Nitrogen Fixers
Plants that convert atmospheric nitrogen into usable forms for soil enrichment
What Are Nitrogen Fixers?
Nitrogen-fixing plants form symbiotic relationships with bacteria in their root nodules, converting atmospheric nitrogen (N₂) into ammonia (NH₃) that plants can use. This process, called biological nitrogen fixation, is one of the most important ecosystem services in regenerative agriculture. When these plants die or are pruned, the nitrogen becomes available to neighboring plants.
Benefits
- Reduces or eliminates the need for synthetic nitrogen fertilizers
- Improves soil structure and organic matter content
- Supports diverse soil microbiology
- Provides free fertilizer for companion plants
- Many species are also edible or provide animal fodder
Example Plants
Clover (White, Red, Crimson)
Trifolium spp.
Low-growing legumes perfect as living mulch or cover crops. Fix 100-150 lbs of nitrogen per acre annually. Excellent for lawns and understory plantings.
Fava Beans
Vicia faba
Cool-season annual that fixes nitrogen while producing edible beans. Great for fall planting and spring harvest. Can fix 200+ lbs N/acre.
Black Locust
Robinia pseudoacacia
Fast-growing nitrogen-fixing tree. Provides rot-resistant timber, firewood, and abundant flowers for pollinators. Fixes 50-150 lbs N/acre.
Siberian Pea Shrub
Caragana arborescens
Hardy nitrogen-fixing shrub for cold climates. Produces edible peas, excellent hedge plant, tolerates poor soils. Fixes 40-100 lbs N/acre.
Alfalfa
Medicago sativa
Deep-rooted perennial legume. Excellent for building soil, producing mulch, and animal fodder. Fixes 150-250 lbs N/acre.
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Implementation Tips
Plant nitrogen fixers around heavy feeders like tomatoes, corn, and brassicas
Chop-and-drop prunings to release nitrogen gradually
Inoculate seeds with appropriate rhizobia bacteria for best results
Mix legumes into cover crop cocktails for balanced soil nutrition
Use perennial nitrogen fixers as hedge plants or guild components
Till in annual legumes before flowering for maximum nitrogen release
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