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Soil biology

Microbes, cover crops and suppressive soils. 19 practices across 12 crops.

Summary of cited sources. TERAknow summarises published guidance from the sources linked on each page. Recommendations are general, not guaranteed: results depend on your soil, climate and variety, so confirm with local extension staff or an agronomist before acting.

Banana · Pisang

Full banana guide
    • Biological & regenerative
    • Soil biology
    • Stage: Planting

    Inoculate with beneficial microbes at planting

    TNAU recommends Pseudomonas fluorescens at planting, then Azospirillum, phosphate-solubilizing bacteria and Trichoderma viride with farmyard manure in month 4.

    Technical detail
    • At planting: 25 g Pseudomonas fluorescens per plant.
    • Month 4: 30 g each of Azospirillum, phosphobacteria and Trichoderma viride, mixed with 5 to 10 kg farmyard manure per plant.
    • These rates come from one Indian guide. Product strains and rates differ, so follow the label of a registered local product.
    Regions
    India (Tamil Nadu)
    Confidence
    Medium confidence: one institutional guide
    Source
    Crop
    Banana guide
    • Biological & regenerative
    • Soil biology
    • Stage: Vegetative growth

    Build a disease-suppressive soil

    Organic matter improves microbial balance and the soil's ability to suppress Fusarium. Low pH raises disease risk; liming and calcium lower it, and urea may raise it.

    Technical detail
    • This supports, but does not replace, hygiene and resistant varieties.
    • FAO calls microbial antagonists promising but notes field studies are scarce. Clean planting material plus Trichoderma harzianum let some farms keep cropping infected soils for a few years.
    • Crop rotation alone did not give long-term control.
    Regions
    Widely applicable
    Confidence
    Emerging evidence: early or small-scale evidence
    Source
    Crop
    Banana guide
    • Biological & regenerative
    • Soil biology
    • Stage: Planting

    Rotate out of banana on Fusarium-affected land

    Fusarium survives in the soil, so replanting banana straight after banana keeps the disease going. Rotation is one of the few field measures that showed benefit in Indonesia.

    Technical detail
    • Indonesian work found that rotation with pineapple and cassava can reduce Fusarium wilt incidence.
    • The same report notes that beneficial microbes such as Trichoderma, Bacillus and Pseudomonas had not yet shown positive results against Fusarium wilt in Indonesian trials. Treat biological products as unproven for this disease.
    • Paddy rice rotation was raised as a possible suppressive option for Southeast Asia, but it was still a research question.
    Regions
    Indonesia · Southeast Asia
    Confidence
    Emerging evidence: early or small-scale evidence
    Source
    Crop
    Banana guide

Rubber · Karet

Full rubber guide
    • Biological & regenerative
    • Soil biology
    • Stage: Land prep & planting

    Establish a legume cover crop between rows

    Creeping legumes protect the soil between young trees, suppress weeds and add nitrogen and organic matter.

    Technical detail
    • Common species: Pueraria phaseoloides, Calopogonium mucunoides, Centrosema pubescens and Desmodium ovalifolium.
    • Keep the cover weeded and clear of the tree rows while trees are small.
    Regions
    Widely applicable
    Confidence
    Medium confidence: one institutional guide
    Source
    Crop
    Rubber guide
    • Biological & regenerative
    • Soil biology
    • Stage: Immature growth

    Rubber agroforestry for smallholders

    Indonesian 'jungle rubber' grows rubber with timber, fruit trees and annual crops in several layers. Improved systems keep this mix but use recommended clones.

    Technical detail
    • Over 80% of Indonesia's rubber area is smallholder land, much of it in mixed systems.
    • Reported benefits: income from several products, biodiversity, water conservation and carbon storage.
    • Trade-off: published yield and income comparisons with monoculture are limited, so returns need checking locally.
    Regions
    Indonesia
    Confidence
    Medium confidence: one institutional guide
    Source
    Crop
    Rubber guide
    • Biological & regenerative
    • Soil biology
    • Stage: Immature growth

    Trichoderma against white root disease

    Local Trichoderma isolates from Indonesia slowed the white root fungus in the lab and reduced disease on potted stumps.

    Technical detail
    • Four of 16 isolates reduced fungal growth by 66 to 71% in the lab.
    • Trials were on potted stumps; field results are not yet established.
    • Use alongside stump removal, not instead of it.
    Regions
    Indonesia (North Sumatra)
    Confidence
    Emerging evidence: early or small-scale evidence
    Source
    Crop
    Rubber guide

Oil palm · Kelapa sawit

Full oil palm guide
    • Biological & regenerative
    • Soil biology
    • Stage: Replanting & land preparation

    Sow a legume cover crop at land preparation

    Legume covers reduce erosion, keep soil moist, limit loss of organic matter and attract natural enemies of pests. Sow once, after land clearing, avoiding very heavy rain or dry spells.

