Nutrients Stock in the Soil
Soil nitrogen reserves are localized in the organic matter. These reserves can be significant, but they are not easily available to plants. Nitrogen becomes available after the mineralization (decomposition) of this organic matter by micro-organisms in the soil. The nitrogen available to the plant is either localized in the soil solution, or adsorbed on the clay–organic matter exchange complex.
Phosphorus reserves are mostly found in organic matter and fixed by aluminum and iron oxides in the soil.
