Sesbania Rostrata Seeds — Stem-Nodulating Nitrogen Fixer for Flooded Fields

Most legumes fix nitrogen exclusively through root nodules formed by Rhizobium bacteria. Sesbania rostrata breaks this rule entirely. In addition to conventional root nodulation, it develops prominent nodules along its stems — structures formed through a unique symbiosis with the bacterium Azorhizobium caulinodans. This dual-nodulation capacity makes sesbania rostrata seeds one of the most valuable biological inputs available for nitrogen-depleted, flood-prone agricultural land.

First described from Senegal in West Africa, S. rostrata gained international attention through research at the International Rice Research Institute (IRRI) in the Philippines during the 1980s. Scientists demonstrated that its sesbania rostrata nitrogen fixation capacity surpassed every other green manure species tested in flooded rice systems. The reason is simple: when paddy fields are submerged, root nodules on conventional legumes become oxygen-starved and cease fixing nitrogen. The stem nodules of S. rostrata, positioned above the waterline, continue operating at full capacity regardless of flooding depth.

Kohenoor International sources sesbania rostrata seeds from specialized growers and supplies them to rice research stations, agricultural development programs, and institutional buyers across Asia, Africa, and Latin America. For a broader introduction to the sesbania genus, visit our guide on What Is Sesbania?

Within 7-10 days of bacterial infection, functional nitrogen-fixing nodules develop along the submerged or waterline-adjacent portions of the stem. These nodules are typically spherical, 3-8 mm in diameter, and arranged in vertical rows corresponding to the positions of the original root primordia. A single sesbania rostrata plant can develop 50-200 stem nodules under optimal conditions.

The critical advantage of sesbania rostrata nitrogen fixation through stem nodules is oxygen access. The nitrogenase enzyme complex responsible for converting atmospheric N₂ to ammonia is extremely sensitive to oxygen — yet it requires aerobic respiration to generate the energy needed for fixation. Root nodules solve this paradox with leghemoglobin (an oxygen-buffering protein), but when roots are submerged in waterlogged soil, diffusion of oxygen becomes limiting. Stem nodules, positioned above or at the waterline, have direct access to atmospheric oxygen, enabling consistently high fixation rates even under deep flooding.

This biological mechanism is why IRRI and other rice research institutions have identified S. rostrata as the single most effective leguminous green manure for continuously flooded rice systems. No other legume maintains nitrogen fixation at the rates sesbania rostrata achieves when the root zone is entirely submerged. For more detail on the nitrogen fixation process across sesbania species, read our article on Sesbania and Nitrogen Fixation: How These Legumes Enrich Your Soil.

• Green Manure in Flooded Rice Paddies: The principal application. Sesbania rostrata is grown for 50-70 days in flooded paddies, then incorporated before rice transplanting. IRRI trials show that a single S. rostrata green manure crop can supply 80-100% of the nitrogen requirement for a subsequent rice crop, reducing urea application by 100-150 kg/ha. This is particularly valuable in Southeast Asian and West African lowland rice systems where continuous flooding is standard practice. For rice-specific applications, see our guide on Sesbania in Rice Farming.
• Soil Reclamation in Waterlogged Soils: Degraded lowlands, floodplains, and seasonally inundated areas that cannot support conventional cover crops benefit from S. rostrata's waterlogging tolerance. The deep root system and stem nodulation allow it to build organic matter and fix nitrogen in environments too wet for other legumes, gradually restoring soil fertility for cropping.
• Biological and Genetic Research: Sesbania rostrata and its symbiont Azorhizobium caulinodans are model organisms in plant-microbe interaction research. The stem nodulation pathway — distinct from the root infection thread pathway — has been extensively studied to understand nodule organogenesis, Nod factor signaling, and the evolution of nitrogen-fixing symbioses. Research institutions worldwide maintain demand for characterized seed lots of this species.
• Integrated Nutrient Management: In rice-based cropping systems, S. rostrata is used in rotation with Sesbania bispinosa or as part of integrated organic-inorganic fertility programs. The exceptionally high N-fixation rate reduces total fertilizer expenditure while maintaining yield targets.

