What is potash for?


7 Uses for Granulated Potash

Potash is the general name given to various inorganic compounds that contain potassium in a water-soluble form. A number of common potassium compounds exist, including potassium carbonate and potassium chloride. Before the industrial era, potash was obtained by leaching wood ashes in a pot (hence the name ‘pot-ash’). This product was used to manufacture soap, glass, and even gunpowder.

Today, deposits of potassium-bearing minerals are mined and processed to compound potash into a more usable, granular form. Astonishingly, the amount of potash produced worldwide each year exceeds 30 million tonnes. While most potash is used in various types of fertilizers, there are many other non-agricultural purposes for this element. Modern processing, such as potash compaction, produces a readily available form of potassium, leaving granular potash open to a myriad of uses.

Top 7 Uses for Granulated Potash:


Common Source Materials: Potassium Carbonate, Potassium Chloride, Potassium Sulfate…
Plants require three primary nutrients: nitrogen, phosphorous, and potassium. Potash contains soluble potassium, making it an excellent addition to agricultural fertilizer. It ensures proper maturation in a plant by improving overall health, root strength, disease resistance, and yield rates. In addition, potash creates a better final product, improving the color, texture, and taste of food.

While some potassium is returned to farmlands through recycled manures and crop residues, most of this key element must be replaced. There is no commercially viable alternative that contributes as much potassium to soil as potash, making this element invaluable to crops. For this reason, the most prevalent use of potash is in the agriculture industry. Without fertilizers assisting crop yields, scientists estimate that 33% of the world would experience severe food shortages. The replenishment of potassium to the soil is vital to supporting sustainable food sourcing. Potash compaction granules blend easily into fertilizers, delivering potassium where it is needed most.

Animal Feed

Common Source Materials: Potassium Carbonate
Another agricultural use for potash (potassium carbonate) is animal feed. Potash is added as a supplement to boost the amount of nutrients in the feed, which in turn promotes healthy growth in animals. As an added benefit, it is also known to increase milk production.

Food Products

Common Source Materials: Potassium Carbonate
The food industry utilizes potash (potassium carbonate) as a general-purpose additive. In most instances, it is added as a source of food seasoning. Potash is also used in brewing beer. Historical Use: Potash was once used in German baked goods. It has properties similar to baking soda, and was used to enhance recipes such as gingerbread or lebkuchen.


Common Source Materials: Potassium Hydroxide
Caustic potash (potassium hydroxide) is a precursor to many ‘potassium soaps,’ which are softer and less common than sodium hydroxide-derived soaps. Potassium soaps have greater solubility, requiring less water to liquefy versus sodium soaps. Caustic potash is also used to manufacture detergents and dyes.

Water Softeners

Common Source Materials: Potassium Chloride
Potash (potassium chloride) is used as an environmentally friendly method of treating hard water. It regenerates the ion exchange resins more efficiently than sodium chloride, reducing the total amount of discharged chlorides in sewage or septic systems.

Deicer (Snow and Ice Melting)

Common Source Materials: Potassium Chloride
Potash (potassium chloride) is a major ingredient in deicer products that clear snow and ice from surfaces such as roads and building entrances. While other chemicals are available for this same purpose, potassium chloride holds an advantage by offering a fertilizing value for grass and other vegetation near treated surfaces.

Glass Manufacturing

Common Source Materials: Potassium Carbonate
Glass manufactures use granular potash (potassium carbonate) as a flux, lowering the temperature at which a mixture melts. Because potash confers excellent clarity to glass, it is commonly used in eyeglasses, glassware, televisions, and computer monitors.

Other Uses for Potash

In addition to the uses described above, potash also lends itself well to a variety of other applications, including aluminum recycling, explosives (in products such as fireworks and matches), and pharmaceuticals. As an essential nutrient available in a variety of compounds and flexible in application, the benefits that potash offers the modern world are nearly endless.

FEECO has been working with the various forms of potash for over 60 years, providing agglomeration and material handling solutions for potash processing facilities around the world. Additionally, the FEECO lab can test feasibility of potash granulation and agglomeration with various binders, equipment, and process variations. Contact us today for more information on granular potash!

