thumb|Polycrystalline potash, with a [[penny (United States coin)|U.S. penny for reference. (The coin is in diameter and copper in color.)]]

Potash ( ) are mined and manufactured salts that contain potassium in water-soluble form. The term potash derives from pot ash, either plant ashes or wood ashes that were soaked in water in a pot, which was the primary means of manufacturing potash before the Industrial Era; the word potassium derives from the term potash.

In 2021, the worldwide production of potash exceeded 71.9&nbsp;million tonnes (~45.4 million tonnes K<sub>2</sub>O equivalent), and Canada is the greatest producer of potash as fertilizer. Potassium was first derived in 1807 by electrolysis of caustic potash (potassium hydroxide).

Terminology

The term potash refers to compounds of potassium and to potassium-bearing materials, usually potassium carbonate. The usage of the term potash dates from 1477, and derives from the Middle Dutch word , denoting pot ashes.

The old method of making potassium carbonate () was either by collecting or by producing wood ash (the occupation of the ash burner), chemically leaching the ashes and then evaporating the resulting solution in large iron pots, which yielded a white residue denominated "pot ash"; approximately 10% by weight of common wood ash can be recovered as potash.

The term potash later identified minerals that contained potassium salts and the artificial commercial product derived from the salts. The table identifies eight (8) potassium compounds with the term potash in their traditional names:

{| class="wikitable"

|-

! Common name !! Chemical name (Formula)

|-

|Potash fertilizer ||colspan="2"| To the early 20th century: potassium carbonate (K<sub>2</sub>CO<sub>3</sub>); from the late-19th century: one or more compounds of potassium chloride (KCl), potassium sulfate (K<sub>2</sub>SO<sub>4</sub>), or potassium nitrate (KNO<sub>3</sub>). Does not contain potassium oxide (K<sub>2</sub>O), which plants do not take up; the amount of potassium is reported as K<sub>2</sub>O equivalent (i.e. if in K<sub>2</sub>O form), however, to allow direct comparison between different fertilizers using different types of potash.

|-

|Caustic potash or potash lye ||potassium hydroxide (KOH)

|-

| or ||potassium carbonate (K<sub>2</sub>CO<sub>3</sub>)

|-

|Chlorate of potash ||potassium chlorate (KClO<sub>3</sub>)

|-

|Muriate of potash (MOP) ||potassium chloride (KCl:NaCl = 95:5 or higher)

Bronze Age

Potash (especially potassium carbonate) has been used in bleaching textiles, making glass, ceramic, and making soap, since the Bronze Age. Potash was principally obtained by leaching the ashes of wood burned for heating and cooking.

14th–17th century

Potash mining

Beginning in the 14th century potash was mined in Ethiopia. One of the world's largest deposits, 140 to 150&nbsp;million tons, is located in the Dallol area of the Afar Region.

Wood-derived potash

Potash was one of the most important industrial chemicals. It was refined from the ashes of broadleaved trees and produced primarily in the forested areas of Europe, Russia, and North America. Although methods for producing artificial alkalis were invented in the late 18th century, these did not become economical until the late 19th century and so the dependence on organic sources of potash remained.

Potash became an important international trade commodity in Europe from at least the early 14th century. It is estimated that European imports of potash required 6 or more million cubic metres each year from the early 17th century. From the 1640s, geopolitical disruptions (i.e. Russo-Polish War (1654–1667)) meant that the centres of export moved from the Baltic to Arkhangelsk, Russia. In 1700, Russian ash was dominant though Gdańsk remained notable for the quality of its potash.

18th century

Kelp ash

On the Orkney islands, kelp ash provided potash and soda ash, production starting "possibly as early as 1719" and lasting for a century. The products were "eagerly sought after by the glass and soap industries of the time."

