Under which conditions are pesticides more likely to leach through soil?

Pesticides are more likely to leach through soil under conditions where the soil structure allows for quicker drainage and lower retention of organic material. Sandy soil has larger particles and more space between them, which facilitates faster water movement. In contrast, soils high in organic matter tend to have greater water retention capabilities, reducing the leaching potential of pesticides.

When examining sandy soil low in organic matter, the larger particles do not hold as much water, allowing pesticides to be easily washed away with rainfall or irrigation. This condition creates a scenario where pesticides can leach more readily compared to heavier soils that retain water and organic matter, which would otherwise trap these chemicals and slow their movement through soil profiles. The absence of organic matter also diminishes the chemical binding capacity that typically helps retain pesticides in the soil. Consequently, conditions of sandy soil with low organic content optimize the likelihood of pesticide leaching.