Hydroponic fertilizers

from Wikipedia, the free encyclopedia

Hydroponic fertilizer are special plant food , which for the hydroponics and hydroponic be used. They are necessary to protect the plants in the artificial environment and to supply them with all the essential nutrients . The composition of hydroponic fertilizers differs in the variety of chemical substances from conventional fertilizers for soil cultures. Plants that are grown in the soil require different fertilizer mixtures.

There are several ways to fertilize plants in hydroponics:

  • with liquid inorganic complete fertilizer , this is automatically added in large systems due to the conductivity measurement of the water.
  • Through the release of fertilizer salt from solid ion exchanger granules.
  • Slurry of organic fertilizer or addition of such nutrient solutions.
  • a humus or compost layer that is applied to the top substrate layer in ebb and flow systems and is only watered from above when there is a need for fertilizer.
  • so-called worm tea , an aqueous solution of the excrement of compost worms or "AACT"; "Actively aerated compost tea" for actively aerated compost tea
  • in the special form of aquaponics through the excrement of faeces and feed residues of the fish kept.

need

Plants selectively take up minerals as needed. The selective uptake changes the chemical equilibrium between cations and anions . By shifting the chemical equilibrium, the pH value changes very rapidly. If the pH value shifts too much in one direction, the plant can no longer absorb all the ions due to the membrane potential . In addition, an increased pH value causes certain nutrients to form salt (precipitation reaction). The nutrients are then no longer available to the plants. This quickly leads to deficiency symptoms. Soils act as a buffer for the equilibrium of the pH value. They are cation exchangers and thus maintain the pH value. Hydroponic fertilizers therefore use chemical buffers.

Plants need macronutrients (such as nitrogen , potassium , phosphorus , calcium , magnesium , sulfur , nitrate ) in increased concentrations to maintain vital metabolic processes and essential micronutrients such as iron , zinc , copper , manganese , boron , molybdenum , nickel , chloride , aluminum , silicon and Titanium in very low concentration to maintain specific metabolic processes. In addition, trace elements such as cobalt , sodium , vanadium and lithium are beneficial for certain plants.

Influences on plants have also been demonstrated for the following chemical elements: arsenic , cerium , chromium , fluorine , gallium , germanium , iodine , lanthanum , manganese , sodium , rubidium , selenium , titanium and others.

Soils naturally contain enough trace elements. All the necessary micronutrients are therefore added to hydroponic fertilizers.

With hydroponic systems, it is important to identify the cause of any water loss. Water loss through evaporation only requires supplementation with fresh water, water loss through leaks also leads to a loss of nutrients, the content of which must be supplemented with water supply.

Chemical buffers

During root breathing , carbon dioxide is produced , which reacts chemically with the irrigation water to form carbonic acid (whereby an equilibrium is established):

In the circulating water of hydroponics, the equilibrium is more on the side of the free hydrogen carbonate ions , depending on the pH value (see carbonic acid # pH indication water ). Hydrogen carbonate ions formed react further with water

Free carbon dioxide acts like a weak acid. In the circulating water, the carbonic acid lowers the pH value. In the soil, the carbonic acid reacts with limestones to form calcium hydrogen carbonate (also called "bicarbonate") (for details see Karst # Weathering ):

A chemical buffer substance now causes the pH value to change much less strongly when an acid (or a base ) is added than would be the case in an unbuffered system . The amount of acid or base that can be absorbed by a buffer without a significant change in pH is called the buffer capacity , or exchange capacity in the soil .

In a specific case, a buffer substance (carbonate or a substance that also keeps metal ions in solution as a chelate ) is added to the fertilizer solution . If the water contains too many protons (because it is too acidic), the buffer substance binds a proton and the reaction equilibrium is shifted towards carbonic acid, carbonic acid is formed. This breaks down into water and carbon dioxide (CO 2 ) and the CO 2 is released into the air (see also carbonic acid-bicarbonate system ). All fertilizer salts of a strong acid with a weak base or strong base with a weak acid act as buffer substances, a salt of a strong base with a weak acid is used to buffer the carbonic acid (see also the chapter “chemical principles” in the article “chemical buffers” " ).

An increase in the pH value also occurs during the microbial oxidation of ammonium to nitrate (therefore hydroponic fertilizers should not contain nitrogen fertilizers based on ammonium salts):

NH 4 + + 2O 2 ↔ NO 3 - + 2H + + H 2 O.

In emersed systems such as hydroponics, too high a pH value of the circulating water can also lead to oxidative stress due to iron toxicity with symptoms similar to chlorosis on leaves (yellowing).