Climate Requirements

Sesbania rostrata is a tropical and subtropical species that requires warm temperatures between 25-35°C for optimal growth. It is a short-day plant, meaning flowering is triggered by day lengths shorter than approximately 12.5 hours. In equatorial regions, this occurs naturally year-round; in higher latitudes (above 20°N/S), flowering and seed set may be limited to certain seasons. The species does not tolerate frost.

Soil and Water Conditions

While S. rostrata grows on a range of soil types, its unique advantage is realized in waterlogged and flooded conditions. For stem nodulation to occur, the lower portion of the stem must be submerged or in contact with saturated soil. Ideal growing conditions involve flooding fields to 5-15 cm depth within 2-3 weeks after seedling emergence. The plant tolerates continuous submergence up to 50 cm at maturity.

Sowing Rate and Method

The recommended sowing rate is 25-30 kg per hectare for green manure purposes. Sow seeds at 2-3 cm depth in moist soil, either by broadcasting or drilling in rows 25-30 cm apart. Pre-soaking seeds for 12-24 hours improves germination uniformity. For detailed germination techniques, see our guide on How to Germinate Sesbania Seeds.

Inoculation

For maximum stem nodulation, inoculating seeds or seedling stems with Azorhizobium caulinodans (strain ORS 571) is recommended, particularly when planting in fields where S. rostrata has not been previously grown. Inoculant is available from specialized agricultural microbiology suppliers. In soils with existing populations of the bacterium, natural infection typically occurs within 2-3 weeks.

Incorporation Timing

Incorporate the crop at 50-70 days after sowing, when the plants have reached 2-3 meters in height and stem nodules are fully active. Use a disc plough or rotavator to chop and incorporate biomass at least 10-14 days before rice transplanting. At incorporation, a well-nodulated S. rostrata crop provides 20-30 tonnes of fresh green biomass per hectare containing 150-300 kg of biologically fixed nitrogen.

The exceptional sesbania rostrata nitrogen fixation capacity has been documented extensively in peer-reviewed literature and institutional research reports. Key studies include:

• Dreyfus & Dommergues (1981): First identification and characterization of stem nodulation in Sesbania rostrata and isolation of the symbiotic bacterium later named Azorhizobium caulinodans. Published in Applied and Environmental Microbiology.
• IRRI Technical Bulletin (1990): Comprehensive field trials at the International Rice Research Institute demonstrating that S. rostrata green manure provided 150-300 kg N/ha — the highest of any sesbania species tested — and could fully replace synthetic nitrogen in lowland rice systems.
• Ladha, Pareek & Becker (1992): Documented stem-nodulating sesbania as a nitrogen source for rice in the IRRI research program, comparing N contribution of S. rostrata against S. cannabina and S. sesban under flooded conditions.
• Ndoye & Dreyfus (1988): Quantified nitrogen fixation by both stem and root nodules of S. rostrata using ¹⁵N isotope dilution, confirming that stem nodules contributed 60-80% of total N-fixation under flooded conditions. Published in Soil Biology and Biochemistry.

For additional technical resources on sesbania research, visit our Research & Technical Data page.

Sesbania rostrata seeds are a specialty product with seasonal availability, typically from October through March. Unlike the more widely cultivated Sesbania bispinosa, S. rostrata seed production is concentrated in limited geographic areas, and supply is subject to seasonal harvest cycles.

Minimum Order Quantity

The minimum order quantity for sesbania rostrata seeds is 500 kg. Larger orders of 5 MT and above can be arranged with advance booking during the harvest season.

Packaging

Seeds are packed in 25 kg or 50 kg polypropylene (PP) woven bags with inner polyethylene liners for moisture protection. Custom packaging and buyer-branded bags are available for orders above 2 MT.

Export Documentation

All shipments from Kohenoor International include Phytosanitary Certificate, Fumigation Certificate, Certificate of Origin (COO), and a seed quality test report from an accredited laboratory. We ship FOB Karachi, CFR, or CIF depending on destination. Typical lead time is 10-15 business days from order confirmation.

For terminology used in international seed trade, refer to our Sesbania Agricultural Glossary.