PJ vs CM vs CP vs MB vs CC: cover crop comparison guide

Cover crop comparison guide: PJ vs CM vs CP vs MB vs CC

PJ, CM, CP, MB, and CC each excel in different conditions. The best choice depends on your soil pH, shade availability, rainfall, slope, and production goals. This guide helps plantation managers select the optimal cover crop species or mixture.

Full comparison table

Criteria PJ (Pueraria javanica) CM (Calopogonium mucunoides) CP (Centrosema pubescens) MB (Mucuna bracteata) CC (Calopogonium caeruleum)
Seeding Rate 4-6 kg/ha 4-6 kg/ha pure, 1-3 kg/ha in mix 3-4.5 kg/ha 320 seedlings/ha (85-100 g seed/ha) 3-4.5 kg/ha
Annual N measured (kg N/ha/yr) Up to 250, accumulated in above-ground biomass in one trial under young rubber, NE Thailand (Clermont-Dauphin et al. 2016). Not a design value; less under a closing canopy or on drought-prone ground. No verified annual rate No verified annual rate No single routine annual rate is asserted No verified annual rate
Share of N from fixation (Ndfa) 85-93% (same trial) Not established Not established 67-84%, 15N isotope dilution under three-year-old oil palm on Jawa Series soil (Cheah, Zaharah & Aminuddin 2010, Oil Palm Bulletin 60) 25-72% in one Papua New Guinea oil palm study (Pipai et al. 2023); no general figure
Biomass-N stock (kg N/ha) Not reported separately ~154, reported biomass nitrogen (Edraiza 2014). A stock, not an annual rate. ~293, reported biomass nitrogen (Edraiza 2014). A stock, not an annual rate. Not established Not established
Shade Tolerance Moderate while the canopy is open; PJ thins as the canopy closes Moderate High: one of the two shade-persistent successors High: this is the shade-tolerant species, which is why it is used under maturing oil palm High: the other shade-persistent successor
Drought Tolerance Moderate Moderate Low-Moderate Low Moderate-High
Annual Biomass 6-12 t DM/ha 8-15 t DM/ha 4-8 t DM/ha up to 28 t/ha open, ~13 t/ha shade (MPOB) 3-7 t DM/ha
pH Range 4.5-6.5 4.0-6.0 4.5-6.5 4.5-7.0 4.0-6.0
Establishment Broadcast seed Broadcast seed Broadcast seed Nursery seedlings, never broadcast Broadcast or drill
Best For Open and immature blocks; hand over before canopy closure Fast pioneer cover, acidic soils Dense shade, acidic soils Immature through maturing palm; heavy biomass, holds under shade Heavy shade, slopes, long-term cover

A note on the nitrogen rows. Annual rates, the share of nitrogen drawn from fixation (Ndfa) and biomass-nitrogen stocks are different quantities, so they sit in separate rows and a stock is never shown as an annual rate. The CP and CM stocks are biomass nitrogen reported in a Philippine field study (Edraiza, 2014, Sage 5(1)). Figures withdrawn because they could not be traced to a sound primary source stay withdrawn: an absolute annual figure for MB, annual rates for CP, CM and CC, and a CC fertiliser-nitrogen equivalent taken from a Nigerian maize green-manure screening. The PJ figure is from Clermont-Dauphin et al. (2016), Agriculture, Ecosystems & Environment 217:79-88.

Species recommendations

PJ: Pueraria javanica

Seeding: 4-6 kg/ha broadcast (pure stand); 3-7.5 kg/ha as the PJ component of a mixture

Use PJ on open and immature blocks with neutral to slightly acidic soils. Moderate drought tolerance suits areas with 1500-2500 mm rainfall. Nitrogen: up to 250 kg N/ha/yr accumulated in aboveground biomass at 85-93% Ndfa in one rubber-intercrop trial in northeast Thailand (Clermont-Dauphin et al. 2016, Agriculture, Ecosystems & Environment 217:79-88). Treat that as a measured upper reference point from a single site, not a design value. The same trial found the cover reduced the drought resilience of the young rubber trees on water-limited ground. Biomass: 6-12 t DM/ha/yr. PJ thins as the canopy closes, so plan a shade-persistent successor.

View PJ Seeds

CM: Calopogonium mucunoides

Seeding: 4-6 kg/ha pure stand, 1-3 kg/ha in mix

Select CM as a fast pioneer on acidic soils (pH 4.0-6.0). Good early biomass (8-15 t DM/ha/yr). Nitrogen: no verified annual fixation rate exists for CM; the reported figure is biomass nitrogen of up to about 154 kg N/ha (Edraiza, 2014), a standing stock rather than an annual rate.

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CP: Centrosema pubescens

Seeding: 3-4.5 kg/ha broadcast

Use CP in dense shade where other legumes struggle. Best for mature rubber and dense cocoa canopies, and one of the two shade-persistent successors. Nitrogen: no verified annual fixation rate exists for CP; the reported figure is biomass nitrogen of up to about 293 kg N/ha (Edraiza, 2014), a standing stock rather than an annual rate. Biomass: 4-8 t DM/ha/yr.