In nutrient solution culture, the extension growth of roots is inhibited at pH values ​​below 4 and at too high pH values ​​(with differences in different plant species). Nitrogen supply with NO 3 - leads to an alkalization and with NH 4 + to an acidification of the rhizosphere .

See also Effects of the pH value on the growth of plants and nutrient availability depending on the soil pH .

Complexing agents

Iron, manganese , zinc and copper ions are quickly oxidized in oxygen-enriched water, which reduces the ability of plants to absorb them. This is particularly important for iron, the deficiency of which can be a cause of chlorosis (yellowing of the leaves). In order to keep such metal compounds, which would otherwise flocculate due to oxygen oxidation or the pH value (as hydroxides), firmly bound in solution, chelating agents or their compounds with, for example, iron, manganese, copper or zinc are added.

Examples of such complexing agents:

Some of the iron chelate complexes of the complexing agents listed above are stable or unstable depending on the pH value, which is why the pH value of the finished nutrient solution or of the soil is essential for the iron absorption capacity of the plants. A pH range between pH 5 and 6 is the best for plants to absorb the (trace) elements iron, copper, manganese, boron and zinc.

EDTA is more likely to be added to fertilizers for soil substrates; it has a high affinity (willingness to bind) to calcium (and then keeps calcium in solution). DTPA has become the standard for hydroponic fertilizers in Europe, the ecotoxicity is largely unexplored.

Soluble humic substances occur naturally in humus soils, peat and lignite. They reduce the toxicity of iron, because they keep the iron bound as an iron (II) complex, but this also reduces the bioavailability of the iron.

Inorganic fertilizers

Every aqueous hydroponic fertilizer is a complete fertilizer in which all the nutrients mentioned are added artificially. Therefore, different formulas and approaches have been developed since the 1950s.

"Most plants grow optimally with a certain ion concentration ratio!"

Name of the ion formula Concentration in the solution [%]
nitrate NO 3 - 50 to 70
Hydrogen phosphate H 2 PO 4 - 3 to 20
sulfate SO 4 2− 25 to 40
potassium K + 30 to 40
Calcium Ca 2+ 35 to 55
magnesium Mg 2+ 15 to 30

The dosage information for liquid inorganic hydroponic fertilizers can be found on the packaging of all products.

In the case of multi- component fertilizers, the ratio of the core nutrients nitrogen (N), phosphorus (P) and potassium (K) is usually given in% of the standard reference base as the "NPK value", for example (13/13/21). This information means that the fertilizer contains 13% N ; 13% P 2 O 5 ; Contains 21% K 2 O , see also NPK fertilizer .

Ion exchange granulate

Ion exchange granules are solid special fertilizers (NPK complete fertilizers) for the long-term supply of nutrients in hydroponics. These provide the plant with a single fertilization over several months. They consist of synthetic resin granules that are loaded with salts (nitrates, phosphates and potassium salts). They also contain the necessary micronutrients.

The ion exchanger granulate is activated when normal tap water is added. It then absorbs naturally contained salts from the tap water and releases nutrient salts charged in the resin in exchange. The salts dissolve over a long period of time (depending on the nutrient uptake of the plant), with the nutrient concentration remaining in equilibrium. This ensures a mild and long-lasting release of nutrients in a concentration that is compatible with plants.

The synthetic resin not only acts as a carrier for the nutrient salts. It is also a buffer to keep the pH stable. It does not dissolve, but only leaves used synthetic resin granulate behind.

Organic fertilizer

Organic fertilizers are often used to supplement inorganic hydroponic fertilizers because inorganic fertilizers are more expensive.

Organic fertilizers are mainly made from animal meal , ashes from plants or animal bones, manure from fattening animals and industrial plant waste.

However, the exclusive use of organic fertilizer has some disadvantages:

  1. Since it is a natural product, the chemical compositions and concentrations of the nutrients vary greatly. Because these depend on many factors, such as B. the food of the animal.
  2. Organic fertilizer can be a source of various plant diseases.
  3. Organic fertilizers are often difficult to process due to their different consistencies and sizes.
  4. Organic fertilizers can give off strong odors.
  5. Organic fertilizers can contain ammonium compounds. So that these are not reduced microbially to ammonia (which is released into the air and is therefore no longer available as fertilizer nitrogen), as in aquaponics, the ammonium must be converted into nitrate with the help of microorganisms in an aerobic process. The conversion usually takes place in trickle filters (see also herbal sewage treatment plants ). Oxidation during the irrigation phase is undesirable because the aerobic process uses up oxygen, which is then lacking for root breathing . Nitrogen supply with NH 4 + instead of NO 3 - leads to a reduced root biomass. In the case of barley, however, it has been shown that plants need less (sugar) energy to absorb ammonium ions than they do to absorb nitrate ions.
  6. If solid organic fertilizer is used, prior processing is necessary (crushing, sterilizing, homogenizing, etc.).

