Nutrition and Fertilisation Reference
Rates from the soil test, timing from the growth stage, verification from the leaf.
This page is the data behind How to fertilise bananas — the tables you come back to when you have a test result in hand or a symptom in the field.
Nutrient roles and demand#
| Nutrient | Role in the plant | Annual demand per stem | Mobile in plant? | Where symptoms appear first |
|---|---|---|---|---|
| Nitrogen (N) | Leaf area, chlorophyll, pseudostem growth | 150–250 g | Yes | Old leaves |
| Phosphorus (P) | Root establishment, energy transfer, flowering | 40–90 g as P₂O₅ | Yes | Old leaves |
| Potassium (K) | Fruit filling, water regulation, disease resistance, quality | 400–700 g as K₂O | Yes | Old leaves, margins |
| Calcium (Ca) | Cell walls, crown and fruit firmness, root tips | 150–250 g as CaO | No | Growing tips, young leaves |
| Magnesium (Mg) | Chlorophyll centre, enzyme activation | 50–90 g as MgO | Yes | Old leaves, interveinal |
| Sulphur (S) | Protein, enzyme synthesis | 20–40 g | Partly | Young leaves |
| Boron (B) | Cell division, pollen tube growth, fruit set | 3–8 g | No | Growing tips — narrow safe range |
| Zinc (Zn) | Auxin synthesis, leaf expansion | 5–15 g | No | Young leaves — small, pale |
| Iron (Fe) | Chlorophyll synthesis | 2–10 g | No | Youngest leaves, interveinal |
| Manganese (Mn) | Photosynthesis, enzyme activation | 2–10 g | No | Young leaves |
| Copper (Cu) | Enzyme function, lignification | 1–5 g | No | Young leaves |
Soil sufficiency (guidelines)#
Interpretation ranges vary by extraction method — use the bands your laboratory reports. The following are common general guidelines for a loam at pH 6–7.
| Parameter | Deficient | Low | Sufficient | High / excessive |
|---|---|---|---|---|
| pH (water) | < 5.3 | 5.3–5.8 | 6.0–7.0 | > 7.8 |
| Organic matter | < 1.5% | 1.5–2.5% | > 3.0% | — |
| P (Olsen) | < 10 mg/kg | 10–20 | 20–40 | > 60 |
| Exchangeable K | < 0.2 cmol/kg | 0.2–0.4 | 0.4–0.8 | > 1.2 |
| Exchangeable Ca | < 2 | 2–5 | 5–12 | > 15 |
| Exchangeable Mg | < 0.5 | 0.5–1.0 | 1.0–3.0 | > 4 |
| CEC | < 8 | 8–12 | 12–30 | > 40 |
| Zn (DTPA) | < 0.5 mg/kg | 0.5–1.0 | 1.0–3.0 | > 5 |
| B (hot water) | < 0.2 mg/kg | 0.2–0.4 | 0.4–1.0 | > 2 |
Leaf tissue sufficiency#
Sample the blade of the most recently fully opened leaf (leaf 5 or 6 counting down from the top) at flowering, from 8–12 plants in representative parts of the block.
| Nutrient | Deficient | Sufficient (typical) | Toxic / excessive |
|---|---|---|---|
| N (%) | < 2.8 | 3.0–4.0 | > 4.5 (soft, disease-prone growth) |
| P (%) | < 0.16 | 0.20–0.30 | — |
| K (%) | < 3.2 | 3.5–5.0 | > 6.0 (induces Mg/Ca shortage) |
| Ca (%) | < 0.3 | 0.4–1.0 | — |
| Mg (%) | < 0.20 | 0.25–0.50 | — |
| S (%) | < 0.16 | 0.20–0.40 | — |
| B (mg/kg) | < 15 | 20–60 | > 100 (toxicity) |
| Zn (mg/kg) | < 15 | 15–50 | > 100 |
| Fe (mg/kg) | < 40 | 50–300 | — |
| Mn (mg/kg) | < 30 | 40–1,000 | > 2,000 |
Deficiency symptom lookup#
| Symptom pattern | Most likely | Confirm with | Fast check |
|---|---|---|---|
| Whole young leaf uniformly pale yellow-green | N | Leaf N < 2.8% | Recently top-dressed? Soil test N |
| Old leaves yellow between veins, green along midrib, then marginal scorch | K | Leaf K < 3.2% | Do the maths: did K supply meet demand? |
| Small, narrow, pale young leaves; shortened internodes; "little leaf" | Zn | Leaf Zn < 15 mg/kg; soil pH > 7 | pH test — most common cause |
| Interveinal yellowing on older leaves, veins remain green, later bronzing | Mg | Leaf Mg < 0.25% | Often after heavy K applications |
| Interveinal yellowing on youngest leaves, sharp green net | Fe | Leaf Fe < 40 mg/kg | High pH or waterlogged soil |
| Thickened, brittle, distorted young leaves; hooked tips; poor bunch set; short fingers | B | Leaf B < 15 mg/kg | Do not overdose — verify before treating |