Download our FREE Potash Processing Handbook

Download our FREE Agglomeration Handbook

Potash is the common name given to a group of minerals and chemicals containing potassium (K), which is a basic nutrient for plants and an important element of fertilizer. Potash is mostly produced in the form of potassium chloride (KCl), but deposits can have different amounts of potassium, so we often measure and refer to it in terms of potassium oxide (K2O) equivalence, for consistency.

Key facts

  • Potash is primarily used to produce fertilizer
  • Canada is the world’s largest producer and exporter of potash
  • Canada has the world’s second largest potash reserves, with 1.2 billion tonnes of potash (potassium oxide equivalent)

Learn more about potash

Potash is primarily used as a fertilizer (approximately 95%) to support plant growth, increase crop yield and disease resistance, and enhance water preservation. Small quantities are used in manufacturing potassium-bearing chemicals such as:

  • detergents
  • ceramics
  • pharmaceuticals
  • water conditioners
  • alternatives to de-icing salt

Potassium is an important element of the human diet. It is essential for growth and the maintenance of tissues, muscles and organs, as well as the electrical activity of the heart.


Canada produced 22.7 million tonnes of potash in 2018, an increase of 2.4 million tonnes compared to 20.3 million tonnes in 2017, making 2018 a record year for Canadian potash output.

Canadian production of potash (potassium chloride), 2009–2018

Text version

This bar chart shows Canada’s annual mine production of potash from 2009 to 2018. Production was 7.2 million tonnes in 2009. It increased to 15.6 million tonnes in 2010 and 17.7 million tonnes in 2011. Production decreased to 15.1 million tonnes in 2012 before steadily increasing towards a value of 18.8 million tonnes in 2015. It then decreased slightly to 17.9 million tonnes in 2016 before increasing to a 10-year peak of 22.7 million tonnes in 2018.

International context

Find out more about potash production on an international scale:

Global potash production was estimated at 68.1 million tonnes in 2018. Canada is the world’s largest potash producer, accounting for 33% of the world’s total in 2018.

Four countries (Canada, Belarus, Russia and China) accounted for 80% of the world’s potash production in 2018.

World production of potash (potassium chloride), 2009–2018 (p)

Text version

This bar chart shows the world’s production of potash from 2009 to 2018. Production was 31.1 million tonnes in 2009 and increased steadily towards a value of 67.1 million tonnes in 2018.

In 2018, the estimated global reserves of potash were 5.8 billion tonnes (potassium oxide equivalent). Canada had the second largest reserves with 1.2 billion tonnes. The following table shows the nations that led in potash reserves.


Canada is the world’s largest exporter of potash. In 2018, Canada exported 21.9 million tonnes of potash, accounting for 41% of the world’s total exports.

Canadian exports of potash (potassium chloride), 2009–2018 (p)

Text version

This bar chart shows Canadian potash exports from 2009 to 2018. Exports were 6.8 million tonnes in 2009 and reached a peak of 17.9 million tonnes in 2015 before a slight decrease to 16.0 million tonnes in 2016. Exports then increased towards a value of 21.9 million tonnes in 2018.

Three countries (Canada, Belarus and Russia) accounted for 79% of the potash traded internationally in 2018.

World exports of potash (potassium chloride), 2009–2018 (p)

Text version

This bar chart shows world potash exports from 2009 to 2018. Exports were at a 10-year low of 19.7 million tonnes in 2009. Exports then increased to 44.2 million tonnes in 2011, 49.6 million tonnes in 2014, 53.1 million tonnes in 2018, with slight export decreases and recoveries in between.


Overall potash prices were in decline from 2012 until the first half of 2017. Prices began to increase in the second half of 2017, reaching US$268/tonne by the end of 2018.

Potassium chloride prices, Vancouver f.o.b, standard, monthly, 2009–2018

Text version

This line chart shows monthly potassium chloride spot prices in U.S. dollars per tonne on standard, bulk, free on board at Vancouver from 2009 to 2018. The price was $844 in January 2009. It then trended upward to reach $870 in February and March 2009. The price began to decrease in April 2009 and was down to $313 by March 2010 before bouncing back to $484 in February 2012. It continued on its downward trend until 2016 when it reached lows of $215 and $216 between September and December of that year, and $214 between February and April 2017. Prices began to increase in the second half of 2017 and had attained $268 by December 2018.

