Afertilizer orfertiliser is any material of natural or synthetic origin that is applied tosoil or toplant tissues to supplyplant nutrients. Fertilizers may be distinct fromliming materials or other non-nutrientsoil amendments. Many sources of fertilizer exist, both natural andindustrially produced.[1] For most modern agricultural practices, fertilization focuses on three main macro nutrients:nitrogen (N),phosphorus (P), andpotassium (K) with occasional addition of supplements likerock flour for micronutrients. Farmers apply these fertilizers in a variety of ways: through dry orpelletized or liquid application processes, using largeagricultural equipment, orhand-tool methods.
Total fertilizer production by type.[13]World population supported with and without synthetic nitrogen fertilizers.[14]Founded in 1812,Mirat, producer ofmanures and fertilizers, is claimed to be the oldest industrial business inSalamanca (Spain).Cropland nitrogen balance by component and region[15]
Management ofsoil fertility has preoccupied farmers since the beginning of agriculture. Middle Eastern, Chinese, Mesoamerican, and Cultures of the Central Andes were all early adopters of agriculture. This is thought to have led to their cultures growing faster in population which allowed an exportation of culture to neighboring hunter-gatherer groups. Fertilizer use along with agriculture allowed some of these early societies a critical advantage over their neighbors, leading them to become dominant cultures in their respective regions.[16][17]Egyptians,Romans,Babylonians, and earlyGermans are all recorded as usingminerals ormanure to enhance theproductivity of their farms.[1] The scientific research of plant nutrition started well before the work of German chemistJustus von Liebig although his name is most mentioned as the "father of the fertilizer industry".[18]Nicolas Théodore de Saussure and scientific colleagues at the time were quick to disprove the simplifications of von Liebig. Prominent scientists whom von Liebig drew wereCarl Ludwig Sprenger andHermann Hellriegel. In this field, a 'knowledge erosion' took place,[19] partly driven by an intermingling of economics and research.[20]John Bennet Lawes, an Englishentrepreneur, began experimenting on the effects of various manures on plants growing in pots in 1837, and a year or two later the experiments were extended to crops in the field. One immediate consequence was that in 1842 he patented a manure formed by treating phosphates with sulfuric acid, and thus was the first to create the artificial manure industry. In the succeeding year, he enlisted the services ofJoseph Henry Gilbert; together they performed crop experiments at theInstitute of Arable Crops Research.[21]
TheBirkeland–Eyde process was one of the competing industrial processes at the beginning of nitrogen-based fertilizer production.[22] This process was used to fix atmosphericnitrogen (N2) intonitric acid (HNO3), one of several chemical processes callednitrogen fixation. The resultant nitric acid was then used as a source ofnitrate (NO3−). A factory based on the process was built inRjukan andNotodden in Norway and largehydroelectric power facilities were built.[23]
The 1910s and 1920s witnessed the rise of theHaber process and theOstwald process. The Haber process producesammonia (NH3) frommethane (CH4) (natural gas) andmolecular nitrogen (N2) from the air. The ammonia from the Haber process is then partially converted intonitric acid (HNO3) in theOstwald process.[24] It is estimated that a third of annual global food production uses ammonia from theHaber–Bosch process and that this supports nearly half the world's population.[25][26] After World War II, nitrogen production plants that had ramped up for wartime bomb manufacturing were pivoted towards agricultural uses.[27] The use of synthetic nitrogen fertilizers has increased steadily over the last 50 years of the 20th century, rising almost 20-fold to the current rate of 100 milliontonnes of nitrogen per year in 2003.[28]
The development of synthetic nitrogen fertilizers has significantly supported global population growth. It has been estimated that almost half the people on the Earth are currently fed due to synthetic nitrogen fertilizer use.[29] The use of phosphate fertilizers has also increased from 9 million tonnes per year in 1960 to 40 million tonnes per year in 2000, but future phosphorus fertilizer availability is now a critical issue.[30]
Agricultural use of inorganic fertilizers in 2021 was 195 million tonnes of nutrients, of which 56% was nitrogen.[31] Asia represented 53% of the world's total agricultural use of inorganic fertilizers in 2021, followed by the Americas (29%), Europe (12%), Africa (4%) and Oceania (2%). This ranking of the regions is the same for all nutrients. The main users of inorganic fertilizers are, in descending order, China, India, Brazil, and the United States of America (see Table 15), with China the largest user of each nutrient.[31]
Amaize crop yielding 6–9 tonnes of grain perhectare (2.5 acres) requires 31–50 kilograms (68–110 lb) ofphosphate fertilizer to be applied;soybean crops require about half, 20–25 kg per hectare.[32]Yara International is the world's largest producer of nitrogen-based fertilizers.[33]
Six tomato plants grown with and without nitrate fertilizer on nutrient-poor sand/clay soil. One of the plants in the nutrient-poor soil has died.Inorganic fertilizer use by region[15]
Fertilizers enhance the growth of plants. This goal is met in two ways, the traditional one being additives that providenutrients. The second mode by which some fertilizers act is to enhance the effectiveness of the soil by modifying its water-holding capacity and aeration.[34] This article, like many on fertilizers, emphasizes the nutritional aspect.
