Corn Production
Planting Dates and Crop Development

Planting late is probably the most common problem in Mississippi corn production. It is well established throughout the corn-producing areas of the United States that early planting produces higher yields than late planting. The standard for determining earliest planting date is when soil temperature at planting depth is maintained at 50 to 55 degrees Fahrenheit. This generally corresponds with the suggested planting dates shown in Figure 1.

Early planting produces higher yields for many reason. Insects and diseases often are avoided through early crop development; for example, early planting is the only defense against Southern rust. The major reason for planting early is to avoid environmental stresses, primarily water and temperature. Corn requires the greatest amount of water during silking. Mississippi studies indicate corn requires about 1.5 inches of water per week during the peak growing period. Rainfall is normally insufficient to meet this requirement. When rainfall is insufficient, good yields depend on water stored in the soil. This is why early plant development and the water-holding capacity of the soil are so important. Corn pollinating in late May and June will have a better moisture relationship in most years than will corn flowering in July and August.

Temperature also affects yield. Analysis of long term weather records and average yields in the Midwest indicates the daytime temperatures above 90 °F and night temperatures above 70 °F reduce yields. Temperatures in these ranges begin in early to mid-July in Mississippi. High temperatures can cause death of pollen and also kernel abortion. A combination of water stress and high temperatures at pollination can be disastrous. Under these conditions pollen shedding is accelerated and siling is delayed, resulting in ear barrenness because of contrast in development timing. Stress during grain filling results in severe competition for photosynthate between vegetative and reproductive components, leaving less for grain filling, thus greatly reducing yield.

Average Annual Rainfall

See Figure 2

Revised by Dr. Erick Larson, Extension Agronomist

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Information Sheet 866
Extension Service of Mississippi State University, cooperating with U.S. Department of Agriculture. Published in furtherance of Acts of Congress, May 8 and June 30, 1914. Ronald A. Brown, Director

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