Best Nutrients For Hydroponics

Becoming a Michelin star chef has never been easier.

You plants know what they like, and it’s your job to cook up a feast.  Thankfully all you need to do is mix the right macro and micronutrients and you’re set.  Without these elements, your plant can’t sustain its full lifecycle.

You don’t even need to turn the gas on.

best Nutrients for hydroponics 

But what do your plants want?  They’re easy to cater for but, admittedly, are fussy.

Each species has specific requirements for optimal growth, so it’s important to find these out first. Macronutrients are elements in the diet which are needed in larger amounts.  They form the basis of proteins and carbohydrates, etc. Some macronutrients are absorbed from the air, we’ve spoken about them in previous articles. These include oxygen, carbon, and hydrogen. However, primary macronutrients including nitrogen, phosphorus, potassium, and secondary macronutrients are sulfur, calcium, and magnesium are absorbed through the root system.

Carbon, nitrogen, oxygen, and hydrogen represent 95% a plant’s dry-weight biomass.

Primary nutrients for plant growth

Nitrogen 

Nitrogen is important for amino acid formation and an essential chlorophyll component, without it there’s limited, slow growth with a purple colouration to stems. It's supplied as a nutrient in the form of a salt, either as a fixed nitrate, such as calcium nitrate, or an ammonium salt. Uptake of the ammonium salt is rapid but the tolerance the plant has before toxicity issues arise is much lower than than nitrates. Ammonium salts can be present in 30 ppm compared to nitrates at 250 ppm. In soil, ammonium salts are converted into nitrates via bacteria, which the plants then absorb through their roots. Hydroponic growing doesn’t accommodate bacteria so no conversion occurs.  Thus, it’s difficult to supply hydroponically grown crops with ammonium salts in a safe manner.

Not having enough nitrogen is a common problem, however, other deficiencies can mask it.  For example, calcium is necessary for the absorption of nitrogen and, if calcium levels are low, symptoms will point to a lack of nitrogen.

Phosphorus

Phosphorus plays an important role in the structural integrity of plants and catalyses various reactions, including photosynthetic reactions. Forming the backbone to nucleic acids and binding lipids to create the main component in cell membranes, phosphorus does it all. As if that wasn’t enough, it releases many small bursts of energy when adenosine triphosphate becomes adenosine diphosphate, powering all other biochemical reaction along the way. 

Deficiency isn’t easy to diagnose.  Other than some stunted growth in the early growth phase there aren’t any obvious symptoms until it’s likely too late for some crops. Phosphorus is translocated to areas of the plant which demand the most energy in times of crisis.  Seed development can be affected even if the deficiency occurs late on in the plant’s life.

Good news though, phosphorus comes in water soluble forms.

Be advised, calcium and phosphorus can’t be stored in the same bottles because their reaction creates an insoluble product called calcium phosphate. This precipitates out, making it inert and unusable.  Hydroponic nutrients often come in separated bottles for this reason.

Potassium

Potassium is needed in all areas of plant development other than metabolism and is more important within the leaves. It’s essential in forming carbohydrates and proteins, moisture control, and catalysing enzymatic reactions. Moreover, fruit colouring, shaping, and brix (the sugar content in aqueous solution) use potassium ions and is the reason potassium-rich growing media produces excellent fruits.

Luxury consumption is the term used to describe the absorption of excess potassium ions from growing media beyond optimal concentrations. There haven't been any reports of negative consequences from this process, though. Potassium deficiency may first show symptoms in older tissue which progresses to growing points at the base of the plant. In corn, potassium deficiency causes a striping effect in the leaf which can be mistaken for magnesium, zinc, or sulfur deficiencies. The symptoms begin at the lower leaves and spread to the top of the canopy as the plant develops over time.  In some species, brown scorching occurs and leaf tips start to curl, chlorosis is apparent between the veins, and purple spots appear on the underside.

Secondary Macronutrients for plant growth

Sulphur

Certain amino acids, vitamins, and hormones contain sulfur. In fact, approximately 90% of sulfur function in plant cells is attributed to amino acid formation.  It’s also needed to synthesise chloroplasts used in photosynthesis during the electron transport chain. Sulfur is typically added to hydroponic systems as magnesium sulfate which dissociates into its constituent ions in solution.  

Sulfur deficiency symptoms are a uniform light green to yellow colouring across the whole plant, however, older leaves seem to be most affected.  Growth in sulfur-deficient plants is stunted and stems start to shift to a harder, woodier version of themselves. In natural environments, sulfur toxicity is usually acquired through air pollution and acid rain production. This is clearly less likely to happen in your closed hydroponics system, just don't add three times the recommended concentrations from the nutrient bottle and you'll be all good. 

Absorption of sulfate ions are easier for the plant when the pH level is low, you can lower the media with saltpetre, or citric acid. You can also use sulfur-containing foliar sprays on the vegetation for added absorption. Note though, sulfur deficiencies aren't likely in hydroponics systems and it may be more prudent to check for other issues first. 

