Best cover crop species for oil palm plantations in Southeast Asia
Best cover crop species for oil palm plantations in Southeast Asia
For oil palm in tropical Southeast Asia, Pueraria javanica (PJ) at 4-6 kg/ha is the standard cover on open and immature ground, with Calopogonium mucunoides as the fast pioneer alongside it. As the canopy closes PJ thins, and Mucuna bracteata, Centrosema pubescens and Calopogonium caeruleum carry the cover forward. Species choice depends on canopy stage, labour availability, and soil condition.
| Species | Seeding Rate | Nitrogen: what is actually measured | Shade Tolerance | pH Range | Establishment |
|---|---|---|---|---|---|
| Pueraria javanica (PJ) | 4-6 kg/ha | ~250 kg N/ha/yr accumulated in aboveground biomass at 85-93% Ndfa in one rubber-intercrop trial in NE Thailand (Clermont-Dauphin et al. 2016). An upper reference point, not a design value. | Moderate while the canopy is open; thins as it closes | 4.5-6.5 | Broadcast seed |
| Calopogonium mucunoides (CM) | 4-6 kg/ha | ~65 kg N/ha accumulated in biomass by a 3-month green manure crop in one PROSEA experiment. Not a fixation rate and not an annual rate. | Moderate | 4.0-6.0 | Broadcast seed |
| Centrosema pubescens (CP) | 3-4.5 kg/ha | 120-270 kg N/ha/yr (PROSEA). An institutional compiled estimate, not a field measurement. | High: shade-persistent successor | 4.5-6.5 | Broadcast seed |
| Mucuna bracteata (MB) | 320 seedlings/ha (85-100 g seed/ha) | 67-84% Ndfa by 15N isotope dilution (Cheah, Zaharah & Aminuddin 2010, Oil Palm Bulletin 60). A proportion, not a quantity; no defensible absolute figure exists. | High: this is the shade-tolerant species, used under maturing palm | 4.5-7.0 | Seedling transplant, never broadcast |
This table previously carried a column of annual nitrogen-fixation ranges for each species. Those ranges could not be traced to any primary source and have been replaced with what the literature actually measures. Where no sound measurement exists, we say so rather than substitute another number.
Pueraria javanica (PJ), the standard cover for open and immature blocks
PJ is the workhorse broadcast cover crop for oil palm. It establishes quickly from broadcast seed at 4 to 6 kg/ha as a pure stand, or 3 to 7.5 kg/ha as the PJ component of a mixture. In the one rubber-intercrop trial where it has been measured in detail, the cover accumulated about 250 kg N/ha/yr in aboveground biomass at 85 to 93% Ndfa (Clermont-Dauphin et al. 2016, Agriculture, Ecosystems & Environment 217:79-88). Treat that as an upper reference point from a single site, not a planning figure. The same trial also found the cover reduced the drought resilience of the young trees on water-limited ground. PJ thins as the canopy closes, so plan a successor.
View PJ ProductMixed stand for a closing canopy
The best-cited published mixture is MPOB TT No. 501 (Information Series 588, June 2012), Table 1 treatment C2: PJ 4 : CP 3 : CC 1, total 8 kg/ha, 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. Both are institutional best-management-practice recommendations from a peat trial, not primary field measurements, and MPOB does not state whether the totals are per gross hectare or per interrow hectare actually sown. Published mixture totals generally run 5 to 15 kg/ha and cluster at 6 to 12, and every published mixture is PJ-dominant.
View CM View CPMucuna bracteata (MB), high biomass and shade-tolerant, nursery-based
MB is the shade-tolerant species of the group, which is why it is used under maturing oil palm, and it carries the heaviest biomass. It is nursery-raised and transplanted at about 320 seedlings per hectare, which is roughly 85 to 100 g of seed per hectare. MB is never broadcast: a kilogram-per-hectare rate for MB is wrong by a factor of roughly forty, so check any quotation that gives one. On nitrogen, 15N isotope dilution puts MB at 67 to 84% of its nitrogen drawn from the atmosphere (Cheah, Zaharah & Aminuddin 2010); that is a proportion, and we do not publish an absolute kg N/ha figure for MB because none we can trace is sound.
View MBSoilBoost EA, complement your cover crop
Pair biological cover crops with SoilBoost EA, a humic acid soil conditioner, to support soil condition and nutrient cycling. It is a soil conditioner: it is not a fertiliser substitute and not a disease treatment.
View SoilBoost EAWe used to state on this page that PJ broadcast at 6 kg/ha reduced synthetic nitrogen inputs by a specific number of kilograms per hectare per year. We could not trace that to any trial, so it has been removed. We will not put a figure on how much fertiliser a cover crop lets you cut, and we would be cautious about anyone who does: the nitrogen a legume contributes depends on how much biomass it actually grew on your site, and applied mineral nitrogen suppresses fixation, so the two interact rather than simply substituting. What is well supported is that legume covers reduce erosion and runoff on exposed ground, suppress weeds during the immature phase, and build organic matter. Species choice should follow canopy stage: PJ and CM on open ground, MB through the maturing phase, CP and CC as the shade-persistent successors.
Will a cover crop compete with oil palm for water during dry season?
It can, and this is worth planning for rather than dismissing. In the northeast Thailand rubber trial that gives us the best PJ nitrogen measurement (Clermont-Dauphin et al. 2016), the legume cover reduced the drought resilience of the young trees on water-limited ground. PJ and CM have shallow fibrous roots that tap the organic-rich surface layer while palm roots extend deeper, so competition is limited in soils with adequate organic matter and rainfall. On sandy or low-rainfall sites (under about 1500 mm/yr), keep the cover managed back from the planting circle and expect to manage it more actively.
Can I overseed cover crops into existing mature palm without replanting?
Yes, but choose for the light level. Broadcast seed post-weeding onto bare soil between palm fronds. Under a closed canopy, CP and CC are the shade-persistent species and will do better than PJ, which thins as light falls. MB tolerates shade well but is transplanted from a nursery rather than broadcast. Allow 6-8 weeks for establishment before applying herbicides near seedlings.
Do I need to inoculate seeds with rhizobia?
Southeast Asian plantation soils often carry sufficient native rhizobia for legume nodulation, but MPOB's published mixture specification includes inoculation at 5 g of Rhizobium (RRI strain) per kg of seed, so it is standard practice rather than an optional extra. Inspect roots for nodules at 6-8 weeks; inoculation matters most on previously uncropped or heavily disturbed ground.
How long before I see nitrogen benefit?
Nodulation and fixation begin within the first few months of establishment, and the nitrogen becomes available to the system gradually as cover biomass decomposes rather than as a single release. How much arrives depends on how much biomass the cover actually grows on your site, which is why we give measured reference points rather than a per-hectare promise.
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