text:
Fertilizer

A fertilizer (American English) or fertiliser (British English) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from liming materials or other non-nutrient soil amendments. Many sources of fertilizer exist, both natural and industrially produced. For most modern agricultural practices, fertilization focuses on three main macro nutrients: nitrogen (N), phosphorus (P), and potassium (K) with occasional addition of supplements like rock flour for micronutrients. Farmers apply these fertilizers in a variety of ways: through dry or pelletized or liquid application processes, using large agricultural equipment or hand-tool methods.

Historically fertilization came from natural or organic sources: compost, animal manure, human manure, harvested minerals, crop rotations and byproducts of human-nature industries (i.e. fish processing waste, or bloodmeal from animal slaughter). However, starting in the 19th century, after innovations in plant nutrition, an agricultural industry developed around synthetically created fertilizers. This transition was important in transforming the global food system, allowing for larger-scale industrial agriculture with large crop yields.

Nitrogen-fixing chemical processes, such as the Haber process invented at the beginning of the 20th century, and amplified by production capacity created during World War II, led to a boom in using nitrogen fertilizers. In the latter half of the 20th century, increased use of nitrogen fertilizers (800% increase between 1961 and 2019) has been a crucial component of the increased productivity of conventional food systems (more than 30% per capita) as part of the so-called "Green Revolution".

The use of artificial and industrially-applied fertilizers has caused environmental consequences such as water pollution and eutrophication due to nutritional runoff; carbon and other emissions from fertilizer production and mining; and contamination and pollution of soil. Various sustainable-agriculture practices can be implemented to reduce the adverse environmental effects of fertilizer and pesticide use as well as other environmental damage caused by industrial agriculture.

History
Management of soil 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 (P Bellwood - 2023 ) . Egyptians, Romans, Babylonians, and early Germans are all recorded as using minerals or manure to enhance the productivity of their farms. The scientific research of plant nutrition started well before the work of German chemist Justus von Liebig although his name is most mentioned as the "father of the fertilizer industry". Nicolas Théodore de Saussure and scientific colleagues at the time were quick to disprove the simplifications of von Liebig. Prominent scientists on whom von Liebig drew were Carl Ludwig Sprenger and Hermann Hellriegel. In this field, a 'knowledge erosion' took place, partly driven by an intermingling of economics and research. John Bennet Lawes, an English entrepreneur, began to experiment 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 of Joseph Henry Gilbert; together they performed crop experiments at the Institute of Arable Crops Research.

The Birkeland–Eyde process was one of the competing industrial processes in the beginning of nitrogen-based fertilizer production. This process was used to fix atmospheric nitrogen (N2) into nitric acid (HNO3), one of several chemical processes generally referred to as nitrogen fixation. The resultant nitric acid was then used as a source of nitrate (NO3−). A factory based on the process was built in Rjukan and Notodden in Norway, combined with the building of large hydroelectric power facilities.

The 1910s and 1920s witnessed the rise of the Haber process and the Ostwald process. The Haber process produces ammonia (NH3) from methane (CH4) (natural gas) gas and molecular nitrogen (N2) from the air. The ammonia from the Haber process is then partially converted into nitric acid (HNO3) in the Ostwald process. It is estimated that a third of annual global food production uses ammonia from the Haber–Bosch process, and that this supports nearly half the world's population. After World War II, nitrogen production plants that had ramped up for wartime bomb manufacturing were pivoted towards agriculture uses. The use of synthetic nitrogen fertilizers has increased steadily over the last 50 years, rising almost 20-fold to the current rate of 100 million tonnes of nitrogen per year.

The development of synthetic nitrogen fertilizer has significantly supported global population growth. It has been estimated that almost half the people on the Earth are currently fed as a result of synthetic nitrogen fertilizer use. The use of phosphate fertilizers has also increased from 9 million tonnes per year in 1960 to 40 million tonnes per year in 2000.

Agricultural use of inorganic fertilizers in 2021 was 195 million tonnes of nutrients, of which 56% was nitrogen. Asia represented 53% of world 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.

A maize crop yielding 6–9 tonnes of grain per hectare (1 ha) requires 31 – of phosphate fertilizer to be applied; soybean crops require about half, 20–25 kg per hectare. Yara International is the world's largest producer of nitrogen-based fertilizers.

Mechanism
Fertilizers enhance the growth of plants. This goal is met in two ways, the traditional one being additives that provide nutrients. The second mode by which some fertilizers act is to enhance the effectiveness of the soil by modifying its water retention and aeration. This article, like many on fertilizers, emphasizes the nutritional aspect. Fertilizers typically provide, in varying proportions:
 * three main macronutrients (NPK):
 * Nitrogen (N): leaf growth and stems
 * Phosphorus (P): development of roots, flowers, seeds, fruit;
 * Potassium (K): strong stem growth, movement of water in plants, promotion of flowering and fruiting;
 * three secondary macronutrients: calcium (Ca), magnesium (Mg), and sulfur (S);
 * micronutrients: copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), zinc (Zn), boron (B). Of occasional significance are silicon (Si), cobalt (Co), and vanadium (V).

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. The macro-nutrients are consumed in larger quantities and are present in plant tissue in quantities from 0.15% to 6.0% on a dry matter (DM) (0% moisture) basis. Plants are made up of four main elements: hydrogen, oxygen, carbon, and nitrogen. Carbon, hydrogen and oxygen are widely available respectively in carbon dioxide and in water. Although nitrogen makes up most of the atmosphere, it is in a form that is unavailable to plants. Nitrogen is the most important fertilizer since nitrogen is present in proteins (amide bond between amino-acids), DNA (puric and pyrimidic bases) and other components (e.g., tetrapyrrolic heme in chlorophyll). To be nutritious to plants, nitrogen must be made available in a "fixed" form. Only some bacteria and their host plants (notably legumes) can fix atmospheric nitrogen (N2) by converting it to ammonia (NH3). Phosphate (PO4(3-)) is required for the production of DNA (genetic code) and ATP, the main energy carrier in cells, as well as certain lipids (phospholipids, the main components of the lipidic double layer of the cell membranes).

Microbiological considerations
Two sets of enzymatic reactions are highly relevant to the efficiency of nitrogen-based fertilizers. The first is the hydrolysis (reaction with water) of urea (CO(NH2)2). Many soil bacteria possess the enzyme urease, which catalyzes the conversion of urea to ammonium ion (NH4+) and bicarbonate ion (HCO3-). Ammonia-oxidizing bacteria (AOB), such as species of Nitrosomonas, oxidize ammonia (NH3) to nitrite (NO2-), a process termed nitrification. Nitrite-oxidizing bacteria, especially Nitrobacter, oxidize nitrite (NO2-) to nitrate (NO3-), which is extremely soluble and mobile and is a major cause of eutrophication and algal bloom.
 * Urease
 * Ammonia oxidation

Classification
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 as "straight fertilizers". "Multinutrient fertilizers" (or "complex fertilizers") provide two or more nutrients, for example N and P. Fertilizers are also sometimes classified as inorganic (the topic of most of this article) versus organic. Inorganic fertilizers exclude carbon-containing materials except ureas. Organic fertilizers are usually (recycled) plant- or animal-derived matter. Inorganic are sometimes called synthetic fertilizers since various chemical treatments are required for their manufacture.

Single nutrient ("straight") fertilizers
The main nitrogen-based straight fertilizer is ammonia (NH3) ammonium (NH4+) or its solutions, including:
 * Ammonium nitrate (NH4NO3) with 34-35% nitrogen is also widely used.
 * 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.
 * Calcium ammonium nitrate Is a blend of 20-30% limestone CaCO3 or dolomite (Ca,Mg)CO3 and 70-80% ammonium nitrate with 24-28 % nitrogen.
 * Calcium nitrate with 15,5% nitrogen and 19% calcium, reportedly holding a small share of the nitrogen fertilizer market (4% in 2007).

The main straight phosphate fertilizers are the superphosphates:
 * "Single superphosphate" (SSP) consisting of 14–18% P2O5, again in the form of Ca(H2PO4)2, but also phosphogypsum (CaSO4 * 2 H2O).
 * Triple superphosphate (TSP) typically consists of 44–48% of P2O5 and no gypsum.

