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Aquaponics Fertilizer, Nutrients, and Deficiency Deep Dive

14 Oct, 2023 174
Aquaponics Fertilizer, Nutrients, and Deficiency Deep Dive - Unimother

We must go deep into chemistry to understand how the aquaponics system turns fish waste into plant fertilizer. Here is the short form for those not interested in that. 

Input = Output - Aquaponics Fertilizer: 

What you feed your fish will also feed your plants. Suppose you provide protein-rich feed to your fish. In that case, your plants in the aquaponics system will receive a lot of nitrogen because amino acids are made of a lot of nitrogen, and plants can even absorb amino acids directly. Carnivore fish, therefore, will grow leafy greens and herbs well. On the other hand, fish that you feed herbivores will grow great flowers, fruits, seeds, and vegetables in your grow bed because of the overabundance of the excreted potassium and phosphorus. Plants use these three nutrients most besides carbon, oxygen, and hydrogen. They are called macronutrients.

Compared to them, micronutrients are only required in small amounts. Still, they are essential, and there are over 20 of them to create enzymes, photosynthesis, and many plant processes that will affect health, immunity, taste, and fragrance. Further below is a table of the most important macro and micronutrients and how you identify the symptoms of your plant being deficient or maybe the excess of one nutrient is blocking the adsorption of other nutrients like trace minerals. 

 

So, how do you ensure that your plants have sufficient micronutrients if so many exist?

Mother made it easy for us. She ensured that all essential micronutrients were mixed in the earth's magma, and each time there was a volcanic eruption, the ash would fly worldwide and fertilize the whole world. 

Nowadays, we don’t have to wait for an outbreak to get sufficient micronutrient levels. Instead, we can use rock dust to get tasty and healthy food.

 

Rock Dust as Aquaponics Fertilizer

Over time as plants absorb minerals, they exchange them for hydrogen (H+) ions, naturally reducing the pH levels more and more in acidic areas. This is called biogenic acidification and can be reversed by adding minerals like rock dust.

Rock dust is essentially ground-up rock, containing a wealth of trace minerals and micronutrients essential for plant growth. In aquaponics, it can be an invaluable addition for a few reasons:

  • Diverse Mineral Content: Rock dust contains many micronutrients, especially from volcanic sources. These include but are not limited to Boron, Calcium, Chlorine, Cobalt, Copper, Iron, Magnesium, Molybdenum, Nitrogen, Phosphorous, Potassium, Silicon, Sodium, Sulfur, Zinc, and many more. Each of these plays a vital role in plant health.
  • Improved Soil Health: While aquaponics systems don't rely on traditional soil, the growing medium can still benefit from adding rock dust. It can improve water retention, enhance microbial activity, and steadily release micronutrients.
  • Enhanced Plant Growth: With a more diverse range of nutrients available, plants can grow more vigorously, produce more abundant yields, and have increased resistance to pests and diseases.
  • Tastier Produce: Plants grown with the right micronutrients often taste better. This is because they can synthesize the compounds that contribute to flavor more effectively.
  • Simple use: Add rock dust to the water or the grow bed. The right amount of minerals will naturally dissolve and provide micronutrients over time.
  • Rock dust will also supply your fish or shrimps with micronutrients and is an excellent micronutrient supply in livestock feed for all vertebrates. This theoretically includes human consumption, but ask your doctor or nutritionist for advice first.

 

 

How Plants Absorb Nutrients in Aquaponics

Plants mainly absorb nutrients from the soil through their roots.

  • Soil Solution: When nutrients are dissolved in water, they form a soil solution.
  • Root Hair Absorption: The fine root hairs of plants absorb the nutrients from the soil solution. This is primarily an active process, meaning it requires energy.
  • Transport to Other Parts: Once inside the roots, the nutrients are transported upwards to stems, leaves, and other parts of the plant through the xylem (a type of vascular tissue).

Factors ensuring effective nutrient absorption in plants:

  • Soil pH: The pH level of the soil affects the availability of nutrients. Most plants prefer slightly acidic to neutral pH levels to absorb nutrients effectively.
  • Soil Moisture: Adequate water is necessary to dissolve nutrients and make them accessible to plant roots.
  • Soil Aeration: Roots need oxygen to respire and generate the energy required for active uptake of nutrients.
  • Soil Texture: The size and arrangement of soil particles (sand, silt, clay) can affect water retention and nutrient availability.
  • Presence of Beneficial Microorganisms: Certain microbes help break down organic matter, making nutrients more accessible to plants.
  • Absence of Soil Contaminants: Pollutants or contaminants can interfere with nutrient uptake.
  • Healthy Root System: A robust and extensive root system increases the absorption surface area.
  • Balanced Soil Nutrients: An excess of one nutrient can inhibit the uptake of another due to antagonistic effects.