Notes and sources

(p) preliminary

f.o.b. free on board

Totals may be different because of rounding.


  • Canadian mine production of potash (potassium chloride), 2009-2018 (p)
    • Natural Resources Canada

International context

  • World production of potash (potassium chloride), by country, 2018 (p)
    • Natural Resources Canada
    • CRU
  • World production of potash (potassium chloride), 2009-2018 (p)
    • Natural Resources Canada
    • CRU
  • World reserves of potash (potassium oxide equivalent), by country, 2018 (p)
    • Mineral Commodity Summaries February 2019, U.S. Geological Survey


  • Canadian exports of potash (potassium chloride), 2009-2018 (p)
    • Natural Resources Canada
  • World exports of potash (potassium chloride), 2018 (p)
    • Natural Resources Canada; CRU
  • World exports of potash (potassium chloride), 2009-2018 (p)
    • Natural Resources Canada; CRU


  • Potassium chloride spot prices, standard, f.o.b. Vancouver, 2009-2018
    • CRU

A Potash Mine

Potash, pronounced pot-ash, is the term commonly used to describe potassium-containing salts used as fertilizer. Most potash is derived from potassium chloride (KCl), which is also known as Muriate of Potash (MOP). As a source of soluble potassium, potash is vital to the agricultural industry as a primary plant nutrient. Potash increases water retention in plants, improves crop yields, and influences the taste, texture, and nutritional value of many plants. Potash was originally made by leaching tree ashes in metal pots. The process left a white residue on the pot, called “pot ash.” MOP vs. SOP MOP is the most common potash, representing approximately 95% of agricultural potash worldwide, but there are several other forms. The second major form of potash is potassium sulphate or Sulphate of Potash (SOP). What’s the difference? MOP is about half potassium, half chloride, which makes it useful in applications where soil chloride content is low. It is used on carbohydrate crops including wheat, oats, and barley. Also, it’s cost-effective compared to other potassium compounds. Unlike MOP, which is mined, most SOP is produced chemically. SOP doesn’t contain any chloride, which can be an advantage in situations where soil chloride content is high, for example, in very dry environments. SOP is considered a specialty fertilizer for crops such as fruits, vegetables, potatoes, tobacco, and tree nuts and though it represents a smaller market than MOP, it is priced at a premium. Where does potash come from? Most of the world’s potash comes from Canada, with the largest deposits located in Saskatchewan and New Brunswick. Russia and Belarus rank as the second and third highest potash producers. In the United States, 85% of potash is imported from Canada, with the remaining produced in Michigan, New Mexico, and Utah. According to the

U.S. Geological Survey, the 2013 production value of marketable potash, f.o.b. mine, was about $649 million. The fertilizer industry used about 85% of U.S. potash sales, and the chemical industry used the remainder. More than 60% of the potash produced was MOP. Potash mining Today, potash comes from either underground or solution mining. Underground potash deposits come from evaporated sea beds. Boring machines dig out the ore, which is transported to the surface to the processing mill, where the raw ore is crushed and refined to extract the potassium salts. When deposits are located very deep in the earth, solution mining is used as an alternative to traditional underground mining. Solution mining employs the use of water or brine to dissolve water soluble minerals such as potash, magnesium or other salts. Wells are drilled down to the salt deposits, and the solvent is injected into the ore body to dissolve it. The solution is then pumped to surface and the minerals are recovered through recrystallization. What both mining techniques have in common is that companies employing either one need to improve operational efficiency and quality control, increase productivity, manage data, and monitor their operations for compliance with product and environmental safety standards. Laboratory information management systems (LIMS) are the ideal solution to accomplish these goals. Other solutions that improve mine operational efficiency include portable x-ray fluorescence (XRF) analyzers, bulk weighing and monitoring products and mineral analyzers and sampling systems.