Although calcium uptake by plant roots has long-time been considered as luxury consumption,[42] it is now considered as an essential element for its various roles in the maintenance of the integrity of plantcell walls and membranes.[43]liming has also a decisive and positive influence oncrop yields by couteractingsoil acidification,[44] a side-effect ofplant growth[45] and nutrient export by crops,[46] improvingsoil structure, and thussoil aeration,[47] and increasing soil biological activity, therebysoil fertility, in particular through increasednitrification.[48]
The nutrients required for healthy plant life are classified according to the elements, but the elements are not used as fertilizers. Instead,compounds containing these elements are the basis of fertilizers. Macro-nutrients are present in plant tissue in quantities from 0.15% to 6.0% on adry matter (DM) (0% moisture) basis but they are sometimes consumed in larger quantities than required (luxury consumption), in particular when fertilizers are used in excess of plant requirements (overfertilization).[49] Plants are made up of four main elements:hydrogen,oxygen,carbon, andnitrogen. Carbon, hydrogen, and oxygen are widely available respectively incarbon dioxide and inwater. Although nitrogen makes up most of theatmosphere, it is in a form that is unavailable to plants. Nitrogen is the most important fertilizer since nitrogen is present inproteins (amide bonds betweenamino acids),DNA (puric andpyrimidic bases), and other components (e.g.,tetrapyrrolicheme inchlorophyll), but is absent from theparent rock and thus cannot be obtained frommineral weathering. To be nutritious to plants, nitrogen must be made available in a"fixed" form. Only some free-living (e.g.Clostridium) andsymbiotic bacteria living in root systems ofhost plants (notablylegumes) can fix atmospheric nitrogen (N2) by converting it toammonia (NH3).Phosphate (PO3−4) is required for the production ofDNA (genetic code) andATP, the main energy carrier incells, as well as certainlipids (phospholipids, the main components of thelipidic double layer of thecell membranes).
Fertilizers are classified in several ways. They are classified according to whether they provide a single nutrient (e.g., K, P, or N), in which case they are classified asstraight fertilizers.Multinutrient fertilizers (orcomplex fertilizers) provide two or more nutrients, for example, N and P combined. Fertilizers are also sometimes classified as inorganic (the topic of most of this article) versus organic. Inorganic fertilizers exclude carbon-containing materials excepturea. Organic fertilizers are usually (recycled) plant- or animal-derived matter (e.g.compost,manure, respectively). Inorganic are sometimes called synthetic fertilizers since various chemical treatments are required for their manufacture.[54]
The main nitrogen-based straight fertilizer isammonia (NH3),ionized in solution asammonium (NH4+), applied in the form ofsalts orderivatives, including:
Urea (CO(NH2)2), with 45-46% nitrogen, another popular source of nitrogen, having the advantage that it is solid and non-explosive, unlike ammonia and ammonium nitrate.
A mixture of single superphosphate and triple superphosphate is called double superphosphate. More than 90% of a typical superphosphate fertilizer is water-soluble.
The main potassium-based straight fertilizer ismuriate of potash (MOP, 95–99% KCl). It is typically available as 0-0-60 or 0-0-62 fertilizer.
NPK fertilizers are three-component fertilizers providing nitrogen, phosphorus, and potassium. There exist two types of NPK fertilizers: compound and blends. Compound NPK fertilizers contain chemically bound ingredients, while blended NPK fertilizers are physical mixtures of single nutrient components.