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 is muriate of potash (MOP, 95–99% KCl). It is typically available as 0-0-60 or 0-0-62 fertilizer.

Multinutrient fertilizers
These fertilizers are common. They consist of two or more nutrient components.

Major two-component fertilizers provide both nitrogen and phosphorus to the plants. These are called NP fertilizers. The main NP fertilizers are About 85% of MAP and DAP fertilizers are soluble in water.
 * Binary (NP, NK, PK) fertilizers
 * monoammonium phosphate (MAP) NH4H2PO4. With 11% nitrogen and 48% P2O5.
 * diammonium phosphate (DAP). (NH4)2HPO4. With 18% nitrogen and 46% P2O5

 * NPK fertilizers

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. 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 lb bag of fertilizer labeled 16-4-8 contains 8 lb 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.

Micronutrients
Micronutrients are consumed in smaller quantities and are present in plant tissue on the order of parts-per-million (ppm), ranging from 0.15 to 400 ppm or less than 0.04% dry matter. These elements are often required for enzymes essential to the plant's metabolism. Because these elements enable catalysts (enzymes), their impact far exceeds their weight%age. Typical micronutrients are boron, zinc, molybdenum, iron, and manganese. These elements are provided as water-soluble salts. Iron presents special problems because it converts to insoluble (bio-unavailable) compounds at moderate soil pH and phosphate concentrations. For this reason, iron is often administered as a chelate complex, e.g., the EDTA or EDDHA derivatives. The micronutrient needs depend on the plant and the environment. For example, sugar beets appear to require boron, and legumes require cobalt, while environmental conditions such as heat or drought make boron less available for plants.

Production
The production of synthetic, or inorganic, fertilizers requires prepared chemicals, whereas organic fertilizers are derived from the organic processes of plants and animals in biological processes using biochemicals.

Nitrogen fertilizers
Nitrogen fertilizers are made from ammonia (NH3) produced by the Haber–Bosch process. In this energy-intensive process, natural gas (CH4) usually supplies the hydrogen, and the nitrogen (N2) is derived from the air. This ammonia is used as a feedstock for all other nitrogen fertilizers, such as anhydrous ammonium nitrate (NH4NO3) and urea (CO(NH2)2).

Deposits of sodium nitrate (NaNO3) (Chilean saltpeter) are also found in the Atacama desert in Chile and was one of the original (1830) nitrogen-rich fertilizers used. It is still mined for fertilizer. Nitrates are also produced from ammonia by the Ostwald process.

Phosphate fertilizers
Phosphate fertilizers are obtained by extraction from phosphate rock, which contains two principal phosphorus-containing minerals, fluorapatite Ca5(PO4)3F (CFA) and hydroxyapatite Ca5(PO4)3OH. Billions of kg of phosphate rock are mined annually, but the size and quality of the remaining ore is decreasing. These minerals are converted into water-soluble phosphate salts by treatment with acids. The large production of sulfuric acid is primarily motivated by this application. In the nitrophosphate process or Odda process (invented in 1927), phosphate rock with up to a 20% phosphorus (P) content is dissolved with nitric acid (HNO3) to produce a mixture of phosphoric acid (H3PO4) and calcium nitrate (Ca(NO3)2). This mixture can be combined with a potassium fertilizer to produce a compound fertilizer with the three macronutrients N, P and K in easily dissolved form.

Potassium fertilizers
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 remove sodium chloride (NaCl) (common salt). Sometimes potash is referred to as K2O, as a matter of convenience to those describing the potassium content. In fact, potash fertilizers are usually potassium chloride, potassium sulfate, potassium carbonate, or potassium nitrate.

NPK fertilizers
There are three major routes for manufacturing NPK fertilizers (named for their main ingredients: nitrogen (N), phosphorus (P), and potassium (K)):
 * 1) bulk blending. The individual fertilizers are combined in the desired nutrient ratio.
 * 2) The wet process is based on chemical reactions between liquid raw materials  phosphoric acid, sulfuric acid, ammonia) and solid raw materials (such as potassium chloride.
 * The Nitrophosphate Process. Step 1. Nitrophosphates are made by acidiculating phosphate rock with nitric acid.
 * Nitric acid + Phosphate rock → Phosphoric acid + Calcium sulphate + hexafluorosilicic acid.
 * Ca5F(PO4)3 + 10 HNO3 →6 H3PO4 + 5 Ca(NO3)2 + HF
 * 6 HF + SiO2 →H2SiF6 + 2 H2O

Step 2. Removal of Calcium Nitrate. It is important to remove the calcium nitrate because calcium nitrate is extremely hygroscopic.
 * Method 1.(Odda process) Calcium nitrate crystals are removed by centrifugation.
 * Method 2. Sulfonitric Process Ca(NO3)2 + H2SO4 + 2NH3 → CaSO4 + 2NH4NO3
 * Method 3.Phosphonitric Process Ca(NO3)2 + H3PO4 + 2NH3 → CaHPO4 + 2NH4NO3
 * Method 4.Carbonitric Process Ca(NO3)2 + CO2 + H2O + 2NH3 → CaCO3 + 2NH4NO3

Organic fertilizers

"Organic fertilizers" can describe those fertilizers with a biologic origin—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 by "organic agriculture" and "environmentally friendly" gardening – related systems of food and plant production that significantly limit or strictly avoid the use of synthetic fertilizers and pesticides. The "organic fertilizer" products typically contain both some organic materials as well as acceptable additives such as nutritive rock powders, ground sea shells (crab, oyster, etc.), other prepared products such as seed meal or kelp, and cultivated microorganisms and derivatives.

Fertilizers of an organic origin (the first definition) include animal wastes, plant wastes from agriculture, seaweed, compost, and treated sewage sludge (biosolids). Beyond manures, animal sources can include products from the slaughter of animals – bloodmeal, bone meal, feather meal, hides, hoofs, and horns all are typical components. Organically derived materials available to industry such as sewage sludge may not be acceptable components of organic farming and gardening, because of factors ranging from residual contaminants to public perception. On the other hand, marketed "organic fertilizers" may include, and promote, processed organics because the materials have consumer appeal. No matter the definition nor composition, most of these products contain less-concentrated nutrients, and the nutrients are not as easily quantified. They can offer soil-building advantages as well as be appealing to those who are trying to farm / garden more "naturally".

In terms of volume, peat is the most widely used packaged organic soil amendment. It is an immature form of coal and improves the soil by aeration and absorbing water but confers no nutritional value to the plants. It is therefore not a fertilizer as defined in the beginning of the article, but rather an amendment. Coir, (derived from coconut husks), bark, and sawdust when added to soil all act similarly (but not identically) to peat and are also considered organic soil amendments – or texturizers – because of their limited nutritive inputs. Some organic additives can have a reverse effect on nutrients – fresh sawdust can consume soil nutrients as it breaks down, and may lower soil pH – but these same organic texturizers (as well as compost, etc.) may increase the availability of nutrients through improved cation exchange, or through increased growth of microorganisms that in turn increase availability of certain plant nutrients. Organic fertilizers such as composts and manures may be distributed locally without going into industry production, making actual consumption more difficult to quantify.

Statistics
China has become the largest producer and consumer of nitrogen fertilizers while Africa has little reliance on nitrogen fertilizers. Agricultural and chemical minerals are very important in industrial use of fertilizers, which is valued at approximately $200 billion. 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. Potash is produced in Canada, Russia and Belarus, together making up over half of the world production. Potash production in Canada rose in 2017 and 2018 by 18.6%. Conservative estimates report 30 to 50% of crop yields are attributed to natural or synthetic commercial fertilizers. Fertilizer consumption has surpassed the amount of farmland in the United States.

Data on the fertilizer consumption per hectare arable land in 2012 are published by The World Bank. The diagram below shows fertilizer consumption by the European Union (EU) countries as kilograms per hectare (pounds per acre). The total consumption of fertilizer in the EU is 15.9 million tons for 105 million hectare arable land area (or 107 million hectare arable land according to another estimate ). This figure equates to 151 kg of fertilizers consumed per ha arable land on average by the EU countries.

Application
Fertilizers are commonly used for growing all crops, with application rates depending on the soil fertility, usually as measured by a soil test and according to the particular crop. Legumes, for example, fix nitrogen from the atmosphere and generally do not require nitrogen fertilizer.

