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After a long winter and the arrival of spring, many growers want to get into the field. However, planting too early can have a negative impact on yield. It is important to plant according to soil temperature and conditions and be aware of potential issues caused by cold, wet soils.
Corn requires a soil temperature of 50° F to germinate and grow. Temperatures below the optimum can cause seeds to remain dormant and become more vulnerable to diseases, insects, and animal predators. Planting into cold and/or wet soils can lead to numerous problems.
In this region, corn is often planted before the optimum window in an attempt to get all the corn acres planted. Decreases in yield potential can occur when corn is planted after the optimum planting window, while early planted corn can have a higher yield potential. The University of Delaware recommends planting half of the corn acres prior to the optimum planting window, if conditions are fit, then plant the remaining corn acres during the optimum planting window. The long term forecast should also be considered when evaluating conditions for planting. Virginia Cooperative Extension indicates that in some years, early planted corn has to be replanted because of warm temperatures in early April followed by cool temperatures later in the month. Therefore, Virginia Cooperative Extension suggests that if the predicted air temperatures are above the corn growth threshold of 50° F for the next few weeks and other conditions are favorable, plan to plant early. If late planting does occur, it may be beneficial to plant earlier maturing corn products.
Table 1 lists the usual planting dates, in most years, based on 20 years of data and knowledge from industry specialists, reported by the USDA. The ‘Beginning Date’ designates when planting is approximately 5% complete, ‘Most Active’ designates when 15% to 85% of planting is complete, and ‘Ending Date’ designates when 95% of planting is complete. Once planting commences, corn seed placement is critical to help maximize yield potential. Remember the following tips to help establish a good crop:
Do not plant too shallow. Planting less than 1.25 inches deep can result in rootless corn or root lodging. Shallow planting can also increase the risk of injury from some soil applied herbicides.
Do not plant deeper than necessary. When soil moisture is abundant, plant around 1.5 to 2 inches deep. When soil moisture is high, planting at depths of 2 to 3 inches can significantly delay emergence. If soil is dry and/or sandy, planting at 3 inches into moisture is less risky than planting shallow in anticipation of rain.
Planting when soil temperature and conditions are favorable is very important to give the crop the best chance of emerging properly and getting off to a good start. Although it is desirable to plant within the historic planting window, rushing to plant in cold, wet conditions can lead to yield-reducing problems later.
Table 1. UDSA Planting Dates in Delaware, Maryland, Virginia, and Pennsylvania.