NPK rating is a rating system describing the amount of nitrogen, phosphorus, and potassium in a fertilizer. NPK ratings consist of three numbers separated by dashes (e.g., 10-10-10 or 16–4–8) describing the chemical content of fertilizers.[56] The first number represents the percentage of nitrogen in the product; the second number, P2O5; the third, K2O. Fertilizers do not actually contain P2O5 or K2O, but the system is a conventional shorthand for the amount of the phosphorus (P) or potassium (K) in a fertilizer. A 50-pound (23 kg) bag of fertilizer labeled 16-4-8 contains 8 lb (3.6 kg) of nitrogen (16% of the 50 pounds), an amount of phosphorus equivalent to that in 2 pounds of P2O5 (4% of 50 pounds), and 4 pounds of K2O (8% of 50 pounds). Most fertilizers are labeled according to this N-P-K convention, although Australian convention, following an N-P-K-S system, adds a fourth number for sulfur, and uses elemental values for all values including P and K.[57]
Micronutrients are consumed in smaller quantities and are present in plant tissue on the order ofparts-per-million (ppm), ranging from 0.15 to 400 ppm or less than 0.04% dry matter.[58][59] These elements are often required asco-enzymes forenzymes essential to the plant'smetabolism. Because these elements enablecatalysts (enzymes), their impact far exceeds theirconcentration. Typical micronutrients areboron,zinc,molybdenum,iron, andmanganese.[35] These elements are provided as water-soluble salts. Iron presents special problems because it converts from soluble (ferrous) to insoluble bio-unavailable (ferric) compounds at moderate soil pH and phosphate concentrations.[60] For this reason, iron is often administered as achelate complex, e.g., theEDTA orEDDHA derivatives. The micronutrient needs depend on the plant and the environment. For example,sugar beets appear to requireboron, andlegumes requirecobalt,[1] while environmental conditions such as heat or drought make boron less available for plants, causingboron deficiency.[61]
The production of synthetic, or inorganic, fertilizers require prepared chemicals,[62] whereas organic fertilizers are derived from thebiological processing of plant and animal remains orexcreta (e.g.urine,feces).[63]
An apatite mine for phosphates inSiilinjärvi, Finland
Phosphate fertilizers are obtained by extraction fromphosphate rock, which contains two principal phosphorus-containing minerals,fluorapatite Ca5(PO4)3F (CFA) andhydroxyapatite Ca5(PO4)3OH. Billions of kg of phosphate rock are mined annually, but the size and quality of the remaining ore is decreasing.[30] These minerals are converted into water-soluble phosphate salts by treatment withacids.[66] The large production ofsulfuric acid is primarily motivated by this application.[67] In thenitrophosphate process or Odda process (invented in 1927), phosphate rock with up to a 20% phosphorus (P) content is dissolved withnitric acid (HNO3) to produce a mixture of phosphoric acid (H3PO4) andcalcium nitrate (Ca(NO3)2). This mixture can be combined with a potassium fertilizer to produce acompound fertilizer with the three macronutrients N, P and K in easily dissolved form.[68]
Potash is a mixture of potassium minerals used to make potassium (chemical symbol: K) fertilizers. Potash is soluble in water, so the main effort in producing this nutrient from the ore involves some purification steps, e.g., to removesodium chloride (NaCl) (commonsalt).[69] Sometimes potash is referred to as K2O, as a matter of convenience to those describing the potassium content. In fact, potash fertilizers are usuallypotassium chloride,potassium sulfate,potassium carbonate, orpotassium nitrate.[70]
Compost bin for small-scale production of organic fertilizerA large commercial compost operation
Organic fertilizers can describe those fertilizers with a biological origin, i.e. derived from living or formerly living materials.Organic fertilizers can also describe commercially available and frequently packaged products that strive to follow the expectations and restrictions adopted byorganic farming andenvironmentally friendly gardening, i.e. related systems of food and plant production that significantly limit or strictly avoid the use of synthetic fertilizers andpesticides. Theorganic fertilizer products typically contain both some organic materials as well as acceptable additives such as nutritive rock powders, groundseashells (crab,oyster, etc.), other prepared products such as seed meal orkelp, and cultivatedmicroorganisms and derivatives.[71]
