If you apply manure to soybeans or alfalfa, instead of corn, it can help keep nitrogen from ending up in the Gulf of Mexico where it can hurt marine animals, according to the USDA-Agricultural Research Service.

Legumes, like soybeans and alfalfa, have some of the highest nitrogen-making, or fixation, rates. However, making nitrogen is optional for legumes, so they will use the nitrogen in manure first before making their own. That, in turn, can eliminate the need for extra commercial fertilizer.