Zinc (Zn++)

Functions

Zinc is essential for many plant functions. Some of them are

Factors Affecting Zn Availability

High Response Crops

While this is an essential element for all plants, these crops have been found to be especially responsive: snapbeans, dry beans, corn, sweet corn, cotton, citrus, most orchard crops, pecans, rice, sorghum, and sudangrass.

Deficiency Symptoms

Toxicity

Zn toxicity is relatively rare under normal field conditions, however it has been observed after unusually high or prolonged applications. It has also occurred in crops grown near abandoned zinc mines. Reported symptoms are chlorotic and necrotic leaf tips, interveinal chlorosis in new leaves, retarded growth of the entire plant, and injured roots resemble barbed wire. However, excessive Zn availability or uptake could just as easily cause deficiencies of other nutrients such as P, resulting in their deficiency symptom being the only apparent symptom. Sewage sludge has been used with success to decrease Zinc availability. Liming and the application of Phosphoric fertilizers have also been used.

Using Zinc in a Fertility Program

Both soil and plant analyses are accurate evaluations of Zinc needs. If a crop is "Zn Responsive" and a high yield program is being used, some Zn is often inexpensive insurance for the higher yield goals.

Recommended rate of Zn

Method

Rate

Broadcast

2 to 16 lb./A

In-row

1 to 8 lb./A

Foliar

0.25 lb./A to 1% solution

Zinc is sometimes applied broadcast at much higher rates than listed above. Normally this is done to correct the soil Zn level in one treatment. This approach can be effective in correcting Zn problems for many years. Zinc-oxides and oxy-sulfates are satisfactory for buildup purposes, but for in-row applications or if immediate uptake is needed, the sulfate form should be used. Remember, as far as the soil application of chelates are concerned; a pound of Zn is a pound of Zn. Chelates are often less prone to causing leaf damage when applied foliar. You can also consider the application of appropriate Zn-containing fungicides as an effective foliar treatment, for mildly low leaf Zn conditions.

Some common fertilizer products containing Zinc

Product

Chemical Formula

Typical Zn Content

Zinc Sulfate

ZnSO4.H2O

36%

Zinc Oxy-Sulfate

ZnO-Zn SO4

38-50%

Zinc Oxide

ZnO

50-80%

Zinc Chloride

ZnCl2

50%

Zinc EDTA Chelate

ZnEDTA

6-14%

Zinc HEDTA Chelate

ZnHEDTA

6-10%