It's essential to maintain a balance of these factors to ensure that plants can absorb and utilize nutrients effectively.

An Overview of Key Components in Aquaponics Fertilization:

  • Transforming fish waste into a form that's usable for plants.
  • Evaluating the energy levels of fertilizers.
  • An anaerobic environment (lacking oxygen) will lower the pH because the bacteria will consume all oxygen and increase the (CO2) which will create carbonic acid (H2CO3) in the water. During nutrient reduction, the bacteria will remove oxygen compounds from oxidized chemical connections to get oxygen, making them more readily available for plants. 
  • In contrast, oxidation processes require plants to expend more energy to access nutrients, and this usually corresponds with increasing pH levels.
  • Interestingly, conditions that are more toxic for fish tend to make nutrients more available for plants. Striking a balance is crucial.
  • To convert a grow bed into an anaerobic environment, consider using sandponics with a layer of 2 - 4 inches (5-10 cm) sand. Incorporate clay pebbles on top to capture debris and introduce worms to clean the medium and make more nutrients accessible to plants.
  • These worms possess a micro gut biome, which includes beneficial fungi and bacteria, an essential part of the nutrient-releasing process.

 When you still look for plants you can cultivate in aquaponics you should check out our plant guide.

Chemistry Of Aquaponics Nutrients and Fertilizer 

What are pH - levels?

pH level measures the acidity and alkalinity of a solution.

pH levels of 0 - 7 are acidic.

pH levels of 7 - 14 are alkaline.

The lower the pH, the more hydrogen (H+) ions.

The higher the pH, the less hydrogen (H+) ions.

The lower the pH, the less hydroxide (OH-) ions.

The higher the pH, the more hydroxide (OH-) ions.

At pH 7, the (H+) and (OH-) are the same.

Infographic of plant nutrient availability in relation to the pH level

 Infographic of plant nutrient availability in relation to the pH level.

 

The decay process of organic matter will result in bio-acidification, where, over time, the pH level gradually decreases as small amounts of minerals are needed for degradation. This process also increases the speed of acidification of the oceans and destroys current ecosystems like coral reefs by revoking calcium structures. Adding a mineral mix like rock dust can raise the pH levels of your aquaponic system. Generally, acids reduce the pH level, while minerals, salts, and metals raise the pH level. This knowledge can help you naturally stabilize your system. 

 

Understanding Anions and Cations in Plant Nutrients Absorption 

The electrical balance in the roots must remain balanced. To take up nutrients, plants have to trade protons like hydrogen (H+) to absorb a cation like potassium (K+). Increasing proton concentration reduces the pH to a more acidic (0 - 7) level.

In the same way, plants also have a way to absorb anions. For example, to absorb nitrate (NO3-), the plant roots release bicarbonate (HCO3-), which increases the pH to more alkaline (7 - 14) levels.

Plants can also directly absorb intact amino acids and thus bypass microbial mineralization of organic nitrogen. Recycling of amino acids is the reason aquaponics is superior to soil-grown plants because a small amount of fish feed will always dissolve while the fish eat. Instead of wasting those amino acids, plants can reuse them as building materials.

The ammonia(NH3), which fish and bacteria release, in acidic pH levels below 7 picks up free hydrogen (H+) ions in the water and reacts to ammonium (NH4+). Contrary, in alkaline pH levels above 7, there are higher levels of free hydroxyl molecules (OH-) and ammonium (NH4+) is converted back into ammonia. A sudden pH change from below 7, for example, 6.5 to above 8, can turn a lot of less toxic ammonium into more toxic ammonia, which could kill your fish. Ammonia (NH3) can diffuse through the plant roots because it’s not electrically charged. Inside the plant, the ammonia will quickly find a free (H+) ion and react to (NH4+), which the plant can use and store.

Certain factors must be ensured for plants to absorb nutrients, like mineral availability, soil temperature, the energy state of the nutrient, humidity levels, photosynthesis, pH of roots/soil, and the relative concentration of minerals in the water. 

High levels of one cation will block other cations from being absorbed. Logically high levels of anions will also block other anions from being absorbed.

