Question

Why are the deltas so fertile?
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Answer 1

Answer:

Delta's are so fertile because sand from different lands is brought by water. Delta is a land form that forms from deposition of sediment carried by a river as the flow leaves it's mouth and enters slower-moving or stagnant water.

Answer 2

Answer:

because they are irrigated by river which leave behind a lot of humus and silt resulting in making soil fertile