Fertilizers of an organic origin (the first definition) includeanimal wastes, plant wastes from agriculture,seaweed,compost, and treatedsewage sludge (biosolids). Beyond manures, animal sources can include products fromanimal slaughters:bloodmeal,bone meal,feather meal,hides,hoofs, andhorns all are typical components.[35] Organically derived materials available to industry such assewage sludge may not be acceptable components oforganic farming andgardeining, because of factors ranging from residual contaminants[72] to public perception.[73] No matter the definition nor composition, most of these products contain less-concentrated nutrients, and the nutrients are not as easily quantified.[74] They can offer soil-building advantages as well as be appealing to those who are trying to farm or garden more naturally.[75]
In terms of volume,peat is the most widely used packaged organicsoil amendment. It is an immature form ofcoal which improvessoil aeration andmoisture and thus soil biological activity but confers no direct nutritional value to the plants. It is therefore not a fertilizer as defined in the beginning of the article, but rather anamendment.[76]Coir (derived fromcoconuthusks),bark, andsawdust are mainly applied asmulch and protects the soil fromdesiccation[77] while preventing the development ofweeds[78] and improving soil structure,[79] but do not confer anynutritional value to the soil. Some organic additives can even have a reverse effect on nutrients. Fresh sawdust can consume soil nutrients as it breaks down and is colonized bywood-decay fungi, causingnitrogen deficiency (nitrogen drawdown) in the absence of nutrient addition.[80] However, this property can be used to capture excess mineral nitrogen.[81] These same organic soil texturizers (as well as compost, etc.) may increase the availability of nutrients through improvedcation-exchange capacity,[82] or through increased growth of microorganisms that in turn increase availability of certain plant nutrients.[83] True organic fertilizers such ascomposts andmanures may be distributed locally without going into industry production, making actual consumption more difficult to quantify.
Fertilizer use (2023). From FAO's World Food and Agriculture – Statistical Yearbook 2025[15]The diagram displays the statistics offertilizer consumption in western and central European countries from data published by The World Bank for 2012.
Inorganic fertilizer use per cropland area by nutrient and regionVariation in the use of fertilizers in cropland by continent, 1964–2023.
China has become the largest producer and consumer of nitrogen fertilizers[86] while Africa has little reliance on nitrogen fertilizers.[87] Agricultural and chemical minerals are very important in industrial use of fertilizers, which is valued at approximately $200 billion.[88] Nitrogen has a significant impact in the global mineral use, followed by potash and phosphate. The production of nitrogen has drastically increased since the 1960s. Phosphate and potash have increased in price since the 1960s, which is larger than the consumer price index.[88] Potash is produced in Canada, Russia and Belarus, together making up over half of the world production.[88] Potash production in Canada rose in 2017 and 2018 by 18.6%.[89][90] Conservative estimates report 30 to 50% of crop yields are attributed to natural or synthetic commercial fertilizers.[70][91] Fertilizer consumption has surpassed the amount of farmland in the United States.[88]
Data on the fertilizer consumption per hectarearable land in 2012 are published byThe World Bank.[92] The diagram below shows fertilizer consumption by theEuropean Union (EU) countries as kilograms per hectare (pounds per acre). The total consumption of fertilizer in the EU reached a peak of 11.6 million tons in 2017 but decreased steadily since that time, down to 9.3 million tons in 2023[93] for 157 million hectares arable land area in 2020, 1.5 million hectares less than in 2010.[94] This figure equates to 70 kg of fertilizers consumed per ha arable land on average by the EU countries in 2020.
