This University of Minnesota Extension guide explains how to diagnose and manage zinc nutrition in crops. Zinc is an essential micronutrient required for enzyme activity, carbohydrate, protein, and chlorophyll formation, so deficiency can reduce growth and yield. Zinc availability is influenced by soil conditions, especially cool temperatures, sandy or highly leached soils, low organic matter, erosion, high calcium carbonate, and certain crop rotations. Excessive phosphorus can also induce deficiency in very low-zinc, calcareous soils, although this generally requires unusually high fertilizer rates. Soil testing, particularly the DTPA zinc test, should guide applications. A response is possible below 0.75 ppm and likely below 0.5 ppm. Recommended rates are 5 to 10 pounds per acre broadcast or 1 to 2 pounds banded when tests are low. Corn is among the crops most likely to respond to zinc, particularly when the soil DTPA zinc test is below 0.75 ppm, and especially below 0.5 ppm. Recommended rates for low-testing soils are 5 to 10 lb zinc per acre broadcast or 1 to 2 lb per acre banded. Starter fertilizer or banding is generally preferred, while broadcast zinc should be incorporated if starter application is not possible. Research does not support widespread use of chelated zinc applied in-furrow, because yield increases have been inconsistent. Corn deficiency commonly causes broad white stripes along the leaf midrib and plant stunting; tissue analysis can help confirm suspected deficiency. Zinc sufficiency range for corn whole tops less than 12” tall and base of ear at initial silk is 20-70 ppm. There was no documented soybean yield increase from zinc applications across 31 Minnesota locations, including soils testing from 0.4 to 3.9 ppm DTPA zinc. Soybean zinc deficiency is uncommon, and its symptoms can resemble iron deficiency chlorosis, so visual diagnosis should be confirmed with tissue analysis. Sinc sufficiency range for soybean (trifoliate leaves) at early flowering is 21-80 ppm.