Hoagland solution is a nutrient solution targeting the hydroponics plants for fulfilling its all basic requirements of nutrients in form of liquid. It was first prepared by Hoagland and Arnon in 1938 and revised by Arnon in 1950. It is the most popularly used nutrient solution in the world for hydroponics farming. It provides all the nutrients to the plants in an appropriate amount as per the requirement for different varieties of plants. There are so many amendments have been done in the Hoagland solution but the actual concentration of the elements is:
N 210 ppm
K 235 ppm
Ca 200 ppm
P 31 ppm
S 64 ppm
Mg 48 ppm
B 0.5 ppm
Fe 1 to 5 ppm
Mn 0.5 ppm
Zn 0.05 ppm
Cu 0.02 ppm
Mo 0.01 ppm
The high amounts of N & K are very suitable for various plants. This solution is beneficial for large number of hydroponically grown plants like lettuce and other aquatic plants with further dilution up to 1/4 or 1/5.
The quantity of iron used should be in proportion with the quantity of phosphate placed inside the solution; if their strength is high there may a possibility of iron precipitation if non adequate chelates like EDTA are used.
Application
The nutrients which are given to the plants are mainly absorbed by their roots. The Hoagland solution are prepared by keeping in mind that it will be high in nutrients. It has a high concentration of N and K so that it is suitable for the higher plants like bell peppers and tomatoes. For example, half- strength of macronutrient solution of Hoagland can go with full dose of micronutrient solution and a tenth- strength ferric EDTA solution to fertilize the new seedlings of tomato plants. The concentration of aqueous stock solutions are kept high, which are very much beneficial for the plants like lettuce and aquatic plants with low nutrient demands as well. We further dilute the solution to its one-fourth or one – fifth of the modified solution before its application.
Components of Hoagland solution
Salts, acids and complexions to make up the Hoagland hydroponic solution formulations (1) and (2):
- Potassium nitrate, KNO3
- Calcium nitrate tetrahydrate, Ca(NO3)2•4H2O
- Magnesium sulfate heptahydrate, MgSO4•7H2O
- Potassium dihydrogen phosphate, KH2PO4 or
- Ammonium dihydrogen phosphate, (NH4)H2PO4
- Boric acid, H3BO3
- Manganese chloride tetrahydrate, MnCl2•4H2O
- Zinc sulfate heptahydrate, ZnSO4•7H2O
- Copper sulfate pentahydrate, CuSO4•5H2O
- Molybdic acid monohydrate, H2MoO4•H2O or
- Sodium molybdate dihydrate, Na2MoO4•2H2O
- 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 |
Some Alternatives of Nutrients’ Components
Na-Fe-EDDHA (C18H16FeN2NaO6) has been produced as Sprint 138 iron chelate, while the original Hoagland’s solution formulations contains ferric tartrate (C12H12Fe2O18), without any sodium ions. While synthesis of sodium-free ferric EDTA complex (C10H12FeN2O8−) in the laboratory is sometimes preferred to buying ready-made products. Some variable micronutrients (like Co, Ni) or rather non-essential elements (like Pb, Hg) are earlier mentioned in Hoagland’s solution in 1933 but they are no longer included in the later circulars. Mostly the metallic elements and also the organic compounds are not essential for the plant nutrition.
Modifications
The nutrient solution which was first prepared by Dennis Hoagland in 1933, named as Hoagland Solution, has been modified many times, mainly for adding ferric chelates to increase the efficiency of iron the solution and for the optimization of composition and concentration of the trace elements present in the solution. In the recipes prepared by Hoagland in 1938, there is subsequent reduction in the number of trace elements to the generally accepted amount of essential elements (Cu, Fe, B, Cl, Mn, Zn and Mo). Later on their concentration has been adjusted as per the optimal growth of plants.
In 1950 Arnon revised the solution; there was only one change in the concentration of Mo (0.011 ppm) to Mo (0.048), whereas the concentration was not changed of the macronutrients of the Hoagland solutions (0), (1) and (3) it was remained same since 1933, with the exception of calcium concentration in the solution which was (160 ppm) in solution (2). There is a difference between solution (1) and solution (2) of nitrate- nitrogen and ammonium- nitrogen on the basis of the stock solutions to prepare the required Hoagland solution. Accordingly, the original Hoagland solution prepared in 1933 and the modified concentrations of 1938 and 1950 for each essential element and sodium element are given below:
- 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 236 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*