**3.4 Irrigation**

Pesticide movement on or within the soil surface is greatly determined by the process of irrigation, which is a common practice in crop production systems. Irrigation facilitates the movement of pesticides on the soil surface as runoff or leaching to the ground water table. When the rate of irrigation exceeds the rate of infiltration, soil promotes runoff that will carry pesticides away to nearby water bodies. Irrigation made the water molecules available on the soil surface, which interferes with the physical and chemical properties of pesticides and thereby facilitates their movement.
