Narrowing row spacing in soybeans is a common practice for many corn and soybean farmers. They gain the benefit of a quicker canopy which helps in the battle against weeds. But do narrow rows make sense in corn?
“Narrow rows are another weed management tool when you achieve crop canopy quicker,” says Mark Licht, Iowa State University cropping systems specialist. “It gives us the best flexibility going into a postemergence application, because we can possibly apply on the early side knowing we will canopy earlier. Also, an application on smaller weeds using a good residual product can reduce weed competition through canopy closure,” he says.
Generally speaking, Licht says narrow-row weed control benefits are similar for both corn and soybeans, because weeds can't out-compete a crop in low-light situations under a crop canopy. “You may have some weed escapes, but you rarely see weeds get above a corn canopy.”
“An application on smaller weeds using a good residual product can reduce weed competition through canopy closure.”
However, weed control isn’t the driving factor for a corn farmer considering a switch from 30-inch rows to narrow rows.
There’s an entire thought process that must examine all in-season operations for your corn program, especially if narrow-row soybeans aren't grown on the farm. “Aside from possible planter changes to 15- or 20-inch corn rows, there could be tire spacing concerns on all equipment, fertilizer sidedress challenges and a new corn header to buy,” Licht says.
Agronomically, narrow corn rows can also create a microclimate within the canopy, depending on plant populations. “With greater leaf wetness and more humidity, you might have a different set of disease pathogens and a greater need for fungicide use,” Licht says.
“With greater leaf wetness and more humidity, you might have a different set of disease pathogens and a greater need for fungicide use.”
To gain the narrow-row benefits of improved weed control, reduced soil moisture evaporation and increased light interception by the crop, yield gains must offset the capital expenses of making the change.
Iowa State University research over 10 site-years concludes a slight yield advantage for 20-inch row corn compared to 30-inch. It also examined various plant populations, indicating that both hybrids and growing season can significantly influence row spacing effect on yield.
Weather can trump both genetics and plant populations. “Regardless of row spacing, higher populations do best in wetter conditions, and lower populations do better in drier conditions,” Licht says.
“We’ve also seen greater corn yield response in narrow rows when grown in higher-yielding environments around 240 to 260 bushels per acre,” Licht says. “But even in 180 to 240 bushel per acre areas, narrow rows did not hurt yield.”
Licht says narrow row corn more consistently outyields 30-inch rows as you move north. “We see better yield response in northern Iowa than southern, and that gradient seems to continue into Minnesota and the northern Corn Belt,” he adds.
On the other hand, six years of University of Illinois research led by plant physiologist Fred Below shows that narrow-row corn can work anywhere with an enhanced management system.
Below and his graduate student team showed that an enhanced management system in 20-inch row corn has a synergistic effect on yield when improving plant nutrition, increasing plant population, and adding fungicides. The research compared 20-inch (enhanced management) versus 30-inch row (standard management) corn yields in three locations over six years. Narrow-row corn increased yield on average by 51 bushels per acre.
For more details on Below’s research, along with Indiana farmers who are transitioning to narrow rows, check out his 2020 Commodity Classic presentation: The Need for Narrow: The Future of Corn Production.
Content provided by DTN/Progressive Farmer.
Find expert insights on agronomics, crop protection, farm operations and more.