Which step is essential for protecting water sources during pesticide applications?

Performing the first rinse in the field is an essential step for protecting water sources during pesticide applications because it helps to minimize the risk of pesticide contamination of nearby water bodies. This step involves rinsing the equipment immediately after the application process, which can help to clear out any residual pesticides that remain in the spray tank or on equipment surfaces.

By conducting the first rinse on-site, you ensure that any leftover chemicals are diluted and disposed of properly on the treated area rather than being transported to a separate location where they might inadvertently enter waterways. This practice aligns with the best management practices for pesticide application, as it directly addresses the environmental impacts associated with pesticide runoff.

In contrast, performing the final rinse in the field might not effectively prevent contamination if the equipment still holds concentrated pesticide residues following the application. Using additional surfactants could improve the efficacy of pesticide applications, but doesn't inherently address the risk to water sources. Increasing the spray pressure may enhance coverage but could increase drift and runoff, potentially leading to contamination of nearby water sources.