Potassium Sulfate Fertilizer 0-0-53

Greenway Biotech, Inc. Potassium Sulfate fertilizer is 100% water soluble Potash fertilizer and contains 53% Potassium and 17% Sulfur. Potassium is one of three main nutrients (Nitrogen (N), Phosphorus (P), and Potassium (K) ) required for growing healthy plants. Potassium has many benefits including:

1. Enhances roots growth in plants.

2. Improve the yield and quality of plants.

3. Balances plants’ metabolism to improve protein synthesis to energize plants for healthy growth.

4. Improves the immune system in plants so they become more resistant to diseases.

In addition, Potassium Sulfate contains 17% Sulfur, which is very important in the growth process for plants and to adjust the pH level of your soil or hydroponics systems.

Potassium Sulfate Fertilizer Application Rate:

Hydroponics: Mix at a rate of 2-3 tablespoons per gallon of water

Foliar: Mix at a rate of 2-3 tablespoons per gallon of water

Soil: Apply 2 pounds per 100 sq.ft.


  • Material Safety Data Sheet
  • Heavy Metal Analysis

Related Blog Articles:

  • What’s the function of Potassium (K) in plants?

Frequently Asked Questions:

  • Potassium Sulfate Fertilizer 0-0-53

Potassium Sulfate 0-0-53 FAQ

1. Is Potassium Sulfate 0-0-53 water soluble?

Yes, Greenway Biotech’s Potassium Sulfate 0-0-53 is 100% water soluble.

2. Can I apply Potassium Sulfate to my lawn? If so, what is the application rate?

Yes, you could apply Potassium Sulfate to your lawn if your soil analysis shows Potassium deficiency.

The application rate depends on the quality of your soil. However, we recommend applying 2 pounds per 100 sq.ft. or 2 tablespoons per gallon of water for maintenance purposes.

3. Is Potassium Sulfate certified organic?

No, Greenway Biotech’s Potassium Sulfate 0-0-53 is NOT certified organic.

4. I am using Potassium Sulfate to grow banana plants. How much Potassium Sulfate do I add per gallon of water?

The application rate varies depending on the quality of your soil and other nutrients you are using. However, we recommend using 2-4 tablespoons per gallon of water in most cases for maintenance purposes.

5. Is Potassium Sulfate suitable for hibiscus plants/trees?

Yes, if your soil is deficient in Potassium and/or if you want to lower the pH level of your soil then Potassium Sulfate is a great product for hibiscus plants. Potassium Sulfate would improve the blooming and the size of the buds.

6. Does Greenway Biotech’s Potassium Sulfate dissolve easily in water? I’ve used potash which claims to be water soluble but precipitates out despite stirring and use of hot water.

Yes, our Potassium Sulfate is 100% water soluble and dissolve easily in water. However, Potassium Sulfate has a lower solubility rate in comparison to other Potash fertilizers such as Potassium Chloride (Muriate of Potash). The maximum solubility rate of Potassium Sulfate is 120 grams per 1 liter of water at 25 °C.

7. How much Potassium Sulfate should I use if I am growing hot pepper plants?

It depends on the quality of your soil and other nutrients you are using. However, we recommend using 1-2 tablespoons per gallon of water for maintenance purposes.

Also, we recommend using our specially formulated Pepper Fertilizer 11-11-40 because not only contains Potassium Sulfate but it also contains all the necessary nutrients and micro-nutrients to have the highest possible yield.

8. Can I apply Potassium Sulfate to my watermelons after they started to fruit?

Yes, you can. However, you need to make sure your soil/plants need Potassium so you won’t overdo it.

9. Can I use Potassium Sulfate to get rid of mites and chiggers?

No, we recommend using Sulfur Powder to get rid of mites and chiggers.

10. Can I use Potassium Sulfate for my queen palms?

Yes, you could certainly apply Potassium Sulfate to your palms if they are potassium deficient. Potassium Sulfate is one of the most efficient and affordable fertilizers to improve and cure potassium deficiencies.


Potassium is an essential plant nutrient and is required in large amounts for proper growth and reproduction of plants. Potassium is considered second only to nitrogen, when it comes to nutrients needed by plants, and is commonly considered as the “quality nutrient.”

It affects the plant shape, size, color, taste and other measurements attributed to healthy produce.

Plants absorb potassium in its ionic form, K+.


