Interaction Between Row Spacing and Yield: Why it Works

Agronomic research has indicated that there is a potential for yield increases with corn grown in row widths less than 30 inches. However, results are often inconsistent and the corn grain yield response to row width seems to be dependent upon a number of environmental and management factors. Very little work has been done to determine the factors that favor a positive yield response to narrow-row corn. The objective of this paper is to define conditions that favor a positive yield response to narrow-row corn. Research conducted in Michigan has shown that in three of four site years, the yield increase from decreasing the row width from 30 to 15 inches was greater on course-textured soils compared to a clay loam. On average the yield increase for the course-textured soils was 9.1 bu/acre versus 4.5 bu/acre for the finer-textured clay loam soils when row width was narrowed from 30 to 15 inches. This may be a result of increased water use efficiency with the narrow row widths under water-limiting conditions associated with the coarse-textured soils. In the presence of a significant environmental yield-limiting factor (e.g., low soil water availability) the efficiency achieved with more equidistant plant spacing is likely to result in increased yield due to the more efficient plant accumulation of resources (e.g., soil water) restricted by that environmental yield-limiting factor. Therefore, the yield response in switching to narrow rows would be expected to be greater under more challenging growing conditions compared to the yield response achieved in switching to narrow rows under more optimal growing conditions. Under more optimum growing conditions the gain from more equidistant spacing is negligible since the potential yield-limiting factors are available in abundance (“saturation”) at the wider row spacing. The same concept can be applied to radiation interception. More efficient radiation interception may be the basis for the observed positive yield response to narrow rows in northern latitudes where light is a more yield-limiting factor compared to southern latitudes.