Free-Living Nitrogen-Fixing Bacteria Add Only a Few Kilograms per Hectare

… more less Azotobacter and Azospirillum fix nitrogen without nodules, but usually supply under about 5 kg N/ha a year (under 0.5 g per m²), against roughly 50–200 kg N/ha from a well-nodulated legume crop; they cannot replace fertilizer or a legume rotation.