Zinc is a component of enzymes involved in photosynthesis, sugar formation and protein synthesis. Proteins which are stabilised by an ionic form of Zinc , known as Zinc finger proteins, have an important role in DNA synthesis and gene regulation. Plants grown in Zinc deficient conditions display defects in fertility, seed production, growth regulation and ability to defend against disease. Oilseed rape tends to be less sensitive than cereals to Zinc deficiency; it is unusual for symptoms of Zinc deficiency to be observed.
Zinc availability and, hence, crop uptake varies considerably, depending on a number of factors.
- Soil pH. The solubility of zinc decreases with increasing pH and deficiency is most prevalent on calcareous soils at pH ≥7.4.
- Soil phosphorus. There is sometimes conflicting evidence of a potential antagonistic effect of P applications on Zn uptake, not least because phosphorus fertilisers can themselves supply zinc as a contaminant. Nitrogen. There is some evidence of increasing N supply being associated with zinc deficiency but this may simply be the result of increased crop growth and, therefore, requirement for zinc.
- Other ions. Evidence of a potential antagonistic effects of other ions such as Fe, Cu and Mg is sparse and, again, conflicting.
- Soil organic matter. Zinc deficiency has often been reported on restored sites where surface soil has been substantially removed/reduced. Research has often shown a strong relationship between organic matter and extractable Zn.
- Soil conditions. Soil compaction, waterlogging and low soil temperatures, all factors impacting negatively on root growth, are therefore also likely to depress zinc uptake. Moreover, low soil temperatures can reduce soil microbial activity and, hence, release of zinc from organically bound zinc.