Liquid vs solid
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 are urea, diammonium phosphate and potassium chloride. Solid fertilizer is typically granulated or powdered. Often solids are available as prills, a solid globule. Liquid fertilizers comprise anhydrous ammonia, aqueous solutions of ammonia, aqueous solutions of ammonium nitrate or urea. 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. The addition of fertilizer to irrigation water is called "fertigation".

Urea
Urea is highly soluble in water and is therefore also very suitable for use in fertilizer solutions (in combination with ammonium nitrate: UAN), e.g., in 'foliar feed' fertilizers. For fertilizer use, granules are preferred over prills because of their narrower particle size distribution, which is an advantage for mechanical application.

Urea is usually spread at rates of between 40 and 300 kg/ha (35 to 270 lbs/acre) but rates vary. Smaller applications incur lower losses due to leaching. During summer, urea is often spread just before or during rain to minimize losses from volatilization (a process wherein nitrogen is lost to the atmosphere as ammonia gas).

Because of the high nitrogen concentration in urea, it is very important to achieve an even spread. Drilling must not occur on contact with or close to seed, due to the risk of germination damage. Urea dissolves in water for application as a spray or through irrigation systems.

In grain and cotton crops, urea is often applied at the time of the last cultivation before planting. In high rainfall areas and on sandy soils (where nitrogen can be lost through leaching) and where good in-season rainfall is expected, urea can be side- or top-dressed during the growing season. Top-dressing is also popular on pasture and forage crops. In cultivating sugarcane, urea is side-dressed after planting, and applied to each ratoon crop.

Because it absorbs moisture from the atmosphere, urea is often stored in closed containers.

Overdose or placing urea near seed is harmful.

Foliar application
Foliar fertilizers are applied directly to leaves. 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.

Chemicals that affect nitrogen uptake
Various chemicals are used to enhance the efficiency of nitrogen-based fertilizers. In this way farmers can limit the polluting effects of nitrogen run-off. Nitrification inhibitors (also known as nitrogen stabilizers) suppress the conversion of ammonia into nitrate, 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. Urease inhibitors are used to slow the hydrolytic conversion of urea into ammonia, which is prone to evaporation as well as nitrification. The conversion of urea to ammonia catalyzed by enzymes called ureases. A popular inhibitor of ureases is N-(n-butyl)thiophosphoric triamide (NBPT).

Overfertilization
Careful use of fertilization technologies is important because excess nutrients can be detrimental. 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 their salt index.

Environmental effects
Synthetic fertilizer used in agriculture has wide-reaching environmental consequences.

According to the Intergovernmental Panel on Climate Change (IPCC) Special Report on Climate Change and Land, production of these fertilizers and associated land use practices are drivers of global warming. The use of fertilizer has also led to a number of direct environmental consequences: agricultural runoff which leads to downstream effects like ocean dead zones and waterway contamination, soil microbiome degradation, and accumulation of toxins in ecosystems. Indirect environmental impacts include: the environmental impacts of fracking for natural gas used in the Haber process, the agricultural boom is partially responsible for the rapid growth in human population and large-scale industrial agricultural practices are associated with habitat destruction, pressure on biodiversity and agricultural soil loss.

In order to mitigate environmental and food security concerns, the international community has included food systems in Sustainable Development Goal 2 which focuses on creating a climate-friendly and sustainable food production system. Most policy and regulatory approaches to address these issues focus on pivoting agricultural practices towards sustainable or regenerative agricultural practices: these use less synthetic fertilizers, better soil management (for example no-till agriculture) and more organic fertilizers.

For each ton of phosphoric acid produced by the processing of phosphate rock, five tons of waste are generated. This waste takes the form of impure, useless, radioactive solid called phosphogypsum. Estimates range from 100,000,000 and 280,000,000 tons of phosphogypsum waste produced annually worldwide.

Water
Phosphorus and nitrogen fertilizers can affect soil, surface water, and groundwater due to the dispersion of minerals into waterways due to high rainfall, snowmelt and can leaching into groundwater over time. Agricultural run-off is a major contributor to the eutrophication of fresh water bodies. For example, in the US, about half of all the lakes are eutrophic. The main contributor to eutrophication is phosphate, which is normally a limiting nutrient; high concentrations promote the growth of cyanobacteria and algae, the demise of which consumes oxygen. Cyanobacteria blooms ('algal blooms') can also produce harmful toxins that can accumulate in the food chain, and can be harmful to humans. Fertilizer run-off can be reduced by using weather-optimized fertilization strategies.

The nitrogen-rich compounds found in fertilizer runoff are the primary cause of serious oxygen depletion in many parts of oceans, especially in coastal zones, lakes and rivers. The resulting lack of dissolved oxygen greatly reduces the ability of these areas to sustain oceanic fauna. The number of oceanic dead zones near inhabited coastlines is increasing.

As of 2006, the application of nitrogen fertilizer is being increasingly controlled in northwestern Europe and the United States. In cases where eutrophication can be reversed, it may nevertheless take decades and significant soil management before the accumulated nitrates in groundwater can be broken down by natural processes.

Nitrate pollution
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. High application rates of nitrogen-containing fertilizers combined with the high water solubility of nitrate leads to increased runoff into surface water as well as leaching into groundwater, thereby causing groundwater pollution. 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.

Nitrate levels above 10 mg/L (10 ppm) in groundwater can cause 'blue baby syndrome' (acquired methemoglobinemia). The nutrients, especially nitrates, in fertilizers can cause problems for natural habitats and for human health if they are washed off soil into watercourses or leached through soil into groundwater. Run-off can lead to fertilizing blooms of algae that use up all the oxygen and leave huge "dead zones" behind where other fish and aquatic life can not live.

Acidification
Soil acidification refers to the process by which the pH 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 indicates acidic soil, while a pH value above 7 indicates alkaline or basic 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 can cause soil acidification when added. This may lead to decrease in nutrient availability which may be offset by liming. These fertilizers release ammonium or nitrate ions, which can acidify the soil as they undergo chemical reactions.

When these nitrogen-containing fertilizers are added to the soil, they increase the concentration of hydrogen ions (H+) in the soil solution, which lowers the pH of the soil.

Cadmium
The concentration of cadmium in phosphorus-containing fertilizers varies considerably and can be problematic. 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. The phosphate rock used in their manufacture can contain as much as 188 mg/kg cadmium (examples are deposits on Nauru and the Christmas islands ). Continuous use of high-cadmium fertilizer can contaminate soil (as shown in New Zealand) and plants. Limits to the cadmium content of phosphate fertilizers has been considered by the European Commission. Producers of phosphorus-containing fertilizers now select phosphate rock based on the cadmium content.

Fluoride
Phosphate rocks contain high levels of fluoride. Consequently, the widespread use of phosphate fertilizers has increased soil fluoride concentrations. 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 soils. Also of possible concern are the effects of fluoride on soil microorganisms.

Radioactive elements
The radioactive content of the fertilizers varies considerably and depends both on their concentrations in the parent mineral and on the fertilizer production process. Uranium-238 concentrations can range from 7 to 100 pCi/g (picocuries per gram) in phosphate rock and from 1 to 67 pCi/g in phosphate fertilizers. Where high annual rates of phosphorus fertilizer are used, this can result in uranium-238 concentrations in soils and drainage waters that are several times greater than are normally present. However, the impact of these increases on the risk to human health from radinuclide contamination of foods is very small (less than 0.05 mSv/y).

Other metals
Steel industry wastes, recycled into fertilizers for their high levels of zinc (essential to plant growth), wastes can include the following toxic metals: lead arsenic, cadmium, chromium, and nickel. The most common toxic elements in this type of fertilizer are mercury, lead, and arsenic. These potentially harmful impurities can be removed; however, this significantly increases cost. Highly pure fertilizers are widely available and perhaps best known as the highly water-soluble fertilizers containing blue dyes used around households, such as Miracle-Gro. These highly water-soluble fertilizers are used in the plant nursery business and are available in larger packages at significantly less cost than retail quantities. Some inexpensive retail granular garden fertilizers are made with high purity ingredients.

Trace mineral depletion
Attention has been addressed to the decreasing concentrations of elements such as iron, zinc, copper and magnesium in many foods over the last 50–60 years. 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. Although improved crop yields resulting from NPK fertilizers are known to dilute the concentrations of other nutrients in plants, 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. It is, therefore, unlikely that organic farming or reduced use of fertilizers 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.

