The composition of hydroponic fertilizers is completely different compared to the fertilizers for earth cultures. Plants that are cultivated in soils require completely different fertilizer mixtures than hydroponics. As a guide: Organic fertilizers often need microorganisms (depending on their composition) to break down the nutrients for the plants. Inorganic fertilizers do not need microorganisms to be able to supply the plant with all nutrients. Of course, the following also applies here: the exception confirms the rule.

Hydroponic fertilizers must be accountable for the special conditions of a hydroponics. These result on the one hand from the lack of microorganisms, which are required for the chemical splitting of the fertilizer substances in the soil - and can only be found there, on the other hand from the lack of buffering of the hydroponic system and from the fact that it is a closed system.

Important boundary conditions include: Hydroponic fertilizers should not contain too many ballast salts (sodium, chloride, etc.). The ammonium and nitrogen content should not account for more than about 50% of the total nitrogen (N) supply in order to avoid acidification of the nutrient solution.

However, this in turn does not apply to very hard (lime-rich) irrigation water. The phosphate content should also be significantly lower - compared to fertilizers for earth culture.

Fertilizer with buffer effect / reservoir or so-called long-term fertilizer

There are ion exchange fertilizers on the market for hydroponics. For decades, the ion exchange fertilizer “ Lewatit HD5 ” has been the only ion exchange fertilizer on the market. It was developed by Bayer AG in the 1970s and marketed under various trade names. The same company later developed the “ Lewatit HD5 plus ” for low-salt irrigation water (soft water).

In the meantime, only the well-known Lewatit HD50 is manufactured. This should be optimized for every degree of hardness of the water. However, the manufacturer still recommends adding lime to soft water to ensure supply. 

Which liquid fertilizer can you use?

The range of liquid fertilizers and nutrient solutions has now become unmistakable (1). In addition to liquid fertilizers for the professional in larger containers, products are offered in smaller quantities for the hobby area. Mostly they are so-called universal fertilizers. However, some manufacturers also offer special fertilizers for hydroponics.

Striking here: almost all manufacturers hold back with specific information about the plants for which the fertilizer should be "optimal. Likewise in dosing depending on the growth development. Even if certain plants are named by name, apparently not detailed here. If you think of tomatoes, you will probably not think of all 3,200 varieties that are currently being grown (source). To believe that one and the same fertilizer delivers consistently good results here also seems completely unbelievable to the layperson.

1) You can find a (always) incomplete list of commercially available fertilizers here. We only keep this list as a list of ingredients for homemade nutrient solutions. You can find out how to do this here in detail using a sample mix. The series of articles begins here: Mix the hydroponic fertilizer yourself: introduction

There are several ways to fertilize plants in hydroponics:

• With liquid inorganic solid fertilizer, this is automatically added in large plants due to the conductivity measurement of the water.

• By fertilizer salt release from solid ion exchanger granules.

• Sludge up organic fertilizer or add such nutrient solutions.

• A humus or compost layer that is applied to the top substrate layer in low-fiber systems and is only watered from above when fertilizer is required.

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Fertiliser programmes

Mixing hydroponic fertiliser yourself ?

The commercially available fertilisers consist of a complete fertiliser supplemented with macronutrients. They are offered by some hydroponics and/or fertiliser companies and vary depending on the hydroponic plant. An example of a fertiliser programme is the hydroponic tomato programme offered by Hydro-Gardens.

In this programme, growers purchase Hydro-Gardens Chem-Gro tomato formula. It has a composition of 4-18-38 and also contains magnesium and micronutrients. To make a nutrient solution, it is supplemented with calcium nitrate and magnesium sulphate, depending on the variety and/or growth stage of the plant.

Advantages of fertiliser programmes

Disadvantages of fertiliser programmes

Modified Sonneveld recipe / herbs

It is at the discretion of the breeder which fertilizers he uses to produce a nutrient solution according to a recipe. The fertilizers commonly used include:

Advantages of nutrient solution recipes

Nutritional solutions allow fertilizers to be adjusted based on the nutrients contained in water sources. An example: A gardener uses a water source with 30 ppm potassium and produces the modified Sonneveld solution for herbs that requires 210 ppm potassium. It would have to add 180 ppm potassium ( 210 ppm - 30 ppm = 180 ppm ) to the water in order to obtain the amount of potassium required in this recipe.
With recipes, nutrients can be easily adjusted. When a leaf analysis report indicates that a plant has iron deficiency. It is easy to add more iron to the nutrient solution.
Since recipes make it easy to adapt, fertilizers can be used more efficiently than in fertilizer programs. Using recipes can be less expensive than using fertilizer programs.

