Some Corn is off to a Slow Start

Libbie Johnson, Escambia County Extension

Although the lingering cool springtime temperatures were a pleasure for us, some area corn fields have not fared so well. Below are a few photos from an irrigated field here in the western panhandle that had as much attention a corn field could get. The producer based his pre-plant fertilizer application on recommendations from his soil report. Generally, he uses a starter fertilizer but this year he used another commercially available product instead. After discussing these photos and reviewing soil reports with Dr. David Wright, it was concluded that the corn was getting off to a slow start because the fertilizer wasn’t readily available for corn that was already having a difficult time in cool and damp ground. Dr. Wright suggested next year returning to the practice of using a starter fertilizer but to have faith in the corn. He predicts that it will develop normally with proper care.

So what is starter fertilizer?

Small amounts of nitrogen, phosphorus, sulfur, and micronutrients are often used as a starter fertilizer. The main advantage of starter fertilizer is better early-season growth, earlier dry down, and with many hybrids, higher yield. Corn planted in February, March, or early April is

exposed to cool soil temperatures, which may reduce phosphate uptake. Banding a starter fertilizer two inches to the side and two inches below the seed increases the chances of roots penetrating the fertilizer band and taking up needed nitrogen and phosphorus. Starter fertilizer can also be used in a surface dribble for strip-till planting with the solution applied 2 inches to the side of the seed furrow for each 20 lbs of nitrogen used.

Currently, the most popular starter fertilizer is ammonium polyphosphate (10-34-0), a liquid. Monoammonium and diammonium phosphates are dry sources and equally effective. There is generally no advantage in using a complete fertilizer (NPK) as a starter, since applying nitrogen and phosphorus is the key to early growth. If soil test levels for P and K are high, a starter with 30–40

lbs/A of nitrogen and 15 lbs/A of P is adequate for starter application. Normally, 10–15 gallons of a starter fertilizer containing one-third to one-half 10-34-0 and the remainder as 28-0-0-5 has been effective for early corn growth. Corn will take up around 15–20 lbs/A of N and 5 lbs/A of P by the time the corn is 15 inches tall. Therefore, high rates of starter P are not necessary unless it is used to supply all of the P for the corn crop in a low soil test field.Please see the complete Field Corn Production Guide for more information on fertilization, pest control, and overall management of field corn. The information on pre-plant fertilizer was taken from the EDIS publication, Field Corn Production Guide, written by Drs. David Wright, Jim Marois, Jim Rich, and Richard Sprenkel.

Roots comparison of healthy corn to the slow corn.

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