Anions:

Hydroxide (OH-), bicarbonate (HCO3-), chloride (Cl-), nitrite (NO2-), nitrate (NO3-), dihydrogen phosphate (H2PO4-), phosphate (PO4-), sulfate (SO4--), tetraborate (B4O7--), dioxido(dioxo)molybdenum (MoO4--), hydrogen phosphate (HPO4--), phosphate (PO4---)

Cations:

Hydronium (H3O+), hydrogen (H+), ammonium (NH4+), potassium (K+), sodium (Na+), calcium (Ca++), manganese (Mn++), zinc (Zn++), nickel(II) (Ni++), cobaltous (Co++), magnesium (Mg++), iron(II) (Fe++), iron(III) (Fe+++)

In the same way, low levels of certain anions can create excess nutrients for other anions in the plant, and low levels of cations will make extra nutrients for other cations.

Also important to know is that single-charged ions are more easily absorbed than double-charged ions. Triple-charged ions will, therefore, require the most energy.

For example, this means that high levels of the single-charged nitrate (NO3-) will block the absorption of double-charged molybdenum (MoO4--) and boron (B4O7--).

The same goes for high levels of potassium (K+) will lead to a deficiency of iron (Fe++, Fe+++), calcium (Ca++), magnesium (Mg++), manganese (Mn++), and so on.

 

All plants can absorb nutrients from the roots and leaves. Therefore, a nutrient shortage can be explicitly applied to a plant as a foliar spray or added to the roots.

 

Table of Essential Elements for Plant Growth

Element (symbol)

Form taken up by plants ranked after availability most to least

Function in the plant

Deficiency Symptoms

Excess Symptoms

Percentage in plant mass

Hydrogen (H)

(OH-), (H3O+), (HCO3-), (H+), (H2O), (H2)

Transport of nutrients

-Drought conditions like: 

-wilting leaves

-damaged dried roots/soil

-hanging branches

-Wilting, yellowing of lower leaves

-similar to drought

-long standing water drowns the plant roots

50 - 95% water


hydrogen 5 - 20% of dry matter


combined with oxygen and carbon 89% of biomass

Carbon (C)

(CO2)

Cellulose, carbohydrates, fruits,

-Necrosis

-chlorosis 

-stunted growth

-twisted leaves

-Increased growth

-less nutritional value

-cause other nutrients to decrease

40 - 50% of dry mass

Oxygen (O)

(CO2), (H20), (O2)

Photosynthesis, respiration, root health

-Constrained plant growth

-rotting roots

-wilting leaves

-Less root growth

-oxidizes many nutrients therefore harder for the plant to use

35 - 45% of dry matter

Nitrogen (N)

(NH3), (NH4+), (NO2-), (NO3-)

Photosynthesis, amino acids, plant protein, leaf growth, chlorophyll production, roots, regulate water and nutrient uptake

-Slow growth, uniform yellowing of older leaves,

-yellow from edge towards leaf veins,

-smaller fruits, later development

-Dark green, gray, brown, thickened leaves

-overfertilization blocks other nutrients to be absorbed like iron

-can’t fruit, flower, or seed

3 - 4% of dry matter

Phosphorus (P)

(HPO4--), (H2PO4-), (PO4-), (FePO4), (PO4---)

Roots, stem strength, flower and seed production, more resistance to plant diseases

Inhibited shoot growth, dark, dull, blue greenish leaves, may pale at severe states, reddish to violet coloring of old plant parts

-Stunted growth

-chlorosis

-yellow bleached foliage caused by blocked nutrients uptake of nitrogen, iron, zinc, and other

0.1- 0.5%  of dry matter

Potassium (K)

(K+)

Water management, frost protection, disease resistance, metabolic processes

Curling and browning leaf tips, chlorosis between leaf veins, short internodes, wilt on sunny days, small leaf blades on new growth

-Chlorosis

-cause inhibited nitrogen, calcium, manganese, zinc, iron, magnesium uptake

1.5 - 4% of dry matter

Silicon (Si)

(H4SiO4), (SiO4H4)

-Responsible for mechanical plant strength

-protect against insect attack, diseases, and environmental stress 

-improved defense response

-Less drought resistance

-less dry matter

-susceptible to fungi, bacteria, and pest insects 

Uncommon, but can possibly compete with other nutrients

0.1 - 10% of dry matter

Calcium (Ca)

(Ca++)

Cell wall, cell membranes, nutrient transport,

water management

-New growth of leaves and stem inhibited

-bushy plant appearance

-cracking of fruits and vegetables

-Reduced plant growth

-yellow/brown spots on fruits and vegetables

0.5 - 3% of dry matter

Magnesium (Mg)