Disadvantages of nutrient solution recipes

It has to be calculated how much fertilizer has to be added to the nutrient solution. (Link to performing calculations). Some people may feel intimidated by the calculations involved. However, the calculations only require uncomplicated mathematical skills based on multiplication and division.
A high-precision scale is also required for the measurement of micronutrients, since the required quantities are very small. Such a scale can be found on Amazon from 30.- €: e.g .: KUBEI 100g / 0.001g.

This is about the calculation of nutrient solutions for your own needs

Picture: Boston Public Library is licensed under CC BY 2.0

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Here we have created a short introduction to the topic of fertilizer and nutrient solutions, with which you can learn the concept, the basics and also the calculation of self-created nutrient solutions. In the last article you will find a brief overview of deficiency symptoms and how you can recognize and correct them. 

Please also keep in mind that the perfect recipe for your own plant requires enormous knowledge, complex technology and a lot of experience. However, for many areas this is not necessary at all. If you, as an entrepreneur, are in competition and have to work to the optimum in order to be profitable, things look different. But this little guide is not aimed at entrepreneurs who need to make money with it. For commercial applications, please do not hesitate to take advantage of our experience, our knowledge and the technology required for this:  just ask us - email or phone call is enough.

A brief introduction to fertilisers & nutrients

Fertiliser: Calculation of nutrient solutions

Fertilizer: Calculate a nutrient recipe

Fertilizer: Essential Nutrients, Function, Deficiency and Exces

Common Concentrations in Nutrients

To ensure a highly optimised nutrient supply throughout the entire growth process, you need analytical equipment. Here a short overview and Selection.

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Now that you have the two basic equations for the production of nutrient solutions, we want to use them to calculate the amounts of fertilizer required for a nutrient solution recipe.

If you are not familiar with the two equations, read this first: Hydroponic systems: Calculating the concentrations of nutrient solutions using the two equations.

Here is our problem: We want to use a modified Sonneveld solution (Matson and Peters, Insidegrower) for herbs in an NFT system. We use two 5-gallon containers and injectors set to a concentration of 100: 1 and call them storage tank A and storage tank B. How much of each fertilizer do we have to put in each storage tank ?

You may be asking: why two storage tanks? This is due to the fact that certain chemicals in our fertilizer solution react with each other as soon as they come into contact with each other. In all nutrient solutions ( fertilizer mixtures ) you have calcium, phosphates and sulfates - among other things, these three chemicals for all plants vital are. The last two react with calcium and are no longer present in the form we need in our nutrient solution. They connect to each other and fall to the bottom of the container as white flakes ( precipitates ). Therefore, phosphates and sulfates must be kept separate from calcium and, when introduced into the nutrient solution of the ( system, saved from direct mixing by means of a dosing pump or measuring cup ).

Modified Sonneveld recipe for herbs

These are the fertilizers that we will use. Some fertilizers contain more than one nutrient in the recipe, while others contain only one. Here is a small overview Commercial fertilizer from which you can put together your recipe

The first thing you notice is that we have three sources of nitrogen (calcium nitrate, ammonium nitrate and potassium nitrate), have two sources of potassium (potassium nitrate and potassium phosphate monobasic) and one source of calcium (calcium nitrate) and phosphorus (single-base potassium phosphate). We can start calculating the calcium or phosphorus in the recipe because only one fertilizer provides each nutrient. Let's start with calcium.

The recipe provides 90 ppm calcium. We calculate how much calcium nitrate we need to use to achieve this by using the first of our two equations.

We need to add 895.3 g calcium nitrate to get 90 ppm calcium. However, calcium nitrate also contains nitrogen. We use the second equation to determine how much nitrogen should be added in ppm.

We add 73.4 mg N / l or 73.4 ppm nitrogen. Our recipe provides 150 ppm nitrogen. If we subtract 73.4 ppm nitrogen from it, we have to add 76.6 ppm nitrogen.

