Answer: leaching

AnswerCrossword Clue
leaching(of a soluble chemical or mineral) Drain away from soil, ash, etc., in this way
leachingMake (a soluble chemical or mineral) drain away from soil, ash, or similar material by the action of percolating liquid, esp. rainwater
leachingthe act of leaching
leachingSubject (soil, ash, etc.) to this process