Radish — NPK Absorption (g/m²) by Growth Stage

Overview

This report details nitrogen (N), phosphorus (P), and potassium (K) uptake (g/m²) at each major growth stage of radish (daikon) from Japanese and international research and extension sources. Cumulative uptake at harvest is well documented; stage-specific quantities are rare, so allocation by uptake curves and stage shares is standard. Direct data and logical estimates are combined with scientific rationale.

Growth Stages and NPK Uptake Patterns

1. Stage Definitions

• (1) Germination (~7–10 days after sowing)
• (2) Seedling / leaf growth (~25 days; leaf number increases, taproot prepares to enlarge)
• (3) Root enlargement (~25–60 days; rapid taproot swelling to market size)
• (4) Flowering (bolting) (usually after harvest on leftover plants)

Definitions align with major Japanese research and extension materials[1][2][3][4].

2. NPK Uptake Curve and Total Uptake

• Cumulative uptake at harvest (standard yield 3.3 kg/m² = 33 t/ha): N 8.1 g/m²; P 1.6 g/m²; K 11 g/m²
• Uptake scales with yield; stage patterns are consistent[5][6][7][8].
• Uptake share by stage: Germination 0–3%; seedling/leaf 5–10%; root enlargement 70–80%; flowering 10–20% (usually not absorbed in market crops)[1][4][9][10].

Estimated Stage-wise Uptake (g/m²)

1. Germination (0–3%)

• N: 8.1 × 0.02 ≈ 0.16 g/m²; P: ~0.03; K: ~0.22
• Negligible for fertilization design[3][4].

2. Seedling / Leaf Growth (5–10%)

• N: 8.1 × 0.075 ≈ 0.61; P: ~0.12; K: ~0.83
• Supports leaf and early root development; total uptake still low[1][4].

3. Root Enlargement (70–80%)

• N: 8.1 × 0.75 ≈ 6.1; P: ~1.2; K: ~8.3
• Central period for nutrient uptake and root quality[1][2][4]. Deficiency directly reduces root size and quality[3][6].

4. Flowering / Bolting (10–20%)

• N: 8.1 × 0.125 ≈ 1.01; P: ~0.20; K: ~1.38
• Market daikon is usually harvested before this uptake; relevant for seed crops[2][4].

Estimation Method and Reliability

• Allocation ratios from Japanese vegetable physiology, extension curves, and papers[1][4][5][7][8][9][10].
• Models show reproducibility across soils and environments[2][6][7][8]; stage allocation is a universal root-crop pattern[4][9][10].

Field Applications

• Nutrient shortage at root enlargement start harms root size and quality; excess in seedling stage is inefficient[3][4].
• Targeted topdressing in root enlargement reduces fertilizer residue and environmental loss[4][7].

Conclusion

1. ~75% of radish NPK uptake occurs during root enlargement.
2. Germination + seedling together are under 10%—over-fertilization is inefficient.
3. Standard total uptake at 3.3 kg/m² yield: N 8.1, P 1.6, K 11 g/m².
4. Stage estimates from consistent Japanese and academic uptake patterns are practical and reliable.
5. Flowering-stage uptake is generally not needed for market daikon.

Sources

1. BSI Bioscience Institute daikon growth stages
2. Environmentally friendly fertilization considering vegetable uptake patterns(Japan Fertilizer Inspection Association)
3. JA Saitama Chuo: Daikon fertilization guide
4. Digested slurry on winter daikon - Japanese Society of Soil Science and Plant Nutrition
5. Macro and micronutrients accumulation in radish (Raphanus sativus ...)
6. Estimating nutrient uptake requirements for radish in China based on QUEFTS model (full PDF)
7. Nutrient Uptake Potential of Nonleguminous Species and Its Interaction with Soil Quality
8. Root yield and nutrient uptake of Radish (Raphanus sativus L.) as influenced by the application of organic and inorganic sources of nitrogen and their combinations
9. Effects of NPK Fertilizer Application Rates and Intra-row Spacing on Yield of Radish (Raphanus sativus L.)
10. Study on Growth and Root Yield of Radish (Raphanus sativus Lam.) as Influenced by Nutrition