What is a key risk when applying manure?

The correct choice highlights a significant concern in manure application, which involves the potential introduction of pathogens and pollutants into the environment. Manure can serve as a vehicle for bacteria, viruses, and parasites that may adversely affect human health and the ecosystem. If manure is not properly managed and applied according to best practices, these pathogens can contaminate water sources through runoff, infiltrate soil, and persist in the environment, posing risks to both agricultural workers and the broader community. Additionally, pollutants such as nitrogen and phosphorus from manure can run off into water bodies, contributing to issues like eutrophication, which damages aquatic ecosystems.

In terms of the other options, while decreased soil organic matter may occur under certain management practices or be a concern in some contexts, it is generally not an immediate risk associated with proper manure application. Reduced crop yield is typically not a direct outcome of manure application when managed appropriately; in fact, when used correctly, manure can enhance crop production by providing essential nutrients. Soil compaction can occur due to heavy machinery used in manure application, but this is more of a secondary effect rather than a direct risk of applying manure itself. Thus, the introduction of pathogens and pollutants stands out as a primary, immediate risk that must be carefully managed in the practice