    Technical detail
    • Smallholder Oil Palm Handbook seed rates: Mucuna bracteata 200 to 300 g/ha; Pueraria phaseoloides 3 to 4 kg/ha; Calopogonium caeruleum 1 to 1.5 kg/ha. Most seed needs scarification (sandpaper or hot water).
    • The same guide supports establishment with soluble P (for example 500 kg/ha TSP) or reactive rock phosphate. These are rates from one guide; adjust to a soil test.
    • Slash inter-row vegetation at knee height about every six months.
    • TNAU also lists Pueraria, Calopogonium, Centrosema and Mucuna; FELCRA uses legume covers during the immature stage.
    Regions
    Indonesia · Malaysia
    Confidence
    High confidence: several institutional sources agree
    Sources
    Crop
    Oil palm guide
    • Biological & regenerative
    • Soil biology
    • Stage: Mature palms

    Stack pruned fronds around each palm

    Pruned fronds returned to the field feed the soil, hold moisture, reduce erosion and suppress weeds. Lay them in a U or C shape, leaving only the palm circle and harvest path open.

    Technical detail
    • PPKS: keep the circle and path at about 1.5 m radius, widening to 2.5 m for tall palms.
    • Smallholder handbook: chop the cut frond in two; put the thick spiny part on the stack between rows and the thin part between neighbouring palms.
    • Over-stacked fronds can shelter rats, so spread them rather than piling them.
    Regions
    Indonesia
    Confidence
    High confidence: several institutional sources agree
    Sources
    Crop
    Oil palm guide

Coffee · Kopi

Full coffee guide
    • Biological & regenerative
    • Soil biology
    • Stage: Productive trees

    Dig rorak pits and keep leaf litter

    Rorak are small trenches beside the trees that collect organic matter and improve root aeration. Shade-tree litter adds nutrients and holds moisture in dry spells.

    Technical detail
    • Puslitkoka/ICRAF: rorak about 60 to 80 cm long, 30 cm wide and 40 to 50 cm deep.
    • Fill rorak with prunings and litter. Leave leaf litter on the ground rather than burning it.
    Regions
    Indonesia
    Confidence
    Medium confidence: one institutional guide
    Sources
    Crop
    Coffee guide

Cocoa · Kakao

Full cocoa guide
    • Biological & regenerative
    • Soil biology
    • Stage: Site & shade

    Choose companion trees that build soil

    A Southeast Sulawesi study found more soil carbon, nitrogen and aggregation under shade-tree canopies, with no net effect of shade on cocoa yield. Gliricidia gave the best results for soil carbon.

    Technical detail
    • ICRAF species cards (South Sulawesi) use 3.8 m x 2.5 m cocoa spacing and put teak, mahogany and sengon on farm boundaries.
    • Nitrogen-fixing companions such as petai, jengkol and sengon are noted for soil fertility.
    • Planting companions too close reduces yields of both crops.
    Regions
    Indonesia (Sulawesi)
    Confidence
    Medium confidence: one institutional guide
    Sources
    Crop
    Cocoa guide
    • Biological & regenerative
    • Soil biology
    • Stage: Mature trees

    Recycle litter, prunings and buried husks

    Leaf litter protects the soil and reduces rain splash. Husks and prunings return nutrients, but must be buried because they carry disease and pests.

    Technical detail
    • ACIAR: leave fallen leaves as mulch, with a 20 cm clear space around the trunk. Mulch improves moisture and stimulates microbial activity.
    • PNG handbook: bury husks, prunings and manure about 10 cm deep in trenches between rows, alternating direction each year.
    • BPTP Bengkulu linked high soil K partly to pod husks spread on the land.
    Regions
    Pacific · Indonesia
    Confidence
    High confidence: several institutional sources agree
    Sources
    Crop
    Cocoa guide

Sugarcane · Tebu

Full sugarcane guide
    • Biological & regenerative
    • Soil biology
    • Stage: Tillering and elongation

    Return suitable organic material to the soil

    Consider organic amendments and retained crop residue as part of a site-specific soil management plan.

    Technical detail
    • TNAU describes farmyard manure and composted sugarcane material as nutrient-management options.
    • Choose materials and application methods based on local soil tests and agronomic advice.
    Regions
    India (Tamil Nadu)
    Confidence
    Medium confidence: one institutional guide
    Source
    Crop
    Sugarcane guide

Coconut · Kelapa

Full coconut guide
    • Biological & regenerative
    • Soil biology
    • Stage: Canopy and root zone

    Use cover crops and green manure where suitable

    Living cover and green manure can support the soil between palms when water and crop competition are managed.

