Comprehensive research report on NPK (nitrogen, phosphorus, potassium) absorption amount (g/m²) in each growth stage of broccoli

Overview

In this report, we investigate the existing major scientific literature, especially Japanese literature, on the uptake (g/m²) of nitrogen (N), phosphorus (P), and potassium (K) during the main growth stages of broccoli (germination, seedling, vegetative growth, flower bud formation, and flowering), and present it based on direct stage-specific uptake data and rational estimation methods. We will also discuss data differences between field cultivation and managed environments (greenhouses, hydroponic cultivation, etc.) and summarize our opinions.

1. Basic knowledge and observation method of NPK absorption pattern

Growth stage definition

• Germination stage: From seed germination to cotyledon development (approximately 0-7 days after sowing)
• Seedling stage: The period when 4 to 6 true leaves have developed and is suitable for potting and planting (21 to 28 days after sowing)
• Vegetative growth period: Rapid growth period of leaves and stems. Until before bud formation begins (30 to 50 days after sowing, 20 to 30 days after planting)
• Flower bud formation period:From the start of differentiation of flower buds (top inflorescence) to the appropriate time for harvest (2 to 3 weeks at the end of the cultivation period)
• Flowering period: From the maturation of flower buds to harvest and after harvest (the period varies depending on the variety and environment)

Absorption amount measurement method

• Fragment sampling method: Collect the above-ground part at regular intervals (every 10 days to 3 weeks) and analyze the dry weight and NPK content. Calculate the amount of absorption at each point and create an integrated curve
• Interval difference method: The difference between the start and end points of each stage on the absorption amount curve becomes the amount of absorption for each stage
• Calculation per unit area: Can convert 1 plant data to 1 m² depending on planting density

2. NPK absorption amount by stage (g/m²): Actual values and estimated values based on field data

The following summarizes the cumulative absorption amount at each stage (at the end of each stage) of common cultivation methods, mainly based on field reports from the Japanese National Agriculture and Food Research Organization (NARO), prefectural agricultural experimental stations, and international organizations. "+" indicates the new additional absorption amount at that stage.

2-1. Germination period (0-7 days)

• N: 0.01 to less than 0.05 g/m² (less than 1% of the total, growth mainly due to intraspecific N)
• P: 0.003 to 0.01 g/m² (very small amount)
• K: Less than 0.01~0.05 g/m²

"In the early growth stage, accumulated nutrients are mainly used, and soil uptake is negligible" [1][2]

2-2. Seedling stage (~28 days, until planting)

• N: 0.1-0.3 g/m² (5-10% of total uptake)
• P: 0.03 to 0.05 g/m² (10 to 20% of total absorption)
• K: 0.1 to 0.3 g/m² (5 to 10% of total absorption)

"The amount of N and K absorbed during the seedling stage is small, but phosphorus tends to be absorbed relatively evenly" [2][7]

2-3. Vegetative growth period (After planting: Approximately 20 to 30 days)

• N: +1.2-1.8 g/m² (cumulative total 1.5-2.0 g/m², 50-60% of total absorption)
• P: +0.07-0.12 g/m² (cumulative total 0.10-0.15 g/m², 40-60% of total absorption)
• K: +1.2-1.7 g/m² (cumulative total 1.5-2.0 g/m², 50-60% of total absorption)

"N/K absorption is in full swing and rapidly increases in parallel with the dry matter increase rate" "The peak of nitrogen absorption is at the bud emergence stage" [7][11]

2-4. Flower bud formation period (rapid enlargement period, just before harvest)

• N: +0.6~1.0 g/m² (cumulative total 2.5~2.8 g/m², reaching 80~90% of total absorption)
• P: +0.07~0.10 g/m² (cumulative total 0.17~0.22 g/m², reaching 80-90% of total absorption)
• K: +0.6-1.0 g/m² (cumulative total 2.5-2.8 g/m², reaching 80-90% of total absorption)

"Sudden dry matter and nutrient accumulation curves. Potassium has an affinity for increasing dry matter" [11][6][14]

2-5. Flowering period (harvest period - seed collection/residue treatment)

• N: +0.05~0.2 g/m² (cumulative total 2.8-3.0 g/m²)
• P: +0.02-0.05 g/m² (cumulative total 0.2-0.25 g/m²)
• K: +0.05-0.2 g/m² (cumulative total 2.8-3.0 g/m²）

"Nutritional absorption has almost reached a plateau. 40% of N and 30-40% of K are concentrated in the flower buds" [11][14][19]

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2-6. Quick reference table of cumulative absorption amount by stage (guideline/field conditions)

< td>2.5–2.8

Growth stage	N (g/m²)	P (g/m²)	K (g/m²)
Germination period	<0.05	<0.01	<0.05
Seedling stage (at time of planting)	0.1–0.3	0.03–0.05	0.1–0.3
Sakae End of nurturing phase	1.5–2.0	0.1–0.15	1.5–2.0
End of flower bud formation phase	0.17–0.22	2.5–2.8
End of flowering period	2.8–3.0	0.2–0.25	2.8–3.0

*There are differences depending on the strain and growth conditions. The maximum value depends on the fertilization system, environment, and yield.

