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Deficiency symptoms:
- Molybdenum (Mo): Low levels will result in reduced growth of seedlings, translucent spots on the leaves of potted trees, and leaf abscission
- Nickel (Ni): Low levels will result in reduced growth of seedlings
Function:
Si
- Enhances mechanical strength of fruit tissues (Dehghanipoodeh et al. 2016, Marodin et al. 2016, Zhang et al. 2017)
- Activates plant defences against insect and pathogen attack (Islam et al. 2020).
- A slow-release product, such as that used by Dann and Le (2017), holds promise for improving tree health but more research is needed.
Mo
- Mo is an essential trace element involved with N metabolism and as a co-factor for several essential enzymes (Wolstenholme 2017).
- Mo levels in sap analyses are quite seasonal and influenced by the weather e.g. low Mo occur in a tree during a dry summer.
- If there is a problem with nitrate or ammonia levels then investigate Mo levels.
Nutrient application example(s):
- Mo is phloem-mobile and can be applied as a foliar spray.
- Mo is the only nutrient whose availability increases with pH i.e. the higher/more alkaline the soil pH, the more available Mo is. In acidic soils, Mo availability of molybdenum is very low.
- S and Mo compete strongly during root uptake from the soil so sulphate-based fertilisers including gypsum will suppress uptake of Mo.
Interactions with other nutrients (Newett et al. 2018):
- There is an inverse relationship between Mn and Mo. Soils with high Mn e.g. in acidic soils with high water content, can be deficient in Mo especially if organic matter levels are low.
