Knowledge base
Fertilizers
Mineral, compound, organic, and micronutrient fertilizers — their composition, the nutrients they supply, and evidence-based principles for their use.
44 entries · every entry is sourced and dated
Application rates, timing, and product choices depend on the crop, soil test, yield goal, and local regulations. Entries describe principles, not universal prescriptions.
- Fertilizer
Agricultural lime
Agricultural lime is finely ground limestone applied to raise soil pH and supply calcium, and magnesium if dolomitic, functioning primarily as a soil amendment rather than a nutrient fertilizer in the conventional sense.
- Fertilizer
Ammonium nitrate
Ammonium nitrate is a straight nitrogen fertilizer supplying nitrogen in both ammonium and nitrate forms, giving crops a portion of immediately available nitrate alongside more slowly nitrifying ammonium, with lower ammonia-volatilisation risk than urea.
- Fertilizer
Ammonium polyphosphate (APP)
Ammonium polyphosphate (APP) is a clear liquid phosphorus fertilizer that also supplies nitrogen, containing a mix of polyphosphate and orthophosphate; it is widely used as a starter fertilizer and as a carrier for metal micronutrients, which polyphosphates help keep in solution.
- Fertilizer
Ammonium sulfate
Ammonium sulfate is a nitrogen fertilizer that also supplies sulfur, making it a common choice where crops or soils are sulfur-responsive, though its ammonium content has an acidifying effect on soil over repeated use.
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Anhydrous ammonia
Anhydrous ammonia is the highest-analysis nitrogen fertilizer in common use, applied as a pressurised liquefied gas injected below the soil surface, where it converts to ammonium; it is economical per unit of nitrogen but hazardous and requires specialised equipment, training, and safety precautions.
- Fertilizer
Biochar
Biochar is a stable, carbon-rich material produced by heating organic biomass in a low-oxygen process called pyrolysis, applied to soil primarily to improve properties such as cation exchange capacity, water retention, and long-term carbon storage rather than as a direct nutrient source.
- Fertilizer
Blood meal
Blood meal is a dried, powdered animal-blood product that is one of the most concentrated organic nitrogen fertilizers, releasing nitrogen relatively quickly for an organic source and widely used in organic production to correct nitrogen deficiency.
- Fertilizer
Bone meal
Bone meal is an organic fertilizer made from ground animal bone that supplies slow-release phosphorus and calcium, along with a modest amount of nitrogen, commonly used in organic production and for perennial or bulb crops with sustained phosphorus needs.
- Fertilizer
Borax
Borax is a soluble sodium borate used as a boron fertilizer, typically supplying around 11% boron; it corrects boron deficiency in responsive crops such as oilseed rape and sugar beet, but the narrow margin between deficiency and toxicity means it must be applied carefully.
- Fertilizer
Calcium ammonium nitrate
Calcium ammonium nitrate is a granular nitrogen fertilizer made by combining ammonium nitrate with calcium carbonate, producing a product with a milder soil reaction than straight ammonium nitrate and a supplementary calcium contribution.
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Calcium nitrate
Calcium nitrate is a highly soluble fertilizer supplying nitrate-nitrogen together with a substantial readily available calcium content, widely used in fertigation and on crops where both rapid nitrogen uptake and calcium delivery to developing tissue are priorities.
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Chelated micronutrients
Chelated micronutrients are trace-element fertilizers in which a metal such as iron, zinc, manganese, or copper is bound within an organic chelating molecule, keeping the nutrient soluble and plant-available across a wider soil pH range than uncomplexed mineral salts of the same elements.
- Fertilizer
Compost
Compost is decomposed organic matter produced by controlled aerobic breakdown of plant and other biodegradable residues, valued more for its contribution to soil organic matter, structure, and biological activity than for its comparatively low and variable nutrient content.
