Malaysian rubber estates are replanted when the old stand is no longer economic. After the old stand is felled, stumps and roots are removed, the land is prepared and the new trees are planted, and productive tapping starts only after several immature years. Part of this unproductive gap is unavoidable, because young trees are not ready to tap. Soil condition affects how smoothly it goes. After decades under one crop, organic matter is low, nutrient cycling is slow, and old rubber roots and stumps left in the ground can carry root disease fungi such as Rigidoporus microporus (white root disease, formerly known as Fomes lignosus). Young trees on such soil can establish unevenly. Rebuilding soil biology from the moment the old stand is cleared gives the new planting a better start.
What long rubber cycles do to soil
A long rubber cycle tends to leave soil with less organic matter, a simpler soil food web and fewer active soil organisms than the forest or mixed vegetation it replaced. Under a closed rubber canopy there is little ground vegetation, and rubber leaf litter breaks down slowly, so less fresh carbon reaches the soil biology. The size of these changes varies with soil type, management and history, so measure your own blocks (organic carbon, pH, available phosphorus) before replanting rather than relying on general figures.
When old rubber is cleared, the young trees inherit this soil. Infected roots and stumps left in the ground are the main source of white root disease, and the fungus spreads to healthy young roots through root contact. Good land preparation, especially removing old roots and stumps, matters more for root disease than anything sown afterwards.
A biology-first establishment plan
The aim is simple: get living roots and ground cover back into the cleared land as early as possible, and keep them there while the young trees establish. Research on rubber replanting supports the idea. In Côte d'Ivoire, a study that followed soil health for 18 months after clear-cutting found that a legume cover crop mainly improved the restoration of carbon transformation (Perron et al., 2022). A companion study that sampled soil microbes every six months for two years after replanting found that the recovery of soil micro-organisms depended strongly on the type of ground cover, and that logging residues combined with a legume cover crop helped microbial community resilience on the sandy site (Kouakou et al., 2025). Across 60 studies, mostly in annual crops, cover cropping raised soil microbial abundance, activity and diversity by 27%, 22% and 2.5% compared with bare fallow (Kim et al., 2020).
Clearing and land preparation:
• Fell, remove stumps and dig out old roots as thoroughly as practical. Old roots left in the soil are where root disease carries over into the next planting.
• Keep tillage shallow and machinery traffic to a minimum, so the soil is not compacted and the surface is ready for the cover crop.
• If you use SoilBoost EA, a humic acid soil conditioner, apply it during land preparation at the rate set on the quotation for your soil test results.
Establishing the legume cover:
• Sow the cover as soon as the land is prepared, at the start of reliable rain. Pueraria javanica (PJ) is sown from seed; the recommended seeding rate is 10 kg/ha sown alone (Chemiseed recommendation, 2026 catalogue), and the quantity for your site is confirmed on the quotation.
• Mucuna bracteata (MB) is not broadcast. Recommended seeding rate: 1 kg/ha sown alone, drilled or planted in holes. MB can also be raised in a nursery and transplanted; in MPOB's oil palm trial on deep peat, 320 seedlings per hectare, two per palm point, were raised from about 500 seeds (75 g) (MPOB TT No. 501). The quantity for your rubber interrows is confirmed on the quotation.
• Keep MB off the young rubber: it is a vigorous climber and must be managed so it does not twine over the trees.
• Fill gaps early if establishment is patchy, so weeds do not take the interrow.
While the cover grows:
• Both legumes fix atmospheric nitrogen once nodulated. The best-measured PJ figure comes from young rubber: up to 250 kg N/ha per year accumulated in above-ground biomass in one northeast Thailand trial (Clermont-Dauphin et al., 2016). For MB, 67 to 84% of plant nitrogen came from fixation in a 15N isotope-dilution study under three-year-old oil palm (Cheah, Zaharah and Aminuddin, 2010); no routine annual rate is asserted for MB.
• Legume roots release sugars, amino acids and organic acids that feed soil microbes, and the cover adds leaf litter and shades the soil surface.
