The excessive use of pesticides and fertilisers poisons a soil and degrades its productivity over time. Organic matter in the soil gets burned off, microbial life decreases and toxic elements build up. Slowly but surely, plants face an increasingly hostile environment. This adds stress, increases susceptibility to diseases and reduces yields and productivity.
The smart strategy has to be to help plants cope with adverse growing conditions while also trying to restore the soil to a naturally healthy state.