Fertilizers are, in fact, more likely to solve trace mineral deficiency problems than cause them: In Western Australia deficiencies of zinc, copper, manganese, iron and molybdenum were identified as limiting the growth of broad-acre crops and pastures in the 1940s and 1950s. Soils in Western Australia are very old, highly weathered and deficient in many of the major nutrients and trace elements. Since this time these trace elements are routinely added to fertilizers used in agriculture in this state. Many other soils around the world are deficient in zinc, leading to deficiency in both plants and humans, and zinc fertilizers are widely used to solve this problem.

Changes in soil biology
High levels of fertilizer may cause the breakdown of the symbiotic relationships between plant roots and mycorrhizal fungi.

Hydrogen consumption and sustainability
Most fertilizer is made from dirty hydrogen. Ammonia is produced from natural gas and air. The cost of natural gas makes up about 90% of the cost of producing ammonia. The increase in price of natural gases over the past decade, along with other factors such as increasing demand, have contributed to an increase in fertilizer price.

Contribution to climate change
The amount of greenhouse gases carbon dioxide, methane and nitrous oxide produced during the manufacture and use of nitrogen fertilizer is estimated as around 5% of anthropogenic greenhouse gas emissions. One third is produced during the production and two thirds during the use of fertilizers. Nitrogen fertilizer can be converted by soil bacteria to nitrous oxide, a greenhouse gas. Nitrous oxide emissions by humans, most of which are from fertilizer, between 2007 and 2016 have been estimated at 7 million tonnes per year, which is incompatible with limiting global warming to below 2 °C.

Atmosphere
Through the increasing use of nitrogen fertilizer, which was used at a rate of about 110 million tons (of N) per year in 2012, adding to the already existing amount of reactive nitrogen, nitrous oxide (N2O) has become the third most important greenhouse gas after carbon dioxide and methane. It has a global warming potential 296 times larger than an equal mass of carbon dioxide and it also contributes to stratospheric ozone depletion. By changing processes and procedures, it is possible to mitigate some, but not all, of these effects on anthropogenic climate change.

Methane emissions from crop fields (notably rice paddy fields) are increased by the application of ammonium-based fertilizers. These emissions contribute to global climate change as methane is a potent greenhouse gas.

Regulation
In Europe, problems with high nitrate concentrations in runoff are being addressed by the European Union's Nitrates Directive. Within Britain, farmers are encouraged to manage their land more sustainably in 'catchment-sensitive farming'. In the US, high concentrations of nitrate and phosphorus in runoff and drainage water are classified as nonpoint source pollutants due to their diffuse origin; this pollution is regulated at the state level. Oregon and Washington, both in the United States, have fertilizer registration programs with on-line databases listing chemical analyses of fertilizers.

In China, regulations have been implemented to control the use of N fertilizers in farming. In 2008, Chinese governments began to partially withdraw fertilizer subsidies, 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.

In March 2022, the United States Department of Agriculture announced a new $250M grant to promote American fertilizer production. Part of the Commodity 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.

Two types of agricultural management practices include organic agriculture and conventional agriculture. The former encourages soil fertility using local resources to maximize efficiency. Organic agriculture avoids synthetic agrochemicals. Conventional agriculture uses all the components that organic agriculture does not use.

title: Fertilizer


text:
Chicken

The chicken (Gallus domesticus) is a large and round short-winged bird, domesticated from the red junglefowl of Southeast Asia around 8,000 years ago. Most chickens are raised for food, providing meat and eggs; others are kept as pets or for cockfighting.

Chickens are common and widespread domestic animals, with a total population of 23.7 billion, and an annual production of more than 50 billion birds. A hen bred for laying can produce over 300 eggs per year. There are numerous cultural references to chickens in folklore, religion, and literature.

Nomenclature
Terms for chickens include:

 * Biddy: a chicken, or a newly hatched chicken
 * Capon: a castrated or neutered male chicken
 * Chick: a young chicken
 * Chook : a chicken (Australia/New Zealand, informal)
 * Cock: a fertile adult male chicken
 * Cockerel: a young male chicken
 * Hen: an adult female chicken
 * Pullet: a young female chicken less than a year old. In the poultry industry, a pullet is a sexually immature chicken less than 22 weeks of age.
 * Rooster: a fertile adult male chicken, especially in North America. Originated in the 18th century, possibly as a euphemism to avoid the sexual connotation of the word cock.
 * Yardbird: a chicken (southern United States, dialectal)

Chicken can mean a chick, as in William Shakespeare's play Macbeth, where Macduff laments the death of "all my pretty chickens and their dam". The usage is preserved in placenames such as the Hen and Chicken Islands. In older sources, and still often in trade and scientific contexts, chickens as a species are described as common fowl or domestic fowl.

Description
Chickens are relatively large birds, active by day. The body is round, the legs are unfeathered in most breeds, and the wings are short. Wild junglefowl can fly; chickens and their flight muscles are too heavy to allow them to fly more than a short distance. Size and coloration vary widely between breeds. Adult chickens of both sexes have a fleshy crest on their heads called a comb or cockscomb, and hanging flaps of skin on either side under their beaks called wattles; combs and wattles are more prominent in males. Some breeds have a mutation that causes extra feathering under the face, giving the appearance of a beard.

Chickens are omnivores. In the wild, they scratch at the soil to search for seeds, insects, and animals as large as lizards, small snakes, and young mice. A chicken may live for 5–10 years, depending on the breed. The world's oldest known chicken lived for 16 years.

Chickens are gregarious, living in flocks, and incubate eggs and raise young communally. Individual chickens dominate others, establishing a pecking order; dominant individuals take priority for access to food and nest sites. The concept of dominance, involving pecking, was described in female chickens by Thorleif Schjelderup-Ebbe in 1921 as the "pecking order". Male chickens tend to leap and use their claws in conflicts. Chickens are capable of mobbing and killing a weak or inexperienced predator, such as a young fox.

A male's crowing is a loud and sometimes shrill call, serving as a territorial signal to other males, and in response to sudden disturbances within their surroundings. Hens cluck loudly after laying an egg and to call their chicks. Chickens give different warning calls to indicate that a predator is approaching from the air or on the ground.

Reproduction and life-cycle
To initiate courting, some roosters may dance in a circle around or near a hen (a circle dance), often lowering the wing which is closest to the hen. The dance triggers a response in the hen and when she responds to his call, the rooster may mount the hen and proceed with the mating. Mating typically involves a sequence in which the male approaches the female and performs a waltzing display. If the female is unreceptive, she runs off; otherwise, she crouches, and the male mounts, treading with both feet on her back. After copulation the male does a tail-bending display.

Sperm transfer occurs by cloacal contact between the male and female, in an action called the 'cloacal kiss'. As with all birds, reproduction is controlled by a neuroendocrine system, the Gonadotropin-Releasing Hormone-I neurons in the hypothalamus. Reproductive hormones including estrogen, progesterone, and gonadotropins (luteinizing hormone and follicle-stimulating hormone) initiate and maintain sexual maturation changes. Reproduction declines with age, thought to be due to a decline in GnRH-I-N.

Hens often try to lay in nests that already contain eggs and sometimes move eggs from neighbouring nests into their own. A flock thus uses only a few preferred locations, rather than having a different nest for every bird. Under natural conditions, most birds lay only until a clutch is complete; they then incubate all the eggs. This is called "going broody". The hen sits on the nest, fluffing up or pecking defensively if disturbed. She rarely leaves the nest until the eggs have hatched.

Eggs of chickens from the high-altitude region of Tibet have special physiological adaptations that result in a higher hatching rate in low oxygen environments. When eggs are placed in a hypoxic environment, chicken embryos from these populations express much more hemoglobin than embryos from other chicken populations. This hemoglobin has a greater affinity for oxygen, binding oxygen more readily.

Fertile chicken eggs hatch at the end of the incubation period, about 21 days; the chick uses its egg tooth to break out of the shell. Hens remain on the nest for about two days after the first chick hatches; during this time the newly hatched chicks feed by absorbing the internal yolk sac. The hen guards her chicks and brood them to keep them warm. She leads them to food and water and calls them towards food. The chicks imprint on the hen and subsequently follow her continually. She continues to care for them until they are several weeks old.

