Why are the alluvial soils of the Gangetic Plain fertile?

The alluvial soils of the Gangetic Plain are exceptionally fertile primarily due to the deep, nutrient-rich layers of sediment deposited by the slow-moving rivers of the Ganges system.12

This fertility is enhanced by the presence of khadar, which is new alluvium found across much of the floodplain; it is characterized by a uniform texture and high productivity. Furthermore, the region benefits from vast sandy aquifers that hold significant groundwater reserves, which, when combined with extensive irrigation systems, support highly productive agriculture. While older alluvium, known as bhangar, exists on slightly elevated terraces, the continuous replenishment of soil through river activity remains a cornerstone of the region's agricultural success.34