(Mg++)

Phosphorus carrier, essential for cell division, protein formation, producing enzymes,  and respiration

-Slow growth

-older, lower leaves turn yellow from the edges and develop chlorosis

-dark purple/red  spots on leaves

-Very high levels inhibit growth

-leaves become dark colored

-weak immunity against diseases

0.25 - 1.6% of dry matter

Sulfur (S)

(SO2, SO4--)

Nitrogen metabolism, enzymes, protein and oil synthesis, flavor and odor 

-Pale green, to yellow starting from young leaves

-small narrow leaves 

-Damaging to root system

-reduced growth

-deformed growth

-thinning of crown and foliage

0.15 - 0.6% of dry matter

Iron (Fe)

(Fe++), (Fe+++)

Synthesis of chlorophyll, other enzymes, and metabolic processes

-function, maintenance, and structure of chloroplast

-Bleached new leaves while veins stay green

-starting at new foliage

-fades from outside to the green veins

-Bronze discolored leaves 

-stunted root growth

0.001 - 0.02% of dry weight

Boron (B)

(H3BO3), (B4O7--)

Cell wall development and strength, cell division, fruit and seed development, hormone development, sugar transport

-Slow growth of leaves and fruits 

-inhibited plant cell expansion

-reduced fertility

-distorted growth

-Yellowing leaf margins/tips

-necrosis

-dropping leaves prematurely

0.002 - 0.06% of dry weight

Manganese (Mn)

(Mn++)

Plant growth and development, metabolic role, cofactor of oxygen evolving complex

-Yellow to white new leaves with wide green areas along the veins

-brown spots on leaves

-becomes curled and crooked 

-Chlorosis in young leaves

-necrotic dark spots on mature foliage

-crinkled leaves

-stunted growth

0.005 - 0.03% of dry weight 

Zinc (Zn)

(Zn++)

Metabolism, enzyme function, ion transport

-Late bloom and leaf out

-atypically pointed narrow, small yellow leaves

-internodes between leaves shortened

-prematurely dropped old leaves

-Reduced yield

-stunted growth

-iron deficiency inducing chlorosis

-reduced nutrient transport

0.0001 - 0.003% of dry weight 

Molybdenum (Mo)

(MoO4--)

Production of enzymes for various plant function, protein synthesis of nitrate

-Accumulation of nitrates in leaves because can’t convert to protein

-stunted growth, similar to nitrogen deficiency

-Rare

-leaves turn purple in tomato and cauliflower

-legumes turn yellow

0.00001 - 0.0002% of dry matter

Copper (Cu)

(Cu)

Enzymatic activities, production of chlorophyll and seeds

-Rare

-yellow brown patches

-shiny dark leaves with greenish blue/purple tone

-disease susceptibility to ergot

-significant yield loss

-buds will not open

-Chlorosis

-necrosis

-stunting

-leaf discoloration

-no root growth

0.0001 - 0.001% of dry matter

Chlorine (Cl)

(Cl-)

Osmotic and stomata regulation, disease resistance, yield increase

-Chlorosis 

-bronze discoloration

-growth reduction

-Damaging roots

-kills soil microorganisms

0.005 - 0.01% of dry weight

Nickel (Ni)

(Ni++)

Enzyme to catalyze urease so urea can convert to ammonium ions

-Necrosis of leaf tips caused by toxic urea concentration

-chlorosis of young leaves with reduced leaf size and upright leaf growth

-Retards seed germinability

-reduced shoot and root growth

0.0005 - 0.001% of dry matter

Cobalt (Co)

(Co++)

Critical role in overall growth of plants, necessary for stem  growth and to reach maturity, maintain cellular homeostasis

-Stunted growth

-part of vitamin b12 which is essential for N2 nitrogen fixation from the atmosphere

-Pale leaves with discolored veins

-can also cause iron deficiency 

0.00001 - 0.0001% of dry matter

Sodium (Na)

(Na+)

Helps water uptake, pH homeostasis, control of membrane electrical potential, regulation of osmotic cell pressure

-Chlorotic leaves

-severe cases cause leaf tips and margin necrosis

Blocks nutrients and water

0.000001 - 0.0000001% of dry matter

 

Aquaponics Nutrients Influencing Factors

The availability of nutrients to plants can be affected by various factors including pH, oxygen levels, temperature, nutrient balance, other plants, and other environmental conditions. Here’s how these factors can cause deficiencies in each nutrient:

