Which of the following factors makes leaching more challenging?

High organic matter in the soil can make leaching more challenging due to its ability to bind with various chemicals, including pesticides. Organic matter has a high cation-exchange capacity, which means it can hold and retain nutrients and other substances that would otherwise be washed away through leaching. This retention can reduce the mobility of pollutants in the soil, potentially leading to a higher concentration of those substances remaining within the root zone instead of being leached down into the groundwater.

In this context, it is essential to recognize the interaction between organic matter and various compounds. Soils with higher organic matter content often have increased microbial activity, which can also stabilize certain chemicals, making them less mobile and less susceptible to leaching. Therefore, the presence of high organic matter can effectively counteract the leaching process by holding onto various substances and limiting their movement through the soil profile.

Understanding this dynamic is crucial for managing soil health and ensuring that pesticide applications do not lead to environmental contamination, particularly concerning groundwater resources.