The key to preventing pollution is to keep chemicals or plant nutrients in place on the field or in the crop root zone where they are useful and not harmful to other uses of water. Tillage, residue management, and crop management techniques that keep soil from eroding are also management techniques to keep sediments and other surface borne pollutants in place. Crop and water management techniques that keep water in the root zone rather than carrying dissolved nutrients and chemicals to ground water via the leaching process also reduce pollution potential. Rainfall patterns in conjunction with crop water use patterns have a major impact on whether or not excess water will leach beyond the crop root zones. However, water management particularly in conjunction with irrigation management practices can either accentuate leaching and potential pollution or minimize that same potential.
Irrigation can supplement rainfall to supply crop water needs.
During the non-growing season, water accumulates in the soil for the next season. Water management at the end of the previous growing season can affect how much room is left in the soil to store off-season precipitation. At the end of the growing season there needs to be concern for completing the current crop's water needs, but also there needs to be soil water storage available for precipitation. Excess precipitation that cannot be stored will likely dissolve left over nutrients and chemicals and leach them below the root zone where they are not available for the next crop. Capturing and utilizing rainfall during the growing season is equally as important as during the non-growing season.