  • Hydrogen, Carbon, and Oxygen:
    • Generally, these are not deficient due to their abundance in water and air. However, poor water with low oxygen or stagnant air could theoretically impact their availability.
    • High fish stocking combined with a low filter capability of the grow bed can result in lots of fish waste remaining in the tank, ideal living conditions for pathogenic bacteria which consume lots of oxygen
  • Nitrogen:
  • Phosphorus:
    • High pH: Can cause phosphorus to precipitate out of solution, making it unavailable to plants.
    • Too much filtering can cause phosphate precipitation of phosphorus with iron and block both nutrients.
    • Cold Temperatures: Can reduce phosphorus availability, especially in outdoor grow beds because the metabolism of plants, worms, insects, bacteria, and fungus almost stands still.
  • Potassium:
    • High pH: Potassium availability can be reduced.
    • Sodium (Na) Competition: High levels of sodium can compete with potassium uptake.
  • Calcium:
    • Low pH: Reduces calcium availability.
    • Most of the time this mineral is in surplus if you keep refilling tap or groundwater.
    • Can be balanced with magnesium at excess calcium levels
    • Waterlogged Conditions: May reduce calcium uptake due to low oxygen levels.
  • Magnesium:
    • High pH: Can reduce magnesium availability.
    • Calcium Competition: High levels of calcium can interfere with magnesium uptake.
    • Very likely to lack if not added externally
  • Sulfur:
    • High pH: Sulfur becomes less available as pH increases.
    • Common deficiency
  • Iron:
    • High pH: Iron becomes less available as pH increases.
    • High Aeration: Can lead to reduced iron availability.
  • Boron:
    • High pH: Reduces boron availability.
  • Manganese:
    • High pH: Reduces manganese availability.
    • Dry Soil Conditions: Can cause manganese deficiency.
  • Zinc:
    • High pH: Zinc becomes less available as pH increases.
    • Phosphorus Competition: High levels of phosphorus can interfere with zinc uptake.
  • Molybdenum:
    • Low pH: Reduces molybdenum availability.
  • Copper:
    • High pH: Reduces copper availability.
    • Poor Aeration: Can lead to reduced copper availability.
  • Chlorine:
    • Generally not deficient but excessive watering can leach chlorine from the soil.
  • Nickel:
    • High pH: Reduces nickel availability.
  • Cobalt:
    • High pH: Reduces cobalt availability.
  • Sodium:
    • Generally not deficient, but competition with other ions like potassium can occur.
  • Silicon:
    • Low Availability in Soil: Silicon availability can vary greatly depending on the soil type.
    • Waterlogged Conditions: May reduce silicon uptake due to low oxygen levels.

 

Macronutrients

Hydrogen (H)

Most of a plant cell's content is water, making up about 80 to 90 percent of its overall weight. Even seemingly dry soil can be a rich source of water for terrestrial plants. Plant roots take in water via root hairs and channel it upwards to the leaves through the xylem. As leaves release water vapor, the act of transpiration coupled with water's molecular properties causes more water to be drawn from the roots to the leaves. Water is vital for maintaining cell integrity, facilitating metabolic activities, transporting nutrients, and aiding in photosynthesis.

Carbon (C)

Plants require various substances, termed nutrients, to live. These nutrients can be organic or inorganic. Organic compounds are carbon-containing molecules, like carbon dioxide from the air. In fact, carbon sourced from atmospheric CO2 forms the bulk of a plant's dry weight. On the other hand, inorganic compounds lack carbon and aren't derived from living entities. These inorganic elements, predominantly found in the soil, are often referred to as minerals.

About 95 to 97% of carbon is absorbed from the atmosphere. The other 3 - 5% derive from the organic matter in the soil/roots. Carbon is an integral structure and part of many plant building blocks like carbohydrates, fats, proteins, and cellulose.

Oxygen (O)

Hydrogen and oxygen, both macronutrients, are integral to numerous organic substances and combine to form water. Oxygen plays a pivotal role in cellular respiration, enabling plants to conserve energy as ATP. Even though plants are known to produce oxygen, they can do so only when the sun shines. Plants need oxygen in the root zone and at night to process their carbohydrates.

Primary Macronutrients

Nitrogen (N)

Even though close to 80 percent of earth’s atmosphere is nitrogen. It is in a chemically and biologically unusable form. It takes lots of energy to break this nitrogen into plant-usable form. Only algae and special microorganisms can fixate atmospheric nitrogen (N2) and transform it into ammonia (NH3).

