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. Calopogonium caeruleum has not been separately quantified for nitrogen fixation in any source we are able to trace. The figure we used to publish on this page turned out to be a fertiliser-nitrogen equivalent from a Nigerian maize green-manure screening with no primary citation behind it, so we have removed it and have not replaced it with another number. 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 no mineral-soil rate exists.

How to establish Calopogonium caeruleum

1. Scarify the seed. A hot-water soak improves germination of hard seed.
2. Broadcast. Sow at 3 to 4.5 kg/ha as a monoculture, or 0.6 to 1.5 kg/ha as the CC component of a mixture, which is how it is usually used.
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, 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 3 to 4.5 kg/ha as a monoculture, or 0.6 to 1.5 kg/ha as the CC component of a mixture; broadcast after scarifying.

How much nitrogen does CC contribute?
We are not able to give you a figure, and we would rather say that than invent one. CC has not been separately quantified for nitrogen fixation in any source we can trace. The number we used to publish traced back to a fertiliser-nitrogen equivalent in a Nigerian maize green-manure screening with no primary citation, so we withdrew it.

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: How Legume Cover Crops Cut Fertiliser Costs

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