If it ain't broke, don't "fix" it

Soybeans, alfalfa, birdsfoot trefoil and crownvetch are not the only legumes.  The prairie community contains many native species able to convert atmospheric nitrogen into usable forms.  These native legumes have nitrogen-fixing bacteria within nodules on their roots.  As the plants decay, the nitrogen compounds are released and become available for use by other plants.  In this way, native legumes help other plants remain strong and vigorous without artificial fertilizer.

Use of fertilizer is not recommended for prairie plantings since the native plants are less effected by poor soils than weeds.  Fertilizing will mostly increase weed competition.  Inoculating legume seeds with the appropriate bacteria helps insure development of nitrogen-fixing root nodules in soils lacking native bacteria.