Inbreeding of White Leghorn chickens tends to cause inbreeding depression expressed as reduced egg number and delayed sexual maturity. Strongly inbred Langshan chickens display obvious inbreeding depression in reproduction, particularly for traits such as age when the first egg is laid and egg number.

Phylogeny

Water or ground-dwelling fowl similar to modern partridges, in the Galliformes, the order of bird that chickens belong to, survived the Cretaceous–Paleogene extinction event that killed all tree-dwelling birds and their dinosaur relatives. Chickens are descended primarily from the red junglefowl (Gallus gallus) and are scientifically classified as the same species. Domesticated chickens freely interbreed with populations of red junglefowl. The domestic chicken has subsequently hybridised with grey junglefowl, Sri Lankan junglefowl and green junglefowl; a gene for yellow skin, for instance, was incorporated into domestic birds from the grey junglefowl (G. sonneratii). It is estimated that chickens share between 71 and 79% of their genome with red junglefowl.

Domestication

According to one early study, a single domestication event of the red junglefowl in present-day Thailand gave rise to the modern chicken with minor transitions separating the modern breeds. The red junglefowl is well adapted to take advantage of the vast quantities of seed produced during the end of the multi-decade bamboo seeding cycle, to boost its own reproduction. In domesticating the chicken, humans took advantage of the red junglefowl's ability to reproduce prolifically when exposed to a surge in its food supply.

Exactly when and where the chicken was domesticated remains controversial. Genomic studies estimate that the chicken was domesticated 8,000 years ago in Southeast Asia and spread to China and India 2,000 to 3,000 years later. Archaeological evidence supports domestic chickens in Southeast Asia well before 6000 BC, China by 6000 BC and India by 2000 BC. A landmark 2020 Nature study that fully sequenced 863 chickens across the world suggests that all domestic chickens originate from a single domestication event of red junglefowl whose present-day distribution is predominantly in southwestern China, northern Thailand and Myanmar. These domesticated chickens spread across Southeast and South Asia where they interbred with local wild species of junglefowl, forming genetically and geographically distinct groups. Analysis of the most popular commercial breed shows that the White Leghorn breed possesses a mosaic of divergent ancestries inherited from subspecies of red junglefowl.

Austronesia

A word for the domestic chicken (*manuk) is part of the reconstructed Proto-Austronesian language, indicating they were domesticated by the Austronesian peoples since ancient times. Chickens, together with dogs and pigs, were carried throughout the entire range of the prehistoric Austronesian maritime migrations to Island Southeast Asia, Micronesia, Island Melanesia, Polynesia, and Madagascar, starting from at least 3000 BC from Taiwan. These chickens might have been introduced during pre-Columbian times to South America via Polynesian seafarers, but evidence for this is still putative.

Americas
The possibility that domestic chickens were in the Americas before Western contact is debated by researchers, but blue-egged chickens, found only in the Americas and Asia, suggest an Asian origin for early American chickens. A lack of data from Thailand, Russia, the Indian subcontinent, Southeast Asia and Sub-Saharan Africa makes it difficult to lay out a clear map of the spread of chickens in these areas; better description and genetic analysis of local breeds threatened by extinction may also help with research into this area. Chicken bones from the Arauco Peninsula in south-central Chile were radiocarbon dated as pre-Columbian, and DNA analysis suggested they were related to prehistoric populations in Polynesia. However, further study of the same bones cast doubt on the findings.

Eurasia
Chicken remains have been difficult to date, given the small and fragile bird bones; this may account for discrepancies in dates given by different sources. Archaeological evidence is supplemented by mentions in historical texts from the last few centuries BC, and by depictions in prehistoric artworks, such as across Central Asia. Chickens were widespread throughout southern Central Asia by the 4th century BC.

Middle Eastern chicken remains go back to a little earlier than 2000 BC in Syria. Phoenicians spread chickens along the Mediterranean coasts as far as Iberia. During the Hellenistic period (4th–2nd centuries BC), in the southern Levant, chickens began to be widely domesticated for food. The first pictures of chickens in Europe are found on Corinthian pottery of the 7th century BC.

Breeding increased under the Roman Empire and reduced in the Middle Ages. Genetic sequencing of chicken bones from archaeological sites in Europe revealed that in the High Middle Ages chickens became less aggressive and began to lay eggs earlier in the breeding season.

Africa
Chickens reached Egypt via the Middle East for purposes of cockfighting about 1400 BC and became widely bred in Egypt around 300 BC. Three possible routes of introduction into Africa around the early first millennium AD could have been through the Egyptian Nile Valley, the East Africa Roman-Greek or Indian trade, or from Carthage and the Berbers, across the Sahara. The earliest known remains are from Mali, Nubia, East Coast, and South Africa and date back to the middle of the first millennium AD.

Diseases

Chickens are susceptible both to parasites such as mites, and to diseases caused by pathogens such as bacteria and viruses. The parasite Dermanyssus gallinae feeds on blood, causing irritation and reducing egg production, and acts as a vector for bacterial diseases such as salmonellosis and spirochaetosis. Viral diseases include avian influenza.

Farming
Chickens are common and widespread domestic animals, with a total population of 23.7 billion. More than 50 billion chickens are reared annually as a source of meat and eggs. In the United States alone, more than 8 billion chickens are slaughtered each year for meat, and more than 300 million chickens are reared for egg production. The vast majority of poultry is raised in factory farms. According to the Worldwatch Institute, 74% of the world's poultry meat and 68% of eggs are produced this way. An alternative to intensive poultry farming is free-range farming. Friction between these two main methods has led to long-term issues of ethical consumerism. Opponents of intensive farming argue that it harms the environment, creates human health risks and is inhumane. Advocates of intensive farming say that their efficient systems save land and food resources owing to increased productivity, and that the animals are looked after in a controlled environment. Chickens farmed for meat are called broilers. Broiler breeds typically take less than six weeks to reach slaughter size, some weeks longer for free range and organic broilers.

Chickens farmed primarily for eggs are called layer hens. The UK alone consumes more than 34 million eggs per day. Hens of some breeds can produce over 300 eggs per year; the highest authenticated rate of egg laying is 371 eggs in 364 days. After 12 months of laying, the commercial hen's egg-laying ability declines to the point where the flock is commercially unviable. Hens, particularly from battery cage systems, are sometimes infirm or have lost a significant amount of their feathers, and their life expectancy has been reduced from around seven years to less than two years. In the UK and Europe, laying hens are then slaughtered and used in processed foods, or sold as 'soup hens'. In some other countries, flocks are sometimes force moulted rather than being slaughtered to re-invigorate egg-laying. This involves complete withdrawal of food (and sometimes water) for 7–14 days or sufficiently long to cause a body weight loss of 25 to 35%, or up to 28 days under experimental conditions. This stimulates the hen to lose her feathers but also re-invigorates egg-production. Some flocks may be force-moulted several times. In 2003, more than 75% of all flocks were moulted in the US.

As pets
Keeping chickens as pets became increasingly popular in the 2000s among urban and suburban residents. Many people obtain chickens for their egg production but often name them and treat them as any other pet like cats or dogs. Chickens provide companionship and have individual personalities. While many do not cuddle much, they will eat from one's hand, jump onto one's lap, respond to and follow their handlers, as well as show affection. Chickens are social, inquisitive, intelligent birds, and many people find their behaviour entertaining. Certain breeds, such as silkies and many bantam varieties, are generally docile and are often recommended as good pets around children with disabilities.

Cockfighting

A cockfight is a contest held in a ring called a cockpit between two cocks. Cockfighting is outlawed in many countries as involving cruelty to animals. The activity seems to have been practised in the Indus Valley civilisation from 2500 to 2100 BC. In the process of domestication, chickens were apparently kept initially for cockfighting, and only later used for food.

In science
Chickens have long been used as model organisms to study developing embryos. Large numbers of embryos can be provided commercially; fertilized eggs can easily be opened and used to observe the developing embryo. Equally important, embryologists can carry out experiments on such embryos, close the egg again and study the effects later in development. For instance, many important discoveries in limb development have been made using chicken embryos, such as the discovery of the apical ectodermal ridge and the zone of polarizing activity.