Potassium has many different roles in plants:

  • In Photosynthesis, potassium regulates the opening and closing of stomata, and therefore regulates CO2 uptake.
  • Potassium triggers activation of enzymes and is essential for production of Adenosine Triphosphate (ATP). ATP is an important energy source for many chemical processes taking place in plant issues.
  • Potassium plays a major role in the regulation of water in plants (osmo-regulation). Both uptake of water through plant roots and its loss through the stomata are affected by potassium.
  • Known to improve drought resistance.
  • Protein and starch synthesis in plants require potassium as well. Potassium is essential at almost every step of the protein synthesis. In starch synthesis, the enzyme responsible for the process is activated by potassium.
  • Activation of enzymes – potassium has an important role in the activation of many growth related enzymes in plants.


Potassium deficiency might cause abnormalities in plants. Usually the symptoms are growth related.

Potassium deficiency symptoms

Potassium deficiency in banana

Potassium deficiency in citrus

Potassium deficiency in potato

Cholrosis – scorching of plant leaves, with yellowing of the margins of the leaf. This is one of the first symptoms of Potassium deficiency. Symptoms appear on middle and lower leaves.

Slow or Stunted growth – as potassium is an important growth catalyst in plants, potassium deficient plants will have slower or stunted growth.

Poor resistance to temperature changes and to drought – Poor potassium uptake will result in less water circulation in the plant. This will make the plant more susceptible to drought and temperature changes.

Defoliation – left unattended, potassium deficiency in plants results in plants losing their leaves sooner than they should. This process might become even faster if the plant is exposed to drought or high temperatures. Leaves turn yellow, then brown and eventually fall off one by one.

Other symptoms of Potassium deficiency:

  • Poor resistance to pests
  • Weak and unhealthy roots
  • Uneven ripening of fruits

Proper fertilizer management can avoid potassium deficiencies and damage to crops.

Continue reading about potassium in soil.

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Potassium in Plants

Potassium is essential in nearly all processes needed to sustain plant growth and reproduction. Plants deficient in potassium are less resistant to drought, excess water, and high and low temperatures. They are also less resistant to pests, diseases and nematode attacks. Because potassium improves the overall health of growing plants and helps them fight against disease, it is known as the “quality” nutrient. Potassium affects quality factors such as size, shape, color and vigor of the seed or grain, and improves the fiber quality of cotton.

Potassium increases crop yields because it:

  • Increases root growth and improves drought tolerance

  • Builds cellulose and reduces lodging

  • Activates at least 60 enzymes involved in growth

  • Aids in photosynthesis and food formation

  • Helps translocate sugars and starches

  • Produces grains rich in starch

  • Increases protein content of plants

  • Maintains turgor, reduces water loss and wilting

  • Helps retard the spread of crop diseases and nematodes.

Potassium Uptake by Crops

Time of potassium uptake varies with different plants. However, plants generally absorb the majority of their potassium at an earlier growth stage than they do nitrogen and phosphorus.

Experiments on potassium uptake by corn showed that 70 to 80 percent was absorbed by silking time, and 100 percent was absorbed three to four weeks after silking. Translocation of potassium from the leaves and stems to the grain was much less than for phosphorus and nitrogen. The period during grain formation is apparently not a critical one for supply of potassium.

Source: TFI

Note: Potassium content of fertilizers is expressed as K₂O, although there is no such compound in fertilizers, nor is it absorbed by or found in the plant in that form. Soil and plant tissue analysis values are usually expressed in terms of percent potassium (K), but fertilizer recommendations are expressed as K₂O. To convert from K to K₂O, multiply K by 1.2. To convert from K₂O to K, multiply K₂O by a factor of 0.83.

Potassium Removal by Crops

Nutrient uptake or utilization is an important consideration, but crops take up far more potassium than they remove with the harvested portion. For example, a 200 bu/acre corn crop takes up or utilizes about 266 lb/acre of potash. But when the corn is harvested as grain, only 0.25 lb/bu is removed, or 50 lb/acre K₂O is harvested and removed from the field. However, if the crop were harvested as silage, then 7.3 lb/ton K₂O are vested and removed from the field. Therefore, a 32-ton/acre silage crop would remove 234 lb/acre K₂O. Harvest management is the major consideration in developing a potash fertilization program. Crops harvested in which the whole plant is removed from the field, like alfalfa hay, must have more potash applied than crops where only grain, lint or fruit are removed. Often with hay and silage crops, removal is an excellent guide for planning the potash fertilization program. With other crops, such as grain, soil tests offer the best guide.

