Oil Palm Replanting Soil in Palawan and Agusan

Sow your cover crop in the same season you fell the old stand. On a replant block in Palawan or Agusan, the window that matters is the first months after clearing, while the interrow soil is still bare and the young palms are short. Get a legume cover established then and you protect the soil, fix nitrogen, and hold weeds before lalang (Imperata cylindrica) takes the ground.

This article covers when to sow on a replant, which species to use on Palawan and Agusan soils, and how to keep the cover off your young palms.

When should I sow cover crops on an oil palm replant?

Sow as soon as the block is cleared and the soil surface is workable, ideally at the start of a reliable wet spell. The replant year is when the interrow gets the most light it will ever get, so a legume cover establishes fastest then and starts fixing nitrogen early. Waiting until the palms are two or three years old means sowing into shade and into ground weeds have already claimed.

On a felled-and-replanted block, the old palm biomass is often windrowed or chipped. Drill the legume seed or plant it in holes along the clean interrow strips between the windrows; broadcasting does not guarantee good germination, especially where the soil dries out easily. Aim to have a closed cover before the second monsoon, when bare slopes in Palawan and Agusan start shedding soil under heavy rain.

Which cover crops suit Palawan and Agusan replant soils?

Use a legume mix built around Pueraria javanica (Neustanthus phaseoloides), with Calopogonium caeruleum and Centrosema pubescens for shade as the canopy closes. Pueraria javanica is slow in its first months (Tropical Forages) but then climbs and covers open interrows (in MPOB's peat trial, MPOB TT No. 501, a mixture of Pueraria, Centrosema and Calopogonium caeruleum reached 80% ground cover at 6 months), and in one trial under young rubber in northeast Thailand accumulated up to 250 kg N per hectare per year in above-ground biomass (Clermont-Dauphin et al. 2016); expect less as the palm canopy closes or where water is short. Recommended seeding rates, each for one species sown alone (our recommendation): 10 kg per hectare for Pueraria javanica or Centrosema pubescens and 5 kg per hectare for Calopogonium caeruleum, drilled or planted in holes. For a mixture, the quantity of each species is set on the quotation for your site. For the record, MPOB's peat trial (MPOB TT No. 501, Table 1 treatment C2) used Pueraria 4 + Centrosema 3 + Calopogonium caeruleum 1 = 8 kg per hectare, which MPOB calls conventional LCC, with 5 g of Rhizobium (RRI strain) inoculant per kg of seed.

Note: Pueraria javanica is a managed tropical legume, not the invasive kudzu (Pueraria montana).

As the young palms begin to shade the interrow over years two and three, Calopogonium caeruleum carries the cover. Tropical Forages describes it as one of the most shade-tolerant tropical legumes: its productivity is relatively constant at 60 to 100 percent light transmission, and it still yielded 1 to 1.5 tonnes of dry matter per hectare per year under mature oil palm at about 10 percent light. Centrosema pubescens adds a second shade-tolerant fixer to the blend.

Agusan lowland blocks often sit on acid, sometimes waterlogged soils, so check drainage on the felled block and pick the planting strips that drain. Palawan blocks run from rolling uplands to flatter coastal ground; on the slopes, a closed legume cover is your first line against erosion in the replant year.

What about Mucuna bracteata on a replant?

Mucuna bracteata fixes nitrogen strongly, with 67 to 84% of its nitrogen drawn from the air (Ndfa), but on a replant it needs active management. The 67 to 84% figure comes from one 15N isotope-dilution study under three-year-old oil palm on Jawa Series soil in Malaysia (Cheah et al. 2010, MPOB Oil Palm Bulletin 60). Goh et al. (2015), in MPOB's Oil Palm Bulletin 70, warn that uncontrolled Mucuna bracteata can smother and entangle the palms, especially in young immature plantings. On a replant block with short palms, keep Mucuna pruned back from the palm circles and the frond bases, or hold it to the interrow centre and use Pueraria or Calopogonium nearer the palms. If you cannot commit to that management, leave Mucuna out of the replant mix.

How do I keep the cover crop off young palms?

Maintain a weeded, cover-free circle around each young palm and prune any climbing legume away from the trunk and fronds. Pueraria and Mucuna both climb, and a young palm under three metres can be overrun. Ring-weed the palm circle through establishment, train the legume across the interrow rather than up the palm, and walk the block monthly in the first two years to cut back any runners reaching the frond bases.

FAQ

How much Pueraria javanica seed per hectare on a replant? Recommended seeding rate (sown alone): 10 kg per hectare, drilled or planted in holes (our recommendation). In a mix, the quantity of each species is set on the quotation for your block.

Can I sow a cover crop straight onto a freshly cleared replant block? Yes. The cleared interrow, before weeds and lalang take hold, is the best time to establish a legume cover. Drill the seed or plant it in holes in a workable surface at the start of a wet spell, and keep the palm circles clear.

Is the cover crop safe around two-year-old palms? Yes, with management. Keep a weeded circle around each palm and prune climbing legumes off the trunk and fronds. Use Pueraria, Calopogonium, or Centrosema near the palms and keep Mucuna bracteata, which can smother short palms, in the interrow centre or out of the mix.

Ready to plan your replant cover?

Tell us your block area, soil, and clearing date, and we will send seeding rates and a species mix for your Palawan or Agusan replant. Request a quote for Pueraria javanica (PJ) or our other cover-crop seeds, message us on WhatsApp at +60 17-237 4058, or email info@kudzuseeds.com.

Sources

• Cheah, S.S., Zaharah, A.R. and Aminuddin, H. (2010). Biological nitrogen fixation by Mucuna bracteata under oil palm field environments. Oil Palm Bulletin 60: 22-27. Malaysian Palm Oil Board. MPOB PDF
• Goh, Y.K., Wong, K.L., Lai, C.H., Tan, S.Y., Mahamooth, T.N., Gan, H.H., Goh, Y.K. and Goh, K.J. (2015). Control of Mucuna bracteata DC. ex Kurz legume covers with herbicides in oil palm plantation: spraying volume and frequency. Oil Palm Bulletin 70: 1-7. Malaysian Palm Oil Board.
• Clermont-Dauphin, C., Suvannang, N., Pongwichian, P., Cheylan, V., Hammecker, C. and Harmand, J.-M. (2016). Dinitrogen fixation by the legume cover crop Pueraria phaseoloides and transfer of fixed N to Hevea brasiliensis: impact on tree growth and vulnerability to drought. Agriculture, Ecosystems and Environment 217: 79-88. https://doi.org/10.1016/j.agee.2015.11.002
• Hasnol Othman, Farawahida Mohamad Darus and Zulkifli Hashim (2012). Best management practices for oil palm cultivation on peat: Mucuna bracteata as ground cover crop. MPOB Information Series 588 / MPOB TT No. 501. Malaysian Palm Oil Board. MPOB PDF
• Tropical Forages, Neustanthus phaseoloides (Pueraria javanica): https://tropicalforages.info/text/entities/neustanthus_phaseoloides.htm
• Tropical Forages (CIAT and ILRI 2020), Calopogonium caeruleum: https://tropicalforages.info/text/entities/calopogonium_caeruleum.htm