Cover crop and soil FAQ

It depends heavily on the species and on how much ground is covered. The most reliable measure is %Ndfa, the share of the plant's nitrogen that came from the air rather than the soil:

• Pueraria javanica reached 85 to 93% Ndfa across four years in young rubber in northeast Thailand, accumulating about 250 kg N/ha/yr in biomass.
• Mucuna bracteata derived 67 to 84% of its nitrogen from fixation under oil palm in Malaysia.
• Calopogonium caeruleum averaged 49% Ndfa (range 25 to 75%) across 13 plantations in Papua New Guinea.

For a legume mixture rather than a single species, the best-supported figure is an extra 151 kg N, 10 kg P and 20 kg K per hectare per year compared with a grass cover, from Malaysian rubber trials.

Historical Malaysian estimates average around 150 kg N/ha/yr over the first five years. A 2014 study that measured only above-ground biomass found just 0.3 to 34.2 kg N/ha. Both are in the literature. The difference is method, not disagreement about the plants.

Sources: Clermont-Dauphin et al. 2016, Agriculture, Ecosystems and Environment 217; Cheah et al. 2010, Oil Palm Bulletin 60 (MPOB); Pipai et al. 2023, Plant and Soil 491; Vrignon-Brenas et al. 2019, Agronomy for Sustainable Development 39, reporting Broughton 1977; Pardon et al. 2016, Agronomy for Sustainable Development 36.

We are not able to give you one, and we would rather say that than invent it.

In a literature search across the peer-reviewed record, these two species appear almost exclusively as components of mixtures. We found no primary study measuring their fixation in isolation under plantation conditions. Figures circulating for them, including on parts of our own site we are correcting, trace back to secondary sources we cannot verify.

What we can say is that both are established mixture components, and that the mixture figure above (an extra 151 kg N/ha/yr over grass cover) was measured on a mix containing both of them alongside Pueraria.

Yes, and negatively. Across 13 plantations, the proportion of nitrogen derived from fixation was strongly negatively correlated with soil nitrate, and dropped significantly wherever soil nitrate-nitrogen exceeded 5 mg/kg.

Put plainly: the more mineral nitrogen you apply, the less your legume bothers to fix. Heavy fertilisation and a legume cover partly work against each other. This is one of the least-known findings in the field and it matters for how you plan the two together.

Source: Pipai et al. 2023, Plant and Soil 491, R² = 0.55.

In a 24-month trial under 10-year-old oil palm at Rembau, Negeri Sembilan, harvested Mucuna bracteata biomass ranged from 7.7 to 24.5 t/ha/yr depending on cutting frequency, with tissue nitrogen of 2.3 to 3.2%. Pueraria phaseoloides produced about 8 t/ha/yr over four years in Thai rubber.

Calopogonium caeruleum yields only about 0.6 t DM/ha/yr under heavy shade (0 to 25% sunlight). That sounds poor until you note it is often the only species still alive under a closed canopy. Its value is persistence, not tonnage.

One honest note on the Mucuna range: it is biomass removed under an experimental cutting regime, not standing biomass, and an El Niño drought ran through part of that trial, so it is likely on the conservative side.

Sources: Mohd Noor et al. 2021, Pertanika Journal of Tropical Agricultural Science 44(1); Clermont-Dauphin et al. 2016; Feedipedia (INRAE, CIRAD, AFZ, FAO).

On mineral soil in a 24-month Selangor trial: Axonopus compressus grass in 3 months, Mucuna bracteata in 6 months, and legume mixtures in 9 months to full cover.

On peat, the picture is completely different. An MPOB bulletin recorded only 31% cover at 6 months, 58% at 12 months and 78% at 24 months for the same species. Both studies are Malaysian.

So a single “covers the ground in X months” claim is not something anyone can honestly make. Soil type and maintenance change the answer by a factor of four.

Sources: Samedani et al. 2015, International Journal of Agriculture & Biology 17(2); Hasnol Othman et al. 2012, MPOB Information Series TT No. 501 (extension bulletin, peat soil).

Calopogonium caeruleum. In a survey of 13 Papua New Guinea plantations it was the only species still present in blocks over five years old. Pueraria phaseoloides was found only in younger plantations. Separately, C. caeruleum is documented as productive under 0 to 25% sunlight and was rated outstandingly shade tolerant against 14 other tropical legumes tested in Malaysia.

This is the practical argument for sowing a mixture rather than a monoculture: fast species close the ground in year one, and a shade-tolerant species is what carries the block through year six.

Sources: Pipai et al. 2023, Plant and Soil 491; Feedipedia (INRAE, CIRAD, AFZ, FAO).

