Pesticide Residue
Pesticide residue is the trace of bug-killing spray that stays in soil long after it was used.
Think of it this way
Spray a tray of cookies with cooking spray, then wipe it off. The tray looks clean, but a thin film of oil still coats the surface. That leftover oil is like pesticide residue — you can’t see it, but it stays behind. Soil works the same way: spray soaks in, but traces of it remain long after.
Explaining pesticide residue by grade level
Long ago, farmers sprayed their trees to keep bugs away. The spray went on the ground too. Years later, the spray is still in the dirt. You can test the soil to find out how much is left.