Explanation:

Alluvial soil has the highest productivity with respect to other soils. It is present mostly along rivers and is carried by its streams during weathering of rocks.. This soil has very soft strata with the lowest proportion of nitrogen and humus but with an adequate amount of phosphate. Most alluvial soils are derived from the sediment being deposited by the river Ganga in the Indo–Gangetic plain, ranging from Punjab in the west to West Bengal and Assam in the east, as well as in the coastal areas of northern parts of Gujarat, Narmada, and Tapi valleys, which are formed by sea waves.
The greater part of Punjab is covered with alluvial soil.