We have corrected the position of Mucuna bracteata in this table, and it is worth explaining why rather than quietly moving a row. Forage datasheets describe MB as needing good light, and its nodulation genuinely is reduced by deep shade. But MB is the species Malaysian estates plant because it holds under a maturing oil palm canopy, and MPOB's own figures show it still producing around 13 t/ha of dry matter at 60 to 70% shade against up to about 28 t/ha in the open. Ranking it below Pueraria javanica, which thins well before that point, misread the datasheet language as a ranking. Our position is that MB is shade-tolerant through the maturing phase, and that CC and CP are the species that persist once the canopy is fully closed.

Sources: Pipai et al. 2023; Feedipedia species datasheets (INRAE, CIRAD, AFZ, FAO); Dissanayaka et al. 2024, Circular Agricultural Systems 4; MPOB shade-biomass figures for Mucuna bracteata.

All five are adapted to the acidic, heavily weathered soils typical of Southeast Asian plantations. Calopogonium caeruleum is the most acid-tolerant of the group. Mucuna bracteata is documented across a range of roughly pH 4.5 to 7.7, with rainfall tolerance from 400 to 3,000 mm a year and temperatures of 19 to 27 °C.

Soil pH is worth testing before you order rather than assuming. Our climate suitability calculator will narrow the species list for your site, and we will check the result with you.

Source: Dissanayaka et al. 2024, Circular Agricultural Systems 4 (review).

Yes, and this is the trade-off most suppliers will not mention.

In a four-year Thai rubber trial, Pueraria phaseoloides improved tree nutrition and growth at the bottom of the slope where soil water storage was good. At upper positions with low water-holding capacity, the same cover crop reduced the trees' ability to survive intense drought.

On shallow or light soils, plan the cover to the soil rather than to the block, and talk to us about species and density before you commit the whole estate.

Source: Clermont-Dauphin et al. 2016, Agriculture, Ecosystems and Environment 217.

Very well, once the canopy closes. At 24 months in a Selangor trial, weed dry weight under cover was 97.3 to 99.9% lower than an unweeded control, and weed density 94.8 to 99.7% lower. The unweeded plots carried 734.7 g/m² of weed biomass against 1.8 to 5.9 g/m² under cover.

Year one is the hard part. In the same trial, weed densities at 9 to 12 months were higher in the legume plots before the canopy closed. Budget for weeding in the establishment phase. Anyone quoting you the 97 to 99% figure without that caveat is quoting an endpoint, not a season.

Source: Samedani et al. 2015, International Journal of Agriculture & Biology 17(2).

Ground cover helps, but on the published Malaysian evidence slope and frond management dominate.

Oil palm soil loss runs at 13 to 78 t/ha/yr on Oxisols and 1 to 28 t/ha/yr on Ultisols, against a natural forest baseline of under 1 t/ha/yr. Contour frond stacking cut runoff from 30.8% to 17.9%, and to 10.7% with silt pits added, bringing erosion below 5 t/ha/yr on its own.

Legume cover produced 5,370 kg/ha of dry matter against 1,930 kg/ha for natural weed cover, contributing 113 kg N, 11 kg P and 106 kg K per hectare. A cover crop is one contributor to erosion control alongside terracing, frond stacking and silt pits, not a replacement for them.

Source: Afandi et al. 2017, Oil Palm Bulletin 75 (MPOB review of Malaysian studies 1977 to 2014).

This is the weakest link in the case for cover crops, and we would rather flag it than oversell it.

The most rigorous recent Malaysian trial, running 24 months under mature oil palm, found no significant effect on any soil physicochemical property measured: not pH, organic carbon, nitrogen, phosphorus, potassium, calcium, magnesium, CEC, bulk density, aggregate stability, porosity or soil water. A 2025 North Sumatra study found no significant differences either. A 2025 systematic review of cover crops across all systems found 34% of studies reported no significant yield effect.

The better-supported benefits are nitrogen contribution, weed suppression after canopy closure, and surface protection. Buy on those.

Sources: Mohd Noor et al. 2021, Pertanika JTAS 44(1); Sakiah et al. 2025, Malaysian Journal of Soil Science 29; Salisu et al. 2025, Agronomy 15:2865.

We will not put a percentage on that, and we would be cautious about anyone who does.

A legume cover contributes nitrogen, and that contribution is real and measurable. But it varies with species, ground cover, soil nitrate and season across the wide range set out in the first answer on this page, and the fixation itself is suppressed by the mineral nitrogen you apply. Treating a cover crop as a fixed fertiliser credit is how estates end up under-nourishing a block.

The sound approach is to establish the cover, measure your own leaf and soil analysis over two to three seasons, and adjust the programme against your own data. Our agronomists will help you set that up.

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, 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. Read those as an institutional best-management-practice recommendation from a peat trial rather than a primary field measurement: no mineral-soil rate exists, and MPOB does not state whether the totals are per gross hectare or per interrow hectare actually sown.