- Fertilizer
Copper sulfate
Copper sulfate is a soluble copper salt used to correct copper deficiency, most often on peat and organic soils, and is also a component of copper-based fungicides; because copper is needed only in tiny amounts and can accumulate to toxic levels, it must be used with care.
- Fertilizer
Diammonium phosphate
Diammonium phosphate is the most widely traded phosphorus fertilizer in the world, supplying high concentrations of both phosphorus and nitrogen, with a locally alkaline reaction around the dissolving granule that briefly raises pH near the fertilizer band.
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Dolomitic lime
Dolomitic lime is a ground calcium magnesium carbonate liming material that raises soil pH while supplying both calcium and magnesium, making it the preferred lime where acid soils are also low in magnesium.
- Fertilizer
Elemental sulfur
Elemental sulfur is a high-analysis sulfur source, around 90% sulfur, that must first be oxidised by soil microorganisms to sulfate before plants can use it, a process that also acidifies soil and makes elemental sulfur a common tool for deliberately lowering soil pH.
- Fertilizer
Epsom salt
Epsom salt is highly soluble magnesium sulfate heptahydrate used to correct magnesium and sulfur deficiency, valued for its quick availability and suitability for foliar sprays, without affecting soil pH.
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Farmyard manure
Farmyard manure is a traditional organic fertilizer made from livestock excreta mixed with bedding material, supplying nutrients at low and variable concentrations while contributing substantially to soil organic matter and structure.
- Fertilizer
Feather meal
Feather meal is a slow-release organic nitrogen fertilizer made from steam-hydrolysed poultry feathers; it is high in nitrogen bound in keratin, which soil microbes break down gradually, giving a longer, more even nitrogen supply than fast-releasing organic sources.
- Fertilizer
Fish emulsion
Fish emulsion is a liquid organic fertilizer made from processed fish or fish by-products, supplying mainly nitrogen with smaller amounts of phosphorus, potassium, and micronutrients; it is fast-acting for an organic source and popular for foliar feeding and fertigation in organic and horticultural systems.
- Fertilizer
Green manure
Green manure refers to a crop grown specifically to be incorporated into the soil while still green, adding organic matter and, when the crop is a legume, biologically fixed nitrogen, rather than being harvested for grain, forage, or other direct product.
- Fertilizer
Greensand
Greensand is a naturally mined glauconite mineral used chiefly in organic and horticultural systems as a slow-release, low-analysis source of potassium and iron and as a soil conditioner, though its nutrient release is slow and modest.
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Gypsum
Gypsum is a naturally occurring or industrially recovered calcium sulfate mineral used both as a nutrient source, supplying calcium and sulfur without changing soil pH, and as a soil amendment to reclaim sodic soils and improve aggregate stability.
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Kieserite
Kieserite is a naturally occurring magnesium sulfate mineral, mined and processed into a granular fertilizer that supplies both magnesium and sulfur in a form more soluble than dolomitic limestone, without materially raising soil pH.
- Fertilizer
Langbeinite
Langbeinite is a naturally mined potassium magnesium sulfate mineral that supplies potassium, magnesium, and sulfur together in a single chloride-free product, making it useful for chloride-sensitive crops and soils that need potassium and magnesium at the same time.
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Manganese sulfate
Manganese sulfate is the most widely used manganese fertilizer, a soluble salt supplying manganese and sulfur, applied especially as a foliar spray to correct manganese deficiency on high-pH and organic soils where soil-applied manganese is quickly made unavailable.
- Fertilizer
Monoammonium phosphate
Monoammonium phosphate is a high-analysis, water-soluble phosphorus fertilizer that also supplies a modest amount of nitrogen, widely used as a starter and blending material because of its low salt index and slightly acidifying reaction near the granule.
- Fertilizer
Muriate of potash
Muriate of potash is the most widely used potassium fertilizer worldwide, supplying potassium as a highly soluble chloride salt mined from underground potash deposits, favoured for its low cost per unit of potassium but used cautiously on chloride-sensitive crops.
