Cover Crops and Soil Glossary

Cover crop concepts

Cover crop

A plant grown to cover and protect the soil rather than for harvest. In tropical plantations, leguminous cover crops are sown between young oil palm, rubber, coconut, and cacao to reduce erosion, suppress weeds, retain moisture, and add nitrogen to the soil. See our complete cover crops guide.

Legume cover crop (leguminous ground cover)

A cover crop from the legume family that hosts nitrogen-fixing rhizobia bacteria in its roots. Legume cover crops add biologically fixed nitrogen to the soil while covering the ground, which is why they are the standard ground cover for immature plantations.

Biological nitrogen fixation

The process by which rhizobia bacteria in legume root nodules convert atmospheric nitrogen into a form plants can use. Fixation rates vary by species, stand density, and growing conditions. Legume cover contributes nitrogen; adjust your fertiliser programme only after soil and leaf analysis shows what the cover supplies on your block. Estimate it with our nitrogen fixation calculator.

Ground cover establishment

The period from sowing until a cover crop forms a continuous living mat over the soil. Faster establishment means earlier erosion and weed protection. Establishment speed depends on species, light, rainfall, and seeding method.

Inter-row

The strip of ground between the planted rows of a plantation crop. Cover crops are usually established in the inter-rows so they protect the soil without competing directly with the main crop in the planting row.

Replanting (immature phase)

The stage when old palms or trees are removed and young ones established. Bare replanted ground is highly exposed to erosion, so cover crops are sown early in the immature phase to stabilise and enrich the soil before the canopy closes. Model exposure with the soil erosion calculator.

Cogon grass (Imperata cylindrica)

An aggressive perennial grass that competes with plantation crops and is difficult to manage once established. A dense legume cover crop helps suppress cogon by shading it out, which can reduce the frequency of herbicide passes needed. See cover crops for cogon-prone fields.

The five cover crop species

Mucuna bracteata (MB)

A vigorous creeping legume. Time to full cover depends on soil and planting density: on mineral soil at 680 seedlings per hectare (1.5 m spacing), Samedani et al. (2015) recorded about 100 percent ground cover at 6 months; on deep peat at 320 seedlings per hectare, MPOB TT No. 501 (2012) recorded 31 percent cover at 6 months and 78 percent at 24 months. It derives roughly 67 to 84 percent of its nitrogen from the atmosphere (Ndfa); absolute figures in kg N per hectare per year are indicative and site-dependent, not design values. The 67 to 84 percent figure comes from one 15N isotope-dilution study under three-year-old oil palm on Jawa Series soil in Malaysia (Cheah, Zaharah and Aminuddin 2010, MPOB Oil Palm Bulletin 60: 22-27). MB is not broadcast. Recommended seeding rate: 1 kg/ha sown alone, drilled or planted in holes (our recommendation). MB can also be raised in a nursery and transplanted: on deep peat, MPOB TT No. 501 used about 320 seedlings per hectare, two per palm point, raised from about 500 seeds (75 g). View MB.

Pueraria javanica (PJ)

A fast, deep-rooting trailing legume valued for erosion control and nitrogen fixation. The best-documented measurement of the species is Clermont-Dauphin et al. (2016), working in a rubber intercrop in northeast Thailand: the legume derived 85 to 93 percent of its nitrogen from the atmosphere (Ndfa), varying by year, and accumulated up to 250 kg N per hectare per year in aboveground biomass. Treat that 250 as a measured upper reference point from one well-established stand under favourable conditions, not a design value: published figures vary widely with site, stand age, and management, and a thin or young stand fixes far less. The same study found that the cover crop reduced the drought resilience of young rubber trees on the water-limited part of the slope, even while improving growth where water was not limiting, so weigh it carefully on drought-prone sites. Legume cover contributes nitrogen; adjust your fertiliser programme only after soil and leaf analysis shows what the cover supplies on your block. Recommended seeding rate (sown alone): 10 kg/ha, drilled or planted in holes (our recommendation). View PJ.

Calopogonium mucunoides (CM)

A fast-establishing trailing legume that provides quick early ground cover, often sown in a mixture with PJ and CC for layered establishment. It covers the soil 3 to 6 months after sowing, sooner on newly cleared fertile land (PROSEA 11). Recommended seeding rate (sown alone): 10 kg/ha, drilled or planted in holes (our recommendation); in a mixture, the quantity of each species is set on the quotation for your site. View CM.