3. Estimation method and rationale

Although it is rare that direct stage-by-stage absorption values are reported, the following rational estimation methods are used in the main basic literature:

1. Cumulative absorption curve method
   N, P, and K absorption curves created from dry matter measurements and composition analysis through periodic crush sampling are assigned to days and morphological indicators (number of leaves, bud appearance, etc.).
2. Interval difference method
   Calculate the difference in the cumulative increase in absorption between each growth stage and use it as the absorption at each stage.
3. Hectare/10a/stock → m² conversion
   Many Japanese materials have data on kg/10a and g/stock, which can be converted as (1 kg/10a = 0.1 g/m²).
4. Literature check
   Estimated by taking into account the characteristics of each growth stage, such as ``Nitrogen absorption peaks during bud emergence'' and ``Phosphorus is absorbed relatively slowly.''

Through these, it becomes possible to estimate the absorption amount by stage based on the evidence [11][14][6][15][19].

4. Field vs. Management Environment Difference

• Field cultivation
  The National Agricultural Research Center and UC Davis/California Fertilizer Guidelines are almost common, and the standard values ​​are N: 2.5~3.0g/m², P: 0.2~0.25g/m², and K: 2.5~3.0g/m². The absorption pattern is similar.
• Managed environment (greenhouse/hydroponics)
  Although the absorption rate is similar, the total amount will be slightly smaller if dry matter production is limited. However, a tendency for increased absorption with stage progression is commonly observed [8][3][4].

5. Summary of Japanese/International Literature

• "The peak of nitrogen absorption is during the budding period" (Nagano Prefecture data) [2]
• "Potassium absorption is maximized from the budding period to the harvesting period. Dry matter and K absorption are parallel" (NARO) [11]
• “The absorption ratio of phosphorus is relatively high in the leaflet and seedling stages” (BSI/Fertilizer Application Science) [14]

Based on these scientific grounds, the above numerical values and estimation of the absorption pattern are highly reliable.

6. Conclusion and practical implications

• Most of the NPK absorption is concentrated from the end of the vegetative growth period to the flower bud formation period, so it is important to focus on additional fertilization and management during this period.
• Phosphorus has a high initial absorption rate, so banding and early application in the basal fertilizer is reasonable.
• The absorption pattern and stage ratio may vary depending on the variety and climate, but the total cumulative amount and absorption concentration period are almost the same.

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References

Sources

[1] Changes in the growth and nutrient absorption characteristics of broccoli cell seedlings in the phosphate/potassium accumulation field in the total basal fertilizer plot: https://agriknowledge.affrc.go.jp/RN/2030811962.pdf
[2] 11 Broccoli - Nagano Prefecture Official Homepage: https://www.pref.nagano.lg.jp/nogi/documents/11burokkori.pdf
[3] Effect of Different levels of Liquid Nitrogen, Phosphorus and Potassium on Growth, Yield and Quality of Broccoli (Brassica Oleraceae Var. Italica) in Hydroponic: https://journalijecc.com/index.php/IJECC/article/view/2424
[4] Influence of NPK on growth, yield and nutrient content in broccoli under drip and conventional irrigation: https://www.cabidigitallibrary.org/doi/pdf/10.5555/20173164714
[7] (PDF) Broccoli growth and nutrient accumulation - ResearchGate: https://www.researchgate.net/publication/313540728_Broccoli_growth_and_nutrient_accumulation
[8] Nutritional and Visual Diagnosis in Broccoli (Brassica oleracea var ...): https://www.nuplant.com.br/docs/2020/doc_2020-75.pdf
[11] Fertilization management method based on the nutrient absorption characteristics of broccoli: https://www.naro.go.jp/laboratory/carc/kenkyu_koryu/files/kantoseika_h24NG04.pdf
[14] "Fertilizer Application" BSI Institute of Biological Sciences Broccoli and Cauliflower: http://bsikagaku.jp/f-fertilization/broccoli.pdf
[15] Broccoli - UC Davis Nutrient Management: http://geisseler.ucdavis.edu/Guidelines/Broccoli.html
[19] CA Fertilization Guidelines - Broccoli Nitrogen Uptake and Partitioning: https://www.cdfa.ca.gov/is/ffldrs/frep/FertilizationGuidelines/N_Broccoli.html