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NPK compound fertilizer
NPK compound fertilizers combine nitrogen, phosphorus, and potassium in a single granulated or blended product, formulated in a wide range of grades to match different crop and soil requirements in one application.
- Fertilizer
Polymer-coated urea
Polymer-coated urea is a controlled-release nitrogen fertilizer in which each urea granule is enclosed in a polymer membrane that meters nitrogen out gradually, reducing losses and often allowing a single application to feed a crop over much of its season.
- Fertilizer
Potassium nitrate
Potassium nitrate is a fully water-soluble, chloride-free fertilizer that supplies both potassium and nitrate-nitrogen, widely used in fertigation and on chloride-sensitive high-value crops where its cost premium over other potassium sources is justified.
- Fertilizer
Poultry manure
Poultry manure is an organic fertilizer derived from chicken or other poultry excreta, often mixed with bedding material as litter, supplying nitrogen, phosphorus, and potassium at concentrations that are typically higher and more variable than cattle-based manures.
- Fertilizer
Rhizobium inoculant
Rhizobium inoculant is a biofertilizer containing living nitrogen-fixing bacteria applied to legume seed or soil; rather than supplying a nutrient salt, it establishes root-nodule symbioses that fix atmospheric nitrogen into forms the legume can use.
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Rock phosphate
Rock phosphate is finely ground, naturally occurring phosphate mineral applied directly as a slow-release phosphorus source, most effective on acid soils where its low water solubility gradually dissolves, and it is also the raw material processed into most manufactured phosphate fertilizers.
- Fertilizer
Seaweed extract
Seaweed extract is a low-nutrient-analysis input derived from marine algae, applied as a foliar spray or soil drench primarily for its content of natural plant-growth compounds rather than as a meaningful source of nitrogen, phosphorus, or potassium.
- Fertilizer
Single superphosphate
Single superphosphate is a lower-analysis phosphorus fertilizer made by treating phosphate rock with sulfuric acid, valued for supplying phosphorus, calcium, and sulfur together, particularly on legume and other sulfur-responsive crops.
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Struvite
Struvite is a magnesium ammonium phosphate mineral that can be recovered from wastewater treatment or livestock manure processing and used as a slow-release phosphorus and nitrogen fertilizer, notable as a nutrient-recovery product within a circular approach to phosphorus supply.
- Fertilizer
Sulfate of potash
Sulfate of potash is a chloride-free potassium fertilizer that also supplies sulfur, favoured on chloride-sensitive crops and where fruit or leaf quality is a priority, though it typically costs more per unit of potassium than muriate of potash.
- Fertilizer
Triple superphosphate
Triple superphosphate is a concentrated, straight phosphorus fertilizer made by treating phosphate rock with phosphoric acid, valued for its high phosphorus content, water solubility, and useful calcium contribution, without added nitrogen or potassium.
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Urea
Urea is the most widely used solid nitrogen fertilizer worldwide, valued for its high nitrogen concentration and relatively low cost per unit of nitrogen, though it is prone to ammonia volatilisation losses if left unincorporated on the soil surface.
- Fertilizer
Urea ammonium nitrate (UAN)
Urea ammonium nitrate (UAN) is a clear liquid nitrogen fertilizer made by dissolving urea and ammonium nitrate in water, supplying nitrogen simultaneously in nitrate, ammonium, and amide forms, and widely used where liquid handling, fertigation, or in-crop application is preferred.
- Fertilizer
Vermicompost
Vermicompost is organic matter processed by earthworms into a finely textured, biologically active material, typically with somewhat more readily available nutrients and a richer microbial community than conventional thermophilic compost.
- Fertilizer
Zinc sulfate
Zinc sulfate is the most widely used zinc fertilizer, a water-soluble salt that also supplies sulfur, applied to soil or as a foliar spray to correct zinc deficiency in crops such as maize, rice, and citrus.