GDDs usually accumulates by the last week of April or the first week in May. Improved seed vigor and seed treatments allow corn seed to survive up to three weeks before emerging if soil conditions are not excessively wet. An early morning soil temperature of 50 degrees Fahrenheit at the 1/2- to 2-inch depth usually indicates that the soil is warm enough for planting. Corn germinates very slowly at soil temperatures below 50 degrees Fahrenheit. Short-term weather forecasts should be monitored to make the best decision on early planting. After April 25, planting when soil moisture conditions allow is usually safe. The latest practical date to plant corn ranges from about June 15 in northern Ohio to July 1 in southern Ohio. Plantings after these dates usually yield no more than 50 percent of normal yields. 

Planting should begin before the optimum date, if soil conditions will allow the preparation of a good seedbed. Growers should have the equipment capability to plant more than half of their corn acres prior to the optimum planting date; this should allow planting all the corn acres prior to the calendar date when corn yields begin to quickly decline. Ohio corn producers usually cannot perform field operations during all days of their optimum planting date range due to spring rains and cool weather conditions that limit soil drying. On average, during the optimal corn planting time in Ohio, only one out of three days are available for effective fieldwork. 

Table 4-9 shows the effect of planting date in Columbus. Yields decline approximately 1 to 1.5 bushels per day for planting delayed beyond the first week of May. Grain yield and test weight were increased by early plantings, whereas grain moisture was reduced, thereby allowing earlier harvest and reducing drying costs. Early planting generally produces shorter plants with better standability. Delayed planting increases the risk of frost damage to corn and may subject the crop to greater injury from various late insect and disease pest problems, such as European corn borer and gray leaf spot. 

Table 4-9: Planting Date Affects Yield, Percent Grain Moisture and Test Weight of Corn Grain (Columbus, OH). 


Planting Date (mo/day)


Percent of Maximum Yield


Percent Grain Moisture


TestWeight (lbs/bu)

























Figure 4-1. Grain yields of corn planted on “normal” Ohio planting dates in late April to mid-May vs. early to mid-June dates, OSU studies, 2005-2014. Pg. 39 

In one out of four years, excessive rainfall in April and May forces farmers in Ohio to plant or replant up to half of their corn acreage as late as early to mid-June. Since 2005, evaluations of corn yield response to early and late planting dates (late April to mid-May versus early- to mid-June plantings dates) at OSU research farms in northwest (NW), northeast (WO), and southwest Ohio (SC), indicate that planting date effects on yield vary considerably across years and locations (Figure 4-1). The change in yield associated with the late planting dates ranged from -43 percent to +38 percent. Averaged across site years, yields decreased about 11 percent. For five of the 14 site years, yields of the later plantings were greater than or comparable to the early plantings which can be related to stressful early season growing conditions (excessively cold and wet) and unusually favorable late season growing conditions. The higher yields associated with June plantings occurred at the northern locations. 

Studies have also been performed to determine if various management practices need to be adjusted to optimize yield when planting corn in early- to mid-June. These studies indicate that Ohio producers generally do not need to modify plant population for late plantings based solely on hybrid maturity. There are differences in yield response among hybrids for early mid-May and June planting dates but these differences were not strongly related to hybrid maturity. Results suggested that in some Ohio environments, plant populations should be reduced regardless of relative maturity to optimize yield. Although planting dates in early to mid-June usually results in lower yields, optimum nitrogen rates for late-planted corn were not consistently lower than early-planted corn. Significantly reducing nitrogen recommendations may place producers at risk of yield loss under certain environmental conditions. 

Corn should be planted only when soils are dry enough to support traffic without causing soil compaction. The yield reductions resulting from mudding the seed in may be much greater than those resulting from a slight planting delay. No-till corn can be planted at the same time as conventional, if soil conditions permit. In reality, however, planting may need to be delayed several days to permit extra soil drying. Planting a full-season hybrid first, then alternately planting early-season and mid-season hybrids, allows the grower to take full advantage of maturity ranges and gives the late-season hybrids the benefit of maximum heat unit accumulation. When compared with short- to mid-season hybrids, full-season hybrids generally show greater yield reduction when planting is delayed. Planting early hybrids first, followed by mid-season, and finally the full-season hybrids spreads the pollination interval for all the corn acres over a longer time period and may be a good strategy for some drought-prone areas with longer growing seasons. 

Planting hybrids of different maturities reduces damage from diseases and environmental stress at different growth stages (improving the odds of successful pollination) and spreads out harvest time and workload. Consider spreading hybrid maturity selections between early-, mid-, and full-season hybrids―for example, a 25-50-25 maturity planting, with 25 percent in early- to mid-season, 50 percent in mid- to full-season, and 25 percent in full-season. Planting a range of hybrid maturities is one of the simplest and most effective way to diversify and broaden hybrid genetic backgrounds. 

When corn planting is delayed past the optimum dates or if a crop needs to be replanted, it may be necessary to switch hybrid maturities. In most delayed plantings situations, however, full-season hybrids still perform satisfactorily and reach physiological maturity (black layer formation) when planted as late as the last week of May. Hybrids planted in late May or early June mature at a faster thermal rate (require fewer heat units) than the same hybrid planted in late April or early May). 

Ohio and Indiana research indicates that the required GDDs units from planting to kernel black layer decreases with delayed planting. For each day that planting was delayed after May 1, the reduction in GDD requirement was about 6.5 GDDs. A hybrid rated at 2,800 GDDs with normal planting dates (such as late April or early May) may require only 2,605 GDDs when planted on May 30. Therefore, a 30-day delay in planting may result in a hybrid maturing in 195 fewer GDDs (30 days multiplied by 6.5 GDDs per day). 

Other factors concerning hybrid maturity need to be considered when planting is delayed. For plantings in late May or later, the drydown characteristics of hybrids should be considered. Although a full-season hybrid may still have some yield advantage over shorter season hybrids planted in late May, it could have significantly higher grain moisture at maturity than earlier maturing hybrids, there will be less calendar time for field drying, and drying costs will be higher. Later planting dates generally increase the possibility of damage from European corn borer (ECB) and Western bean cutworm (WBC) and warrants selection of Bt hybrids that control these lepidopteran pests if suitable maturities are available.