The chicken was the first bird species to have its genome sequenced. At 1.21 Gb, the chicken genome is similarly sized compared to other birds, but smaller than nearly all mammals: the human genome is 3.2 Gb. The final gene set contained 26,640 genes (including noncoding genes and pseudogenes), with a total of 19,119 protein-coding genes, a similar number to the human genome. In 2006, scientists researching the ancestry of birds switched on a chicken recessive gene, talpid2, and found that the embryo jaws initiated formation of teeth, like those found in ancient bird fossils.

In culture, folklore, and religion
Chickens feature widely in folklore, religion, literature, and popular culture. The chicken is a sacred animal in many cultures and deeply embedded in belief systems and religious practices. Roosters are sometimes used for divination, a practice called alectryomancy. This involves the sacrifice of a sacred rooster, often during a ritual cockfight, used as a form of communication with the gods. In Gabriel García Márquez's Nobel-Prize-winning 1967 novel One Hundred Years Of Solitude, cockfighting is outlawed in the town of Macondo after the patriarch of the Buendia family murders his cockfighting rival and is haunted by the man's ghost. Chicken jokes have been made at least since The Knickerbocker published one in 1847. Chickens have featured in art in farmyard scenes such as Adriaen van Utrecht's 1646 Turkeys and Chickens and Walter Osborne's 1885 Feeding the Chickens. The nursery rhyme "Cock a doodle doo", its chorus line imitating the cockerel's call, was published in Mother Goose's Melody in 1765. The 2000 animated adventure comedy film Chicken Run, directed by Peter Lord and Nick Park, featured anthropomorphic chickens with many chicken jokes.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Chicken


text:
Eastern Europe

Eastern Europe is a subregion of the European continent. As a largely ambiguous term, it has a wide range of geopolitical, geographical, ethnic, cultural, and socio-economic connotations. Its eastern boundary is marked by the Ural Mountains, whilst its western boundary is defined in various ways. Most definitions include the countries of Belarus, Russia, Ukraine, Moldova and Romania while less restrictive definitions may also include some or all of the Balkans, the Baltic states, the Caucasus and the Visegrád group.

The region represents a significant part of European culture; the main socio-cultural characteristics of Eastern Europe have historically been defined by the traditions of the East Slavs and Greeks, as well as by the influence of Eastern Christianity as it developed through the Eastern Roman Empire and the Ottoman Empire. Another definition was created by the Cold War, as Europe was ideologically divided by the Iron Curtain, with "Eastern Europe" being synonymous with communist states constituting the Eastern Bloc under the influence of the Soviet Union.

The term is sometimes considered to be pejorative, through stereotypes about Eastern Europe being inferior (poorer, less developed) to Western Europe; the term Central and Eastern Europe is sometimes used for a more neutral grouping.

Definitions
Several definitions of Eastern Europe exist in the early 21st century, but they often lack precision and may be anachronistic. These definitions are debated across cultures and among experts, even political scientists, as the term has a wide range of geopolitical, geographical, cultural, and socioeconomic connotations. It has also been described as a "fuzzy" term, as the idea itself of Eastern Europe is in constant redefinition. The solidification of the idea of an "Eastern Europe" dates back chiefly to the (French) Enlightenment.

There are "almost as many definitions of Eastern Europe as there are scholars of the region". A related United Nations paper adds that "every assessment of spatial identities is essentially a social and cultural construct".

Geographical
While the eastern geographical boundaries of Europe are well defined, the boundary between Eastern and Western Europe is not geographical but historical, religious and cultural and is harder to designate.

The Ural Mountains, Ural River, and the Caucasus Mountains are the geographical land border of the eastern edge of Europe. E.g. Kazakhstan, which is mainly located in Central Asia with the most western parts of it located west of the Ural River, also shares a part of Eastern Europe.

In the west, however, the historical and cultural boundaries of "Eastern Europe" are subject to some overlap and, most importantly, have undergone historical fluctuations, which makes a precise definition of the western geographic boundaries of Eastern Europe and the geographical midpoint of Europe somewhat difficult.

Religious and cultural influence
After the East–West Schism in 1054, significant parts of Eastern Europe developed cultural unity and resistance to Catholic Western and Central Europe within the framework of the Eastern Orthodox Church, Church Slavonic language and the Cyrillic alphabet.

A large section of Eastern Europe is formed by countries with dominant Orthodox churches, like Belarus, Bulgaria, Cyprus, Georgia, Greece, Moldova, Montenegro, North Macedonia, Romania, Russia, Serbia, and Ukraine, for instance, as well as Armenia, which is predominantly Armenian Apostolic. The Eastern Orthodox Church has played a prominent role in the history and culture of Eastern and Southeastern Europe. To a lesser degree, forms of Eastern Protestantism and Eastern Catholicism have also been influential in Eastern Europe. Countries where Eastern Protestantism or Eastern Catholicism hold historical significance include Belarus, Croatia, Greece, Hungary, Lithuania, Poland, Romania, Russia, Slovakia, Slovenia and Ukraine. The schism refers to the historical break of communion and theology between the Eastern (Orthodox) and Western (Catholic) churches. Later developments meant that the divide was no longer solely between Catholic and Orthodox churches. From the 16th century, both Western and Eastern forms of Protestantism began to emerge in Europe. Additionally, Eastern Catholic Churches began to spread in Europe during the 16th and 17th centuries, following the establishment of the Ukrainian Greek Catholic Church in 1596. However, the concept of Eastern Catholicism itself predates this.

Since the Great Schism of 1054, Europe has been divided between Catholic (and later additionally Protestant) churches in the West, and the Eastern Orthodox Christian (often incorrectly labelled "Greek Orthodox") churches in the east. Due to this religious cleavage, Eastern Orthodox countries are often associated with Eastern Europe. A cleavage of this sort is, however, often problematic; for example, Greece is overwhelmingly Orthodox, but is very rarely included in "Eastern Europe", for a variety of reasons, the most prominent being that Greece's history, for the most part, was more influenced by Mediterranean cultures and dynamics.

Cold War (1947–1991)
The fall of the Iron Curtain brought the end of the Cold War east–west division in Europe, but this geopolitical concept is sometimes still used for quick reference by the media. Another definition was used during the 40 years of Cold War between 1947 and 1989, and was more or less synonymous with the terms Eastern Bloc and Warsaw Pact. A similar definition names the formerly communist European states outside the Soviet Union as Eastern Europe.

Historians and social scientists generally view such definitions as outdated or relegated. Many former Communist states in this region, although their formal alliances were severed by the fall of the Berlin Wall, continued to feel a moral duty to support states that have not been "liberated from the tyranny of capitalism". This shared duty collapsed when most of the former Soviet satellites abandoned socialism and adopted capitalism.

EuroVoc
EuroVoc, a multilingual thesaurus maintained by the Publications Office of the European Union, classifies Bulgaria, Croatia, Czechia, Hungary, Poland, Romania, Slovakia and Slovenia, plus the candidate countries Albania, North Macedonia and Serbia as Central and Eastern European.

Baltic states
UNESCO, EuroVoc, National Geographic Society, Committee for International Cooperation in National Research in Demography, and the STW Thesaurus for Economics place the Baltic states in Northern Europe, whereas the CIA World Factbook places the region in Eastern Europe with a strong assimilation to Northern Europe. They are members of the Nordic-Baltic Eight regional cooperation forum whereas Central European countries formed their own alliance called the Visegrád Group. The Northern Future Forum, the Nordic Investment Bank, the Nordic Battlegroup, the Nordic-Baltic Eight and the New Hanseatic League are other examples of Northern European cooperation that includes the three countries collectively referred to as the Baltic states.
 * Estonia
 * Latvia
 * Lithuania

Caucasus states
The South Caucasus nations of Armenia, Azerbaijan, and Georgia are included in definitions or histories of Eastern Europe. They are located in the transition zone of Eastern Europe and Western Asia. They participate in the European Union's Eastern Partnership program, the Euronest Parliamentary Assembly, and are members of the Council of Europe, which specifies that all three have political and cultural connections to Europe. In January 2002, the European Parliament noted that Armenia and Georgia may enter the EU in the future. However, Georgia is currently the only South Caucasus nation actively seeking NATO and EU membership.
 * Armenia
 * Azerbaijan
 * Georgia

There are two de facto republics with limited recognition in the South Caucasus region that exist under the presence of Russian military. Both states participate in the Community for Democracy and Rights of Nations:
 * Abkhazia
 * South Ossetia

Former republics with limited recognition:
 * Chechen Republic of Ichkeria (1991–2000) – existed in former Soviet territory until it was driven into exile during the Second Chechen War
 * Republic of Artsakh (1991–2023) – breakaway state from Azerbaijan that ceased to exist by 1 January 2024

Post-Soviet states
Some European republics of the former Soviet Union are considered a part of Eastern Europe:
 * Belarus
 * Moldova (sometimes considered a part of the Balkans or Southeast Europe)
 * Russia
 * Ukraine

Unrecognized states:
 * Transnistria

Central Europe
The term "Central Europe" is often used by historians to designate states formerly belonging to the Holy Roman Empire, the Habsburg Empire, and the Polish–Lithuanian Commonwealth.