Fertilizers are commonly used for growing all crops, with application rates depending onsoil fertility, usually as measured by asoil test and according to the particular crop.Legumes, for example,fix nitrogen from the atmosphere and generally do not require nitrogen fertilizer, hence their promising use for ensuring agriculture sustainability.[95]
The timing of application of fertilizers (here only mineral fertilizers will be considered) is a function of crop requirements, weather condition and market opportunities. It varies in nature and amount according to the type of agriculture (e.g.intensive farming versusconservation agriculture,grassland versusarable land), and the presence or absence of signs ofnutrient deficiencies. Timing fertilization with peak nutrient uptake demand is essential for optimizing both yield and quality. In general, nutrient uptake rates are highest from early to midgrowing season, which is why fertilization near the time of seeding is generally very effective. With fall-planted grains (e.g.winter wheat), fall N fertilization followed by springtopdressing is likely the best combination of fertilization practices to optimize yield.[96] The application of a soluble mineral fertilizer (e.g.ammonium nitrate) is avoided during heavy rainfall because most of it would be lost for the crop[97] and would rapidly pollute theaquifer.[98] Inconservation agriculture (includingno-till farming,permaculture) as well as other non-organic alternatives tointensive farming (e.g.smallholding agriculture) the application of mineral fertilizers is reduced to the strict requirements of the cultivated plants and sometimes is quite unnecessary.[99]
After harvest of a main crop (e.g.wheat,maize,potatoes) acatch crop can be sown, using plant species with a rapid growth rate and high demand of nitrogen (e.g.white mustard).[100] This allows excess nitrogen, in particular the very mobilenitrate anion, to be taken up and transformed in plantproteins[101] before contaminating thegroundwater, and the associatedgeochemical processes, which would rapidly occur in the absence of plant cover.[102] The catch crop is further buried, allowing its transformation inhumus in which nitrogen is fixed according to various stablechemical bonds.[103]
Fertilizers are applied to crops both as solids and as liquid. About 90% of fertilizers are applied as solids. The most widely used solid inorganic fertilizers areurea,diammonium phosphate andpotassium chloride.[104] Solid fertilizer is typically granulated or powdered. Often solids are available asprills, a solid globule. Liquid fertilizers comprise anhydrousammonia, aqueous solutions ofammonia, aqueous solutions ofammonium nitrate orurea. These concentrated products may be diluted with water to form a concentrated liquid fertilizer (e.g.,UAN). Advantages of liquid fertilizer are its more rapid effect and easier coverage.[35] The addition of fertilizer to irrigation water is calledfertigation.[70] Granulated fertilizers are more economical to ship and store, not to mention easier to apply.[105][106]
Acontrolled-release fertiliser (CRF) is agranulatedfertiliser that releasesnutrients gradually into thesoil (i.e., with acontrolled release period).[107] Controlled-release fertilizer is also known ascontrolled-availability fertilizer,delayed-release fertilizer,metered-release fertilizer, orslow-acting fertilizer. Usually slow- and controlled-release fertilizers refer to nitrogen-based fertilizers, e.g.ureaform, needing degradation by a wide spectrum ofsoil organisms before nitrogen could be liberated as nitrate.[108] Slow-release fertilizers (SRF) and controlled-release fertilizers (CRF) offer various benefits over conventional ones, ensuringsustainability in fertilizing practice.[109][110]
Foliar fertilizers are applied directly to leaves. They can reduce the total amounts of fertilizer applied and achieve high fertilizer efficiency.[111] This method is almost invariably used to apply water-soluble straight nitrogen fertilizers and used especially for high-value crops such as fruits. Urea is the most common foliar fertilizer.[35] However,chelation of the foliar-applied nutrient is recommended for improving absorption and migration of the targeted nutrient and thereby avoiding loss to the soil and the groundwater.[111]
N-Butylthiophosphoryltriamide, an enhanced efficiency fertilizer
Various chemicals are used to enhance the efficiency of nitrogen-based fertilizers. In this way farmers can limit thepolluting effects of nitrogen run-off.Nitrification inhibitors (also known as nitrogen stabilizers) suppress the conversion ofammonia intonitrate, an anion that is more prone to leaching. 1-Carbamoyl-3-methylpyrazole (CMP),dicyandiamide,nitrapyrin (2-chloro-6-trichloromethylpyridine) and 3,4-dimethylpyrazole phosphate (DMPP) are popular.[112]Urease inhibitors are used to slow the hydrolytic conversion of urea into ammonia catalyzed byureases, ammonia being prone to evaporation[113] as well as nitrification.[114] A popular inhibitor of ureases isN-(n-butyl)thiophosphoric triamide (NBPT).
