Mobility of nutrients in the soil has considerable influence on availability of nutrients to
plants and method of fertilizer application. For plants to take up these nutrients, two processes are important:
(1) movement of nutrient ions to the absorbing root surface, and
(2) roots reaching the
area where nutrients are available. In the case of immobile nutrients, the roots have to reach the area of nutrient availability and forage volume is limited to root surface area. For highly mobile nutrients, the entire volume of the root zone is forage area. Based on the mobility in the soil, the nutrient ions can be grouped as mobile, less mobile and
immobile.
The mobile nutrients are highly soluble and are not adsorbed on clay complex; e.g.:
N03-, S042-, B03-, Cl-, Mn2+.
Less mobile nutrients are also soluble, but they are adsorbed on clay complex and so their mobility is reduced; e.g.: NH+, K+, Ca+, Mg++, Cu++.
Immobile nutrient ions are highly reactive and get fixed in the soil; e.g.: HPO42-, H2PO4-
, Zn++.
Mobility in Plants
Knowledge of the mobility of nu\fients in the plant helps in finding what nutrient is
deficient. A mobile nutrient in the plant, moves to the growing points in case of deficiency.
Deficiency symptoms, therefore, appear on the lower leaves.
1. N, P and K are highly mobile.
2. Zn is moderately mobile.
3. S, Fe, Mn, Cu, Mo and CI are less mobile.
4. Ca and B are immobile.
Chemical Nature
The nutrients can be classified into cations and anions and metals and non-metals based
on their chemical nature.
Cations: K, Ca, Mg, Fe, Mn, Zn, Cu,
Anions: NO3, H2, PO4, SO4
Metals: K, Ca, Mg, Fe, Mo, Zn, Cu,
Non-metals: N, P, S, B, Mo, Cl
