Narrow-Row Corn Production – When Does It Increase Yields?.

The lack of consistent yield increases for narrow-row corn in research trials and on-farm experience in the central Corn Belt has resulted in low grower adoption of this practice. Pioneer Agronomy Sciences researchers conducted small-plot replicated studies in 62 environments (including 11 US states and Ontario, Canada) from 1991 to 1999 and from 2003 to 2006 to evaluate the effects of narrow rows 15 to 22.5 inches wide on corn yields. These studies included four replicates, three plant population levels, and four to eight hybrids per environment. The mean advantage for narrow rows over 30-inch rows was 2.0%, with environment means ranging from about -10% to 12%. A response of 2% or greater was achieved at 32 of 62 environments. Averaged across all environments per state, the advantage for narrow rows over 30-inch rows was 0.1% in Nebraska, 2.0% in Iowa (positive response at 14 of 21 environments) and 1.9% in Illinois (positive response at 6 of 8 environments). The advantage for narrow rows was greater in the northwest Corn Belt states of Minnesota, North Dakota and South Dakota, where the average yield increase was 3.9% with 15 of 16 environments showing a positive response. In Indiana, all three environments showed large positive responses, which differed from the results of surrounding states. Hybrid by row width interactions were rare in these studies, which means that selection of specific hybrids for narrow-row culture is unnecessary (but breeding programs focused on adaptability to narrow rows could change hybrid response in future hybrids). Where narrow rows increased yields, it is probable that the efficiency of light interception or moisture extraction by the corn plants was improved by the narrow-row arrangement, however, these factors were not generally measured in the studies. In future studies, careful tracking of field attributes and weather data during critical yield-determining stages (at least up to canopy closure) could help explain the variability in narrow-row yield responses across environments.