Careful use of fertilization technologies is important because excess nutrients can be detrimental to the cultivated plant.[115]Fertilizer burn can occur when too much fertilizer is applied, resulting in damage or even death of the plant. Fertilizers vary in their tendency to burn roughly in accordance with theirsalt index.[116][117]
For each ton ofphosphoric acid produced by the processing ofphosphate rock, five tons of waste are generated. This waste takes the form of impure, useless, radioactive solid calledphosphogypsum. Estimates range from 100,000,000 and 280,000,000 tons of phosphogypsum waste produced annually worldwide.[129]
Red circles show the location and size of manydead zones
Phosphorus and nitrogen fertilizers can affect soil, surface water, and groundwater[88] due to the dispersion of minerals into waterways under high rainfall,[130][131] snowmelt and canleach intogroundwater over time.[132] Agriculturalrun-off is a major contributor to theeutrophication offreshwater bodies. For example, in the US, about half of all the lakes surveyor by theUnited States Environmental Protection Agency (US EPA) wereeutrophic in 2007 with a further alarming increase to 80 per cent in 2012.[133] The main contributor to eutrophication isphosphate, which is normally a limiting nutrient, besides nitrogen; high P concentrations promote the growth ofcyanobacteria andalgae, the demise of which consumes oxygen.[134]Cyanobacteria blooms ('algal blooms') can also produce harmfultoxins that can accumulate in thefood chain, and can be harmful to humans.[135][136] Fertilizer run-off can be reduced by using weather-optimized fertilization strategies.[130]
The nitrogen-rich compounds found infertilizer runoff are the primary cause of seriousoxygen depletion in many parts ofoceans, especially in coastal zones,lakes andrivers.[137] The resulting lack of dissolved oxygen greatly reduces the ability of these areas to sustain oceanicfauna.[138] The number of oceanicdead zones near inhabited coastlines is increasing.[139]
As of 2006, the application of nitrogen fertilizer is being increasingly controlled in northwestern Europe[140] and the United States.[141][142] In cases whereeutrophication can be reversed, it may nevertheless take decades[143] and need significant soil management[144] before the accumulated nitrates ingroundwater can be broken down by naturaldenitrification.[145]
Only a fraction of the nitrogen-based fertilizers is converted to plant matter. The remainder accumulates in the soil or is lost as run-off.[146] High application rates of nitrogen-containing fertilizers combined with the highwater solubility of nitrate leads to increasedrunoff intosurface water as well asleaching intogroundwater, thereby causinggroundwater pollution.[147][148][149] The excessive use of nitrogen-containing fertilizers (be they synthetic or natural) is particularly damaging, as much of the nitrogen that is not taken up by plants is transformed into nitrate which is easily leached.[150]
Nitrate levels above 10 mg/L (10 ppm) in groundwater can cause 'blue baby syndrome' (acquiredmethemoglobinemia).[151] The nutrients, especially nitrates, in fertilizers can cause problems for natural habitats and for human health if they are washed off intowatercourses or leached through the soil intogroundwater.[152][153] Run-off can lead to fertilizingalgal blooms that use up all the oxygen and leave huge "dead zones" behind where other fish and aquatic life can not live.[154]
Soil acidification refers to the process by which thepH level of soil becomes more acidic over time. Soil pH is a measure of the soil's acidity or alkalinity and is determined on a scale from 0 to 14, with 7 being neutral. A pH value below 7 indicatesacidic soil, while a pH value above 7 indicatesalkaline orbasic soil.
Soil acidification is a significant concern in agriculture and horticulture. It refers to the process of the soil becoming more acidic over time.
Nitrogen-containing fertilizers release ammonium or nitrate ions, which cansoil acidification as they undergobiochemical reactions.[155] When nitrogen-containing fertilizers, whether mineral or organic, are added to the soil, they increase the concentration of hydrogen ions (H+) in the soil solution, which lowers the pH of the soil.[156][157] This may lead to decrease innutrient availability which may be offset byliming.[158]
Soil acidification occurs also throughacid rain, a man-induced global concern despite severe measures to suppress or mitigate industrialgas emissions since the 1970s.[159] Among reported causes of acid rain, nitrogen fertilizers (whether mineral or organic), and the subsequent emissions ofnitrous andnitric oxides are prominent in regions of intensive agriculture.[160] The mechanisms are complex, involving ammonia volatilization from manure (whether stored or spread) or urea and direct redeposition followed bynitrification in the soil or previous oxidation tonitrogen oxides in the atmosphere before redeposition asnitric acid.[161]
