" They" would be tobacco growers or employees of tobacco growers. I've never grown tobacco, so again, no personal experience, but I believe tobacco is grown in very sandy, loose soil. Whatever watering system is setup for normally watering just gets left on longer, and the water helps carry away excess nutrients which drains through the sandy loose soil..?? As far as only feeding strictly what the plants need, sounds like that's what all farmers do, no matter what crop?? Anyone know any tobacco farmers??