Row spacing for both corn and soybean is an important decision to make for any crop producer and can lead to high yielding crops. Corn row spacing is important to maximize yield as well as to keep balanced with economic output.
Corn row widths continue to decrease as time moves forward. The most common row spacing for corn across the Corn Belt is 30-inches. This is compared to 36- and 38-inch row spacing dating back to the 1960s. Over the last decade, there has been increasing interest in 20-inch row spacing. This narrowing of row spacing improved light interception during pollination.
Research by Iowa State University has examined the effects of 20-inch and 30-inch row spacing on corn yields and found that it varied from location to location and from year to year. Farmers should consider row spacing based on field productivity where higher yielding fields (>240 bu/a) positively respond to 20-inch rows. For more information, read Row Spacing for Corn in the encyclopedia section.
Row spacing when planting soybean is a management decision that is a priority when looking to achieve high-yielding soybean. Over several years, research across Midwestern states has consistently shown that soybean planted in narrow rows—less than 30-inch—has a yield advantage when compared to rows 30-inches or greater.
The primary reason for this advantage is light utilization; canopy closure is approximately 15 days earlier in 15-inch rows compared to 30-inch rows. Canopy closure earlier in the growing season results in greater light interception and higher growth rates.
Planting dates can influence the potential advantage of narrow rows. Planting in late April or early May will result in higher yields than planting in late May or June regardless of row spacing. However, narrow rows are even more advantageous in late-planting situations because they are able to capture available sunlight more quickly. Still, this advantage will not fully compensate for the yield penalty of late planting.