sugar

Like the nutrient solutions for plant cell cultivation, hydroponic fertilizer solutions, sucrose or treacle are also added. This promotes "useful microorganisms" ( Trichoderma , mycorrhiza and useful bacteria) that live in the rhizosphere on the root hairs . The microorganisms supply enzymes that improve the absorption of nutrients. Trichoderma for example chitinase , which makes cell walls of harmful organisms permeable, and cellulase , which enables fungal hyphae to access plant roots.

For example, certain Pseudomonas strains in the fine root area can increase the growth of tomatoes, cucumbers, lettuce and potatoes in hydroponic systems.

Rooting agents

Rooting hormones and other phytohormones such as indole butyric acid (IBA) , indole acetic acid (IES or IAA) , 1-naphthylacetic acid or gibberellic acid (GA or GA 3 ) are added to some nutrient solutions .

By thiamine (vitamin B 1 ) can be the growth of adult plants and increase of roots, as well as by a mixture of 10 -5 bis 10 -7 mol pyrimidine and thiazole . Also, vitamin H and vitamin K lead to improved root growth.

A so-called willow water from soaked willow shoots, which is often recommended in the grower scene (see also Grow! And Indoor Growing ) and for (private) horticulture, contains growth substances useful for rooting, and honey is also added for the same purpose of better root formation in cuttings

See also auxins # cell division and differentiation .

For the Stecklingsbewurzelung (using aeroponics or Fogponics ) Bewurzelungsmittel also be used in powder form (with the base rock powder, such as talc ), in aqueous solution or potassium hydroxide solution neutralized polyacrylic acid gel (the same substance as in superabsorbent offered -Babywindeln).

Exudates

Exudates (excretions from the roots) accumulate in the circulating water of the hydroponics .

CO 2 obtained from natural gas or oil has lower levels of 14 C than CO 2 from the air, where the radioactively decaying 14 C isotope is continuously reproduced by cosmic radiation. 14 C can therefore be used as an indicator and tracer to determine the path or content of molecules based on petroleum in plants with the help of scintillation spectrometers . This has proven that up to 20% of the carbon fixed by photosynthesis in a vegetation period is released into the soil. 64 - 86% of them were inhaled by microorganisms, 2 - 5% remained in the soil. Most of the root exudates from maize (79%) were water-soluble (64% of which were carbohydrates , 22% amino acids or amides and 14% organic acids).

It is obvious that more exudates are washed out of the soil with hydroponics than with soil culture and economical watering (without seepage water). Too much rain or constant watering thus deprives the microorganisms of the rhizophore of their food (which is repeatedly fed to the rhizosphere when the irrigation water is circulated in hydroponics).

Nutrient solutions

Various nutrient solutions are used undiluted for hydroculture, for example:

Abram Steiner's nutrient solution

The following table shows the composition of all nutrients in a stock solution developed by Abram Steiner:

nutrient Concentration [mg / L]
nitrogen 170
phosphorus 50
potassium 320
Calcium 183
magnesium 50
sulfur 148
iron 4th
manganese 2
boron 2
zinc 0.2
copper 0.5
molybdenum 0.1

Historically the first nutrient solution according to Sachs and Stöckhardt

One liter of the finished solution contains:
1 g of potassium nitrate,
0.5 g of calcium sulphate,
0.4 g of magnesium sulphate,
0.5 g of calcium hydrogen phosphate
and a trace of iron (III) chloride.

Nutrient solution according to Wilhelm Knop

One liter of the finished solution contains:
1.00 g Ca (NO 3 ) 2 calcium nitrate
0.25 g MgSO 4 * 7 H 2 O magnesium sulfate
0.25 g KH 2 PO 4 potassium dihydrogen phosphate
0.25 g KNO 3 potassium nitrate
traces FeSO 4 * 7 H 2 O iron (II) sulfate .

Medium according to Pirson and Seidel

One liter of solution contains:
1.5 milli moles of KH 2 PO 4
2.0 mM KNO 3
1.0 mM CaCl 2
1.0 mM MgSO 4
18 uM Fe Na EDTA
8.1 uM H 3 BO 3
1, 5 µM MnCl 2 .

