Plants require specific nutrients to survive and develop properly. These are called essential nutrients because (1) plants cannot complete their lifecycle without them; (2) they perform specific functions that no other nutrient can replace; and (3) they are directly involved in the plant’s metabolic or structural processes.[1]
In addition to the three non-mineral essential nutrients—hydrogen, oxygen and carbon—plants require 14 essential mineral nutrients. These are categorized as primary macronutrients, secondary macronutrients or micronutrients, depending on the amount needed (e.g., micronutrients are required in smaller amounts than macronutrients).[2]
Since hydroponic systems lack soil, growers must supply all the essential mineral nutrients through fertilizers. In this blog post, we’ll explain how plants absorb nutrients, the roles of each essential nutrient in plant health and development, the different types of fertilizers available and additional substances that support plant growth.
How plants absorb nutrients
Plants primarily absorb carbon and oxygen from the atmosphere but take in oxygen and hydrogen from water. Water dissociates into H+ and OH– ions, making them available for root uptake. Plants also absorb dissolved mineral nutrients through their roots by three processes:
- Ion absorption: Plants absorb nutrients as simple inorganic ions, which are either cations (positively charged) or anions (negatively charged).
- Mass flow: Nutrients move to the root surface with water uptake during transpiration.
- Transport pathway: Ions travel through several plant cells and tissues to the xylem, where they are transported to shoots.
Most fertilizers dissolve readily in water, making nutrients immediately available to plants.
Plants primarily absorb carbon and oxygen from the atmosphere but take in oxygen and hydrogen from water. Water dissociates into H+ and OH– ions, making them available for root uptake. Plants also absorb dissolved mineral nutrients through their roots by three processes:
- Ion absorption: Plants absorb nutrients as simple inorganic ions, which are either cations (positively charged) or anions (negatively charged).
- Mass flow: Nutrients move to the root surface with water uptake during transpiration.
- Transport pathway: Ions travel through several plant cells and tissues to the xylem, where they are transported to shoots.
Most fertilizers dissolve readily in water, making nutrients immediately available to plants.
Essential nutrients and their roles
Each essential nutrient plays a distinct role in plant development that is vital to their survival. Below are the 14 mineral nutrients plants require, along with their key functions. The ionic forms included are the forms that plants can absorb.
Primary macronutrients
- Helps create amino acids, known as the building blocks of proteins.
- Supports structural development and physiological functions.
- Serves as a vital component of several vitamins.
- Aids in cell division.
- Is required for all the enzymatic reactions in a plant.
- Plays a key role in photosynthesis as a structural component of chlorophyll.
- Contributes to the transcription, translation and replication of genetic information, as it is a component of nucleotides and the nucleic acids deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
Phosphorus, ionic forms H2PO4− and HPO4 2−:[5]
Phosphorus, ionic forms H2PO4− and HPO4 2−:[5]
- Transfers energy via the pyrophosphate bond in ATP,[6] which maintains electrochemical gradients across membranes and provides metabolic energy for photosynthesis and respiration.
- Serves as a structural component of nucleic acids, phospholipids and certain amino acids.
- Contributes to genetic information as part of RNA and DNA structures.
- Supports root, seed and fruit development and plays a role in flower initiation.
- Is required in large quantities in young, rapidly dividing cells with high metabolic activity, such as shoots and root tips.
Potassium, ionic form K+:[7]
Potassium, ionic form K+:[7]
- Regulates water use by controlling the opening and closing of stomata.
- Enhances the translocation of photosynthates (sugars) for growth or storage in fruits or roots.
- Improves disease resistance, seed and grain size and the quality of fruits and vegetables.
- Influences cell extension and plant growth.
- Facilitates long-distance nutrient transport through pressure-driven flow.
- Helps establish electrochemical gradients across membranes, aiding the membrane transport of various chemicals.
Secondary macronutrients
- Regulates nutrient transport.
- Supports enzyme functions.
- Stabilizes cell membrane structure.
- Fortifies cell walls by forming stable but reversible linkages with pectins, increasing resistance to drought, damage and stress.
- Strengthens plant tissues.
- Contributes to normal root system development.
- Boosts nutrient uptake.
