Explanation:

Alluvial Soils The proportion of nitrogen is generally low, but potash, phosphoric acid and alkalis are adequate, while iron oxide and lime vary within a wide range.
Black Soils Chemically, the black soils are rich in lime, iron, magnesia and alumina. They also contain potash. But they lack in phosphorus, nitrogen and organic matter.
Laterite Soils With rain, lime and silica are leached away, and soils rich in iron oxide and aluminium compound are left behind.