Culture medium according to Epstein

One liter of ready-made solution contains:
1 mM KNO 3
1 mM Ca (NO 3 ) 2
1 mM NH 4 H 2 PO 4
1 mM (NH 4 ) 2 HPO 4
1 mM MgSO 4
0.02 mM Fe-EDTA
0.025 mM H 3 BO 3
0.05 mM KCl
0.002 mM MnSO 4
Trace elements:
0.002 mM ZnSO 4
0.0005 mM CuSO 4
0.0005 mM MoO 3

Trace element additive according to DR Hoagland (1884-1949)

One liter of finished solution contains:
55 mg Al 2 (SO 4 ) 2
28 mg KJ
28 mg KBr
55 mg TiO 2
28 mg SnCl 2 2 H 2 O
28 mg LiCl
389 mg MnCl 2 4 H 2 O
614 mg B ( OH) 3
55 mg ZnSO 4
55 mg CuSO 4 · 5 H 2 O
59 mg NiSO 4 · 7 H 2 O
55 mg Co (NO 3 ) 2 · 6 H 2 O

Culture media for cell cultivation

Since the development of roots in cuttings in hydroponic cultures does not differ significantly from the development of single cells or callus tissue in in vitro cultures, the same nutrient media or special additives are used as for plant tissue cultures (see Murashige-Skoog medium ) used in hydroponics. For the differentiation of the plant cells, however, the quantitative ratio of auxin to cytokinin is decisive. At a ratio of 10: 1 a callus is formed, at 100: 1 roots form, at a different dilution stems or flowers. By varying different hydroponic nutrient solutions, it is usually (and more quickly than with soil culture) "switched" to forced root formation, growth phase or flower formation

Web links

  • Libia I. Trejo-Téllez and Fernando C. Gómez-Merino: Nutrient Solutions for Hydroponic Systems (English) (PDF file)