Here is an excellent overview of biological nitrogen fixation.

Unfortunately, synthetic fertilizer kills those bacteria and releases nitrogen into the atmosphere.

 

An Important difference between aquaponics and modern agriculture is that

no synthetic fertilizers, pesticides, or antibiotics are used, and all nitrogen gets recycled.

 

Nitrogen cycle

Amino acids contain nitrogen and when consumed by fish, they release ammonia, which is highly toxic to fish but the best fertilizer for plants as they have the lowest oxidation level.

Nitrite (NO2-) is also toxic for fish but already oxidized so it’s harder for plants to break it up than ammonia. For plants to utilize nitrate, they have to reduce it back to nitrite or ammonium to convert it into amino acids. 

Nitrogen is mainly result in leaf growth.

 

  • Nitrogen Role:
    • Nitrogen is crucial for plants as it's needed to make amino acids, proteins, and chlorophyll (which helps plants photosynthesize or make food from sunlight).
  • Ammonium and Nitrate:
    • Plants can absorb nitrogen in many forms: amino acids, ammonia (NH3), ammonium (NH4+),  nitrite (NO2-), and nitrate (NO3-). The balance between these can affect plant growth because ammonium interferes with cations like (Ca++) and (Mg++) while nitrite and nitrate can block the adsorption of anions like (SO4--) or (MoO4--).
  • Metabolizing Nitrogen:
  • This process can happen in both the roots and the leaves, but it’s more energy-efficient in the leaves because sunlight helps the process along.
  • This is why aquaponics is superior to soil agriculture, as fish breathe out ammonia (NH3), which comes from the natural breakdown of manure and organic material. Fish breathe it out naturally (toxic in high doses), and it has the highest plant availability. Ammonia is used commercially as a synthetic nitrogen fertilizer because plants don’t need to exchange ions to absorb ammonia.
  • in algae nitrogen is transformed into amino acids while also producing omega 3 from the carbon: ideal decentralized filter in combination with amphipods as decentralized algae remover that is not available to fish, either in location or the don’t eat algae.
  • Amphipod offer are healthy protein producer to feed fish, essential omega 3 and chitin, rich in fiber 
  • Temperature’s Effect:
    • Warm temperatures speed up plant processes, using up energy and oxygen, which can impact how well ammonium is metabolized in the roots. Cold temperatures slow down nitrate transport to leaves, possibly delaying plant growth.
  • Different Plants, Different Needs:
    • Different plants might prefer different ammonium-to-nitrate ratios depending on their growth stage and the soil conditions. For example, flowering and fruiting plants might do better with lower to close to nonexistent ammonium/nitrate amounts.
  • Impact on Soil pH:
    • When plants take up ammonium, they release protons like hydrogen (H+) and hydronium (H3O+), making the soil more acidic. When they take up nitrate (NO3-), they release electrons like bicarbonate (HCO3-) and hydroxide (OH-), making the soil more alkaline. Knowing this is important to manage pH levels, especially in soil-less systems like hydroponics.
  • Ammonium Toxicity:
    • Too much ammonium can harm plants, especially in anaerobic, wet soils where the conversion of ammonium to nitrate is slow. Low oxygen levels can lead to ammonium buildup, which can be toxic to plants.
  • Optimizing in Hydroponics:

 

Potassium (K)

Potassium plays a key role in the transportation of water, nutrients, and sugars within plants. It's instrumental in triggering various enzymes, influencing the formation of proteins, starches, and the energy molecule, adenosine triphosphate (ATP). This, in turn, can impact the efficiency of photosynthesis.

Furthermore, potassium controls the stomata's functions, which manage the exchange of moisture, oxygen, and carbon dioxide in plants. A lack of adequate potassium can hinder plant growth and result in diminished yields.

For perennial plants, like alfalfa, potassium contributes to their survival through colder months. Some other vital functions of potassium include:

  • Boosting root development and enhancing resilience against drought.
  • Preserving cell pressure, minimizing water loss, and preventing wilting.
  • Facilitating photosynthesis and the creation of nutrients.
  • Decreasing respiration, conserving energy in the process.
  • Aiding in the movement of sugars and accumulation of starch.
  • Resulting in starch-rich grains.
  • Elevating the protein levels in plants.
  • Strengthening plant cell walls and preventing them from collapsing.
  • Acting as a defense mechanism against certain plant diseases.

