Zinc
Zinc is important in early plant growth and in grain and seed formation. It also plays a role in chlorophyll and carbohydrate production.
Zinc is relatively immobile within the plant. Deficiency symptoms appear first on younger leaves. Young leaves become mottled and show interveinal chlorosis, striping or banding.
| Crop | Zinc deficiency symptoms |
|---|---|
| Sweet corn | Young plants with interveinal chlorosis on new leaves; pale-to-white bands between leaf margin and mid-vein in lower part of leaf |
| Legumes | Thin, short stems; pale green-to-bronzed foliage with yellow mottling; interveinal chlorosis with veins that appear darker(more mottled chlorosis than manganese deficiency) |
| Tree fruit, strawberries | Chlorosis of young leaves; green halo along serrated margins of immature leaf blades; blind bud, little leaf, and resetting |
| Onions | Stunted growth; twisted, yellow-striped foliage |
Zinc deficiencies are most often seen on sandy soils with high pH levels. Heavily eroded knolls may also have deficiency problems. Large applications of phosphorus may aggravate zinc deficiencies. Livestock manure is often an excellent source of zinc.
Zinc deficiencies can impair the ability of plants to regulate the accumulation of phosphorus. This results in excess phosphorus uptake by plants. For this reason, tissue analysis of zinc-deficient plants will often show high levels of phosphorus.
The OMAFRA-accredited soil zinc test reports a “Zinc Index Value”. This index evaluates zinc availability based on soil zinc level and soil pH.
| Zinc Soil Index1 | Suggested Treatments |
|---|---|
| Greater than 200 | Contamination of the sample or of the field is likely. |
| 25 to 200 | Soil zinc availability is adequate for most field-grown crops. |
| 15 to 25 | Zinc availability is adequate most most field crops. If the field sampled is uneven in soil texture, pH, or erosion, some areas may respond to zinc applications. |
| Less than 15 | Zinc is likely to be deficient and should be applied in the fertilizer. |
| Zinc Index = 203 + 4.5(DTPA extractable zinc in mg/L soil) – 50.7(soil pH) + 3.33(soil pH)2 | |
| 1 These values are indices of zinc availability based on extractable soil zinc and soil pH. | |
| Zinc Index* | Onions | Other Crops |
|---|---|---|
| Zinc (Zn) required - kg/ha** | ||
| 0-7 | 4 | *** |
| 8-14 | 4 | 0 |
| 15-100 | 0 | 0 |
| 100+ Above Normal | 0 | 0 |
| * Zinc index reported = 203 + 4.5 (DTPA extractable soil zinc in mg/L of soil) - 50.7 (soil pH) + 3.33 (soil pH)2 | ||
| ** Foliar applications of zinc may be used in place of or with soil applications, but rate/ha should be reduced. Foliar applications are preferred for fruit crops. | ||
| *** Your zinc soil test is very low, but zinc deficiency is not expected on this crop. If zinc deficiency symptoms do appear, a zinc spray may be applied to the crop. | ||