Let us now calculate how much single-base potassium phosphate we have to use to deliver 31 ppm phosphorus.

We need to add 262 g of potassium phosphate monobed to get 31 ppm phosphorus. However, potassium phosphate also contains single-base potassium. We use the second equation to determine how much potassium should be added in ppm.

We add 39 mg K / l or 39 ppm potassium. Our recipe provides 210 ppm potassium. If we subtract 39 ppm of potassium from it, we see that we still have to add 171 ppm of potassium.

We have only one other source of potassium, namely potassium nitrate. Let's calculate how much we have to use of it.

We need to add 885 g of potassium nitrate to get 171 ppm of potassium. However, potassium nitrate also contains nitrogen. We use the second equation to determine how much nitrogen should be added in ppm.

We add 61 mg N / l or 61 ppm nitrogen. Our recipe provides 150 ppm nitrogen. We supplied 73.4 ppm nitrogen from calcium nitrate and had to add 76.6 ppm nitrogen. Now we can subtract 61 ppm nitrogen. We still have to add 15.6 ppm nitrogen. The only source of nitrogen that we have is ammonium nitrate.

Let us now calculate how much ammonium nitrate we have to use to deliver 15.6 ppm nitrogen.

We need to add 86.7 g of ammonium nitrate to get 15.6 ppm nitrogen.

At this point we have completed the nitrogen, phosphorus, potassium and calcium part of the recipe. For the other nutrients, we only need to use the first equation, since the fertilizers that we use for their supply contain only one nutrient in the recipe.

We need to add 498.5 grams of magnesium sulfate to get 24 ppm magnesium.

We need to add 18.9 grams of Sequestren 330 to get 1 ppm of iron.

We need to add 1.5 grams of manganese sulfate to get 0.25 ppm manganese.

It is easier to weigh small amounts of fertilizers in milligrams. The conversion from milligrams to grams is therefore carried out as follows

We need to add 692 milligrams of zinc sulfate to get 0.13 ppm zinc.

We need to add 0.17 milligrams of copper sulfate to get 0.023 ppm copper.

We need to add 2.8 milligrams of borax to get 0.16 ppm borax.

We need to add 0.12 milligrams of sodium molybdate to get 0.024 ppm molybdenum.

Summary:

Now all calculations have been completed. Now we have to decide in which storage tank, A or B, we give the individual fertilizers. In general, the calcium should be kept in a tank other than the sulfates and phosphates, as they can form precipitates that can clog the drip bodies of the irrigation system. Using this guideline, we can put the calcium nitrate in one tank and the monobasic potassium phosphate, magnesium sulfate, manganese sulfate, zinc sulfate and copper sulfate in the other tank. The rest of the fertilizers can be placed in both tanks.

You should also consider the amount of nutrients in irrigation water. For example, if we use irrigation water that contains 10 ppm magnesium, we only need to add 14 ppm more with our fertilizer (24 ppm Mg, which are required in the recipe, minus 10 ppm Mg in water). This is a great way to use nutrients more efficiently and fine-tune your fertilizer plan.

With some micronutrients, you have to decide for yourself what you want to add. You could do a small experiment to find out whether you need to add 0.12 milligrams of sodium molybdate to your stock solution, for example, or whether you are satisfied with the performance of your plants without this addition.

One last point to consider. Sometimes the calculations don't work as well as here for fertilizers that contain more than one required nutrient, and you may need to add more of a nutrient, than is provided in the recipe to provide the other nutrient.

For example, if you apply calcium nitrate to meet calcium needs, the solution may not contain enough nitrogen. In such cases, you have to decide which nutrient you want to give priority to. For example, you could apply calcium nitrate to meet the plants' nitrogen needs because the excess amount of calcium does not harm the plants. Or you choose to apply it based on the plant's calcium needs because the lack of nitrogen is just a few ppm.

Here you will find what problems there may be with a lack and excess of fertilizer

At this point we can give you recommendations for your plantations with modern analysis technology. Contact us...

