Back in 2009, No-Till Farmer editors produced an article in which Fred Below listed the “7 Corn Growing Wonders of the World.” The University of Illinois crop physiologist determined that combining these critical factors could have as much as a 260-bushel per acre impact on corn yields.

In simple terms, these yield-boosting factors included the weather, nitrogen, hybrid selection, previous crop, plant population, tillage and plant growth regulators/biologicals.

Weather Rules

Below recently looked at which of these seven critical factors might have had the biggest impact in terms of increasing yields this year with last spring’s excessively wet conditions through much of the Corn Belt. Like many corn growers, the late planting season hit home with Below as many of his research plots didn’t get planted until after June 1. And he’s convinced delayed planting can easily cost a grower 15%-20% of their potential yield.

So what does Below think growers should do to protect yields in a weather-stressed late planting situation?

Below’s suggestion is to narrow row widths to boost the number of corn plants per acre to intercept and capture more yield-boosting sunlight. He believes increasing plant populations is the factor most under your control in dealing with late planting situations.

But if you’re no-tilling corn in 30-inch rows — as 87% of the growers responding to the most recent No-Till Farmer’s most recent benchmark study say they’re doing —it’s difficult to switch to switch to 20-inch rows at the last minute. While more corn plants can be planted in 30-inch rows, Below is convinced the biggest late season planting benefit comes from reducing row widths.

Below says the maximum density corn can tolerate in 30-inch rows is around 38,000 plants per acre. With no-tillers having a 31,987 average plant population, the typical grower boosts these numbers by 400 plants per year, That means no-tillers will be at the maximum of 38,000 plants per acre by 2035.

With 30-inch rows and 32,000 plants per acre, there’s an average of 4.8-inch spacing between plants within the row. With 20-inch rows, the plant spacing increases to 7.1 inches, due to more rows per acre.

By shifting to narrower rows, Below says growers should be able to boost yields by 10-15 bushels per acre due to the increase in light interception with more plants.

More Plants, More Yield

In a 6-year “high-tech” corn project, Below found 20-inch rows, plant populations as high as 44,000 plants per acre and increased fertility made the biggest yield difference despite higher costs for fertilizer and seed.

Compared with a normal corn growing system, his “high-tech” system boosted yields dramatically. However, Below believes growers will need more fungicides to deal with more disease potential caused by less air mass flowing down between the narrower rows.

Regardless of row width, Below believes most no-tillers are already ahead of the corn production game. With more surface residue and higher organic matter levels leading to improved water-holding capacity, he says no-till has an advantage over more intensive tillage. He also believes no-till also favors nitrogen availability.

While some university research suggests narrow rows are better suited to a high-yield environment, the real yield impact may be under water-stressed conditions such as occurred last spring. Yet others believe that when corn plants are placed further apart, there may be a bigger narrow-row yield benefit with drier conditions and in poorer soils.

15- vs. 30-Inch Rows

In 394 yield comparisons conducted over 7 years, Marion Calmer found a 12.3-bushel-per-acre yield advantage with 15-inch rows compared to 30-inch rows. The Alpha, Ill., grower credits narrower rows with providing plants with more sunlight interception, increased water retrievability and lower air temperatures around the ear.

While we know early planting pays big dividends, Below says planting dates are controlled by the weather, as was the unfortunate case last spring. But especially with late planting, Below makes the case that moving to narrower rows and dramatically increasing plant populations offer much more yield potential.

No-tillers should do the math on their own farms, looking at the total cost of changing row widths and higher fertilizer, seed and fungicide costs. Yet being in a position where a no-tiller could narrow row widths at the last minute with last spring’s wet weather may have been a good idea.