Hoagland solution

Modifications

The artificial 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 trace elements other than iron, 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 (Ca 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:

• 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 / 2.9 ppm* / 5 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 or Hewitt and a tenth-strength ferric EDTA solution of Jacobson 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 or of the original or a modified HS.

Components

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

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 chelate (Fe-EDDHA−)* or Iron(III)-EDTA−**

Components for Hoagland solution (1)

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

Components for Hoagland solution (2)

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

Alternatives for some components

Micronutrients

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.

References

References

1. Hoagland, D.R.. (1933). "Nutrition of strawberry plant under controlled conditions. (a) Effects of deficiencies of boron and certain other elements, (b) susceptibility to injury from sodium salts". Proceedings of the American Society for Horticultural Science.
2. Hoagland. (1938). "The water-culture method for growing plants without soil". Berkeley, Calif. : University of California, College of Agriculture, Agricultural Experiment Station.
3. Hoagland. (1950). "The water-culture method for growing plants without soil". (Circular (California Agricultural Experiment Station), 347. ed.). Berkeley, Calif. : University of California, College of Agriculture, Agricultural Experiment Station. (Revision).
4. "The water-culture method for growing plants without soil".
5. Smith, G. S.. (1983). "Comparison of nutrient solutions for growth of plants in sand culture". The New Phytologist.
6. Jacobson, L.. (1951). "Maintenance of Iron Supply in Nutrient Solutions by a Single Addition of Ferric Potassium Ethylenediamine Tetra-Acetate". Plant Physiology.
7. Arnon, D.I.. (1938). "Microelements in culture-solution experiments with higher plants". American Journal of Botany.
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10. "Importance of soil solution". Plantlet.
11. (1922). "Absorption of nutrients and plant growth in relation to hydrogen ion concentration". Journal of General Physiology.
12. Genzel, F.. (2021). "Impact of moderate cold and salt stress on the accumulation of antioxidant flavonoids in the leaves of two Capsicum cultivars". Journal of Agricultural and Food Chemistry.
13. He, F.. (2019). "Effects of root cooling on plant growth and fruit quality of cocktail tomato during two consecutive seasons". Journal of Food Quality.
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15. Epstein E. (1972). [[Mineral Nutrition of Plants: Principles and Perspectives]]. John Wiley & Sons, New York, pp. 412.
16. Schropp, W.. (1942). "Über die Wirkung der A-Z-Lösungen nach Hoagland und einiger ihrer Bestandteile auf das Pflanzenwachstum". Journal of Plant Nutrition and Soil Science.
17. (1962). "A revised medium for rapid growth and bio assays with tobacco tissue cultures". Physiologia Plantarum.
18. Kumudha, A.. (2015). "Methylcobalamin – a form of vitamin B12 identified and characterised in Chlorella vulgaris". Food Chemistry.