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Photometry

Basics In hydroponics and the associated aquaponics, there are different methods to supply the plants with nutrients. These can be divided into active and passive systems. Passive systems have the advantage of being independent of the power supply. Their efficiency is lower than that of active approaches.   Passive and Active Hydroponic Systems Passive hydroponic systems are systems that function without a power supply. Active hydroponics uses pumps, aerators, humidifiers or spray nebulisers. These require electricity. Active hydroponic systems are more complex in design, but many times more effective in terms of plant growth due to the oxygen input.	Overview Wick Irrigation Ebb - Flood Systems NFT - Nutrient Film Technique DWC - Deep Water Culture DFT - Deep Water Nutrient Film Technique (Deep Flow Technique) Drip Irrigation Aeroponics - Mist from nutrient solution Aquaponics - Plant cultivation and fish farming Aquaponics - CHOP ( Constant Height, One Pump)   Schematic of an aquaponics system
A brief overview of the most common systems in aqua- and hydroponics
Passive Hydroponics: Wick Watering
The wick system (Wick Watering) does not require any moving parts or electricity. The plants are cultivated in a substrate that is supplied with the nutrient solution through the capillary action of the "wick". Supplying the plants via this system is not very effective. In addition, the wick can largely lose its nutrient transport properties due to mineral deposits. Another disadvantage is that no extra oxygen is supplied to the roots. The system is technically simple but plant growth is slower than with other active hydroponic systems. Pros: cheap purchase without electricity without technology low nutrient consumption low control effort   Cons: very low yield slow growth
Active Hydroponics: Ebb and Flood Systems
Ebb and flood systems (Ebb and Flood or Flood and Drain) use pumps (4) that flood the plants with the nutrient solution in a time-controlled manner (2). The plants are embedded in a net pot. After the pump is turned off, the excess nutrient solution is returned to the reservoir (1) via an overflow (3). Often a residual amount is left to make the system less vulnerable in case the pumps should ever fail, enough water remains in the plant basin as the overflow ensures a minimum water supply. By raising and lowering the liquid level (2), oxygen is introduced in the root area, which leads to more intensive plant growth. An electronic control system must adapt the ebb and flow rhythm to the requirements of the plants. Pros: low nutrient consumption low water consumption high yield in case of power or pump failure: no crop loss   Cons: high purchase costs power supply necessary Control effort
Active Hydroponics: NFT - Nutrient Film Technic
NFT or Nutrient Film Technic (NFT) systems provide a permanent flow of nutrients that flow around the roots in a thin "film". A pump conveys the nutrient solution to an inclined plane on which the plant roots lie, thus providing them with a continuous supply. The constant flow prevents nutrient build-up. NFT systems also add oxygen to the nutrient solution, for example through downpipes or intermeshing systems. The plant substrate is usually dispensed with, so that the roots have direct access to nutrients and oxygen and can thus grow quickly. A disadvantage is the loss of all plants in case of defective pumps or power failure. Pros: low nutrient consumption low water consumption very high yield   Cons: high purchase costs power supply necessary Control effort in case of power or pump failure: loss of harvest
Active Hydroponics: DWC - Deep Water Culture.
In deep water culture systems, also known as DWC systems, already rooted plants are placed in a net pot on a floating plate in the liquid reservoir, like a raft. To stabilise the plant, the net pot can be filled with substrate, such as clay balls. The roots hang directly in the nutrient solution, which is enriched with oxygen. This is done by means of an air pump and aeration stones that introduce very fine air bubbles into the water. Since the roots are constantly supplied with oxygen-rich nutrient solution, the plants grow very quickly and vigorously. The system is simple and safe, even in the event of a power failure nothing will happen to the plants. Thanks to the large water reservoir, the system can be left alone for a few days without having to worry about it. With the DWV system, the plants can also sit on a kind of raft and float on the nutrient solution. Pros: low nutrient consumption low water consumption very high yield fast growth (oxygen) in case of power or pump failure: no crop loss Cons: high purchase costs power supply necessary Control effort
Active Hydroponics: DFT - Deep Flow Technique (Deep Water Nutrient Film)
