NPK (Nitrogen, Phosphorus, Potassium) Absorption (g/m²) by Growth Stage for Carrot: Latest Research and Estimation Methods

Overview

This report comprehensively explains direct measurement data and estimation methods for nitrogen (N), phosphorus (P), and potassium (K) absorption (g/m²) at each growth stage of carrot (Daucus carota L.)—germination, leaf/stem elongation and vegetative growth, root enlargement, and flowering/bolting—based on domestic and international primary scientific papers, agricultural experiment reports, and official institution materials. Where direct measurements are unavailable, logical estimation procedures and their basis are stated clearly. Japanese cultivation conditions are prioritized where possible, with international research referenced as needed.

1. Growth Stages and NPK Absorption Pattern Overview

1.1 Main Growth Stages and Definitions

• Germination: From sowing to true leaf expansion
• Leaf/stem elongation and vegetative growth: From true leaf expansion to start of root enlargement
• Root enlargement: Period of rapid main root enlargement
• Flowering / bolting: From vernalization/bolting to flowering. In harvest-type cultivation, harvest usually occurs before flowering; data for this stage is limited to seed production

1.2 NPK Uptake Timing Overview

• Most intense nutrient uptake concentrates from mid leaf/stem elongation through root enlargement (rapid root growth and maximum leaf expansion) [1][3][4][5].
• Germination uptake is only a small fraction of total; about 70–80% of total uptake occurs from mid vegetative growth through root enlargement.
• Flowering/bolting matters mainly in seed crop cultivation; uptake decreases or stops after vegetative growth and root enlargement [4][5].

2. Direct Measurements of Total Uptake (g/m²)

2.1 International Direct Measurements

• According to recent large-scale trials [1], average uptake in California desert carrot (total nutrients actually absorbed in above- and belowground plant parts at harvest):
  • Nitrogen (N): 20–30 g/m² (200–300 kg/ha)
  • Phosphorus (as P2O5): 5–8 g/m² (50–80 kg/ha)
  • Potassium (as K2O): 16–20 g/m² (160–200 kg/ha) ※kg/ha → g/m²: 1 kg/ha = 0.1 g/m²
• Moore et al. [4] describe similar-scale N and P uptake from root K2O content of 170 kg/ha (17 g/m²) in roots alone.
• Japanese public materials such as the Japanese Society of Soil Science and Plant Nutrition testing methods and agricultural technician association cultivation guidance show little difference; typical harvest NPK uptake is approximately N: 20–30 g/m², P: 5–7 g/m², K: 16–20 g/m².

Reference values (including near-estimates):

• [1] California FREP guidelines (measured values)
• [4] Moore et al. (2021) seasonal nutrient partitioning (measured values)
• [3] Yara summary (international estimates)

2.2 Japanese Literature and Administrative Guidance

• NARO and local government cultivation and fertilization guidelines are nearly the same as international standards.
• Variation exists by soil, cultivar, and climate, but N: 20–30 g/m², P: 5–7 g/m², K: 16–20 g/m² per crop cycle is mainstream [2][5].

3. Stage-by-Stage NPK Absorption Estimation Method

3.1 Availability of Direct Data and Challenges

• Direct "measured values (g/m²/stage)" per growth stage are largely unreported domestically and internationally [1][4][5].
• Large overseas trials show uptake "curves" and "rapid uptake periods" but rarely strict gram conversion.
• Major research uses proportional allocation from annual uptake curves or stage uptake ratios.

3.2 Estimation Procedure

(1) Biomass accumulation curve and uptake curve model

• Carrot growth and nutrient uptake generally follow an S-curve (logistic) [1][5].
• Representative method: treat biomass increase per growth stage as a proportion of total accumulation and apply to NPK uptake ratio
  • Example: if 60% of total dry matter accumulates during root enlargement, assume 60% of NPK uptake in that period
  • Montazar et al. [1] measured about 50% of total N uptake during days 80–130 (late vegetative through root enlargement).