In some media, "Central Europe" can thus partially overlap with "Eastern Europe" of the Cold War Era. The following countries are labelled Central European by some commentators, though others still consider them to be Eastern European.
 * Czech Republic
 * Croatia (can variously be included in Southeastern or Central Europe)
 * Hungary (most often placed in Central Europe but sometimes in Southeastern Europe)
 * Lithuania (can variously be included in Northeastern or Central Europe)
 * Poland
 * Romania (can be included in Southeastern Europe or partially in Central Europe)
 * Serbia (most often placed in Southeastern Europe but sometimes partially included in Central Europe)
 * Slovakia
 * Slovenia (most often placed in Central Europe but sometimes in Southeastern Europe)

Southeastern Europe
Some countries in Southeast Europe can be considered part of Eastern Europe. Some of them can sometimes, albeit rarely, be characterized as belonging to Southern Europe, and some may also be included in Central Europe.

In some media, "Southeast Europe" can thus partially overlap with "Eastern Europe" of the Cold War Era. The following countries are labelled Southeast European by some commentators, though others still consider them to be Eastern European.

Partially recognized states:
 * Albania
 * Bosnia and Herzegovina
 * Bulgaria
 * Cyprus (Geographically located in Asia, though most often considered a part of Southeastern Europe)
 * Croatia (can variously be included in Southeastern or Central Europe)
 * Greece (Sometimes grouped in Southern Europe with countries like Italy, Spain and Portugal)
 * Hungary (most often placed in Central Europe but sometimes in Southeastern Europe)
 * Moldova (usually grouped with the non-Baltic post-Soviet states but sometimes considered part of Southeastern Europe)
 * Montenegro
 * North Macedonia
 * Romania (can variously be included in Southeastern or Central Europe)
 * Serbia (mostly placed in Southeastern but sometimes in Central Europe)
 * Slovenia (most often placed in Central Europe but sometimes in Southeastern Europe)
 * Turkey (East Thrace, the portion west of the Turkish Straits)
 * Kosovo

Kazakhstan
Despite being frequently classified as a Central Asian country, about 4% of Kazakhstan's territory, situated west of the Ural River, geographically lies in Eastern Europe, thus technically making it a transcontinental country.

Classical antiquity and medieval origins
Ancient kingdoms of the region included Orontid Armenia, Caucasian Albania, Colchis and Iberia (not to be confused with the Iberian Peninsula in Western Europe), of which the former two were the predecessor states of Armenia and Azerbaijan respectively, while the latter two were the predecessor states of modern-day Georgia. These peripheral kingdoms were, either from the start or later on, incorporated into various Iranian empires, including the Achaemenid Persian, Parthian, and Sassanid Persian Empires. Parts of the Balkans and some more northern areas were ruled by the Achaemenid Persians as well, including Thrace, Paeonia, Macedon, and most of the Black Sea coastal regions of Romania, Ukraine, and Russia. Owing to the rivalry between the Parthian Empire and Rome, and later between Byzantium and the Sassanid Persians, the Parthians would invade the region several times, although it was never able to hold the area, unlike the Sassanids who controlled most of the Caucasus during their entire rule. The earliest known distinctions between east and west in Europe originate in the history of the Roman Republic. As the Roman domain expanded, a cultural and linguistic division appeared. The mainly Greek-speaking eastern provinces had formed the highly urbanized Hellenistic civilization. In contrast, the western territories largely adopted the Latin language. This cultural and linguistic division was eventually reinforced by the later political east–west division of the Roman Empire. The division between these two spheres deepened during Late Antiquity and the Middle Ages due to a number of events. The Western Roman Empire collapsed in the 5th century, marking the start of the Early Middle Ages. By contrast, the Eastern Roman Empire—the Byzantine Empire—had a survival strategy that kept it alive for another 1,000 years.

The rise of the Frankish Empire in the west, and in particular the Great Schism that formally divided Eastern and Western Christianity in 1054, heightened the cultural and religious distinctiveness between Eastern and Western Europe. Much of Eastern Europe was invaded and occupied by the Mongols.

During the Ostsiedlung, towns founded under Magdeburg rights became centers of economic development and scattered German settlements were founded in parts of Eastern Europe. Introduction of German town law is often seen as a second great step after introduction of Christianity at the turn of the first and second millennia. The ensuing modernization of society and economy allowed the increased role played by the rulers of Bohemia and Poland.

1453 to 1918
The conquest of the Byzantine Empire, center of the Eastern Orthodox Church, by the Ottoman Empire in the 15th century, and the gradual fragmentation of the Holy Roman Empire (which had replaced the Frankish empire) led to a change of the importance of Catholic/Protestant vs. Eastern Orthodox concept in Europe. Armour points out that Cyrillic-alphabet use is not a strict determinant for Eastern Europe, where from Croatia to Poland and everywhere in between, the Latin alphabet is used. Greece's status as the cradle of Western civilization and an integral part of the Western world in the political, cultural and economic spheres has led to it being nearly always classified as belonging not to Eastern, but Southern or Western Europe. During the late-sixteenth and early-seventeenth centuries, Eastern Europe enjoyed a relatively high standard of living. This period is also called the east-central European golden age of around 1600. At the beginning of the 17th century, numeracy levels in eastern Europe were relatively low, although regional differences existed. During the 18th century, the regions began to catch up with western Europe, but did not develop as rapidly. Areas with stronger female autonomy developed more quickly in terms of numeracy.

Serfdom
Serfdom was a prevalent status of agricultural workers until the 19th century. It resembled slavery in terms of lack of freedom, with the distinction that the landowners could not buy and sell serfs separately from the specific plots of land that they were permanently attached to. The system emerged in the 14th and 15th century, the same time it was declining in Western Europe. The climax came in the 17th and 18th century. The early 19th century saw its decline, marked especially by the abolition of serfdom in Russia in 1861. Emancipation meant that the ex-serfs paid for their freedom with annual cash payments to their former masters for decades. The system varied widely country by country, and was not as standardized as in Western Europe. Historians, until the 20th century, focused on master-serf economic and labor relations, portraying the serfs as slave-like, passive, and isolated. 20th century scholars downplayed the evils and emphasize the complexities.

Interwar period (1919–1939)
A major result of the First World War was the breakup of the Russian, Austro-Hungarian, and Ottoman empires, as well as partial losses to the German Empire. A surge of ethnic nationalism created a series of new states in Eastern Europe, validated by the Versailles Treaty of 1919. Poland was reconstituted after the partitions of the 1790s had divided it between Germany, Austria, and Russia. New countries included Finland, Estonia, Latvia, Lithuania, Ukraine (which was soon absorbed by the Soviet Union), Czechoslovakia, and Yugoslavia. Austria and Hungary had much-reduced boundaries. The new states included sizeable ethnic minorities, which were to be protected according to the League of Nations minority protection regime. Throughout Eastern Europe, ethnic Germans constituted by far the largest single ethnic minority. In some areas, as in the Sudetenland, regions of Poland, and in parts of Slovenia, German speakers constituted the local majority, creating upheaval regarding demands of self-determination.

Romania, Bulgaria, and Albania likewise were independent. Many of the countries were still largely rural, with little industry and only a few urban centres. Nationalism was the dominant force but most of the countries had ethnic or religious minorities who felt threatened by majority elements. Nearly all became democratic in the 1920s, but all of them (except Czechoslovakia and Finland) gave up democracy during the depression years of the 1930s, in favor of autocratic, strong-man or single-party states. The new states were unable to form stable military alliances, and one by one were too weak to stand up against Nazi Germany or the Soviet Union, which took them over between 1938 and 1945.