| Purplish-red cast on young leaves, stunting | P | Leaf P < 0.16% | Also happens in cold weather |
| Pale young leaves with green veins, necrotic edges | Mn / S | Tissue test | Distinguish from Fe: Mn shows necrosis |
| White/yellow scorch on leaves facing the sun after foliar spray | Spray burn / salt | — | Rate, timing, water quality |
| Lower leaves yellow, dark wet rot at collar, bad smell | Root rot / waterlogging | Dig and inspect corm | Not a nutrient problem |
| Yellowing with dark streaks, puckered or narrow upright leaves | Virus (BBTV or streak) | Visual + lab | Do not treat as nutrition |
| Marginal yellowing plus white crust on soil surface | Salt / fertiliser burn | EC test | Flush the root zone |
Planning a season's programme#
| Step | Input | Output |
|---|---|---|
| 1. Soil test | pH, OM, P, K, CEC, micronutrients | Corrective actions (lime, gypsum, P, Zn) |
| 2. Stand count | Actual live mats/ha | Per-hectare and per-stem targets |
| 3. Yield target | t/ha from historical data | Nutrient removal estimate |
| 4. Demand table | g N, P₂O₅, K₂O, Ca, Mg per stem per year | Total kg/ha |
| 5. Product choice | Analysis of available fertilisers | kg product/ha per application |
| 6. Split schedule | Growth stage timing | 4–6 dated applications |
| 7. Verification | Leaf tissue at flowering | Adjustment for next cycle |
Work all of this with the fertiliser calculator.
Product conversions (common)#
| To supply 1 kg of… | Apply… |
|---|---|
| N from urea (46-0-0) | 2.17 kg urea |
| N from ammonium sulphate (21-0-0) | 4.76 kg |
| N from CAN (27-0-0) | 3.70 kg |
| K₂O from muriate of potash (0-0-60) | 1.67 kg KCl |
| K₂O from sulphate of potash (0-0-50) | 2.00 kg K₂SO₄ |
| P₂O₅ from single superphosphate (0-20-0) | 5.00 kg SSP |
| P₂O₅ from triple superphosphate (0-46-0) | 2.17 kg TSP |
Note: muriate of potash (chloride) is cheapest and fine for most bananas unless chloride-sensitive; sulphate of potash suits chloride-sensitive sites and processing fruit but costs more.
Fertigation notes#
- Use only fully soluble products.
- Never mix calcium with phosphate or sulphate in the same tank — precipitation and blocked emitters.
- Alternate N sources: nitrate-dominant in cool/wet conditions (reduces denitrification loss), ammonium-dominant in warm/dry conditions (reduces leaching).
- Split daily injection into 2–4 doses.
- Flush lines with clean water after every injection cycle.
Organic nutrient planning#
| Source | Typical analysis (N-P-K) | Rate guidance |
|---|---|---|
| Composted farmyard manure | 1.0–1.5 – 0.5–1.0 – 0.8–1.5 | 10–25 t/ha/year as basal and top-dress |
| Poultry manure (composted) | 2.5–3.5 – 1.5–2.5 – 1.5–2.0 | 3–8 t/ha — hot, so compost first |
| Vermicompost | 1.5–2.5 – 1.0–2.0 – 1.0–2.0 | 3–8 t/ha, high biological value |
| Compost tea / liquid | Dilute | Foliar or fertigation supplement |
| Cover crop residues | Variable | Returned in situ; N from legumes only |
| Rock phosphate | 0 – 18–24 – 0 | Slow P source on acid soils |
| Wood ash | 0 – 1–3 – 3–8 | K + Ca + pH lift; use sparingly |
| Neem cake / seed meal | 4–6 – 1–2 – 1–2 | N + pest-suppressive properties |
Reality check: organic systems typically produce 10–30% less fruit than high-input systems but carry lower input costs and access premium markets. Plan the economics, not the agronomy alone — see Organic banana farming.
Timing rules that are easy to forget#
- Lime 6–12 weeks before planting.
- No fertiliser in direct contact with a fresh corm.
- Never fertilise a dry root zone.
- Stop N 4–6 weeks before harvest.
- Peak K during flowering and filling.
- Boron by foliar, in small doses, per label.
- Adjust every rate to the real stand count.
- Re-test soil every 2–3 years and tissue every year.
Next steps#
- Execution detail: How to fertilise bananas.
- Compute your rates: Fertiliser calculator.
- Site constraints: Soil and land preparation.
- Feed through the drip: Fertigation.