4 Agronomic Practices that Pay

By Gene Johnston 

Today, your skills as an economist may supersede those as an agronomist. Yes, you can do some things to get higher corn yields, but here’s the real question: Will it pay?

Jeff Coulter, University of Minnesota (U of M) Extension corn agronomist, shares this list of four agronomic practices and his latest research and thoughts about yields and payoff.

1. Seeding rates and fertilizer

Seeding rates on most farms have been rising in recent years, especially in high-yield environments. At the same time, farmers have been debating fertilizer rates, particularly nitrogen (N). Should it go higher to support the higher stands and yield goals?

“We’ve done three years of research at three locations across southern Minnesota,” says Coulter. “Most of our trials are fertilized for a yield goal of 250 bushels per acre, except for the N. We’ve varied the nitrogen fertilizer from 65 pounds per acre to 110, 155, and 200 pounds per acre of N in split applications. Then, on top of that, we’ve layered planting populations of 30,000 plants per acre to 36,000 and 42,000.”

The first take-home point, says Coulter, is that higher corn seeding rates don’t require more N fertilizer. At all seeding rates, yields with 155 pounds of N per acre usually match yields at 200 pounds. While the 2014 highest yields tended to come with 200 pounds of N, it wasn’t by much. At $3.50-per-bushel corn, projected returns were usually maxed out at 155 pounds of nitrogen.”

While the highest seeding rate of 42,000 plants per acre (ppa) occasionally produced higher yields at two of three research locations, it was not the most profitable.

“The rate of 36,000 corn seeds per acre yielded nearly as well as 42,000, and the projected net returns advantage went to the 36,000 stand,” he says. “If you consider 36,000 plants per acre and 155 pounds of nitrogen per acre as a benchmark, that allows you to compare yields with this system to those with 42,000 seeds per acre, with or without an additional 45 pounds of nitrogen per acre. At two of our three research locations, the higher inputs occasionally produced greater yield. Frankly, at $3.50-per-bushel corn, that just isn’t enough to cover the extra cost.”

For example, the 42,000 ppa seeding rate and 200-pound-per-acre nitrogen application yielded 4 bushels more per acre in a trial at the U of M’s Southwest Research and Outreach Center at Lamberton. The projected net return, though, was $26 per acre less than the benchmark 36,000/155. At Rochester, Minnesota, the difference in net return was $48 per acre in favor of the benchmark.

“The 36,000 seeding rate with 155 pounds of nitrogen produced net returns that were consistently among the greatest in most locations and years,” says Coulter.

2. Narrow rows
In theory, this spreads the plants out, giving less competition between plants and allowing for higher plant populations. Coulter says Minnesota trials have compared 30-inch rows with 20-inch rows.

“We maxed yields in those trials at about 34,300 plants per acre, with no response to the narrower rows,” he says.

He’s also experimented with twin-row corn, comparing standard 30-inch rows with twin rows spaced 22 inches and 8 inches apart. In theory, that, too, gives less plant competition. In the Minnesota trials, though, little yield impact has occurred.

3. Hybrid maturities
Longer-maturity hybrids of 105 days have shown a 10-bushel-an-acre yield advantage compared with 95-day hybrids, says Coulter.

“You have to balance that to drydown, though. For every one day added to maturity length, we see about .25% to .50% wetter corn at harvest. There’s a line in there where the extra yield of longer-maturity hybrids doesn’t pay for the extra drying cost.”

Minnesota hybrid trials have evaluated 80 to 150 hybrids most years. Yield differences between the top 10 hybrids and the lowest 10 hybrids have shown a 40- to 70-bushel-per-acre spread, Coulter says.

4. Starter fertilizer

Coulter sees inconsistent response to starter (10-34-0) applied at planting for corn following soybeans.

“It’s not related to planting date or hybrid maturity,” he says. “I have to point out that these research fields are pretty well fertilized already, and maybe that’s why starter hasn’t consistently paid off. Greater frequency of yield response to starter has occurred when corn follows corn and there are lower soil-test levels, when the soil is fine textured, and when there is abundant surface residue at planting.”

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