North America

By the 18th century, higher quality American potash was increasingly exported to Britain. In the late 18th and early 19th centuries, potash production provided settlers in North America badly needed cash and credit as they cleared wooded land for crops. To make full use of their land, settlers needed to dispose of excess wood. The easiest way to accomplish this was to burn any wood not needed for fuel or construction. Ashes from hardwood trees could then be used to make lye, which could either be used to make soap or boiled down to produce valuable potash. Hardwood could generate ashes at the rate of 60 to 100 bushels per acre (500 to 900 m<sup>3</sup>/km<sup>2</sup>). In 1790, the sale of ashes could generate $3.25 to $6.25 per acre ($800 to $1,500/km<sup>2</sup>) in rural New York State – nearly the same rate as hiring a laborer to clear the same area. Potash making became a major industry in British North America. Great Britain was always the most important market. The American potash industry followed the woodsman's ax across the country.

The first US patent

The first US patent of any kind was issued in 1790 to Samuel Hopkins for an improvement "in the making of Pot ash and Pearl ash by a new Apparatus and Process". Pearl ash was a purer quality made by calcination of potash in a reverberatory furnace or kiln. Potash pits were once used in England to produce potash that was used in making soap for the preparation of wool for yarn production.

19th century

After about 1820, New York replaced New England as the most important source; by 1840 the center was in Ohio. Potash production was always a by-product industry, following from the need to clear land for agriculture. Later in the century, the cartel ended as new potash producers emerged in the USSR and Canada.thumb|Potash evaporation ponds at the [[Intrepid Potash mine near Moab, Utah]]

Mining

Shaft mining and strip mining

All commercial potash deposits come originally from evaporite deposits and are often buried deep below the earth's surface. Potash ores are typically rich in potassium chloride (KCl), sodium chloride (NaCl) and other salts and clays, and are typically obtained by conventional shaft mining with the extracted ore ground into a powder. Most potash mines today are deep shaft mines as much as 4,400 feet (1,400 m) underground. Others are mined as strip mines, having been laid down in horizontal layers as sedimentary rock. In above-ground processing plants, the KCl is separated from the mixture to produce a high-analysis potassium fertilizer. Other potassium salts can be separated by various procedures, resulting in potassium sulfate and potassium-magnesium sulfate. Saskatchewan is the world’s largest producer of potash.

Dissolution mining and evaporation methods

Other methods include dissolution mining and evaporation methods from brines. In the evaporation method, hot water is injected into the potash, which is dissolved and then pumped to the surface where it is concentrated by solar induced evaporation. Amine reagents are then added to either the mined or evaporated solutions. The amine coats the KCl but not NaCl. Air bubbles cling to the amine + KCl and float it to the surface while the NaCl and clay sink to the bottom. The surface is skimmed for the amine + KCl, which is then dried and packaged for use as a K rich fertilizer—KCl dissolves readily in water and is available quickly for plant nutrition.

Recovery of potassium fertilizer salts from sea water has been studied in India. During extraction of salt from seawater by evaporation, potassium salts get concentrated in bittern, an effluent from the salt industry.

Production

Potash deposits are distributed unevenly throughout the world. with the most significant deposits present under the great depths of the Prairie Evaporite Formation in Saskatchewan, Canada.

The Permian Basin deposit includes the major mines outside of Carlsbad, New Mexico, to the world's purest potash deposit in Lea County, New Mexico (near the Carlsbad deposits), which is believed to be roughly 80% pure. (Osceola County, Michigan, has deposits 90+% pure; the only mine there was converted to salt production, however.) Canada is the largest producer, followed by Russia and Belarus. The most significant reserve of Canada's potash is located in the province of Saskatchewan and is mined by The Mosaic Company, Nutrien and K+S. but commercial exploitation lagged until Deng Xiaoping's Reform and Opening Up Policy in the 1980s. The 1989 opening of the Qinghai Potash Fertilizer Factory in the remote Qarhan Playa increased China's production of potassium chloride sixfold, from less than a year at Haixi and Tanggu to just under a year.

In 2013, almost 70% of potash production was controlled by Canpotex, an exporting and marketing firm, and the Belarusian Potash Company. The latter was a joint venture between Belaruskali and Uralkali, but on July 30, 2013, Uralkali announced that it had ended the venture.

