Placing Fertilizer With Seed Requires Care

Too much delays germination; too little is a waste.

Published on: Apr 29, 2008

As spring planting begins to pick up pace, some agricultural producers may consider placing fertilizer with the seed during planting. That can be a good practice, but only if done with great care, says Kansas State University´s Dave Mengel.

"All fertilizers are salts so can cause germination problems if too much is placed with the seed," said Mengel, who is a soils scientist with K-State Research and Extension. "Too much fertilizer may inhibit germination completely, which results in a stand loss."

In other instances, too much fertilizer placed with the seed may simply delay germination, or it may result in weak seedlings with poorly developed root systems, he said. Either way, the affected seedlings will be at a competitive disadvantage, and a loss of yield potential could result.

Mengel suggests keeping several points in mind when evaluating seed- placed fertilizer:

The potential for injury is greater in sandy and/or dry soils.

Nitrogen (N) and potassium (K) are the fertilizer components responsible for seedling injury. For corn, the maximum rate to place with seed is 6 to 8 pounds of N + K per acre.

For grain sorghum, reduce that rate 25 to 30 percent.

Place no fertilizer with soybean or sunflower seeds.

Some fertilizers should never be applied with seed. Do not apply ammonium thiosulfate by itself in direct contact with the seed. Don´t place urea-containing fertilizers with seed.

Further details are available on K-State´s Extension agronomy Web site: www.agronomy.ksu.edu/ (click on Extension; Agronomy e-Updates; e-Update 4/17/08).