Occluded phosphorus in soil refers to:

Correct option is B

· Occluded P = P entrapped within Fe & Al sesquioxide coatings, inaccessible to roots.
· Formed during prolonged weathering.
Why other options are wrong
· (a) P fixed in clays = non-occluded adsorption, not occlusion.
· (c) Available P is H₂PO₄⁻ / HPO₄²⁻.
· (d) Fertilizer P is not occluded.