- Activates enzymes, induces water movement and salt balance in plant cells, and uses potassium to control the opening and closing of stomata.
- Plays a significant role in photosynthesis as a major component of chlorophyll.
- Helps activate the phosphorylation processes that regulate cell protein function.
- Facilitates sugar transport.
- Enhances disease resistance.
- Forms plant proteins as a constituent of specific amino acids and stabilizes protein structure.
- Influences enzymes that regulate redox[17] and acid-base reactions.
- Is part of certain amino acids, such as cysteine and methionine, and is present in several coenzymes.
- Supports photosynthesis as part of the electron transport chain.
- Aids in seed production, chlorophyll formation, nodule formation in legumes and protein stabilization.
- Interacts with other essential nutrients that benefit crops.
- Improves nitrogen fixation.
- Boosts plant growth and yield.
Micronutrients
- Supports biosynthesis of cell walls and membrane integrity.
- Aids in synthesizing RNA bases and regulating cellular activity.
- Promotes root growth.
- Plays a crucial role in pollen germination and pollen tube growth.
- Facilitates carbohydrate transport.
- Enhances nitrogen fixation and assimilation.
- Transports proteins, metabolizes cell walls, transfers respiration and photosynthesis electrons and transduces hormone signals.
- Functions as a carrier molecule in chloroplasts and mitochondria.
- Contributes to antioxidant systems, respiration and ethylene sensing.
- Plays an important role in plant respiratory and photosynthetic reactions.
- Supports chlorophyll synthesis and maintenance.
- Contributes to protein metabolism.
- Functions as a component of many vital enzymes.
- Aids in cellular respiration, the tricarboxylic acid (TCA) cycle and DNA biosynthesis.
- Assists with sulphate and nitrate reduction.
- Facilitates oxygen transport.
- Serves as a catalyst and cofactor in cellular redox reactions.
- Activates several metabolic functions, including respiration.
- Supports oxidation-reduction processes in photosynthesis.
- Protects plants against oxidative stress.
- Aids in biogenesis of chlorophyll, amino acid (tyrosine) and several other secondary metabolites such as flavonoids and lignin.
Molybdenum, ionic form MoO4:[27]
Molybdenum, ionic form MoO4:[27]
- Plays a role in nitrogen assimilation as an essential component of the enzymes nitrate reductase and nitrogenase.
- Reduces nitrates into plant-usable forms.
- Functions as the metal component in urease, the enzyme that catalyzes the conversion of urea to ammonium.
- Exists in multiple oxidation states, allowing it to participate in redox reactions.
- Assists with seed germination.
- Supports internode elongation and hormone production.
- Aids in tryptophan synthesis, which is crucial for indole acetic acid (a phytohormone).
- Contributes to various plant metabolism functions.
- Plays a key role in RNA and protein synthesis.
- Promotes carbohydrate metabolism, auxin metabolism and pollen formation.
- Helps form chlorophyll.
- Regulates carbonic anhydrase for carbon fixation in plants.
Beneficial nutrients
While not among the 14 essential nutrients, cobalt, selenium, silicon and sodium provide benefits to plants. Fertilizer regulators classify these as “non-plant-food ingredients,” but plants absorb them just like essential nutrients, and they play roles in plant nutrition.[35]
Selecting a fertilizer
Fertilizers are available in dry and liquid formulations, with nutrients derived from either organic or inorganic sources. The choice of fertilizer depends on the hydroponic system, as well as the grower’s goals and preferences.
Fertilizer form: dry or liquid
- Dry fertilizers come in granules or powders and must be dissolved into a plant-available liquid form for use in hydroponic systems.
- Liquid fertilizers are supplied as concentrated solutions, typically diluted before application and added directly to the hydroponic system.
The following table highlights important differences between the two:
Fertilizer form: dry or liquid
- Dry fertilizers come in granules or powders and must be dissolved into a plant-available liquid form for use in hydroponic systems.
- Liquid fertilizers are supplied as concentrated solutions, typically diluted before application and added directly to the hydroponic system.
The following table highlights important differences between the two:
- Dry fertilizers come in granules or powders and must be dissolved into a plant-available liquid form for use in hydroponic systems.
