Zinc (Zn) is the micronutrient most often deficient for corn in Kentucky. This problem occurs every year but is more commonly seen in years with a cool, wet spring. Although the environment, soil type and past erosion each have an effect, the most important factors controlling plant available Zn are the soil pH, extractable soil phosphorus (P) and extractable soil Zn. While the amount of Zn in the plant increases as the available soil Zn increases, increasing levels of soil P and pH are strongly associated with reduced levels of Zn in the plant.
Murdock, Lloyd W. and Howe, Paula L., "Zinc Fertilizer Rates and Mehlich III Soil Test Levels for Corn" (2001). Agronomy Notes. 8.