Potash (K2O) refers to a group of potassium bearing minerals, the most common being potassium chloride (KCl). Potassium (K) is the seventh most common element in the earth's crust, and is found in every cell of plants and animals and is essential to their growth.
Potash has been used throughout history in the manufacture of glass and soap, but is used primarily as a fertilizer, with 95 % of all potash produced being used in this way, as there is no known substitute that rivals its effectiveness in this capacity. Potash contains one of the three most important nutrients to plants, which are nitrogen, phosphorus and potassium. Potassium helps produce healthier, higher yields, and without potassium fertilizer, world production of food, feed and fiber would drop by one-third or more.
Under severe potassium deficiency, plants will often develop visible symptoms including discoloured leaves, declining quality and lack of food crop yield. Potassium is necessary for eight primary plant functions including: enzyme activation, efficient use of water, photosynthesis, transport of sugars, water and nutrient movement, protein synthesis, starch formation and crop quality. Potassium helps to slow crop diseases, reduces water loss, and aids in cellular respiration. Nitrogen use efficiency is also improved when potassium is readily available. In food production, potassium creates crops with a better appearance, more pleasing flavour, enhanced feed value, improved harvest ability, or longer shelf life. This produces better food and better profit potential for farmers.
Potash fertilizer is often necessary to provide adequate amounts of potassium and represents the most cost effect method of increasing crop yields despite escalating prices. Commercial production of potash in the U.S. began when supplies from Germany were stopped due to military conflicts. Carlsbad, New Mexico, became the hub of American production. Other production was subsequently developed in Utah and California. In the 1960s, vast, high quality potash reserves were also discovered in Canada and as a result, Canada now supplies about three-fourths of the potash used in U.S. crop production.
Potash is mined from naturally occurring ore deposits which can often be covered by several thousand feet of earth. Potash bearing deposits occur in many regions of the world including The Dead Sea in Jordan and the Great Salt Lake in Utah, as well as in underground evaporate structures such as those in the Holbrook Basin in Arizona, and were created when ancient seas evaporated millions of years ago leaving minerals and compounds behind.
These evaporates are essentially made up of a mixture of sylvite and halite called sylvinite, which is the most frequently mined mineral compound due to its potassium-rich composition, with Sylvite containing 63.2% K2O equivalent. Halite (NaCl), or sodium chloride, appears as a mass of interlocking crystals. It is transparent, colorless or sometimes has a smoky grey or brownish hue. Sylvite (KCl), potassium chloride, is similar in appearance to halite but has the characteristic of relatively greater solubility. Sylvite crystals are clear or cloudy and can vary in color from white to pink, light orange or red.
Fertilizer potash is mostly derived from these potash rocks. It requires only separation from the salt and other minerals. Potash is generally mined in two ways: conventional underground mining and solution mining.
Conventional Underground Mining
Most potash occurrences are too deep underground for open-cast mining and thus this type of mining is therefore called underground mining. In deep mining, the "room and pillar" method progresses along the potash seam, while pillars and timber are left standing to support the potash mine roof.
Blasting methods utilize explosives to blast and break down ore, and are most often applied in cases where potash seams are extremely variable or other limiting factors make continuous mining techniques impractical. Blasting is most effective in managing mine sites with large variances in ore thickness, and requires less initial capital and maintenance than continuous mining, though generally results in higher costs overall.
Continuous mining is used when the potash seam is sufficiently thick, stable and uniform. This allows miners to calibrate and apply continuous mining machines economically, despite their high initial cost and substantial maintenance, because they are incredibly efficient, are able to cut smoothly, provide low disturbance entry, and possess a high capacity. In addition, continuous mining allows for the use of conveyor belt ore haulage, allowing for the automation of the entire ore extraction process.
In general, two types of continuous mining machines are used: Borer miners and Drum miners. Borer miners apply uniform cutting pressure, have fixed cutting heads, and possess a higher capacity though they only cut a fixed seam thickness and width. Drum miners have rotating cutting heads that cut sideways against the face and despite their lower capacity, are better able to adapt to changing thicknesses.
In contrast, solution mining is used when underground mines are very deep, have irregular deposits, or have become flooded and nworkable. The primary reasons to utilise solution mining is based on the thickness of mineralization, the grade of the potash bed, the depth of burial, the presence of faults, and the dip of potash beds, as an excessive dip can limit recovery.
In solution mining, heat brine, a salt water solution, is injected into the mine and circulated throughout to dissolve potash and salt from the walls. Once the compounds have dissolved, submersible pumps transport the solution to an evaporation pond, where the liquid cools and potash and salt crystals consequently settle to the bottom.
This potash is eventually collected with floating dredges and then pumped to a mill for further processing.
Worldwide Potash Production
Currently, potash is produced in only 12 countries, while more than 150 countries utilising it. According to the International Fertilizer Industry Association, or IFA, six countries accounted for approximately 87% of the world's aggregate potash production in 2007. During this time period, the top seven potash producers controlled approximately 83% of world production. Five of the top ten producers are further concentrated into two marketing groups, which together controlled approximately 57% of global potash production in 2007. The main producing countries include Canada, Belarus, Russia and Israel. At this time Saskatchewan, Canada, is the largest potash producing region in the world, accounting for almost a quarter of world production. The Untied States also produces potash, about 1,200,000 tonnes a year, but consumes 5,200,000 tonnes, to make it one of the largest net importers of potash in the world.