Zinc Levels in No-Till and High Phosphorous/pH Soils

Richard Taylor, Extension Agronomist; rtaylor@udel.edu

I’ve noticed several soil tests recently that showed very low levels of zinc and at the same time high levels of available phosphorus and pH levels in the mid to upper 6 range. Growers should evaluate their most recent soil test reports especially if they are in continuous no-till systems. The combination of cold, wet soils in no-till production systems and high phosphorus, low zinc, and moderate to high pH levels can lead to some early season zinc deficiencies. Be sure to scout these fields frequently for symptoms of zinc deficiency.

The soil tests reports I’ve seen have shown zinc levels as low as 1.8 lb Zn/acre up to almost 5 lbs per acre and these values seem too low to me. Fields at these levels may need either a foliar zinc application once the corn is up and growing or a broadcast application of zinc sulfate to prevent early season zinc deficiency from injuring a corn crop. Another option is the use of an acidifying starter fertilizer possibly with a little zinc added to the fertilizer. The acidification of a narrow band near the corn seed can easily boost zinc uptake and prevent early season problems.

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