The vast majority of corn acres in the U.S. and Canada are currently planted in 30-inch rows (85 percent), with narrow row spacing (less than 30-inches) used on fewer than 5 percent of corn acres. Regional adoption of narrow rows varies widely, with the highest adoption rate in the northern Corn Belt states of Minnesota, Wisconsin, North Dakota and South Dakota.
 
Mark Jeschke, DuPont Pioneer agronomy research manager, indicates the primary rationale for narrow row spacings in corn is that by reducing the crowding of plants within a row, the crop will be able to better utilize available light, water, and nutrients by reducing competition among individual plants.
 
Over the years, research on narrow row corn has produced variable results, which suggests that multiple factors likely influence corn yield response to row spacing. Yield benefits with narrow row corn have been observed more frequently in the northern portion of the Corn Belt. Even among northern locations, however, yield benefits to narrow rows were inconsistent.
 
For example, a university study during 2009 and 2010 found no yield advantage to narrow rows at two southern Minnesota locations. While a survey of several recent university corn row studies comparing narrow rows to 30-inch rows, found an average yield advantage of 2.8 percent with narrow or twin rows was observed in northern studies, compared to no advantage on average (-0.2 percent) for narrow rows in Iowa, Indiana and Nebraska.
 
Similar results have been observed in DuPont Pioneer research. Results from76 research studies conducted by Pioneer between 1991 and 2010 showed an average yield advantage of 2.7 percent with narrow or twin rows in the northern Corn Belt states compared to a 1 percent advantage across studies in the central Corn Belt.
 
The extensive history of research on corn row spacing has repeatedly shown that it is a very complex issue with many interacting factors. Yield results have often been inconsistent and highly variable across environments, making it difficult for growers to determine the best solution for their individual farms.
 
However, the accumulated body of DuPont Pioneer and university research conducted over the past 20 years does not indicate that the current standard 30-inch row spacing is limiting to corn productivity for most of the Corn Belt. This research also provides little evidence to suggest that narrow rows will consistently increase yield relative to 30-inch rows on productive soils under current agronomic practices.