Dear Student,
a. Alluvial soil can be classified on the basis of their age and accordingly there is Old alluvium which is known as Bangar and new alluvium is known as khadar soil.
b. Bangar soil is less fertile because of more concentration of kankar nodules, also this soil is found away from river bodies.
c. Khadar soil comprises of fine particles and is found closer to rivers, hence is fertile
Regards