Source: TFI

Potassium Deficiency Symptoms

Potassium is a highly mobile element in the plant and is translocated from the older to younger tissue. Consequently, potassium deficiency symptoms usually occur first on the lower leaves of the plant, and progress toward the top as the severity of the deficiency increases. One of the most common signs of potassium deficiency is the yellow scorching, or firing (chlorosis), along the leaf margin. In severe cases, the fired margin of the leaf may fall out. However, with broadleaf crops, such as soybeans and cotton, the entire leaf may shed, resulting in premature defoliation of the crop.

Potassium-deficient crops grow slowly and have poorly developed root systems. Stalks are weak, and lodging of cereal crops such as corn and small grain is common. Legumes are not strong competitors for soil potassium and are often crowded out by grasses in a grass-legume pasture. When potassium is not sufficient, winter killing of perennial crops such as alfalfa and grasses can occur.

For more information on potassium deficiency,

Symptoms in Corn

Firing or scorching appears on outer edge of leaf while midrib remains green. May be some yellow striping on lower leaves. (Sorghum and most grasses also react this way.) Poor root development, defective nodal tissues, unfilled, chaffy ears, and stalk lodging are other symptoms in corn.

Symptoms in Soybeans

Firing or scorching begins on outer edge of leaf. When leaf tissue dies, leaf edges become broken and ragged/delayed maturity and slow defoliation/shriveled and less uniform beans, many worthless.

Symptoms in Alfalfa

With classical symptoms (shown at top right), first signs of K deficiency are small white or yellowish dots around outer edges of leaves. Then edges turn yellow and tissue dies and becomes brown and dry. However, for alfalfa grown on soils high in sodium (Na), the K deficiency symptoms have a different appearance, as indicated in the photo at left.

Symptoms in Cotton

Cotton “rust” – first a yellowish or bronze mottling in the leaf. Leaf turns yellowish green, brown specks at tip around margin and between veins. As breakdown progresses, whole leaf becomes reddish brown, dies, sheds prematurely. Short plants with fewer, smaller bolls or short, weak fibers. In the past, K deficiency symptoms have been described as occurring on older, mature leaves at the bottom of the plant. In recent years, symptoms have been observed at the top on young leaves of some heavily fruited cotton varieties.

Symptoms in Wheat

Frequently, no outstanding hunger signs on leaf itself (no discoloration, scorching, or mottling), but sharp difference in plant size and number, length, and condition of roots. Lodging tendency. Smaller kernels. In advanced stages, withering or burn of leaf tips and margins, beginning with older leaves.

Symptoms in Potatoes

Upper leaves, usually smaller, crinkled and darker green than normal with small necrotic patches. Middle to lower leaves show marginal scorch and yellowing. Early indicator: dark green, crinkled leaves, though varieties differ in normal leaf color and texture.

Symptoms in Canola

Potassium deficiency reduces growth, resulting in smaller leaves and thinner stems. Plants are more easily lodged and may wilt. Under severe deficiency, the edges of older leaves become yellow, or scorched and may die completely, but remain attached to the stem.

Symptoms in Rice

Rice deficient in K may show symptoms as stunted plants, a slight reduction in tillering, and short, droopy, dark green upper leaves. Yellowing may appear in interveinal areas of lower leaves, starting from the top and eventually drying to a light brown. Long thin panicles and black, deteriorated roots may be related to K deficiency.

Symptoms in Apples

Yellowish green leaves curl upward along entire leaf…scorched areas develop along edges that become ragged. Undersized and poorly colored fruit may drop prematurely. Poor storage, shipping and canning qualities in fruit.

Symptoms in Sugarbeets

The first sign of K deficiency appears as tanning and leathering of the edges of recently matured leaves. When the soil solution is very low in Na, a severe interveinal leaf scorch and crinkling proceeds to the midrib. Under high Na conditions, tanning and leaf scorch lead to a smooth leaf surface.

