Irrigation Reduces Soil Quality and Rains Usually Don't.Why

Irrigation reduces soil quality and rains usually don't.Why?

A) Rains deliver less water to soil than irrigation does.
B) Water used for irrigation contains fertilizer and pesticides that affect soil quality.
C) Rainwater contains less inorganic material.
D) The fast water flow during irrigation removes organic material from soil.
E) The fast water flow during rains is able to remove toxic materials from topsoil.