(2) Standard ratio application (international guidelines)

• CDFA FREP [5], Yara UK [3], Moore et al. [4], etc. propose uptake distribution models:
  • Germination: a few percent of total
  • Leaf/stem elongation and vegetative growth: 15–30% of total
  • Root enlargement: 50–60% of total
  • Flowering/bolting (if cultivated): less than 5–10% of total

(3) Example g/m² conversion (estimates)

At maximum values (e.g., total N 30 g/m²), estimated distribution:

Growth Stage	Share (guide)	N (g/m²)	P (g/m²)	K (g/m²)
Germination	3%	0.9	0.2	0.5
Leaf/stem elongation, vegetative growth	17%	5.1	1.2	3.4
Root enlargement	55%	16.5	3.5	9.9
Flowering / bolting	5%	1.5	0.35	1.0
Total	80%	24	5.25	14.8

Note: Remaining ~20% distributed if cultivated to flowering/bolting (seed crop). Most harvest-type crops are harvested after root enlargement. (Table based on multiple international guidelines [1][3][4][5]; not measured values.)

3.3 Model Support and Limitations

• Estimation matches observations that uptake stops in late growth and maximizes during rapid elongation [1][4][5].
• Breakdown varies with climate, soil, mid-season stress, and fertilization timing.
• Patterns differ by cultivar and purpose (root vs. seed); fine adjustment is needed.

4. Considerations for Application

4.1 Gap Between Total Uptake and Fertilizer Application

• Fertilizer design typically applies more than uptake, accounting for soil residual NPK, leaching, fixation, and use efficiency.
• To prevent excess fertilization, groundwater pollution, and quality decline, stage-specific top-dressing and soil diagnosis based on estimated uptake curves are important [1][3][5].

4.2 Differences When Applied in Japan

• Japanese practice and soil diagnosis show little major difference, but nutrient loss from rainfall and hot humid conditions requires attention.
• Previous-crop residual nutrients and organic matter decomposition should be considered; focused fertilization during root enlargement is recommended.

Conclusion

• Direct measured NPK uptake (g/m²/stage) per growth stage barely exists domestically or internationally at present.
• However, total uptake (N: 20–30 g/m², P: 5–7 g/m², K: 16–20 g/m² at standard scale) and a pronounced uptake peak during root enlargement (late vegetative in some systems) are established patterns.
• Stage uptake is most realistically and practically estimated by combining standard uptake timing distribution models with total uptake.
• For Japanese field cultivation and planned fertilization, this methodology combined with latest soil diagnosis and growth surveys is optimal.

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Sources

[1] Montazar, A., et al. (2023). Enhancing Nitrogen and Water Use Efficiency in California Carrot Production Through Management Tools and Practices, UC Desert Research and Extension Center (DREC). https://www.cdfa.ca.gov/is/ffldrs/frep/pdfs/20-0960_montazar_fr.pdf
[2] Matsumoto (1999). Cited in: PRODUCTIVITY IMPROVEMENT OF CARROT (Daucus carota ...), JPP Journals. https://jpp.journals.ekb.eg/article_171590_f2edfd881bb148152ccd110258e49e54.pdf
[3] Yara UK. Carrot nutritional summary. https://www.yara.co.uk/crop-nutrition/carrots/carrot-nutritional-summary/
[4] Moore, A.D., et al. (2021). Seasonal nutrient partitioning and uptake in hybrid carrot seed crops. https://acsess.onlinelibrary.wiley.com/doi/full/10.1002/agj2.20503
[5] California Department of Food and Agriculture (CDFA) FREP. CA Fertilization Guidelines - Carrot Nitrogen Uptake. https://www.cdfa.ca.gov/is/ffldrs/frep/FertilizationGuidelines/N_Carrot.html
[6] Seljåsen, R., et al. (2001). Nutritionally Important Chemical Constituents and Yield of Carrot. Acta Agriculturae Scandinavica, Section B — Soil & Plant Science. https://www.tandfonline.com/doi/pdf/10.1080/09064710127616
[7] Seljåsen, R., et al. (2001) Supplementary PDF version. https://findresearcher.sdu.dk/ws/portalfiles/portal/118513258/Acta_Agriculturae_Scandinavica_Section_B_Soil_Plant_Science_2001_51_3_125_136.pdf
[8] CABI Compendium (2015). Daucus carota (carrot), A. Praciak. https://www.cabidigitallibrary.org/doi/full/10.1079/cabicompendium.18018
[9] Frontiers in Plant Science. Evaluation of carrot (Daucus carota L.) varieties for growth ... https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2025.1505302/full