Which practice can result in hazardous pesticide residues in the environment?

Applying pesticides on barren soil can lead to hazardous pesticide residues in the environment because this practice lacks the natural filters and absorption capabilities provided by plant roots and surrounding vegetation. When pesticides are applied to barren soil, they have a higher chance of leaching into groundwater or being carried away by runoff, especially during rainfall, as there are no plants to absorb or break down these chemicals. This can lead not only to contamination of nearby water sources but may also affect non-target organisms in the surrounding ecosystem.

In contrast, using lower concentration formulations, incorporating pesticides into the soil after application, or avoiding synthetic pesticides altogether are practices that are generally aimed at reducing environmental impact or enhancing pesticide effectiveness, leading to less potential for hazardous residues.