If you plan to squeeze your 30" corn rows down to 22" or less, you probably don't have to abandon your favorite hybrid.
Farmer and seed company trials show that hybrids that shine at 30" usually are also the best performers in narrower spacings.
Here's what the comparisons reveal:
"We've found that, if a hybrid yields high in 30" rows, it yields even better in 15s. But it ranks virtually the same in both row widths," reports farmer-inventor Marion Calmer, Alpha, IL.
"However, we want to caution farmers against using hybrids that are prone to leaf diseases, such as gray leaf spot, in 15" rows," he says. "Because of the denser canopy, more moisture is held in the soil. Also, morning dew stays longer on the leaves. Those conditions promote leaf diseases in susceptible hybrids."
Calmer, father of the 15" corn head, discourages switching to ultra-high populations when converting to 15" rows.
"We started out with 36,000 plants/acre in 1995 because I thought that would be best. However, we've been reducing it ever since. Our research shows 30,000 plants to be optimum."
Calmer points out that 28,000 plants/acre produce equidistant spacing of 15 x 15".
Grower Dan Leffelman, Sublette, IL, has had two years experience with 15" rows. He's leaning toward the shorter hybrids and/or upright-leaf hybrids, assuming they're proven performers in yield trials.
Asgrow agronomist Randy Gettle, Mapleton, MN, has compared 30" and 22" rows at 28,000 and 34,000 plants/acre. He tested 29 hybrids in 1998.
"The bottom line," says Gettle, "is that in three years of testing we've seen no interaction between hybrids and row spacings. If a hybrid did well in 30s, it did well in 22s. In 1998, for example, one of our experimentals had the top yield in both row spacings and at both populations."
Last summer at Estherville, IA, Golden Harvest agronomist Rick Smelser compared six hybrids in 15", 22" and 30" row widths. They ranged from 90 to 103 days in maturity and were of various heights.
"There was no indication that any of the hybrids were better- suited for narrow rows than any others," he reports. "However, there was a gradual increase in yield as we went narrower in row width, and also slightly less moisture at harvest in 15" rows vs. 22" or 30" rows."
Golden Harvest agronomists also found no hybrid-by-row- width interaction in two previous years of comparisons with different hybrids.
In testing at 12 Pioneer locations in 1998, researchers found that most sites did not show a hybrid-by-row-spacing interaction. However, there was an interaction at three locations.
NC+ agronomist Jim Cisco points out that hybrids turn over so fast these days that it's difficult to screen them for differences in response to row spacings before they're history.
"Customers like to see new and improved; that's the way the seed industry works today," he says.
"Varieties don't last more than three or four years. Yet, to create reliable recommendations, we need to collect enough information to determine whether a hybrid is responding to 15" rows or just environmental conditions.
"One of the paradoxes of the seed business is that we have the greatest knowledge of a hybrid's behavior about the time we're phasing it out."
At least one company recommends certain hybrids for narrow rows, based on plant stature.
"We have targeted three hybrids for narrow rows," says Scott Hart, Garst agronomist for central Iowa. "They're short-stalked and have good disease resistance, especially to gray leaf spot. For farmers who increase populations in narrow rows, these shorter plants also mean relatively less residue to deal with."