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sunn hemp

Crotalaria juncea L.

Family: Fabaceae · Genus: Crotalaria

Indian hemp

Placenta I High Fertilizer biomass 🌱 Nitrogen fixer
scott.zona · CC BY · iNaturalist

Annual green-manure legume, fixes up to ~450 kg N/ha, ideal for the Placenta I phase. Breaks nematode cycles and contributes large amounts of fertilizer biomass. Pasini lists it among Accumulation-system species and as an herbaceous fertilizer biomass.

📚 Synonyms

Scientific synonyms: Crotalaria benghalensis Lam., Crotalaria sericea Willd., Crotalaria fenestrata Sims, Crotalaria tenuifolia Roxb.

Götsch succession

Götsch stage
Placenta I
Ecological role
Pioneer
Primary stratum
High
Strata
High, Medium
Biomass class
Fertilizer biomass

Environment

Light requirement
Full sun
Water requirement
Moderate
Drought tolerance
High
Waterlogging tolerance
Low
Soil pH range
5–8.4
Preferred soil texture
Loamy, Sandy, Clayey
Hardiness zones
10–12
Frost tolerance
-2.0 °C

Morphology

Mature height
2–3.5 m
Root system
Taproot
Root depth
Deep
Growth rate
Very fast
Lifespan
≤ 1 year
Time to first harvest
2 months

Biomes & climate

Köppen classes

Where it fits in a guild

Sunn hemp takes the High stratum in the Placenta I phase of succession — in a guild it shares the line with species from the other strata, each harvesting light at its own height, in its own time. It also fixes nitrogen, feeding the soil for its line neighbors.

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Emergent High · ≈4 m Medium Low Ground cover

🪴 Cultivation

Fast-growing annual green manure. In Brazil sow Sept–March at ~25 kg/ha in 0.5 m rows (~30 seeds/linear m) or 8 kg/ha broadcast (40–50 kg/ha internationally). Nodulates with cowpea-type rhizobia, fixing ~150–300 kg N/ha (source-dependent). Cut/incorporate ONCE at early full flowering (~60 days tropics; 110–140 days Brazil) before it lignifies; drought-tolerant, frost-sensitive (killed below ~ -2 °C).

✂️ Management & Pruning

Annual crop — cut and incorporate ONCE at early flowering; it does not resprout.

📅 Phenology

Flowering months: February, March, April

Fruiting months: May, June

❓ Frequently asked questions

How long until the first harvest of sunn hemp?

The first harvest of sunn hemp comes around 2 months after planting.

How tall does sunn hemp grow?

At maturity, sunn hemp reaches 2–3.5 m tall.

When does sunn hemp fruit?

Fruiting of sunn hemp occurs in May, June.

When does sunn hemp flower?

Flowering of sunn hemp occurs in February, March, April.

What stage and stratum does sunn hemp occupy in a syntropic system?

In a syntropic system, sunn hemp belongs to the placenta i stage, occupying the high stratum.

Does sunn hemp fix nitrogen?

Yes — sunn hemp is a nitrogen-fixing species that helps fertilize the system's soil.

Functions

🌱 Nitrogen fixer 🌿 Biomass producer Soil decompactor

Propagation

Seed

Citations

  1. Pasini, F. & Guimarães, L. (2017) — Conceitos e princípios práticos da agrofloresta sucessional, Tabela 3 (Incaper) , p. 116 (primary_stratum)
  2. Pasini, F. & Guimarães, L. (2017) — Sistema de Acumulação , p. 117 (gotsch_stage, biomass_class, nitrogen_fixer)
  3. Crotalaria juncea como adubo verde — Embrapa
  4. Crotalaria juncea como adubo verde — Embrapa (nitrogen_fixer, cultivation_notes)
  5. Tropical Forages — Crotalaria juncea (ph_min, ph_max, root_system, root_depth, waterlogging_tolerance, soil_texture_preference, cultivation_notes)
  6. Feedipedia — Crotalaria juncea (sunn hemp) (frost_tolerance_c, time_to_first_harvest_months, synonyms, nitrogen_fixer, pruning_notes)
  7. PFAF — Crotalaria juncea (hardiness_zone_min, hardiness_zone_max, frost_tolerance_c)
  8. Aegro — Crotalária no Brasil (semeadura, ciclo, fenologia) (phenology, time_to_first_harvest_months, cultivation_notes)

External references

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