It confuses pests that can't get past the fish smell. It has a high concentration of nitrogen and can burn plants if overused. Its odor is not as strong as that of fish emulsion, but it is more expensive. Nutrient concentrations vary widely with the kind of animal they are from. Although concentrations are lower than in manufactured fertilizers, manures improve soil structure and increase its water holding capacity.
Fresh manures can cause food-borne illnesses by contaminating vegetables with pathogens.
They also can burn tender roots. Therefore, gardeners are encouraged to use composted manures or apply fresh manures at least 60 days before harvesting any garden vegetables that will be eaten raw.