COLUMBUS – Pop-up or placement of the fertilizer directly with the seed has the potential to cause significant stand reduction, according to Ed Lentz, agronomist at Ohio State.
This depends on soil moisture and soil texture (damage potential increases with dry conditions and sandy soils).
To lower this risk, Lentz said to apply no more than 5 pounds per acre of combined nitrogen and potassium on soils with a cation exchange capacity less than seven and no more than 8 pounds per acre on soils with a cation exchange capacity more than eight for pop-up applications.
Lower equipment costs and faster application are the main advantages for the pop-up system.
Injury risk and the restriction on nitrogen rates are the main disadvantages. (Research has shown that most of the yield advantage from starter fertilizers comes from nitrogen.)
Suggestions. Unfortunately, some producers have been told that the plants emerge faster and utilize fertilizer more efficiently when applied close to the seed, Lentz said. Some have suggested that this occurs because of the liquid, low salt formulation.
Lentz said research has not shown that seedlings emerge faster from a pop-up system compared to a two-by-two placement system (2 inches below and to the side of the seed).
For the first three weeks after emergence the plant relies on nutrients from the seed and not fertilizer, Lentz said. By the time the seed reserves are depleted, nodal root development should be adequate to reach the two-by-two band.
Dry and liquid fertilizers generally behave similarly in the soil for a given macronutrient, meaning liquids are not more available to the plant than dry material.
Producers should base their decisions on their application equipment and fertilizer cost rather than liquid vs. dry material, Lentz said.
Using both. Some producers have been encouraged to use both a pop-up and a two-by-two band starter for maximum growth and yield benefits. There is no research data to support this theory, he said.
According to Lentz, it would be redundant to use both systems in the same field and would only increase fertilizer costs and application time.
Preferred. A two-by-two band is the preferred placement of starter fertilizer because of the low risk of injury to the seed and seedlings, and consistency in performance.
Pop-ups may be used because of equipment availability and application ease, but in some years, stand losses may occur depending on weather conditions and nitrogen and potassium rates, Lentz said.
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