Individual evidence

  1. ↑ Matt LeBannister: With a Little Help From Your (Many) Friends: Beneficial Microbe Populations in the Indoor Garden
  2. ↑ a b c d e Sholto Douglas, James: Advanced guide to hydroponics: (soiless cultivation) . Ed .: London: Pelham Books. ISBN 978-0-7207-1571-2 .
  3. ↑ a b c d e J. Benton, Jones: Hydroponics: A Practical Guide for the Soilless Grower (2nd ed.) . Ed .: Taylor & Francis. ISBN 978-0-8493-3167-1 .
  4. ^ Nutrients , private website of the late agricultural journalist Rainer Maché .
  5. ↑ Ulrich Eckhardt: Investigations on iron assimilation in plants . Diss., Humboldt University, Berlin 2000.
  6. ↑ a b Wolfgang Merbach: Plant nutrition, root performance and exudation. Springer-Verlag, 2013, ISBN 978-3-663-01125-5 , p. 74 ( limited preview in the Google book search).
  7. ↑ a b c d e f g Chelates in hydroponic solutions
  8. ^ New Moon Publishing, Inc .: The Best of The Growing Edge International, 2000-2005. New Moon Publishing, Inc., 2005, ISBN 978-0-944557-05-1 , p. 182 ( limited preview in Google Book Search).
  9. ↑ LLBarton, J.Abadía (editor): Iron Nutrition in Plants and Rhizospheric Microorganisms, Springer, Dordrecht, 2007, ISBN 978-1-4020-4742-8
  10. ↑ George W. Ware: Reviews of Environmental Contamination and Toxicology. Springer Science & Business Media, 2012, ISBN 978-1-4612-1964-4 , p. 99 ( limited preview in Google book search).
  11. ↑ VUORINEN, PJ, KEINÄNEN, M., PEURANEN, S. & TIGERSTEDT, C. (1999): Effects of iron, aluminum, dissolved humic material and acidity on grayling (Thymallus thymallus) in laboratory exposures, and a compari-son of sensitivity with brown trout (Salmo trutta); Boreal Environment Research 3: 405-419, Helsinki January 19, 1999; cited in: Rainer Kruspe, Jürgen Neumann, Michael Opitz, Susanne Theiss, Wilfried Uhlmann, Kai Zimmermann: River organisms and iron - Qualitative and quantitative influences on flowing water organisms by iron using the example of the Lusatian lignite succession landscape ; Series of publications, issue 35/2014; State Office for Environment, Agriculture and Geology, Free State of Saxony; Page 53; (PDF file)
  12. ^ J. Benton Jones, Jr .: Complete Guide for Growing Plants Hydroponically . Ed .: Taylor & Francis Group, LLC. ISBN 978-1-4398-7669-5 .
  13. ↑ AJ Bloom, SS Sukrapanna, RL Warner: Root respiration associated with ammonium and nitrate absorption and assimilation by barley. In: Plant physiology. Volume 99, Number 4, August 1992, pp. 1294-1301, PMID 16669035 , PMC 1080623 (free full text).
  14. ^ MK Razdan: Introduction to Plant Tissue Culture. Science Publishers, 2003, ISBN 978-1-57808-237-7 , p. 22 ( limited preview in Google book search).
  15. ↑ Dorina Podar: Plant Growth and Cultivation , in: Frans JM Maathuis (editor): Plant Mineral Nutrients: Methods and Protocols , Methods in Molecular Biology, vol. 953, doi: 10.1007 / 978-1-62703-152-3_2 , (PDF file) , page 37.
  16. ↑ Eric Hopper: Below The Surface: Root Growth Stimulation and Microorganisms PDF (1163 K)
  17. ↑ Ron van Peer and, Bob Schippers: Plant growth responses to bacterization with selected Pseudomonas spp. strains and rhizosphere microbial development in hydroponic cultures , Canadian Journal of Microbiology, 1989, 35 (4): 456-463, doi: 10.1139 / m89-070 .
  18. ^ A b Fritz von Wettstein: Advances in botany. Springer-Verlag, 2013, ISBN 978-3-642-92427-9 , p. 284 ( limited preview in the Google book search).
  19. ↑ Thorsten Hemberg: The Effect of Vitamin K and Vitamin H 'on the Root Formation in Cuttings of Phaseolus Vulgaris L. , Department of Botany of the Royal Pharmaceutical institute, Stockholm, 1952, doi: 10.1111 / j.1399-3054.1953.tb08929. x
  20. ^ A b Maria Hutter: Weidenwasser helps cuttings , website of the Salzburg Chamber of Agriculture
  21. ↑ Deron Caplan, Jonathan Stemeroff, Mike Dixon, Youbin Zheng: Vegetative propagation of cannabis by stem cuttings: effects of leaf number, cutting position, rooting hormone, and leaf tip removal. , Canadian Journal of Plant Science, 2018, 98 (5): 1126-1132, doi : 10.1139 / cjps-2018-0038 .
  22. ↑ Otto Henke, Gerhard Schäller: Occurrence and importance of plant growth substances, Botanica Marina, Volume 8, Issue 1, pages 156–166, ISSN (Online) 1437-4323, ISSN (Print) 0006-8055, 1964 (written) and 2009 ( republished)
  23. ↑ Okunlola Ibironke, Oyedokun Victor: Effect of Media and Growth Hormones on the Rooting of Queen of Philippines (Mussaenda philippica) , (PDF file) , J. Hortic 2016, 3: 1, doi: 10.4172 / 2376-0354.1000173
  24. ↑ Birgit W. Hütsch, Jürgen Augustin, Wolfgang Merbach: Plant rhizodeposition - An important source for carbon turnover in soils , Journal of Plant Nutrition and Soil Science, 165 (4): 397 - 407 August 2002
  25. ↑ Tom Alexander: Best of Growing Edge. New Moon Publishing, Inc., 2000, ISBN 978-0-944557-03-7 , p. 52 ( limited preview in Google Book Search).
  26. ^ Faulkner, SP: The Growing Edge . 4th edition. No. 9 , p. 43-49 .
  27. ^ André Pirson, Franz Seidel: Cell and metabolic physiological investigations on the roots of Lemna minor L. taking into account potassium and calcium deficiency . Planta 38: 431473. 1950
  28. ↑ modified nutrient medium according to Pirson and Seidel, quoted from Daniela Schraut: Effects of external stress conditions on the radial water and ABA flows and the endogenous ABA content of the root tissue of maize seedlings (Zea mays L.) . (Note: The substances are noted in the source without crystal water , because of the specification in mM, raw materials with or without crystal water can be used)
  29. ^ Epstein, E .: Mineral Nutrition of Plants: Principles and Perspectives. John Wiley and Sons, Inc., New York, London, Sydney, Toronto. 1972.
  30. ↑ modified nutrient medium according to Epstein, quoted from Nicole Geißler: Investigations on the salt tolerance of Aster tripolium L. and its influence by increased atmospheric CO2 concentration , Gießen, 2006 (Note: The substances are noted in the source without crystal water because they are stated in mM raw materials with or without crystal water can be used)
  31. ↑ AZ solution
  32. ^ Munk, Basic Studies in Biology - Bd. Botany, 2001, Spektrum Verlag; quoted in: Scriptum 'Phytohormone' of the University of Graz (PDF file)
  33. ↑ Erwin Beck, Katja Hartig: How Hormones Control Cell Division in Plants , Biol. Unserer Zeit, 4/2009 (39), (PDF file)