A population should be high enough so limited sunlight penetrates through the fully developed crop canopy at silking. Incomplete light interception limits yield because all available energy is not being used. Light interception varies with plant population, hybrid, row width, and growth conditions. Late maturing hybrids normally intercept more light than do the early maturing hybrids because late maturing hybrids have more and larger leaves. Thus, early maturing hybrids should generally be planted thicker than the late maturing hybrids to compensate for their sparser leaf canopies.
Numerous studies show increased corn yields resulting from narrow row widths.
This has led to around 80 percent or more of corn producers in the United States using 30-inch or narrower planting equipment. Increased yields are obtained in narrow rows primarily because of more efficient light interception and utilization resulting from improved plant spacing. Improved plant spacing from narrow rows has allowed increased hybrid selection for more upright leaf orientation, which allows a thicker plant population and greater photosynthetic efficiency. However, this advantage is squandered in wide rows because hybrids with upright leaf orientation can not intercept light in the wide row middles. By Dr. Erick J. Larson, Extension Agronomist Mississippi State University does not discriminate on the basis of race, color, religion, national origin, sex, age, disability, or veteran status.