Active Hydroponics: DFT - Deep Water Nutrient Film Technique (Deep Flow Technique) The Deep Flow Technique, better known as DFT, is a variation of the NFT technique, also known as the Nutrient Film Technique. Instead of the thin nutrient film, the plants are flowed around by a nutrient solution about 2-4 cm high. The principle procedure is the same and works recirculatory. The deep flow technique DWT makes this cultivation system safer, because in case of pump failure the roots are still supplied. However, the method has hardly become established in the industry, because especially with longer / larger systems, the supply of oxygen to the plants varies and the plants grow unevenly as a result. It counts as one of the active hydroponics systems. Pros: low nutrient consumption low water consumption very high yield   Cons: high purchase costs power supply necessary Control effort in case of power or pump failure: loss of harvest
Active hydroponics: drip irrigation
With drip irrigation (drip system), the nutrient solution is dripped onto the substrate around the plants via a drip line. The nutrient solution flows past the roots and supplies them directly. The excess liquid flows off, supplying oxygen to the root area. Non-recovery system: In industrial cultivation there are non-recovery systems to achieve a high yield without measuring technology. Here, the plants are always supplied with fresh and equally adjusted nutrient solution. The nutrient is not returned to the cycle to avoid the spread of pathogens. This method uses more water and unused nutrients are lost. This system does not require control of nutrients but relies on experience with nutrient use. One can run the system "blind". Pros: very high yield fast growth in case of power or pump failure: no crop loss little control effort Cons: high purchase costs power supply necessary high nutrient consumption High water consumption   Recirculating system: The nutrient solution is fed back into the system, which means that only the nutrients that the plant actually needs are consumed. The flow rate is adjusted to the needs of the plants. Due to the closed system, however, it is necessary to control the nutrients in order to adjust them to the growth phase-dependent consumption. This system needs a regular control of the nutrient concentration. Pros: very high yield fast growth in case of power or pump failure: no crop loss Cons: high initial costs power supply necessary Control effort	Ohne Kreislauf                       Mit geschlossenem Kreislauf
Active hydroponics: Aeroponics - fog of nutrient solution
In an aeroponic growing system, the roots of cuttings or plants are not suspended in a liquid but in a mist of nutrient solution. The plants are hung with net pots in a chamber where the roots are sprayed or fogged with nutrient solution through water nozzles / fog nozzles. Aeroponic systems offer the optimal supply of the roots with everything they need to grow, they work very effectively and deliver maximum plant growth and therefore belong to the active hydroponic systems. However, the technical effort is high because of the high water pressure for the nozzles or the nebulisers used. In addition, technical measures must be taken to prevent the nozzles from clogging. A disadvantage is that a failure of the nebulisers is not tolerated by the free-hanging roots for a long time. Pros: very high yield fast growth   Cons: high purchase costs power supply necessary high nutrient consumption high water consumption Control effort
Active hydroponics: aquaponics - plant cultivation and fish farming
Aquaponics (aquaponic) is made up of aquaculture (fish farming) and hydroponics (plant farming), so two farming systems are combined. The excreta of the fish are used to supply the plants with nutrients, they are recycled and serve as fertiliser. The excreta are converted into nutrients that can be used by plants with the help of microorganisms. At the same time, the water is cleaned so that it can be returned to the fish tank and the fish have good living conditions. This creates a win-win cycle. In addition to growing lettuce and vegetables, fish are bred for food or ponds are kept clean with ornamental fish.	Fish farming can be combined with all systems that allow separation and control of nutrients through a circuit.
Active hydroponics: aquaponics - sump tank (CHOP: Constant high, one pump)
The decisive advantage of introducing a sump tank is that the height of the water level - especially in the fish tank - always remains constant. Only when water enters the fish tank from above through the pump does water flow back through the overflow. On the one hand, this means less stress for the fish and, on the other hand, the tank is filled with water even if the system fails (e.g. due to a burst pipe), as the water level can never drop below the overflow.

Overview of the most common systems

Passive hydroponics: wick irrigation
Active hydroponics: Ebb and flow systems
Active hydroponics: NFT - Nutrient Film Technology
Active Hydroponics: DWC - Deep Water Culture
Active Hydroponics: DFT - Deep Water Nutrient Film Technique (Deep Flow Technique)
Active hydroponics: Drip irrigation
Active hydroponics: Aeroponics - Fog from nutrient solution
Active hydroponics: Aquaponics - plant cultivation and fish farming
Active Hydroponics: Aquaponics - CHOP - Sump Container (Constant Height, One Pump)

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