Centrosema pubescens (CP)

A shade-tolerant creeping legume that persists under closing canopies and tolerates substantial shade. Suited to older stands and shaded systems such as cacao. Recommended seeding rate (sown alone): 10 kg/ha, drilled or planted in holes (our recommendation). View CP.

Calopogonium caeruleum (CC)

A persistent perennial twining legume used for long-term cover, especially on slopes and in maturing plantations. It is slow to establish (up to about 20 months to full cover, PROSEA 4) and is commonly the persistence component of a PJ, CM, and CC mixture. Recommended seeding rate (sown alone): 5 kg/ha, drilled or planted in holes (our recommendation); in a mixture, the quantity of each species is set on the quotation for your site. View CC.

Soil inputs

Soil conditioner

A product that improves the physical, chemical, or biological condition of soil rather than primarily supplying nutrients as a fertiliser does. SoilBoost EA is an example: a Leonardite-derived humic acid soil conditioner with 0.45 percent sulphur and pH 3.84. It is a soil conditioner, not a fertiliser and not a substitute for one, and it is neither a fungicide nor a pesticide. It is manufactured exclusively for Chemiseed Sdn. Bhd. and Kudzu Seeds Trading.

Humic acid

A group of stable organic molecules from decomposed organic matter, associated with nutrient availability, soil structure, and microbial activity. Humic acid is the active fraction of SoilBoost EA, which is derived from leonardite. See how Leonardite humic acid works.

Leonardite

A soft, oxidised lignite (brown coal) that is one of the richest natural sources of humic and fulvic acids. SoilBoost EA is produced from leonardite ore. See our full explainer on Leonardite humic acid: source, composition, and how it works.

Fulvic acid

A low molecular weight fraction of the humic substances in leonardite. Smaller and more mobile than humic acid, it is associated with micronutrient transport and uptake. SoilBoost EA is derived from leonardite, which contains both fractions; no fulvic acid content is declared for the product.

Biostimulant

A substance that supports a plant’s natural processes, such as nutrient uptake, root development, or stress tolerance, without being a fertiliser or pesticide.

Cation exchange capacity (CEC)

A measure of the soil’s ability to hold and exchange positively charged nutrients such as potassium, calcium, magnesium, and ammonium. Higher CEC means the soil retains more nutrients against leaching. Soil organic matter contributes to CEC; we do not claim that SoilBoost EA raises soil CEC.

Chelation

The process by which humic and fulvic molecules form stable, water-soluble complexes with metal micronutrients such as iron, zinc, and copper, keeping them available to plant roots instead of precipitating in the soil. It is one of the mechanisms commonly attributed to humic substances in soils.

Seed quality and trade

Tested to ISTA and AOSA methods

ISTA (International Seed Testing Association) and AOSA (Association of Official Seed Analysts) publish standardised methods for testing seed germination and purity. Seed lots tested to these methods give buyers a consistent, comparable quality basis. Lot results are available on request.

Germination rate

The percentage of seeds in a lot that germinate under standard test conditions. It is reported per lot from testing and varies between lots. Some species, such as Mucuna bracteata and Pueraria javanica, have hard seed coats and benefit from scarification to improve and synchronise germination.

Phytosanitary certificate

An official document issued by a national plant protection organisation (NPPO), in the Philippines the Bureau of Plant Industry, confirming that a consignment has been inspected at origin and meets the importing country’s plant health requirements. Its content and format follow ISPM 12. The certificate attests to inspection at origin; it does not by itself authorise import, and import permits and admissibility remain the responsibility of the buyer.

ISPM 7 and ISPM 12

Two International Standards for Phytosanitary Measures published under the IPPC, and often confused. ISPM 7, Phytosanitary certification system, sets out how a national plant protection organisation must structure and operate its certification service; it applies to the NPPO, in the Philippines the Bureau of Plant Industry, and not to an exporter. ISPM 12, Phytosanitary certificates, governs the certificate itself: its content, wording and issuance for a consignment. A seed company is therefore never “ISPM 7 compliant”. It ships under a certificate issued to ISPM 12 by an NPPO that runs its certification system to ISPM 7.