But university corn trials show mixed results Twenty-two growers from five states and Ontario averaged 7.4-bu/acre higher corn yields last fall in 15" rows than in 30" rows. That was a 4.8% difference.

The on-farm trials were coordinated by Alpha, IL, farmer-inventor Marion Calmer, father of the 15" corn head, and University of Wisconsin ag agent Jim Leverich.

"Twenty-one of the 22 farmers showed a yield advantage for the narrower rows," says Calmer. "The greatest yield benefit for 15s was 11.9 bu/acre. The least advantage was 0.3 bu/acre."

One farmer had a 1.5-bu/acre better yield in 30" rows.

Todd Schlacter, Lena, IL, compared eight hybrids in 30" and 15" rows. His results showed an 8-bu/acre edge for the 15s.

"The 15" rows seemed to have the most advantage on our less productive ground," Schlacter reports. "In our 1999 plots, the 15" rows yielded 20-21 bu better."

Schlacter uses a 32-row Kinze planter. He built a 15" corn head using Calmer's design.

Gene Miller, Leaf River, IL, switched from 38" to 15" rows in 1997. He reports a 7- to 15-bu/acre advantage for the narrow spacings.

"But the biggest benefit may be the way narrow rows discourage the deer," points out Miller. "We have much less damage now."

Despite the advantage for 15" rows in on-farm comparisons, a number of university trials have indicated little benefit for narrow spacings - at least not enough to justify a switch.

University of Illinois agronomist Emerson Nafziger, using university testing procedures, conducted 15" vs. 30" plots at six locations in that state last summer.

On average, the 15s yielded 1.1 bu/acre higher, but that wasn't statistically significant. Previous University of Illinois testing has shown similar results.

Nafziger also compared light interception for the two row widths. Interception was similar for both row spacings at plant heights of 3', 4' and 9'. Research has indicated that the greater the light interception, the higher the yield.

In 1995-99 Iowa State University comparisons, 30" rows averaged 161 bu/acre; 15" rows, 160 bu/acre.

Similar results have been reported in other middle Corn Belt states. But narrow rows have shown more of an advantage in states farther north. Here are a few examples:

- In 26 University of Wisconsin trials, grain yield was greater in narrow rows in six trials and less in four trials. In silage trials, yields were greater in seven of 13 comparisons.

- In three years of field-scale plots in Monroe County, WI, 20" rows outyielded 30" rows by 15 bu/acre (8%).

- Michigan State University tests during 1997-99 showed 15" rows averaging about 184 bu/acre, 20" rows about 182 bu/acre and 30" rows about 177 bu/acre.

- At the University of Minnesota, 20" corn averaged 7.7 bu/acre better than 30" corn.

Calmer and Leverich both point out that soil compaction may affect yield when rows are narrowed.

"In our opinion, compaction can be a major factor in the success or failure of a narrow-row system," says Leverich. "We need to make sure that when we narrow up equipment we don't drive on rows and cause compaction. Otherwise, we may lose any potential yield gain. Many trials that compared row spacings have not minimized wheel traffic on rows. That may be the reason they don't show a substantial yield increase."

Calmer says reduced tractor weight, coulters, track eliminators, tracks or wide radial tires with low air pressure will help alleviate compaction.

Narrow rows might boost yields, but extra costs need to be considered, too.

Mark Maidak, extension educator in JoDavies and Carroll counties in Illinois, did some projections. He assumed a 150-bu/acre yield level, a 6-bu/acre yield increase (4%) for narrowed rows, and a $2/bu corn price. That's a $12/acre added gross.

Maidak also assumed a corn-soybean rotation where soil insecticides could potentially be eliminated.

He estimated cost increases for fertilizer, hauling, drying and insurance/interest totaling $5.70/acre. That's a net operating benefit of $6.30/acre.

"Then the cost of narrow-row equipment must be considered," says Maidak. "To justify the switch, net per-acre operating benefits need to exceed per-acre capital costs."

One of the main reasons more farmers don't switch to 15" rows for corn is lack of commercially available corn heads. Producer-inventor Marion Calmer is changing that.

Calmer is offering a kit to change John Deere 30"- or 36"-row corn heads to 15" rows. He says the heads can then be adapted to fit Deere or Case IH combines.

Check his Web site (www.calmersagresearch.com) for current information, or phone 309-334-2609.

By the way, some experts say it's possible, but difficult, to harvest 15" rows with a 30" head. The operator needs to start early, slow down, raise the head a little and concentrate on centering the divider snoots between two 15" rows.