World War II and onset of the Cold War
Russia ended its participation in the First World War in March 1918 and lost territory, as the Baltic countries and Poland became independent. The region was the main battlefield in the Second World War (1939–45), with German and Soviet armies sweeping back and forth, with millions of Jews and others killed by the Nazis in the Generalplan Ost, and millions of others killed by disease, starvation, and military action, or executed after being deemed as politically dangerous. During the final stages of World War II the future of Eastern Europe was decided by the overwhelming power of the Soviet Red Army, as it swept the Germans aside. It did not reach Yugoslavia and Albania, however. Finland was free but forced to be neutral in the upcoming Cold War.

Throughout Eastern Europe, German-speaking populations were expelled to the reduced borders of Germany in one of the largest ethnic cleansing operations in history. Regions where Germans had formed the local population majority were re-settled with Polish- or Czech-speakers.

The region fell to Soviet control and Communist governments were imposed. Yugoslavia, Albania (and later Romania) had their own Communist regimes independent of Moscow. The Eastern Bloc at the onset of the Cold War in 1947 was far behind the Western European countries in economic rebuilding and economic progress. Winston Churchill, in his well-known "Sinews of Peace" address of 5 March 1946, at Westminster College in Fulton, Missouri, stressed the geopolitical impact of the "iron curtain": "From Stettin in the Baltic to Trieste in the Adriatic an iron curtain has descended across the Continent. Behind that line lie all the capitals of the ancient states of Central and Eastern Europe: Warsaw, Berlin, Prague, Vienna, Budapest, Belgrade, Bucharest, and Sofia."

Eastern Bloc
Eastern Europe after 1945 usually meant all the European countries liberated from Nazi Germany and then occupied by the Soviet army. It included the German Democratic Republic (also known as East Germany), formed by the Soviet occupation zone of Germany. All the countries in Eastern Europe adopted communist modes of control by 1948. These countries were officially independent of the Soviet Union, but the practical extent of this independence was quite limited. Yugoslavia and Albania had Communist control that was independent of the Kremlin.

The communists had a natural reservoir of popularity in that they had destroyed the Nazi invaders. Their goal was to guarantee long-term working-class solidarity. The Soviet secret police, the NKVD, working in collaboration with local communists, created secret police forces using leadership trained in Moscow. This new secret police arrived to arrest political enemies according to prepared lists. The national Communists then took power in a gradualist manner, backed by the Soviets in many, but not all, cases. For a while, cooperative non-Communist parties were tolerated. The Communist governments nationalized private businesses, placing them under state ownership, and monitored the media and churches. When dividing up government offices with coalition partners, the Communists took control of the interior ministries, which controlled the local police. They also took control of the mass media, especially radio, as well as the education system. They confiscated and redistributed farmland, and seized control of or replaced the organizations of civil society, such as church groups, sports, youth groups, trade unions, farmers' organizations, and civic organizations. In some countries, they engaged in large-scale ethnic cleansing, moving ethnic groups such as Germans, Poles, Ukrainians and Hungarians far away from where they previously lived, often with high loss of life, to relocate them within the new post-war borders of their respective countries.

Under Stalin's direct instructions, these nations rejected grants from the American Marshall Plan. Instead, they joined the Molotov Plan, which later evolved into the Comecon (Council for Mutual Economic Assistance). When NATO was created in 1949, most countries of Eastern Europe became members of the opposing Warsaw Pact, forming a geopolitical concept that became known as the Eastern Bloc. This consisted of:
 * First and foremost was the Soviet Union (which included the modern-day territories of Russia, Belarus, Ukraine and Moldova and the illegally occupied Lithuania, Latvia and Estonia). Other countries dominated by the Soviet Union were the German Democratic Republic, People's Republic of Poland, Czechoslovak Socialist Republic, People's Republic of Hungary, People's Republic of Bulgaria, and Socialist Republic of Romania.
 * The Socialist Federal Republic of Yugoslavia (SFRY; formed after World War II and before its later dismemberment) was not a member of the Warsaw Pact. It was a founding member of the Non-Aligned Movement, an organization created in an attempt to avoid being assigned to either the NATO or Warsaw Pact blocs. The movement was demonstratively independent of both the Soviet Union and the Western bloc for most of the Cold War period, allowing Yugoslavia and its other members to act as a business and political mediator between the blocs.
 * The Socialist People's Republic of Albania broke with the Soviet Union in the early 1960s as a result of the Sino-Soviet split, aligning itself instead with China. Albania formally left the Warsaw pact in September 1968 after the suppression of the Prague Spring. When China established diplomatic relations with the United States in 1978, Albania also broke away from China. Albania and especially Yugoslavia were not unanimously appended to the Eastern Bloc, as they were neutral for a large part of the Cold War period.

Since 1989
With the fall of the Iron Curtain in 1989, the political landscape of the Eastern Bloc, and indeed the world, changed. In the German reunification, the Federal Republic of Germany peacefully absorbed the German Democratic Republic in 1990. In 1991, COMECON, the Warsaw Pact, and the Soviet Union were dissolved. Many European nations that had been part of the Soviet Union declared or regained their independence (Belarus, Moldova, Ukraine, as well as the Baltic States of Latvia, Lithuania, and Estonia). Czechoslovakia peacefully separated into the Czech Republic and Slovakia in 1993. Many countries of this region joined the European Union, namely Bulgaria, the Czech Republic, Croatia, Estonia, Hungary, Latvia, Lithuania, Poland, Romania, Slovakia and Slovenia. The term "EU11 countries" refer to the Central and Eastern European member states, including the Baltic states, that accessed in 2004 and after: in 2004 the Czech Republic, Estonia, Latvia, Lithuania, Hungary, Poland, Slovenia, and the Slovak Republic; in 2007 Bulgaria, Romania; and in 2013 Croatia.

The economic changes were in harmony with the constitutional reforms: constitutional provisions on public finances can be identified and, in some countries, a separate chapter deals with public finances. Generally, they soon encountered the following problems: high inflation, high unemployment, low economic growth, and high government debt. By 2000 these economies were stabilized, and between 2004 and 2013 all of them joined the European Union. Most of the constitutions define directly or indirectly the economic system of the countries parallel to the democratic transition of the 1990s: free-market economy (sometimes complemented with the socially [and ecologically] oriented sector), economic development, or only economic rights are included as a ground for the economy.

In the case of fiscal policy, the legislative, the executive and other state organs (Budget Council, Economic and Social Council) define and manage the budgeting. The average government debt in the countries is nearly 44%, but the deviation is great because the lowest figure is close to 10% but the highest is 97%. The trend shows that the sovereign debt ratio to GDP in most countries has been rising. Only three countries are affected by high government debt: Croatia, Hungary and Slovenia (over 70% of the GDP), while Slovakia and Poland fulfill the Maastricht requirement but only 10% below the threshold. The contribution to cover the finances for common needs is declared, the principle of just tax burden-sharing is supplemented sometimes with special aspects. Tax revenues expose typically 15–19 % of the GDP, and rates above 20% only rarely can be found.

The state audit of the government budget and expenditures is an essential control element in public finances and an important part of the concept of checks and balances. The central banks are independent state institutions, which possess a monopoly on managing and implementing a state's or federation's monetary policy. Besides monetary policy, some of them even perform the supervision of the financial intermediary system. In the case of a price stability function, the inflation rate, in the examined area, relatively quickly dropped to below 5% by 2000. In monetary policy the differences are based on the euro-zone: Estonia, Latvia, Lithuania, Slovakia, Slovenia use the common currency. The economies of this decade – similar to the previous one – show a moderate inflation. As a new phenomenon, a slight negative inflation (deflation) appeared in this decade in several countries (Croatia, Estonia, Hungary, Poland, Romania, Slovakia, and Slovenia), which demonstrates sensitivity regarding international developments. The majority of the constitutions determine the national currency, legal tender or monetary unit. The local currency exchange rate to the U.S. dollar shows that drastic interventions were not necessary. National wealth or assets are the property of the state or local governments and, as an exclusive property, the management and protection of them aim at serving the public interest.

title: Eastern Europe