Potash is water soluble and transporting it requires special transportation infrastructure.

Use

{| class="wikitable sortable" style="float:right"

|+Production of potash and reserves at some current mines (being <2% of global reserves)<br/>(both in <chem>K2O</chem> equivalent)<br/>(2021, in million tonnes)

! Country

! Production

! Reserves

|-

|Canada

|align=right| 14.2 (28.57%)

|align=right| 1,100 (33.33%)

|-

|Russia

|align=right| 9.1 (17.14%)

|align=right| 400 (12.12%)

|-

|Belarus

|align=right| 7.6 (16.48%)

|align=right| 750 (22.73%)

|-

|China

| align="right" | 6.0 (14.76%)

| align="right" | 170 (5.15%)

|-

|Germany

| align="right" | 2.8 (6.90%)

| align="right" | 150 (4.55%)

|-

|Israel

|align=right| 2.4 (5.14%)

|align=right| Large (?%)

|-

|Jordan

|align=right| 1.6 (3.37%)

|align=right| Large (?%)

|-

|Chile

| align="right" | 0.9 (1.85%)

| align="right" | 100 (3.03%)

|-

|United States

| align="right" | 0.5 (1.04%)

| align="right" | 220 (6.67%)

|-

|Spain

| align="right" | 0.4 (0.79%)

| align="right" | 68 (2.06%)

|-

|Brazil

| align="right" | 0.3 (0.58%)

| align="right" | 2.3 (0.01%)

|-

|Other countries

| align="right" | 0.4 (0.76%)

| align="right" | 300 (9.09%)

|- class="sortbottom"

|World total

| align="right" | 46.3 (100.00%)

| align="right" | >3,300 (100.00%)

|}

Fertilizers

Potassium is the third major plant and crop nutrient after nitrogen and phosphorus. It has been used since antiquity as a soil fertilizer (about 90% of current use). As part of various compounds, potassium makes up about 2.6% of the Earth's crust by mass and is the seventh most abundant element, similar in abundance to sodium at approximately 1.8% of the crust. Potash is important for agriculture because it improves water retention, yield, nutrient value, taste, color, texture

Demand for food and animal feed has been on the rise since 2000. The United States Department of Agriculture's Economic Research Service (ERS) attributes the trend to average annual population increases of 75&nbsp;million people around the world. Geographically, economic growth in Asia and Latin America greatly contributed to the increased use of potash-based fertilizer. Rising incomes in developing countries also were a factor in the growing potash and fertilizer use. With more money in the household budget, consumers added more meat and dairy products to their diets. This shift in eating patterns required more acres to be planted, more fertilizer to be applied and more animals to be fed—all requiring more potash.

After years of trending upward, fertilizer use slowed in 2008. The worldwide economic downturn is the primary reason for the declining fertilizer use, dropping prices, and mounting inventories.

The world's largest consumers of potash are China, the United States, Brazil, and India. Brazil imports 90% of the potash it needs.

Potash imports and exports are often reported in K<sub>2</sub>O equivalent, although fertilizer never contains potassium oxide, per se, because potassium oxide is caustic and hygroscopic.

Pricing

At the beginning of 2008, potash prices started a meteoric climb from less than US$200 a tonne to a high of US$875 in February 2009. These subsequently dropped dramatically to an April 2010 low of US$310 level, before recovering in 2011–12, and relapsing again in 2013. For reference, prices in November 2011 were about US$470 per tonne, but as of May 2013 were stable at US$393. After the surprise breakup of the world's largest potash cartel at the end of July 2013, potash prices were poised to drop some 20 percent. At the end of December 2015, potash traded for US$295 a tonne. In April 2016 its price was US$269. In May 2017, prices had stabilised at around US$216 a tonne down 18% from the previous year. By January 2018, prices have been recovering to around US$225 a tonne. World potash demand tends to be price inelastic in the short-run and even in the long run.