• Plant the young rubber on schedule; the cover stays in the interrows through the immature years and is kept off the planting rows and young trees.
Phosphorus and soil acidity:
• Base phosphate and lime decisions on a soil test. Acidic replant soils often have low available phosphorus, and young rubber needs phosphorus for root development, so follow the Malaysian Rubber Board's fertiliser recommendations for your soil series.
How to judge the economics on your estate
A biology-first replant adds some costs early (cover crop seed, establishment labour, soil conditioner) and aims to recover them through more even establishment, fewer replacement trees and less weeding in the immature years. The balance depends on your soil, labour costs, seedling prices and how well the cover is managed, so work it out with your own figures: compare the cost of establishing and maintaining the cover with the cost of replacement trees, weeding and fertiliser in blocks managed with and without it. We do not quote a standard saving per hectare.
Key decision points
Legume Selection: Mucuna bracteata is widely used on degraded, acidic replant soils because it covers the ground quickly and produces a lot of biomass, but it needs active management around young trees. Pueraria javanica produces finer biomass that decomposes faster. Centrosema pubescens is a fallback on heavy clay soils where water retention is high. Many estates sow a mixture rather than a single species; the recommended rates are for one species sown alone, and for a mixture the quantity of each species is set on the quotation for your site.
Tillage: Avoid deep ploughing. Burying old rubber roots and stumps leaves woody material in the soil where root disease fungi can persist. Shallow harrowing is enough to prepare a seedbed for legume seed and to work in SoilBoost EA granules.
Monitoring: Check young trees for root disease symptoms in the first years after replanting. Where you find them, have the cause confirmed and follow the Malaysian Rubber Board's guidance on root disease management. Neither the cover crop nor SoilBoost EA is a root disease treatment. Monitor soil pH and available phosphorus, and correct them according to soil test results.
References
Perron, T., Kouakou, A., Simon, C., Mareschal, L., Gay, F., et al. (2022). Logging residues promote rapid restoration of soil health after clear-cutting of rubber plantations at two sites with contrasting soils in Africa. Science of the Total Environment, 816, 151526. https://doi.org/10.1016/j.scitotenv.2021.151526
Kouakou, A.K., Collart, P., Perron, T., Kolo, Y., Gay, F., Brauman, A., & Brunel, C. (2025). Soil microbial recovery to the rubber tree replanting process in Ivory Coast. Microbial Ecology, 88(1), 13. https://doi.org/10.1007/s00248-025-02506-3
Kim, N., Zabaloy, M.C., Guan, K., & Villamil, M.B. (2020). Do cover crops benefit soil microbiome? A meta-analysis of current research. Soil Biology and Biochemistry, 142, 107701. https://doi.org/10.1016/j.soilbio.2019.107701
Cheah, S.S., Zaharah, A.R., & Aminuddin, H. (2010). Biological nitrogen fixation by Mucuna bracteata under oil palm field environments. Oil Palm Bulletin, 60, 22-27.
Clermont-Dauphin, C., Suvannang, N., Pongwichian, P., Cheylan, V., Hammecker, C., & 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 & Environment, 217, 79-88.
Hasnol Othman, Farawahida Mohamad Darus, & 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.
Tropical Forages: an interactive selection tool (2020 edition, CIAT and ILRI). Neustanthus phaseoloides (Pueraria phaseoloides): https://www.tropicalforages.info/text/entities/neustanthus_phaseoloides.htm
Related resources
- Best cover crop for rubber
- Pueraria javanica vs Mucuna bracteata comparison
- Soil enhancer vs fertilizer: what is the difference?
- Cover crop comparison: PJ, CM, CP, MB, CC
SoilBoost EA is a soil conditioner. It is not a fungicide, pesticide, plant protection product, or standalone treatment for Fusarium TR4, Phytophthora, or any crop disease. It may support soil structure and root-zone conditions as part of a broader agronomy program, but disease management must follow local agronomist, regulatory, sanitation, drainage, and resistant-variety guidance. Cover crops are not a disease treatment either.