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

Pesticides are more likely to leach through sandy soils that are low in organic matter. This is due to the characteristics of sandy soil, which has larger particle sizes and greater porosity compared to other soil types. Because of the larger spaces between the particles, water can move through sandy soil more quickly, creating a pathway for pesticides to travel downwards.

Moreover, the lack of organic matter in sandy soils means there are fewer binding sites for pesticides to adhere to, which increases their mobility and potential to leach into groundwater. Organic matter generally helps to retain water and nutrients, providing a more stable environment for pesticide retention. In contrast, the combination of rapid drainage and minimal retention capabilities in sandy soils increases the likelihood of leaching.

While clay soils rich in organic matter, loamy soils with adequate moisture, and heavy, compacted soils have characteristics that typically promote higher retention of pesticides, sandy soils, especially when low in organic matter, facilitate faster leaching due to their structure and composition.