AVAILABILITY OF SOIL NUTRIENTS
The availability of elements in soils is influenced by soil pH.
Soil and plant analysis, as well as visual symptoms, are the main diagnostic tools.
Manganese
- Is a common micro element deficiency.
- The deficiency is often seen on sandy and organic soils, as well as on calcareous and limed soils of high pH.
- Foliar application of manganese sulphate in a dose of 1-2 kg per ha can be used.
- Several fungicides contain manganese.
Boron
- Availability of B decreases at high and low pH.
- If needed B is only applied in relatively small amounts, since B is toxic to potatoes if applied in too high doses.
Zinc
- Zn-deficiency is associated with high pH of soils.
- A high availability of P can also induce deficiency in soils that are marginally Zn deficient.
- Zn deficiency interacts with the attack by Alternaria.
- ZnSO4, containing 35% Zn is the most common Zn fertilizer and is used at in a dose of 15-20 kg per ha. For foliar application a 0.2% solution Zinc sulphate is used.
- Zn containing fungicides is used where Zn deficiency is a problem.
- Zn is needed during the early stages of growth. Reason that dipping of seed in a 0.2% has given good results.
Iron
- Deficiency may occur on calcareous soils, especially during cool, wet periods.
- When leaf symptoms are observed, the foliage is sprayed once or twice with a 0.5-2% solution of FeSO4