Potassium (K) is highly water soluble and high levels of calcium, salt, or magnesium can inhibit potassium intake. Food waste like vegetables and fruits contains high amounts of potassium. Sufficient potassium levels help protect the plants from frost and diseases. Potassium is essential for fruiting, flowering, and seed development.

 

Phosphorus (P)

Phosphorus (P) is the most limiting nutrient after water, carbon, and nitrogen (N). Organic matter, clay, and specific mineral compositions contain phosphorus. Most of the time, enough phosphorus is present but bound to other cations and fixated in an unavailable form for plants to absorb. In agriculture, phosphorus runoff causes groundwater pollution and algae blooms in water bodies. The nutrient recycling of an aquaponics system makes it superior to store-bought food.

Phosphorus can come in three forms:

 

 

Secondary Macronutrients

Calcium (Ca)

Even though plants need calcium to build the cell wall and membrane.  It's a pivotal factor in ensuring the stability and integrity of plant tissues. In nature, it rarely ever is a deficiency. Excess calcium often happens when tap water is used, as it usually contains calcium but not other minerals like magnesium. Which will result in the blocking of iron and manganese.

 

Magnesium (Mg)

​​Magnesium (Mg) is crucial for numerous core functions and chemical reactions in plants. It plays a significant role in the creation of chlorophyll, the generation and movement of energy-rich compounds, triggering enzymes, and forming proteins. However, with the rise of high-yield crops that respond well to fertilizers, combined with rigorous farming without restoring Mg, soil becoming more acidic, and the leaching away of available Mg, this essential nutrient has turned into a constraint for achieving optimal crop yields.

 

Sulfur (S)

Sulfur is vital for the proper growth and functioning of plants. It's an integral part of proteins, amino acids, vitamins, and other essential molecules. While a significant portion of sulfur in the soil is tied up in organic matter and not directly available to plants, they primarily absorb sulfur in its anionic form (SO4--). However, this form is water-soluble and can easily wash away from the soil. Sulfur and its compounds play a role in both regular metabolic functions and stress responses in plants. They also mediate in the broader signaling networks of plants. Plants absorb sulfate from the soil using specialized transport mechanisms. They can also tap into the transport systems of symbiotic organisms like bacteria and fungi, especially when sulfur levels in the soil are low. Given its importance in plant metabolism, understanding sulfur is crucial for the health of plants, animals, and humans who depend on them. If plants don't get enough sulfur, their growth can be stunted, leading to reduced yields.

 

Micronutrients

Silicon (Si)

Even though silicon is not an essential plant nutrient, it enhances root, stem, and shoot growth, sugar content (Brix), and disease resistance to bacteria, fungi, insects, droughts, and heat stress while also increasing the protein content for better yields. Sufficient silicon in plants also encourages lateral branching for bushier plants. Up to 50% of decreased pesticide use of mono silicic acids on plants because the diseases are better noticed as plants respond better to stress when infected with pathogens like fusarium wilt and powdery mildew. It also protects the plants from absorbing heavy metals like aluminum and cadmium.

 

Boron (B)

Boron (B) is a vital trace element necessary for the proper growth and functioning of plants. A deficiency in boron can disrupt plant metabolism and growth. This element plays a crucial role in maintaining the stability and performance of cell walls and membranes. Additionally, boron is instrumental in regulating the movement of ions (like H+, K+, PO43−, Rb+, and Ca2+) across cell membranes, aiding cell growth and division, managing nitrogen and carbohydrates, and assisting in sugar transportation. It also influences various cellular components and processes, such as cytoskeletal proteins, enzymes attached to the plasma membrane, DNA/RNA functions, and the metabolism and transport of specific compounds like indoleacetic acid, polyamines, ascorbic acid, and phenols.

 

Chlorine (Cl)

Traditionally, Chloride (Cl−) was seen as a minor nutrient that plants largely ignored due to its common presence in nature, its counteraction with nitrate (NO3−), and its potential harm at high levels. However, recent perspectives have changed. Instead of viewing (Cl−) as a detrimental ion that's unintentionally absorbed when plants intake (NO3−), it's now regarded as a beneficial macronutrient that plants regulate and transport with precision. When present as a macronutrient, (Cl−) contributes to increased plant growth, larger leaves, extended leaf and root cells, improved water management, enhanced (CO2) diffusion in leaf cells, and more efficient use of water and nitrogen. Although plants thrive best with a balanced intake of both (Cl−) and (NO3−), their preference for one over the other can vary based on the plant species, variety, and environmental factors such as water scarcity or salt levels.