The concentration ofcadmium in phosphorus-containing fertilizers varies considerably and can be problematic.[162] For example,mono-ammonium phosphate fertilizer may have a cadmium content of as low as 0.14 mg/kg or as high as 50.9 mg/kg.[163] Thephosphate rock used in their manufacture can contain as much as 188 mg/kg cadmium[164] Examples are deposits onNauru[165] and theChristmas Islands.[166] Continuous use of high-cadmium fertilizer can contaminate soils[167] andplants.[168] Limits to the cadmium content of phosphate fertilizers have been considered by theEuropean Commission.[169][170][171] Producers of phosphorus-containing fertilizers now select phosphate rock based on the cadmium content.[134]
Phosphate rocks contain high levels offluoride in the form offluorapatite.[172] Consequently, the widespread use of phosphate fertilizers has increased soil fluoride concentrations.[168] It has been found that food contamination from fertilizer is of little concern as plants accumulate little fluoride from the soil; of greater concern is the possibility of fluoride toxicity to livestock that ingest contaminated soil.[173][174] Also of possible concern are the effects of fluoride on soil microorganisms.[173][174][175]
Theradioactive content of the fertilizers varies considerably and depends both on their concentrations in the parent mineral and on the fertilizer production process.[168][176]Uranium-238 concentrations can range from 7 to 100 pCi/g (picocuries per gram) in phosphate rock[177] and from 1 to 67 pCi/g in phosphate fertilizers.[178][179][180] Where high annual rates of phosphorus fertilizer are used, this can result inuranium-238 concentrations in soils anddrainage waters that are several times greater than are normally present.[179][181] However, the impact of these increases on therisk to human health from radinuclide contamination of foods is very small (less than 0.05 mSv/y).[179][182][183]
Steel industry wastes such as steelslag are often recycled as asoil amendment or for the production of fertilizers due to their high Ca and Mg content and varioustrace elements necessary for plant growth.[184] However, they can also includetoxic metals.[185] Among them arearsenic,[186]cadmium,[186]chromium,[187] andnickel,[188] while steel slag amendment rather contribute to immobilizelead in the soil and thus to decrease its toxicity to the cultivated plant.[189] The most common toxic elements in this type of fertilizer aremercury, lead, and arsenic.[190][191][192] Given the high cost of removing potentially harmful properties from steel slags,[193] a better solution is toimmobilize them. The incorporation ofbiochar to steel slag make even the mixture a good amendement for the (passivation) ofheavy metals in agricultural soil.[194] Highly pure fertilizers are widely available and perhaps best known as the highly water-soluble fertilizers containing blue dyes used around households, such asMiracle-Gro. These highly water-soluble fertilizers are used in theplant nursery business and are available in larger packages at significantly less cost thanretail quantities. Some inexpensive retail granular garden fertilizers are made with high purity ingredients.[195]
Attention has been addressed to the decreasing concentrations ofmicronutrients such asiron,zinc,copper andmagnesium in many foods over the last 50–60 years.[196][197]Intensive farming practices, including the use of synthetic fertilizers, are frequently suggested as reasons for these declines and organic farming is often suggested as a solution.[197] Although improved crop yields resulting from NPK fertilizers are known to dilute the concentrations of other nutrients in plants,[196][198] much of the measured decline can be attributed to the use of progressively higher-yielding crop varieties that produce foods with lower mineral concentrations than their less-productive ancestors.[196][199][200] It is, therefore, unlikely thatorganic farming or reduced use of fertilizers (e.g.conservation agriculture) will solve the problem; foods with high nutrient density are posited to be achieved using older, lower-yielding varieties or the development of new high-yield, nutrient-dense varieties.[196][201]
Fertilizers are, in fact, more likely to solve trace mineral deficiency problems than cause them: in Western Australia deficiencies ofzinc,copper,manganese,iron andmolybdenum were identified as limiting the growth ofbroad-acre crops and pastures in the 1940s and 1950s.[202] Soils in Western Australia are very old, highly weathered and deficient in many of the major nutrients and trace elements.[202] Since this time these trace elements are routinely added to fertilizers used in agriculture in this state.[202] Many other soils around the world are deficient in zinc, leading to deficiency in both plants and humans,[203] and zinc fertilizers are widely used to solve this problem.[204]
High levels of fertilizer may cause the breakdown of thesymbiotic relationships between plant roots andmycorrhizal fungi,[205] in particular when in excess of plant requirements.[206] It is still debated whether and how fertilizers affectsoil animals. Both organic and organic–mineral fertilizers increase the abundance of soil fauna whereas mineral fertilizers had no such effect, withidiosyncratic responses of soil animal groups masking overall effects.[207] Chemical fertilizers stimulates the growth ofmicrobial populations but did not change their richness and diversity, while decreases inenzymatic activity have been registered.[208]