    Technical detail
    • TNAU lists several green manure and cover crop options for coconut gardens.
    • Select species for the site and avoid competition around young palms.
    Regions
    India (Tamil Nadu)
    Confidence
    Medium confidence: one institutional guide
    Source
    Crop
    Coconut guide

Tomato · Tomat

Full tomato guide
    • Biological & regenerative
    • Soil biology
    • Stage: Field establishment

    Manure, bokashi and straw mulch

    Organic matter keeps the soil loose and moist. Mulch also steadies soil moisture and temperature, which reduces blossom-end rot.

    Technical detail
    • Jambi guide: about 10 t/ha manure a week before planting, or about 5 t/ha bokashi.
    • Rock phosphate at 300 to 350 kg/ha can replace SP-36, applied at least 1 week before planting.
    • Dry straw mulch is listed against blossom-end rot and sunscald.
    Regions
    Indonesia
    Confidence
    Medium confidence: one institutional guide
    Source
    Crop
    Tomato guide

Potato · Kentang

Full potato guide
    • Biological & regenerative
    • Soil biology
    • Stage: Field establishment

    Solarize, add organic matter and use Trichoderma as part of a package

    Soil-borne diseases build up on intensively cropped highland soils. Solarization and organic inputs are part of Indonesian low-input packages.

    Technical detail
    • Balitsa (2021): solarize under white plastic for 2 to 4 weeks until the soil reaches 50 C.
    • The Tosari conservation trial combined reduced fertilizer with organic manure, Trichoderma and IPM.
    • The separate effect of Trichoderma was not reported.
    Regions
    Indonesia
    Confidence
    Emerging evidence: early or small-scale evidence
    Sources
    Crop
    Potato guide

Mango · Mangga

Full mango guide
    • Biological & regenerative
    • Soil biology
    • Stage: Planting

    Build soil organic matter with compost and green manure

    Organic guides in Tamil Nadu fill pits with farmyard manure and vermicompost, and grow green manure between rows.

    Technical detail
    • TNAU organic scheme: 20 kg FYM and 5 kg vermicompost per pit, with Azospirillum and Phosphobacteria inoculants.
    • Later, 10 to 20 kg compost per tree per year, and sunhemp or dhaincha sown as green manure with the monsoon.
    • These are rates from one guide; adjust to a soil test.
    Regions
    India (Tamil Nadu)
    Confidence
    Medium confidence: one institutional guide
    Source
    Crop
    Mango guide

Durian · Durian

Full durian guide
    • Biological & regenerative
    • Soil biology
    • Stage: Canopy building

    Mulch the drip zone and use composted manure

    Organic mulch and well-fermented manure support soil life and root health. High inorganic nitrogen raises canker and root rot risk.

    Technical detail
    • ACIAR: mulch under the drip zone with straw and manure, but keep mulch off the trunk in the wet season.
    • Ferment green manure and chicken manure in planting holes for 8 to 10 weeks before planting; ACIAR mentions an EM starter culture.
    • TFNet adds lime and organic fertilizer to keep trees vigorous.
    Regions
    Vietnam · Thailand · Malaysia
    Confidence
    High confidence: several institutional sources agree
    Sources
    Crop
    Durian guide
    • Biological & regenerative
    • Soil biology
    • Stage: Fruit growth

    Beneficial microbes against Phytophthora

    Trichoderma fungi and Bacillus bacteria have been reported to reduce disease incidence. Use them alongside drainage and sanitation, not instead of them.

    Technical detail
    • The TFNet report mentions observations rather than field trial rates. Local evidence is limited.
    Regions
    Malaysia · Widely applicable
    Confidence
    Emerging evidence: early or small-scale evidence
    Source
    Crop
    Durian guide

Citrus · Jeruk

Full citrus guide
    • Biological & regenerative
    • Soil biology
    • Stage: Field establishment

    Build organic matter and correct acidity together

    Regular manure feeds soil life and roots, and mixing dolomite into the organic matter corrects acid soils.

    Technical detail
    • PTKJS (one guide): manure about 20 to 40 kg per tree per year for trees 1 to 4 years old and 40 to 60 kg after year 4; below pH 5.5, mix about 1 to 2 kg dolomite per 100 kg organic matter.
    • Indonesian guide (1993): below pH 5 roots struggle; above pH 6 micronutrient deficiencies are common. Straw mulch after planting.
    • UF/IFAS: soil and irrigation water pH around 6.0 to 6.5 supports nutrient availability. Test soil before liming.
    Regions
    Indonesia · Widely applicable
    Confidence
    High confidence: several institutional sources agree
    Sources
    Crop
    Citrus guide
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