 

Iron (Fe)

Iron plays a pivotal role in energy transfer processes and acts as an essential component for numerous crucial enzymes. It's irreplaceable for most bacteria, making it indispensable for almost all living organisms. In plants, iron is vital for processes like photosynthesis and the creation of chlorophyll. The amount of accessible iron in the soil not only determines where specific plants grow in nature but also influences the productivity and nutritional value of crops. A lack of iron intake in plants can lead to slowed growth, yellowing between leaf veins, and diminished vitality. For food crops, maintaining adequate iron levels is essential to address iron deficiency anemia, a widespread nutritional issue globally. However, an overabundance of iron can harm cells. Thus, plants have developed mechanisms to enhance iron absorption when it's scarce and limit it when there's an excess.




Manganese (Mn)

Manganese (Mn) plays a pivotal role in various plant cellular functions. It's especially crucial for the oxygen-evolving component of the photosynthesis process, facilitating the water-splitting action in photosystem II (PSII). While Mn's role in photosynthesis and other functions is critical, the significance of its uptake and distribution in plants hasn't been given due attention. Different transport proteins, derived from varied gene families, help maintain Mn levels across different plant cell areas. These proteins support various Mn-dependent activities, including sugar addition to molecules, protection against reactive oxygen species, and photosynthesis. Yet, the balance of Mn can be upset if there's too little or too much available. Dry, airy soils with a lot of calcium or organic matter can lead to Mn shortage, a common problem that hinders plant growth. On the other hand, Mn excess is a concern in waterlogged and acidic soils where the metal becomes overly accessible. Therefore, plants have developed precise systems to manage Mn absorption, movement, and storage.

 



Molybdenum (Mo)

Molybdenum plays a crucial role in helping plants process nitrogen. For non-leguminous plants, like cauliflowers, tomatoes, and maize, molybdenum helps them utilize the nitrates they absorb from the soil. If a plant doesn't have enough molybdenum, it accumulates nitrates in its leaves without converting them into proteins. This leads to stunted growth, resembling the effects of nitrogen shortage, and can also cause the leaf edges to burn due to the excess nitrates.

For leguminous plants, such as beans, peas, and clovers, molybdenum has a dual role. It aids in processing the nitrates from the soil, similar to non-leguminous plants. Additionally, it assists in capturing atmospheric nitrogen through bacteria in the root nodules. For these legumes, the need for molybdenum is even higher when fixing nitrogen from the air than when processing nitrates from the soil.

 

 

Zinc (Zn)

Zinc (Zn) is a fundamental micronutrient for plants, crucial for various cellular and biochemical processes. The concentration of Zn is critical; if it's too low or too high, it can affect plant health. This metal is involved in many of the plant's activities, supporting its growth, maturation, and yield. Many proteins and enzymes in plants depend on Zn for their structure and function. Therefore, understanding how Zn behaves in the soil, how plants absorb and transport it, and how they react to its shortage is pivotal. Many crops globally suffer from a lack of Zn, leading to notable decreases in yield and affecting the nutritional value of the produce.




Copper (Cu)

Copper (Cu) is a vital mineral needed for plants to grow and flourish, playing roles in a wide range of physical, chemical, and biological functions. It serves as a key element in numerous enzymes, aiding in processes such as photosynthesis, breathing, and electron transport. Moreover, copper is a fundamental part of certain defense-related genes. While it's essential, too much Cu can be detrimental, hindering plant growth and yield. Extensive research has highlighted the negative impacts of excessive Cu on plant processes like seed sprouting, growth, and photosynthesis, as well as on the plant's defense mechanisms. This overload can also suppress the synthesis of chlorophyll and the activity of antioxidant enzymes.

 

Nickel (Ni)

Nickel plays an integral role in the functioning of eight enzymes, specifically Glx I (EC 4.4.1.5), ARD (EC 1.13.11.54), Ni-SOD (EC 1.15.1.1), Hydrogenase (EC 1.12.98.2), MRC (EC 2.8.4.1), CODH (EC 1.2.99.2), ACS (EC 2.3.1.169), and urease (EC 3.5.1.5). Among these, urease, which is reliant on Nickel, is crucial for nitrogen processing in plants. Acting as a co-factor, Nickel empowers urease to transform urea into ammonium ions, providing plants with a usable nitrogen source. In the absence of Nickel, this urea transformation doesn't occur. Additionally, Nickel is commonly found stored in various parts of plants, especially in the leaves.

 

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