- Soil organic matter (SOM)
- Deficiency of micronutrients is more likely to occur in soils with low SOM.
- Usually the greater the content of active (not lignified) soil organic matter the greater the availability. This is due to the release of the micronutrients through decomposition of OM and chelating compounds.
- Soil pH
- As pH decreases, the availability of Fe, Zn, Cu, Mn, Ni, and B increases
- As pH increases, the availability of Mo increases
- Redox potential (soil wetness and aeration)
- Fe Cu, Mn are more available under waterlogged than aerated conditions
- In well-drained (aerated or oxygenated) soils, pH controls availability of Fe and Mn.
- Soil texture
Deficiency of micronutrients are more likely in coarse-texture, sandy soils
Mycorrhizal fungi increase the uptake of micronutrients, especially Zn and Cu
- Soil pH is the most important factor affecting Mo availability.
At low pH values, Mo is adsorbed by silicate clays and the oxides of Al and Fe, and Mo is not easily available when in this state.
Liming the soil increases availability.
- It is easy to over-apply Mo and create a toxic situation.