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Dhaincha green manuring (Sesbania)

Dhaincha green manuring is the practice of broadcast-sowing Sesbania aculeata (called jeelugu in Telugu) ahead of paddy transplanting and ploughing the standing legume back into the soil before the rice crop is established. The technique is a low-cost, biologically-fixed nitrogen source for transplanted rice and a cornerstone of organic N management in lowland paddy systems.

Principle

Sesbania is a fast-growing tropical legume that fixes atmospheric nitrogen through root nodules colonised by Rhizobium and, in some species (S. rostrata), stem nodules as well. A 60-day pure-stand crop accumulates 80-86 kg N/ha and produces 21-23 t/ha of green biomass. Incorporating this biomass releases nitrogen and organic carbon to the soil as the residue mineralises, supporting the following rice crop without synthetic fertiliser.

Implementation

Seed is broadcast 30-45 days before paddy transplanting, typically at 30-40 kg/ha. The crop is ploughed in at 45-60 days when plants reach approximately 60 cm height, with incorporation timed one week to one day before paddy transplant. Research from ANGRAU and other state agricultural universities indicates that a 60-day Sesbania crop incorporated one day before transplanting supports paddy yields equivalent to a 120 kg urea-N/ha application.

Adoption context

Dhaincha is widely sown in summer-fallow lowland paddy tracts of Andhra Pradesh, Telangana, Tamil Nadu, Odisha, West Bengal, Uttar Pradesh and Punjab between rabi rice harvest and kharif transplanting. It is the recommended green manure under several state organic and natural farming missions and is compatible with conservation agriculture rotations.

Limitations

The 45-60 day window between rabi harvest and kharif transplant must be available; in double-rice systems this slot is absent. Sesbania requires standing soil moisture to germinate and grow rapidly, limiting it to assured-irrigation tracts. Incorporation requires a tractor or animal-drawn plough capable of burying 20+ t/ha of bulky biomass, which can clog small implements.

See also Sunn Hemp Green Manure, Sunn Hemp Green Manure 2, Mulching Organic Residue and In Situ Residue Decomposition.

References

  1. Sesbania rostrata as green manure for lowland rice. Springer.
  2. Effect of in-situ green manuring on rice. ANGRAU Journal of Research / ICAR ePubs.