The combination ofsoil acidification and high nitrogen content was probably unknown to most soil organisms before the advent ofindustrial agriculture. More generally, soils are either acidic and nutrient-poor, or neutral to basic and nutrient-rich (nitrogen included), in relation to the pH-dependent capacity ofclay minerals to hold nutrients.[209] This unexpected combination of excess nutrient availability and acidstress causes a depletion in the sustainability of animal and microbial communities by weakening the linkages between aboveground and belowground components ofagroecosystems.[210] Otherecosystems are also affected by nitrogen-enriched acid rains originationg from intensive agricultural practices.Sphagnum bogs are now shifting fromcarbon sinks (thanks to the accumulation of recalcitrant sphagnum litter andanoxic conditions) to carbon sources under the influence of nitrogen deposition and subsequent stimulation ofdecomposer activity.[211] Other nutrient-poor ecosystems are also strongly affected, such as heathlands, with a surprising combination of highersoil organic matter accumulation and highersoil enzyme activity.[212]
Two types of agricultural management practices includeorganic farming andconventional agriculture. The former encouragessoil fertility using local resources to maximize efficiency. Organic agriculture avoids synthetic agrochemicals. Conventional agriculture uses all the components that organic agriculture does not use.[213]
Nitrogen fertilizer was used at a rate of about 110 million tons (of N) per year in 2012.[223][224]Nitrous oxide (N2O) is the third most importantgreenhouse gas aftercarbon dioxide andmethane. It has 296 times greater greenhouse effect per ton thancarbon dioxide. 2025 emissions contributed the equivalent of 700 megatons of CO2 to the atmosphere.[225] It also contributes tostratosphericozone depletion.[226] Altering processes and procedures could reduce these emissions.[227]
Methane emissions from crop fields (notably ricepaddy fields) are increased by the application of ammonium-based fertilizers. These emissions contribute to global climate change as methane is a potent greenhouse gas.[228][229]
In Europe, problems with high nitrate concentrations inrunoff are being addressed by the European Union's Nitrates Directive.[230] WithinBritain, farmers are encouraged to manage their land more sustainably in 'catchment-sensitive farming'.[231] In theUS, high concentrations of nitrate and phosphorus in runoff anddrainage water are classified as nonpoint source pollutants due to their diffuse origin; this pollution is regulated at the state level.[232]Oregon andWashington, both in theUnited States, have fertilizer registration programs with on-linedatabases listing chemical analyses of fertilizers.[233][234]Carbon emission trading andeco-tariffs affect the production and price of fertilizer.[235]
InChina,regulations have been implemented to control the use of N fertilizers in farming. In 2008, Chinese governments began to partially withdraw fertilizersubsidies, including subsidies to fertilizer transportation and to electricity and natural gas use in the industry. In consequence, the price of fertilizer has gone up and large-scale farms have begun to use less fertilizer. If large-scale farms keep reducing their use of fertilizer subsidies, they have no choice but to optimize the fertilizer they have which would therefore gain an increase in both grain yield and profit.[236]
In March 2022, theUnited States Department of Agriculture announced a new $250M grant to promote American fertilizer production. Part of theCommodity Credit Corporation, the grant program will support fertilizer production that is independent of dominant fertilizer suppliers, made in America, and utilizing innovative production techniques to jumpstart future competition.[237]
In theEuropean Union TheRusso-Ukrainian war and the subsequent strong increase in energy and mineral fertiliser prices highlighted the need for greater autonomy and efficiency in the production and use of fertilisers. The amended Temporary Crisis and Transition Framework for State Aid[238] enabled EU countries to provide specific support to farmers and fertiliser producers. Funds generated by measures such as the cap on the market revenues of certainelectricity generators and the solidarity contribution can also be used, subject to the applicable conditions, for purposes of national support schemes.[239]
^abMbow, Cheikh; Rosenzweig, Cynthia (2019)."Food security"(PDF).Climate change and land: an IPCC special report on climate change, desertification, land degradation, sustainable land management, food security, and greenhouse gas fluxes in terrestrial ecosystems. pp. 437–550. Retrieved18 December 2025.
^Uekötter, Frank (2010).Die Wahrheit ist auf dem Feld: eine Wissensgeschichte der deutschen Landwirtschaft (in German) (3rd ed.). Göttingen, Germany:Vandenhoeck & Ruprecht.ISBN978-3-5253-1705-1.
^Dumanski, Julian; Peiretti, Roberto; Benites, José R.; McGarry, Diane; Pieri, Christian (31 August 2006)."The paradigm of conservation agriculture".World Association of Soil and Water Conservation (WASWAC). Retrieved16 December 2025.
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