- Liquid fertilizers are supplied as concentrated solutions, typically diluted before application and added directly to the hydroponic system.
The following section highlights important differences between the two:
Dry Fertilizers
Characteristics:
Granular or solid
Consistency/distribution:
Inconsistent (different nutrients in different granules
Ionic form absorbed:
Some nutrients (e.g., phosphorus) locked in granules until accessed by roots
Salt content:
Potentially high, can be “hot”
Amount of nutrient supply:
No difference in total nutrients supplied
Plant response:
Less control for growers and longer to break down
Liquid fertilizers
Characteristics:
Liquid concentrates
Consistency/distribution:
Consistent nutrient distribution throughout the liquid solution
Ionic form absorbed:
Nutrients more mobile and readily available
Salt content:
Lower and more root friendly
Amount of nutrient supply:
No difference in total nutrients supplied
Plant response:
Readily available with immediate results
Characteristics
Dry fertilizers
Liquid fertilizers
Available form
Granular or solid
Liquid concentrates
Consistency/distribution
Inconsistent (different nutrients in different granules)
Consistent nutrient distribution throughout the liquid solution
Ionic form absorbed
Some nutrients (e.g., phosphorus) locked in granules until accessed by roots
Nutrients more mobile and readily available
Salt content
Potentially high, can be “hot”
Lower and more root friendly
Amount of nutrient supply
No difference in total nutrients supplied
No difference in total nutrients supplied
Plant response
Less control for growers and longer to break down
Readily available with immediate results
While both forms have advantages and limitations, the choice between dry and liquid fertilizers depends on crop requirements, application methods and grower preferences.
Fertilizer source: organic or inorganic
Growers also need to consider the source of a fertilizer’s nutrients, as there are some crucial differences between organic and inorganic sources, especially in terms of nutrient amounts and availability.
Organic fertilizer
Organic fertilizers contain one or more essential plant nutrients along with carbon, hydrogen and oxygen. Their nutrient content comes from natural sources, such as:
- Animals: manure, guano, worm castings or other animal byproducts
- Plants: compost, kelp, alfalfa
Organic fertilizers release nutrients slowly, providing long-term fertility while being environmentally friendly. However, their nutrient composition can vary, and they may not be immediately available to plants. They are primarily used in outdoor cultivation, where they improve soil health by enhancing structure, water retention and microbial activity.
Organic fertilizer
Organic fertilizers contain one or more essential plant nutrients along with carbon, hydrogen and oxygen. Their nutrient content comes from natural sources, such as:
- Animals: manure, guano, worm castings or other animal byproducts
- Plants: compost, kelp, alfalfa
Organic fertilizers release nutrients slowly, providing long-term fertility while being environmentally friendly. However, their nutrient composition can vary, and they may not be immediately available to plants. They are primarily used in outdoor cultivation, where they improve soil health by enhancing structure, water retention and microbial activity.
Inorganic fertilizer
Inorganic fertilizers also contain essential plant nutrients, but carbon is not an essential component of their chemical structure. Their nutrients are sourced from:
- Chemicals, manufactured industrially through chemical reactions.
- Minerals, derived from natural materials like rock or mineral salts, then purified for plant absorption. Despite coming from natural sources, these fertilizers are not permitted in certified organic farming due to extensive processing.
- Synthetic compounds, usually byproducts of the petroleum industry.
Inorganic fertilizer
Inorganic fertilizers also contain essential plant nutrients, but carbon is not an essential component of their chemical structure. Their nutrients are sourced from:
Inorganic fertilizer
Inorganic fertilizers also contain essential plant nutrients, but carbon is not an essential component of their chemical structure. Their nutrients are sourced from:
- Chemicals, manufactured industrially through chemical reactions.
- Minerals, derived from natural materials like rock or mineral salts, then purified for plant absorption. Despite coming from natural sources, these fertilizers are not permitted in certified organic farming due to extensive processing.
- Synthetic compounds, usually byproducts of the petroleum industry.
Unlike organic fertilizers, which retain their natural forms with minimal processing, inorganic fertilizers undergo refinement to produce purified, readily absorbable nutrients. This allows for fast, efficient nutrient delivery and precise nutrient formulation, making them ideal for hydroponic systems.