Adding inorganic sulfur to a magnesium fertiliser is the best cure.  Epsom salts work for hydroponics.

Calcium

Calcium is a constituent in plant cell walls and, if concentrations are low, abnormal growth of new tissue is seen.  Calcium activates certain enzymes within the cell too and without it, the enzymes cannot catalyse the reactions of their substrates.

Transport of calcium through the plant is dependent upon the rate of transpiration, so, if transpiration is slowed by external factors calcium deficiency can arise, even when the nutrient is in plentiful supply within the growing medium. The areas of the plant which aren’t responsible for maintaining the majority of transpiration, such as the fruit, are first to suffer from the effects of calcium deficiency.

Magnesium

The chlorophyll molecule is a complex framework of proteins and other biomolecules and the magnesium atom is the focal point for all of this and drives photosynthesis. Furthermore, a lot of enzymes within plants require magnesium to function correctly, the majority are necessary growth and protein synthesis.

When a plant is low on magnesium the leaves start to yellow and produce green veins - referred to as interveinal chlorosis. The pH of the nutrient solution make much of a difference to the plant’s capacity to absorb magnesium, although pH increase makes it more available. Toxic concentrations of magnesium, potassium, and calcium cause absorption competition between one another and result in the deficiencies of the losing nutrients. 

Micronutrients for plant growth

Iron

Although iron isn’t a structural component of chlorophyll, it's necessary for chlorophyll’s synthesis. Similarly to mammals, iron is responsible for the transport of oxygen throughout plants. It’s also persent in certain enzymes such as cytochromes of the electron transport chain. Iron's role is widespread. There are two oxidation states for iron, Fe2+ and Fe3+ which vary in their solubility in water, Fe 2+ is oxidised to Fe 3+ in the presence of oxygen and becomes insoluble. The ions of heavy metals such as iron, zinc, and copper can't be transported across the cell membrane in their raw form. Biological chelates are produced by the plant which bind the metal ions to form structures called ionophores, iron-specific ionophores are termed siderophores.

Leaf chlorosis, where the leaf turns yellow, occurs with iron deficiency. Symptoms will begin at the tips of younger growth which can eventually turn white and travel to older tissues, browning the veins in the process.

Molybdenum

Like many micronutrients, molybdenum is a cofactor for enzymes.  Specifically, these enzymes help construct amino acids and metabolise nitrogen.

Regarding nitrogen metabolism, molybdenum is a constituent in the enzymes nitrogen reductase and nitrogenase.  The former is necessary in nitrogen reduction and the latter in biological nitrogen fixation.

Boron

Boron’s really important for plants and yet, mercilessly, is the least abundant in natural settings.

Used in the formation of the cell wall, low levels of boron results in subpar growth, especially in faster propagating tissue.  Moreover, it’s critically important during reproduction.

Copper

Lignin synthesis, as well as other processes, use enzymes activated by copper.  Photosynthesis and respiration rely on the element too, alongside protein and carbohydrate metabolism.

Cupping and chlorosis of the leaves may occur, with necrotic spots appearing, specifically on the edges.  Newly grown leaves are smaller and lose their sheen, some could wilt.

Too much potassium, phosphorus or additional micronutrients can cause an unintentional copper deficiency.

Zinc

The enzymes which zinc activates are involved in protein synthesis, chlorophyll generation, and the extraction of sugar from starch. Cold weather damage is mitigated to some degree by sufficient zinc concentrations, too.

Nutrient products for hydroponics

You can prepare your nutrient solution from either powdered or liquid forms for your hydroponic setup.

The liquid formulations are the pre-dissolved nutrient salts in water, they’re more popular and easier to handle.  This does make them more expensive, however, you’re paying for your confidence in the correct concentrations and not having to work anything out.  All you need to do is measure out what you need and you’re good to go.

As your plants mature they’ll need an ever-evolving mix of nutrients in differing ratios.  Liquid nutrient solutions usually come with a pH buffer too, maintaining the pH within a certain threshold so less adjustment is necessary.

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Have you seen our other Articles on hydroponics?

The Basics Of Hydroponics  |  The Kratky Method  |  Types Of Hydroponics  |  Deep Water Culture  |  The Drip System  |  The Wick System  |  Lighting In Hydroponics  |  The Ebb And Flow System  |  Nutrient Film Technique  |  Nutrients For Plant Growth  |  Ventilation For Hydroponics  |  Growing Media Used In Hydroponics Hydroponics  |  The Best Way To Cure Root Rot  | How To Choose A Grow Tent | The Best LED Grow Lights | Everything You Need To Know About Nutrient Lockout | The Best Air Pumps For Hydroponics | The Best PH Meters For Hydroponics | What Mom Never Told You About The GH Dual Diaphragm Air Pump |

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