The incidental nutrients are so called not because they are incidental to plant health; for they are all either essential or beneficial, but that their supply is largely a passive process and so incidental to the general mechanisms of nutrient supply within the soil matrix.
Thus if one manages the biotic, basic and minor nutrients then in all likelihood the remaining nutrients required for plant, animal and human nutrition will all be in sufficient concentration and availability for crop needs. These last seven, whilst essential or beneficial to plant health do not generally need addressing or attending to by the Agriculturist: Thus they are the Incidental Nutrients and covered here for academic purposes only.
Aluminium: Whilst a beneficial plant nutrient aluminium is associated more with toxicity in soils. This toxicity results from the break down of the clay mineral releasing the Aluminium, which is a trivalent cation (Al3+), into solution where it quickly occupies exchange sites on the remaining clay minerals. Aluminium and Hydrogen are the principal acidic cations in soil systems and left unchecked they can lead to irreversible acidification of land severely limiting it’s productivity and usefulness. This can occur if the soil pH is permitted to fall below pH5.0.
Molybdenum An element needed in very small amounts by the plant but a necessary one that can be found to be limiting in soils. Deficiency symptoms mimic that of nitrogen whereas toxicities, which are always a result of over application, turn a plant orange.
Chlorine Chlorine, an anion, is generally abundant in soils but can become leached from sandy soils inland and far from the sea although it is more likely to reach toxic levels under irrigated situations and where there is insufficient precipitation to flush Chlorine ions out of the soil.
Selenium Another beneficial nutrient
Silicon One of the last nutrients to be recognised as beneficial Silicon promotes better cell wall structure leading to stronger stem development and considerable reduction in lodging.
The Accidental Nutrients
In addition to the 22 elements required by plants for their own growth processes plants also passively accumulate elements that are essential for animal and human nutrition. In particular Vanadium and Iodine, neither of which are needed by or used by plants but are essential for Animal and Human Nutrition. If plants did not extract and accumulate Vanadium and Iodine then animal and Human life would suffer the consequences of Iodine deficiency and goiter
Free Cultural Works (CC-BY-NC-SA)Malcolm McEwen 2011