Calopogonium caeruleum (CC): Cover Crop Guide for Tropical Plantations

Calopogonium caeruleum (CC) is a hardy perennial leguminous cover crop used in tropical oil palm and rubber plantations for long-term, persistent ground cover. It tolerates shade, fixes nitrogen, and holds up as the canopy closes, which makes it a useful component of cover crop mixtures for the later plantation years. CC is broadcast-seeded.

What is Calopogonium caeruleum?

Calopogonium caeruleum is a robust perennial legume grown as a cover crop in plantation systems. It is slower and less aggressive than fast pioneers but more durable, persisting under increasing shade where other species thin out. It fixes nitrogen in association with Rhizobium and contributes organic matter over the long term.

Why plantations use Calopogonium caeruleum

Persistence and shade tolerance

CC keeps soil covered into the later years of a plantation, when light is reduced and pioneer species have declined. Along with Centrosema pubescens it is one of the two shade-persistent successors: Pueraria javanica thins as the canopy closes, and Mucuna bracteata, which is itself shade-tolerant and used under maturing oil palm, eventually gives way under a fully closed canopy. This extends ground cover, weed suppression, and soil protection across the rotation.

Nitrogen and organic matter

As a legume, CC fixes nitrogen and adds organic matter through its biomass and litter. We cannot put a number on how much. No single species-specific annual fixation rate is published for Calopogonium caeruleum from verified evidence. The one measurement we can trace is a share, not a quantity: in a survey of oil palm plantations in Papua New Guinea, CC drew 28 to 75% of its nitrogen from fixation, averaging 49% (Pipai et al. 2023, Plant and Soil 491). We would rather leave the gap than invent a figure a buyer might plan against.

Part of a balanced mixture

CC is commonly included in conventional cover crop mixtures. The best-cited published example is MPOB TT No. 501 (Information Series 588, June 2012), Table 1 treatment C2: Pueraria javanica 4 : Centrosema pubescens 3 : Calopogonium caeruleum 1, total 8 kg/ha, which MPOB calls conventional LCC, with 5 g of Rhizobium (RRI strain) inoculant per kg of seed. That is an institutional best-management-practice recommendation from a peat trial rather than a primary field measurement, and MPOB gives no mineral-soil rate.

How to establish Calopogonium caeruleum

1. Scarify the seed. A hot-water soak improves germination of hard seed.
2. Broadcast. CC is usually sown in a mixture: Tropical Forages gives about 1 to 1.5 kg/ha of CC with 5 to 7.5 kg/ha of Pueraria javanica, and MPOB TT No. 501 uses 1 kg/ha of CC in an 8 kg/ha mixture. For other situations the rate is set on the quotation for your site.
3. Plan for the long term. Establish alongside faster species so CC can take over the persistence role as the canopy develops. CC establishes slowly and can take up to 20 months to reach full cover (PROSEA 4), so it must go in well before closure.

Where Calopogonium caeruleum fits, and where it does not

Well suited to: maturing and mature oil palm and rubber, long-term cover under increasing shade, and mixtures needing a durable, persistent component.

Less suitable for: situations needing the fastest possible early cover, where a pioneer such as Calopogonium mucunoides establishes more quickly. CC is a persistence species, not a rapid pioneer.

Compared with other cover crops

CC is the durability specialist for the later years. Calopogonium mucunoides and Pueraria javanica establish faster but thin as light falls; Centrosema pubescens is the other shade-persistent successor; Mucuna bracteata produces the most biomass, is shade-tolerant enough to be used under maturing oil palm, and is transplanted rather than broadcast. See the five-species comparison and the cover crops guide.

Frequently asked questions

What is Calopogonium caeruleum?
A hardy, shade-persistent perennial legume cover crop for long-term ground cover in tropical plantations.

How much CC seed per hectare?
About 1 to 1.5 kg/ha sown with 5 to 7.5 kg/ha of Pueraria javanica (Tropical Forages), or 1 kg/ha within the 8 kg/ha MPOB TT No. 501 mixture; broadcast after scarifying. Otherwise the rate is set on the quotation for your site.

How much nitrogen does CC contribute?
We are not able to give you a figure, and we would rather say that than invent one. No single species-specific annual fixation rate is published for CC from verified evidence; one Papua New Guinea oil palm study estimated 28 to 75% of its nitrogen from fixation (Pipai et al. 2023).

Is CC shade-tolerant?
Yes. It is one of the two shade-persistent successors, alongside Centrosema pubescens, and is suited to maturing and mature stands.

Related reading

• Multi-Species Cover Crop Mixes: Why Blending PJ, CM, and CC Outperforms Single-Species Planting
• How to Choose the Right Cover Crop for Your Malaysian Estate
• Best Cover Crops for Tropical Climates in Malaysia
• Nitrogen Fixation in Tropical Plantations: What Legume Cover Crops Contribute

Sources: Tropical Forages database (CSIRO, CIAT, ILRI); MPOB TT No. 501 / Information Series 588 (June 2012); PROSEA 4 (1992); Pipai et al. (2023). Published data for Calopogonium caeruleum is more limited than for the other species, and no traceable annual nitrogen-fixation quantity exists for it; figures given here are for seeding and biomass and depend on site, soil, rainfall, and management. Last reviewed August 2026.