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MB: Mucuna bracteata

Establishment: 320 nursery-raised seedlings/ha, about 85-100 g of seed per hectare. MB is transplanted, never broadcast: a kg/ha rate for MB is wrong by a factor of roughly forty.

MB is the shade-tolerant species of the group, which is why it is used under maturing oil palm, and it carries heavy biomass (up to 28 t/ha open, ~13 t/ha under 60-70% shade, MPOB). Nitrogen: 67-84% of its nitrogen comes from the atmosphere by 15N isotope dilution (Cheah, Zaharah & Aminuddin 2010, Oil Palm Bulletin 60). That is a proportion, not a quantity: we do not publish an absolute annual kilograms-per-hectare figure for MB because none we can trace is sound. Requires nursery preparation and adequate moisture.

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CC: Calopogonium caeruleum

Seeding: 3-4.5 kg/ha (broadcast or drill)

Choose CC for the deepest shade and longer-term ground cover under mature canopies. It is more drought tolerant than CM and PJ and persists where faster species thin out, though it establishes slowly and can take up to 20 months to reach full cover. Suits mature oil palm and rubber, plus sloping blocks where erosion control matters. Nitrogen: no single species-specific annual fixation rate is published for CC from verified evidence; one Papua New Guinea oil palm study measured 25 to 72% of its nitrogen from fixation (Pipai et al. 2023). The figure we used to publish was a fertiliser-nitrogen equivalent from a Nigerian maize green-manure screening with no primary citation, so we have removed it rather than replace it with another number. Biomass: 3-7 t DM/ha/yr.

View CC Seeds

Mixed stand recommendations

The best-cited published mixture (MPOB TT No. 501): Information Series 588, June 2012, Table 1 treatment C2 - PJ 4 : CP 3 : CC 1, total 8 kg/ha, which MPOB calls conventional LCC, with 5 g of Rhizobium (RRI strain) inoculant per kg of seed. Treatment C4, where Mucuna bracteata carries part of the cover, is PJ 3 + CP 1 = 4 kg/ha. MPOB TT 501 is a peat trial and this is an institutional best-management-practice recommendation, not a primary field measurement; no mineral-soil rate exists, and MPOB does not state whether the 8 kg/ha is per gross hectare or per interrow hectare actually sown.

Defensible totals: published mixture totals run 5-15 kg/ha and cluster at 6-12 kg/ha. Per-species component ranges are PJ 3-7.5, CM 1-3, CP 0.5-3, CC 0.6-1.5 kg/ha. Every published mixture is PJ-dominant - an equal-parts blend is not a standard, and we no longer publish one.

Three distinctions worth stating before you order: the total rate is not the per-species component rate; a gross hectare is not the interrow hectare you actually sow; and grazed-pasture rates (0.5-1.0 kg/ha) are not cover crop rates.

PJ + CM: fast establishment with high early biomass. Suits newly opened and immature blocks.

Adding CP or CC: blend a shade-persistent species in from the start so it is established before the canopy closes and PJ thins out.

Frequently asked questions

Which species fixes the most nitrogen?

We cannot rank them honestly, and we would rather say that than invent an order. The measurements that exist are not comparable with each other. PJ: up to 250 kg N/ha/yr accumulated in aboveground biomass at 85-93% Ndfa, from one rubber-intercrop trial in northeast Thailand (Clermont-Dauphin et al. 2016) - an upper reference point from a single site. MB: 67-84% Ndfa by isotope dilution (Cheah, Zaharah & Aminuddin 2010), a proportion rather than a quantity. CP and CM: no verified annual rate; the reported figures are biomass nitrogen stocks of up to about 293 and 154 kg N/ha (Edraiza 2014), not annual rates. CC: no species-specific annual rate; one Papua New Guinea oil palm study measured 25-72% Ndfa (Pipai et al. 2023). Choose by site and canopy stage rather than by a nitrogen league table.

Can I use the same species across my entire estate?

Mixed-aged plantations benefit from species diversity. Open and immature blocks suit PJ and CM; as the canopy closes PJ thins, and MB, CP or CC should already be established to carry the cover forward. MB is the shade-tolerant option with heavy biomass; CP and CC are the shade-persistent successors. Using one species risks performance loss in unsuitable conditions.

What is the cost difference between broadcast and nursery establishment?

Broadcast seeds (PJ, CM, CP, CC) cost RM 80-150/ha. Nursery seedlings (MB) require RM 400-600/ha upfront but establish faster. Calculate total cost per estate area and timeline.

How do I know if my soil pH suits these species?

All five species tolerate acidic to neutral soils. CM and CC are most acid-tolerant (down to pH 4.0). MB has the widest range (4.5-7.0). Most Malaysian plantation soils fall within 4.5-6.5, suitable for all five species.

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