Row width trends in soybeans
In recent years, soybean acreage in North America has been somewhat evenly divided between drilled, 15-inch, and 30-inch row spacings. However, row spacing practices vary widely across different areas. Among the four largest soybean-producing states there are substantial differences in row spacing practices, with a majority of growers in Illinois and Indiana favoring 15-inch and narrower spacings, compared to Iowa and Minnesota where soybeans planted in 30-inch rows are much more common (Figure 2). Row spacings of 36 inches and wider are rare in the northern and central Corn Belt, but more common in southern raised-bed systems. Similarly, 22-inch rows are common in sugar beet producing areas such as Minnesota, but not generally found elsewhere.
click image to zoomFigure 3. Changes in soybean acreage planted in the most common row spacings from 2006 to 2011 in North America. Source: Pioneer Brand Concentration Survey. One consistent trend across North America over the last several years has been the move away from drilled soybeans. Drilled soybeans have declined from 29 percent of soybean acres in 2006, to 21 percent in 2011 (Figure 3). Even in areas such as Canada and the northeastern U.S. where drilled narrow rows is still the most common soybean row configuration, drilled acreage has dropped over the last five years. Planters generally provide better seed placement and seedling emergence than drills, which has helped reduce seeding rates and associated costs, although improvements in seed placement with newer drills make this less of an issue than it has been in the past (Holshouser et al., 2006).
In many cases, this decline in drilled soybeans has been accompanied by an increase in acres planted to 15-inch rows, which is now the most common row spacing for soybean. However, acreage planted to 30-inch rows has also increased in almost all regions of North America over the last few years, reversing the long-term trend away from wide rows. In some areas this increase has been substantial. For example, Illinois went from 18 percent to 29 percent of soybean acres planted to 30-inch rows over the last five years (USDA-NASS survey). This recent shift toward wider row spacings runs counter to the higher yields consistently demonstrated in narrower rows, which indicates that other factors beyond yield are driving grower decisions in this area.