It is important that all label precautions be observed. Soil injection and incorporation pose the greatest likelihood for groundwater contamination. An irrigation pump may fail while the pesticide-metering equipment continues to operate. There are state laws requiring backflow prevention devices on any irrigation system equipped to inject chemicals. These devices are also required by Federal pesticide labels.
Water solubility means the pesticide is inclined to dissolve in water.
The higher a pesticide's water solubility, the greater the amount of pesticide that can be carried in solution to groundwater. Soil with high organic matter content and silt and clay soils have slow water movement. Coarse, sandy soils with low organic content allow more rapid movement of surface water downward. As soil water percolates downward, the distance it has to travel can determine whether or not a chemical will reach groundwater. Obviously, the greater the depth to groundwater, the more soil particles the water must flow through, making contamination less likely.