Best cover crop for oil palm: species selection guide by growth stage

Immature oil palm, mineral soil (year 0-3)

Primary choice: Mucuna bracteata (MB)

MB fixes 67-84% of its nitrogen from the atmosphere (Cheah, Zaharah & Aminuddin 2010, MPOB Oil Palm Bulletin 60, 15N isotope dilution). That is a proportion, not a quantity per hectare, and no defensible absolute kg N/ha figure exists for MB. Documented for soil cover, weed suppression, nutrient recycling, and reduced rhinoceros-beetle pressure. On 0-25% slopes in immature oil palm, Wawan, Dini & Hapsoh (2019) recorded improved soil moisture, infiltration, and organic matter under MB.

Management note: MB is vigorous and can smother young palms. Active circle maintenance is required.

Immature oil palm, peat soil

Primary choice: Mucuna bracteata (MB)

MPOB recognises MB as part of best-management practice on peat: about 320 seedlings/ha (six-week-old seedlings, two per palm point), raised from about 500 seeds (75 g), for soil-moisture conservation, limiting peat subsidence, and reducing peat-fire risk (MPOB TT No. 501, 2012). In that trial on deep peat at Teluk Intan, MB cover reached 31% at 6 months, 58% at 12, 75% at 18 and 78% at 24 months. MB is never broadcast, so a kilogram-per-hectare rate does not apply to it.

Lower management capacity

Alternative: PJ + CM mix

Where teams cannot maintain active MB circle management, PJ and CM provide good ground cover with less aggressive growth on open ground. CM tolerates acidic clay soils; PJ tolerates strongly acid soils and temporary waterlogging. Both thin as light at ground level falls, so plan a shade-persistent successor.

Replanting phase (slopes)

Primary choice: PJ-dominant legume mix

Erosion control is the priority. In young rubber in Côte d'Ivoire, Perron et al. (2024) measured up to 88% less runoff and 98% less soil loss than bare soil where a Pueraria cover was combined with spread logging residues, on 1 m2 plots. PJ's moderate growth suits slope management. The best-cited published mixture is MPOB TT No. 501 (2012) treatment C2: PJ 4 : CP 3 : CC 1, total 8 kg/ha, with 5 g Rhizobium (RRI strain) per kg of seed.

Maturing canopy

MB carries the cover through

MB is the shade-tolerant species of the plantation legume covers, which is why it is used under maturing oil palm, although its growth slows as shade deepens. PJ and CM thin well before this point.

Mature oil palm (closed canopy)

The shade-persistent successors

Under a fully closed canopy, Calopogonium caeruleum (CC) and Centrosema pubescens (CP) are the species that persist; CC also tolerates strongly acid soils. Both must be established before closure (CC alone may take about 20 months to reach full cover, according to PROSEA 4, 1992), because starting a new cover under a closed canopy is difficult.