Irrigation Reduces Soil Quality, but Rains Usually Do Not

Irrigation reduces soil quality, but rains usually do not. 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 lower amounts of salt.
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.