Corn row spacing is important to maximize yield as well as to keep balanced with economic output.
Row widths continue to decrease as time moves forward. The most common row spacing for corn across the Corn Belt is 30-inches. This is compared to 36- and 38-inch row spacing dating back to the 1960s. Over the last decade, there has been increasing interest in 20-inch row spacing. This narrowing of row spacing improved light interception during pollination (VT/R1 stage).
However, research shows mixed results regarding the yield advantage of narrow row spacing—under 30-inches—over wide spacing, over 30-inches. Some research has shown a 3 to 10% yield increase, while others showed no increase or even a yield decrease. The most consistent yield increases were in the north-central United States at 7-10%.
There is speculation that there is a seeding rate interaction with row spacing; however, it is important to remember that both seeding rates and row spacing are greatly impacted by the hybrid that is chosen.
Research by Iowa State University has examined the effects of 20-inch and 30-inch row spacing on corn yields and found that it varied from location to location and from year to year. Farmers should consider row spacing based on-field productivity. In high yielding environments, greater than 235 bushels per acre, yield increased 8-10 bushels per acre when planted in 20-inch rows compared to 30-inch. In environments with less than 180 bushels per acre, both 20- and 30-inch spacing had similar yields.
Some advantages exist with narrower row widths; these include using the same planting equipment for corn and soybean to achieve higher soybean yield potential, reduced weed competition, increased shading of the soil, increased light interception per plant, and less in-row crowding. Plant populations continue to increase every year (~300-400 plants per acre per year). Using wide row widths forces more plants to be in a concentrated area, whereas narrower rows allow better disbursement.
Licht M.A., Parvej M.R., Baum M.E. 2019. Guide to Iowa Corn Planting. CROPR 3161. Iowa State University Extension and Outreach, Ames, IA.