Zinc concentration in the soil can decrease 30 fold for every pH unit increase between 5.0 and 7.0..
Bronzing and yellowing between the veins of the leaf, the leaf margins and midribs remain green. Growth is retarded, internodes are shortened, maturity is delayed. The leaves become small, thick and brittle with upturned margins. Plants are usually stunted.
Functions in plant:
Needed in protein formation. Influences consumption of sugar in the plant. Necessary for many enzyme reactions in plant, including the forming of one of the plant hormones.
Mobility in plant: Slightly mobile in plant and immobile in soil.
Influence of soil pH: The availability goes down as pH goes up; over liming can induce deficiencies.
Factors affecting level: High pH, some soils (sandy or peaty) have a low total Zn content; removing Zn in topsoil by levelling or erosion; higher organic matter (such as topsoil) soils are generally higher in Zn.
Factors affecting utilisation: pH; high phosphate or magnesium levels may depress Zn; cold root zones limit uptake; a P:Zn ratio of greater than 150:1 is likely to depress Zn.
Level in soil: 2-40 kg per hectare available; approx 20-600 kg per hectare total.
Adequate level in plant: Cotton 20-80 ppm, soybeans 20-70 ppm, rice 20-50 ppm, apricot 20-100 ppm.
Broadcast and incorporate 20-40 kg Zn per hectare. Thorough distribution is essential because of poor mobility. Foliar - deficiencies can be often corrected early when sprays of a 0.25-1.0% solution of Zn are applied.
Zinc is closely related to the organic matter of the soil. Zinc problems often show up where NPK fertilization is at a high level.