Across the published sources, mixture totals run 5 to 15 kg/ha and cluster at 6 to 12 kg/ha. We previously gave a narrower figure of 10 to 15 kg/ha here, which sat in the upper half of the defensible range; we have corrected it. Three distinctions are worth holding onto when you compare quotations: a mixture total is not a per-species component rate, a gross hectare is not the interrow hectare you actually sow, and grazed-pasture rates of 0.5 to 1.0 kg/ha are not cover crop rates. There is also no Philippine institutional rate: PNS/BAFS 238:2018 recommends legume cover cropping but gives no figure, so any Philippine number is an extrapolation from Malaysian practice. Our seed calculator will work the quantities for your area, and we check the output on estate-scale quotations.

Yes. These are hard-seeded tropical legumes and untreated seed will disappoint you regardless of its quality.

For Mucuna bracteata, a 2024 review reports untreated germination of 53% against 93% after scarification. A field study in Riau, Indonesia recorded 88 ± 9.1% germination from shell nicking combined with a fungicide treatment, with mean germination time of 4.25 days.

We supply scarification guidance with the seed and will walk your team through it. Germination test certificates are issued per lot on request.

Sources: Dissanayaka et al. 2024, Circular Agricultural Systems 4; Hastuti et al. 2024, BIO Web of Conferences 94:06002.

Cool, dry and off the floor. Store on elevated pallets rather than in contact with a concrete slab, keep seed moisture low, and protect against storage pests and humidity.

Viability declines with time and with storage conditions, so we do not quote a shelf life. What we do instead is issue a germination test certificate for the specific lot supplied, dated. If you are holding seed for a later planting window, tell us and we will advise on retesting.

Selection comes down to canopy stage and shade, not crop alone. An immature block and a closed-canopy block on the same estate want different species.

Generally no. Most tropical legume covers are perennial and are managed rather than killed. Periodic slashing controls biomass, circle weeding maintains clearance around young palms and trees, and cut material is left as mulch.

Mucuna bracteata in particular is vigorous and needs active management. A 2024 review notes it requires proper maintenance and pruning because of its aggressive vegetative growth, and that it can compete with young seedlings of the main crop. A cover that establishes well is a cover you will need to manage.

Source: Dissanayaka et al. 2024, Circular Agricultural Systems 4.

Yes, and they are the buyer's responsibility to confirm before ordering. Import and export both require permits, and most destinations require a phytosanitary certificate for a seed consignment. Some species are restricted in some jurisdictions on invasiveness grounds.

Chemiseed exports from Malaysia, so the certificate is issued by Malaysia's national plant protection organisation, the Department of Agriculture Malaysia (Jabatan Pertanian Malaysia), under the IPPC framework. That certificate is the document described by ISPM 12. ISPM 7 is a different standard covering how an NPPO runs its certification system: it applies to national authorities, not to companies, so no seed company is or can be "ISPM 7 certified". SoilBoost EA is a mined mineral product rather than plant material, so a phytosanitary certificate is generally not the applicable document for it.

We supply phytosanitary certificates, certificates of origin, germination test certificates and technical documentation to support your import. Check your destination country's rules before placing an order, and tell us the destination early so we can prepare the right paperwork. Our terms of service set this out in full.

SoilBoost EA is a humic soil conditioner derived from leonardite ore. Humic acid is typically 96.55% by the supplying laboratory's proprietary humic acid method, or 60.6% by the CDFA method — the same sample measured two ways, so the figure only means something alongside the method. Sulfur is 0.45% as sent (25.81% sample moisture) or 0.61% on a dry-weight basis, and pH is 3.84. It is a separate product from the seed, used to condition the root zone.

Analysis is run per batch, on request, so the figures above are typical values rather than guaranteed constants and they do vary: a second batch assayed 92.59% by the laboratory method and 35.71% by the CDFA method. Typical analysis. A certificate of analysis for the batch supplied is available on request.

It is a soil conditioner, not a fertiliser, and not a substitute for a fertiliser programme. Response to humic substances is real on average but variable: meta-analyses report roughly +12% crop yield and +19 to +22% biomass, while about half the trials in the largest meta-analysis improved growth by less than 5%. Source material matters more than dose, and overdosing reduces the response rather than increasing it. Those meta-analyses, including Ma, Cheng and Zhang (2024), tested humic acid products as a class and did not test SoilBoost EA, and the response diminishes outside roughly pH 6 to 8.

Our honest read of that evidence, with the caveats intact, is on the research page. Trial it on a limited area with an untreated comparison strip before committing an estate.

Sources: Rose et al. 2014, Advances in Agronomy 124; Ma et al. 2024, Agronomy 14:2763.