The trend toward building larger livestock operations, storing manure, and intermingling livestock production and nonagricultural land use has led to increased complaints about odor from manure. The strongest odor from dairy operations is generated when stored liquid manure is agitated and spread.
Feed stored in silos or being processed also produces some odor.
The gases with the strongest odors are the sulfurous or ammonia-derived gases. Odor sensation is a personal response. Not all people are equally sensitive, and they do not always agree about the severity of an odor once it is detected. Nonfarm people who move into rural areas, for example, generally do not tolerate odor as well as a neighboring farmer does. The human nose is still the best means of determining the strength of an odor.