Starter Fertilizer Question Hinges on Planting Date

Study of late-planted corn found little benefit for starter.

A farmer asked me several years ago if he should buy starter fertilizer tanks when purchasing his new planter. He went without starter fertilizer applied two inches to the side and two inches below the row for many years. Since he now plants earlier than in the past, farms lots of acres and farms a variety of soils over a wide area, he opted to get his newer planter with starter fertilizer attachments. That gives him the flexibility to apply starter fertilizer in situations where he believes it will pay dividends, and leave it off in cases where he may not need the extra expense.

Whether or not to apply starter fertilizer is especially up in the air this year since fertilizer prices, especially for starter materials, are still relatively high compared to historic numbers. What a study conducted by Jeff Phillips at the Throckmorton Research farm near Romney, one of the farms operated by the Purdue University Extension farms systems, found was that applying starter fertilizer on late-planted corn didn't make much difference, at least not in most cases.

Phillips, an Extension ag educator in Tippecanoe County and former Purdue agronomy researcher, also was interested in plant populations. He combined the two variables into one experiment. He discovered that a harvest population of about 30,000 plants per acre performed best at that location last year. He also found that there was no consistent, significant advantage for applying starter fertilizer.

The two hybrids Phillips used in the study were provided by Bird Hybrids, Tiffin, Ohio. They were the same two hybrids used in the population study at the Corn Illustrated plots near Edinburgh, Ind., in '08. At Edinburgh, one hybrid was hurt by a cool, wet spell in May, and emergence trailed the other hybrid. Final populations were off 2,000 to 6,000 plants per acre. Yield was 10 to 15 bushels per acre less. Starter fertilizer was not applied in that study.

In the Romney test, Phillips found that the hybrids reversed themselves. Unable to plant until the last days of May, emergence and stand establishment was not an issue. Since both hybrids were at nearly equal populations at harvest in various plots, the hybrid that fell short at Edinburgh excelled and beat the other hybrid at Romney.

"Our observations on starter fertilizer are in line with what agronomists have said for a long time," Phillips says. "Since we planted late, we wouldn't expect to see as much difference as if we planted early. That's exactly what our results showed."

If the plot could have been planted in cooler soils, say May 1, and endured the cool, wet spell that engulfed the state last year, or if soils were limiting on phosphorus, or if the plots were no-tilled, the results might have been different, he notes. Today, when starter does pay, nitrogen often makes up a large percentage of the fertilizer, with some phosphorus added. That's especially true in heavy residue and no-till conditions.

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