However, a balanced approach that integrates both organic and inorganic fertilizers can help optimize soilless cannabis cultivation. For more information on the differences between organic and inorganic fertilizers, check out our white paper Plants Can’t Tell the Difference.
Supplements to boost growth
While essential nutrients—as their name implies—are vital for growing a healthy plant, high-value crops like cannabis also benefit from tailored supplements incorporated into the feeding program, especially in indoor cultivation. These supplements increase yield and quality, making them crucial components of cannabis production.
Supplements to consider include the following:
- Amino acids to support protein synthesis, stress tolerance and overall plant health.
- Chelators to facilitate nutrient uptake by preventing nutrient precipitation and enhancing availability.
- Humic substances to increase plant height, chlorophyll content and photosynthetic efficiency.
- Plant growth hormones to promote growth and development by enhancing cell division, elongation and differentiation.
- Plant growth-promoting rhizobacteria to introduce beneficial microorganisms that improve nutrient uptake and stress tolerance.
- Plant growth regulators like triacontanol to stimulate photosynthesis, nutrient uptake and overall growth performance.
Conclusion
Plants cannot reach their full potential in terms of growth, yield and quality without essential nutrients. In hydroponic systems, they can only access essential nutrients through fertilizers. To ensure plants receive the right nutrient balance, growers must understand not only the different macro and micronutrient requirements, but also the various fertilizer forms and sources available.
Emerald Harvest Team
All element icon images credit goes to Freepik
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[2] Goldy, Ron. 2013. “Knowing Nutrient Mobility is Helpful in Diagnosing Plant Nutrient Deficiencies.” Published November 13. https://www.canr.msu.edu/news/knowing_nutrient_mobility_is_helpful_in_diagnosing_plant_nutrient_deficienc
[3] Uchida, R. 2000. “Essential Nutrients for Plant Growth: Nutrient Functions and Deficiency Symptoms.” In Plant Nutrient Management in Hawaii’s Soils, Approaches for Tropical and Subtropical Agriculture, edited by J.A. Silva and R. Uchida. University of Hawaii at Manoa. https://www.ctahr.hawaii.edu/oc/freepubs/pdf/pnm3.pdf.
[4] Grusak, Michael A. 2001. “Plant Macro- and Micronutrient Minerals.” In Encyclopedia of Life Sciences. Nature Publishing Group. https://doi.org/10.1038/npg.els.0001306.
[5] See footnotes 3 and 4.
[6] Adenosine triphosphate, “the energy currency of life”.
[7] See footnotes 3 and 4.
[8] LibreTexts Biology. n.d. “31.1C: Essential Nutrients for Plants.” Accessed January 17, 2025.
[9] Thor, Kathrin. 2019. “Calcium—Nutrient and Messenger.” Frontiers in Plant Science 10: 440. https://doi.org/10.3389/fpls.2019.00440.
[10] Weng, Xiaohang, Hui Li, Chengshuai Ren, et. al. 2022. “Calcium Regulates Growth and Nutrient Absorption in Poplar Seedlings.” Frontiers in Plant Science 13: 887098. https://doi.org/10.3389/fpls.2022.887098.
[11] Tripathi, Durgesh Kumar, Vijay Pratap Sing, Devendra Kumar Chuahan, Sheo Mohan Prasad, and Nawal Kishor Dubey. 2014. “Role of Macronutrients in Plant Growth and Acclimation: Recent Advances and Future Prospective.” In Improvement of Crops in the Era of Climatic Changes, edited by P. Ahmad, M. Wani, M. Azooz, and L.S. Phan Tran. Springer. https://doi.org/10.1007/978-1-4614-8824-8_8.
[12] See footnote 3.
[13] Huber, Don M., and Jeff B. Jones. 2012. “The Role of Magnesium in Plant Disease.” Plant and Soil 368: 73-85. https://doi.org/10.1007/s11104-012-1476-0.
[14] See footnotes, 3, 4, 8 and 10.
