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. It reduces dependence on synthetic nitrogen fertiliser. Fixation rates vary by species, ground cover, and conditions, and are highest at full cover in immature plantings. 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, supporting reduced reliance on repeated herbicide passes. See cover crops for cogon-prone fields.

The five cover crop species

Mucuna bracteata (MB)

A vigorous creeping legume that gives the fastest canopy closure of the common species, reaching full ground cover in about six months. It derives roughly 67 to 84 percent of its nitrogen from the atmosphere and fixes on the order of 150 to 200 kg N per hectare per year. Established by nursery transplant, not broadcast. View MB.

Pueraria javanica (PJ)

A fast trailing legume valued for erosion control and nitrogen fixation, with deep roots reaching 2 to 3 metres. It can fix up to 250 kg N per hectare per year at full ground cover (typically around 150), deriving 85 to 93 percent from the atmosphere. Pure-stand seeding is 4 to 6 kg per hectare. 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. Pure-stand seeding is 4 to 6 kg per hectare. View CM.

Centrosema pubescens (CP)

A shade-tolerant creeping legume that persists under closing canopies, tolerating up to about 80 percent shade. Suited to older stands and shaded systems such as cacao. Pure-stand seeding is 3 to 4.5 kg per hectare. 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) and is commonly the persistence component of a PJ, CM, and CC mixture. View CC.

Soil inputs

Soil conditioner

A product that improves the physical, chemical, or biological condition of soil rather than primarily supplying nutrients like a fertiliser. SoilBoost EA is a humic acid soil conditioner that supports soil structure, nutrient holding, and root-zone conditions.

Humic acid

A group of stable organic molecules from decomposed organic matter that improve nutrient availability, soil structure, and microbial activity. Humic acid is the active basis of SoilBoost EA, which Kudzu Seeds Trading offers to its markets.

Leonardite

A soft, oxidised lignite (brown coal) that is one of the richest natural sources of humic acid. SoilBoost EA is derived from leonardite ore.

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. Humic substances can help raise effective CEC.

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. 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, in the Philippines the Bureau of Plant Industry, confirming that exported plant material meets the importing country’s plant health requirements in line with ISPM standards. It is part of compliant cross-border seed supply.