Row widths continue to decrease as time moves forward. Current row widths employed by producers typically vary from 15" to 38", with most producers at 30" today. Yet more and more acres are planted to narrower row widths. In general, this means 15" or 20" row widths. Numerous advantages exist with narrower row widths; these include using the same planting equipment for corn and soybean, 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 (400 plants per acre per year). Using wide row widths force more plants to be in a concentrated area, whereas narrower rows allow better dispersement.
In general, more of a yield response to narrow rows is expected to occur in northern production states, likely due to their shorter growing seasons. What has Iowa State University research shown in terms of yield response? Six years of research (1995-2000) conducted in Iowa showed a null yield effect when comparing 15" row width to 30". This data is included in the Corn Planting Guide (Table 6) and is extracted here for your reference. Year to year response varied; yet in general, corn planted in a 15" row width yielded the same as 30". It is important to note that yields will not be reduced when using narrow row widths.
Ongoing research is conducted at ISU investigating the yield response of a twin row corn production system compared to 30" row widths. Previous research (2003-2005) conducted at the SW Research and Demonstration Farm (Lewis, IA) has shown no significant yield difference between a twin row configuration and 30" row spacing during any of the three years. A twin row configuration places two rows atop the previous row. The twin rows are only 7-8" apart. See the Image Gallery for a picture of what this system looks like.
As plant populations significantly increase from where they are today, we expect the yield differential to shift more towards narrow row systems than 30". Yet at this time, we recommend producers use 15", 20", or 30" row widths. These three options will allow maximum yields to be realized if other factors have been properly managed including plant population, weed control, hybrid selection, and residue management.
Corn Planting Guide. Iowa State University Extension. PM 1885.
Text written for the ISU Corn Production website (www.agronext.iastate.edu/corn) by Lori Abendroth and Roger Elmore in December 2006.