[15] Siegl, Alina, Leila Afjehi-Sadat, and Stefanie Wienkoop. 2024. “Systemic Long-Distance Sulfur Transport and its Role in Symbiotic Root Nodule Protein Turnover.” Journal of Plant Physiology 297: 154260. https://doi.org/10.1016/j.jpplph.2024.154260.
[16] Narayan, Om Prakash, Paras Kumar, Bindu Yadav, Meenakshi Dua, and Atul Kumar Johri. 2022. “Sulfur Nutrition and its Role in Plant Growth and Development.” Plant Signaling & Behavior 18 (1): 2030082. https://doi.org/10.1080/15592324.2022.2030082.
[17] Reduction-oxidation.
[18] See footnotes 3, 4 and 8.
[19] Vera Maldonado, Peter, Felipe Aquea, Marjorie Reyes-Diaz, et. al. 2024. “Role of Boron and Its Intersection with Other Elements in Plants.” Frontiers in Plant Science 15: 1332459. https://doi.org/10.3389/fpls.2024.1332459.
[20] Chen, Guang, Jia Li, Huimin Han, Ruiyang Du, and Xu Wang. 2022. “Physiological and Molecular Mechanisms of Plant Responses to Copper Stress.” International Journal of Molecular Sciences 23 (21): 12950. https://doi.org/10.3390/ijms232112950.
[21] Xu, Ending, Yuanyuan Liu, Dongfang Gu, et. al.2024. “Molecular Mechanism of Plant Responses to Copper: From Deficiency to Excess.” International Journal of Molecular Sciences 25 (13): 6993. https://doi.org/10.3390/ijms25136993.
[22] See footnotes 3 and 8.
[23] Rout, Gyana R, and Sunita Sahoo. 2015. “Role of Iron in Plant Growth and Metabolism.” Reviews in Agricultural Science 3: 1-24. https://doi.org/10.7831/ras.3.1.
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[25] See footnote 3.
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[27] See footnotes 3 and 8.
[28] Carter, Eric L., Nicholas Flugga, Jodi L. Boer, Scott B. Mulrooney, and Robert P. Hausinger. 2009. “Interplay of Metal Ions and Urease.” Metallomics 1 (3): 207-221. https://doi.org/10.1039/b903311d.
[29] Ghosh, Suptish, Debabrata Bagchi, Indranil Mondal, Tobias Sontheimer, Rajenahally V. Jagadeesh, Prashanth W. Menezes. 2024. “Deciphering the Role of Nickel in Electrochemical Organic Oxidation Reactions.” Advanced Energy Materials 14 (22): 2400696. https://doi.org/10.1002/aenm.202400696.
[30] Genchi, Giuseppe, Alessia Carocci, Graziantonio Lauria, Maria Stefania Sinicropi, and Alessia Catalano. 2020. “Nickel: Human Health and Environmental Toxicology.” International Journal of Environmental Research and Public Health 17 (3): 679. https://doi.org/10.3390/ijerph17030679.
[31] Note that Ni is not included in fertilizer formulations, as it is required in such minute quantities, even by micronutrient standards, that it is almost impossible for a plant to suffer an Ni deficiency. Ni deficiencies can typically be induced only in controlled lab conditions.
[32] See footnotes 3 and 8.
[33] A., Suganya, A. Saravanan, and N. Manivannan. 2020. “Role of Zinc Nutrition for Increasing Zinc Availability, Uptake, Yield, and Quality of Maize (Zea Mays L.) Grains: An Overview.” Communications in Soil Science and Plant Analysis 51 (15): 2001–21. https://doi.org/10.1080/00103624.2020.1820030.
[34] McCauley, Ann, Clain Jones, and Jeff Jacobsen. 2011. “Plant Nutrient Functions and Deficiency and Toxicity Symptoms.” Last updated June 2011. https://apps.msuextension.org/publications/pub.html?sku=4449-9.
[35] Pilon-Smits, Elizabeth A. H., Colin F. Quinn, Wiebke Tapken, Mario Malagoli, and Michela Schiavon. 2009. “Physiological Functions of Beneficial Elements.” Current Opinion in Plant Biology 12 (3): 267-274. https://doi.org/10.1016/j.pbi.2009.04.009.
