Английская Википедия:Hoagland solution

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The Hoagland solution is a hydroponic nutrient solution that was newly developed by Hoagland and Snyder in 1933, modified by Hoagland and Arnon in 1938, and revised by Arnon in 1950. It is one of the most popular standard artificial solution compositions for growing plants, in the scientific world at least, with more than 20,000 citations listed by Google Scholar. The Hoagland solution provides all essential elements for plant nutrition and is appropriate for supporting normal growth of a large variety of plant species.

Modifications

The solution described by Dennis Hoagland in 1933, known as Hoagland solution (0), has been modified several times, mainly to add ferric chelates to keep iron effectively in solution, and to optimize the composition and concentration of other trace elements, some of which are not generally credited with a function in plant nutrition. In Hoagland's nutrient recipes of 1938, referred to as Hoagland solution (1, 2), the number of trace elements was subsequently reduced to the generally accepted essential elements (B, Mn, Zn, Cu, Mo, Fe, and Cl). Later research confirmed that their concentrations had been adjusted for optimal plant growth.

In Arnon's revision of 1950, only one concentration (Mo 0.011 ppm) was changed compared to 1938 (Mo 0.048 ppm), while the concentration of macronutrients of the Hoagland solutions (0), (1), and (2) remained the same since 1933, with the exception of calcium (160 ppm) in solution (2). The main difference between solution (1) and solution (2) is the different use of nitrate-nitrogen and ammonium-nitrogen based stock solutions to prepare the respective Hoagland solution of interest. Accordingly, the original 1933 and the modified concentrations of 1938 and 1950 for each essential element and sodium are shown below, the calculation of the latter values being derived from Tables 1 and 2: Шаблон:Div col

• N 210 ppm
• P 31 ppm
• S 64 ppm
• Cl 0.14 ppm / 0.65 ppm
• B 0.11 ppm / 0.5 ppm
• Na 0 ppm / 0.023 ppm / 1.2 ppm*
• Mg 48.6 ppm
• K 235 ppm
• Ca 200 ppm / 160 ppm
• Mn 0.11 ppm / 0.5 ppm
• Zn 0.023 ppm / 0.05 ppm
• Cu 0.014 ppm / 0.02 ppm
• Mo 0.018 ppm / 0.048 ppm / 0.011 ppm
• Fe 1 ppm / 5 ppm / 2.9 ppm*

Applications

Plant nutrients are usually absorbed from the soil solution. The Hoagland solution, originally intended to imitate a (nutrient-) rich soil solution, has high concentrations of N and K so it is very well suited for the development of large plants like tomato and bell pepper. For example, a half-strength macronutrient solution (1) of Hoagland can be combined with a full micronutrient solution of Long Ashton and a tenth-strength ferric EDTA solution to fertilize tomato seedlings. Due to relatively high concentrations in the aqueous stock solutions (cf. Tables 1 and 2) the Hoagland solution is very good for the growth of plants with lower nutrient demands as well, such as lettuce and aquatic plants, with the further dilution of the preparation to Шаблон:Frac or Шаблон:Frac of the modified solution.

Components

Salts, acids and complex ions to make up the Hoagland hydroponic solution formulations (1) and (2): Шаблон:Div col

1. Potassium nitrate, KNO₃
2. Calcium nitrate tetrahydrate, Ca(NO₃)₂•4H₂O
3. Magnesium sulfate heptahydrate, MgSO₄•7H₂O
4. Potassium dihydrogen phosphate, KH₂PO₄ or
5. Ammonium dihydrogen phosphate, (NH₄)H₂PO₄
6. Boric acid, H₃BO₃
7. Manganese chloride tetrahydrate, MnCl₂•4H₂O
8. Zinc sulfate heptahydrate, ZnSO₄•7H₂O
9. Copper sulfate pentahydrate, CuSO₄•5H₂O
10. Molybdic acid monohydrate, H₂MoO₄•H₂O or
11. Sodium molybdate dihydrate, Na₂MoO₄•2H₂O
12. Ferric tartrate or Iron(III)-EDTA⁻ or Iron chelate (Fe-EDDHA⁻)

Components for Hoagland solution (1)

To prepare the stock solutions and a full Hoagland solution (1)

Table 1

Component	Quantities in solution
	g/L	mL/L
Macronutrients
2M KNO3	202	2.5
2M Ca(NO3)2•4H2O	472	2.5
2M MgSO4•7H2O	493	1
1M KH2PO4	136	1
Micronutrients
H3BO3	2.86	1
MnCl2•4H2O	1.81	1
ZnSO4•7H2O	0.22	1
CuSO4•5H2O	0.08	1
H2MoO4•H2O, or	0.09	1
Na2MoO4•2H2O	0.12	1
Iron
C12H12Fe2O18, or Sprint 138 iron chelate*	5 15	1 1.5

Components for Hoagland solution (2)

To prepare the stock solutions and a full Hoagland solution (2)

Table 2

Component	Quantities in solution
	g/L	mL/L
Macronutrients
2M KNO3	202	3
2M Ca(NO3)2•4H2O	472	2
2M MgSO4•7H2O	493	1
1M NH4H2PO4	115	1
Micronutrients
H3BO3	2.86	1
MnCl2•4H2O	1.81	1
ZnSO4•7H2O	0.22	1
CuSO4•5H2O	0.08	1
H2MoO4•H2O	0.02	1
Iron
C12H12Fe2O18, or Sprint 138 iron chelate*	5 15	1 1.5

Alternatives for some components

Sprint 138 iron chelate is produced as Na-Fe-EDDHA (C₁₈H₁₆FeN₂NaO₆), while Hoagland's original solution formulations contain ferric tartrate (C₁₂H₁₂Fe₂O₁₈), but no sodium ions. Synthesizing a sodium-free ferric EDTA complex (C₁₀H₁₂FeN₂O₈⁻) in a laboratory is sometimes preferred to buying ready-made products. Variable micronutrients (e.g., Co, Ni) and rather non-essential elements (e.g., Pb, Hg) mentioned in Hoagland's 1933 publication (known as "A-Z solutions a and b") are no longer included in his later circulars. Most of these metallic elements, as well as organic compounds, are not necessary for normal plant nutrition. As an exception, there is evidence that, for example, some algae require cobalt for the synthesis of vitamin B12.

See also

• Murashige and Skoog medium
• Long Ashton Nutrient Solution

External links

• Modified composition of the Hoagland solution
• National Academy of Sciences: A Biographical Memoir of Dennis Robert Hoagland by Walter P. Kelley
• "A-Z solution", Supplementary Nutrient Solution (Solution A), according to Hoagland and Snyder (1933)
• The Hoaglands Solution for Hydroponic Cultivation