All photos are provided courtesy of The Fertilizer Institute (TFI) and its TFI Crop Nutrient Deficiency Image Collection. The photos above are a sample of a greater collection, which provides a comprehensive sampling of hundreds of classic cases of crop deficiency from research plots and farm fields located around the world. For access to the full collection, you can visit TFI’s website.

Relatively Unavailable Potassium

From 90 to 98 percent of the total potassium present in soils is found in insoluble primary minerals that are resistant to chemical breakdown. They release potassium slowly, but in small quantities compared to total needs of growing crops.

Slowly Available Potassium

This form makes up 1–10 percent of the total potassium supply, and may originate from dissolved primary minerals or from potassium fertilizers. This potassium is attracted to the surface of clay minerals, where it may be firmly bound or fixed between the clay layers in a form slowly available to plants. The actual amount available depends on the type and amount of clay present.

Readily Available Potassium

Readily available forms of potassium make up only 0.1 to 2 percent of the total potassium in the soil, and consist of potassium dissolved in the soil solution and held on the exchange positions of the clay and organic matter. This potassium is “exchangeable” because it can be replaced by other positively charged ions (cations) such as hydrogen, calcium and magnesium. This exchange happens rapidly and frequently. The potassium in the soil solution may be taken up by the plant or lost from the soil by leaching, especially on sandy, coarse-textured soils.

Potassium and Balanced Crop Nutrition

Adequate supplies of other plant nutrients are required to obtain maximum responses to potassium fertilizer; however, there are several unique relations between potassium and other nutrients.

High-potassium fertilization can decrease the availability of magnesium to the plant, and may result in magnesium deficiency of crops grown on soils that are already low in magnesium. This problem is often encountered with crops grown on sandy soils, particularly in the coastal plain soils of the southern United States. Conversely, crops grown on soils high in magnesium can suffer potassium deficiency, especially if the soils are high phosphorus and low in potassium. This problem is especially severe in the soils of the Mississippi River flood plain.

Leaching of potassium in acidic, sandy soils may be reduced by liming the soil to a pH of 6.2 to 6.5; however, applications of high rates of limestone to a soil low in potassium may induce potassium deficiency of crops growing on those soils. This problem occurs more on soils with predominantly 2:1 type clays (such as montmorillonite clays) rather than the 1:1 type (such as kaolinitic clays).

Percent of soil samples that tested below critical levels for K for major crops in 2010. Source: TFI

Potassium Fertilizers

Elemental potassium (K) is not found in a pure state in nature because of its high reactivity. It can be purified, but must be kept in oil to retain its purity and prevent violent reactivity. Potash deposits occur as beds of solid salts beneath the earth’s surface and brines in dying lakes and seas.

Placement of Potassium Fertilizers

The common potassium fertilizers are completely water soluble and, in some cases, have a high salt index. Consequently, when placed too close to seed or transplants, they can decrease seed germination and plant survival. This fertilizer injury is most severe on sandy soils, under dry conditions and with high fertilizer rates — especially nitrogen and potassium. Some crops such as soybeans, cotton and peanuts are much more sensitive to fertilizer injury than corn. Placement of the fertilizer in a band approximately 3 inches to the side and 2 inches below the seed is an effective method of preventing fertilizer injury. Band placement of potassium fertilizer is generally more efficient than broadcast application when the rate of application is low or soil levels of potassium are low.


Broadcast application of potassium under minimum tillage results in much of the applied potassium remaining in the top 1 to 2 inches of the soil; whereas, with conventional tillage, it is distributed throughout the plow layer. Corn usually absorbs sufficient potassium under no-till due to its extensive root system in the surface layer of the soil. Leaf analysis of corn shows lower potassium content under minimum tillage than with conventional tillage due to either the location of the applied potassium or to poorer aeration. Sufficient potassium can be supplied by using a higher rate of potassium fertilization with no-till systems.

Potash Development Association

Download pdf: The role of potash in plants (4.00K)
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The role of potash in plants

May 2015

Ian Matts, Company Agronomist, Yara UK

Potassium is one of the major nutrients required by all crops and is present in large quantities in the plant in the form of the cation K+. It plays a major role in achieving the maximum economic yield, as part of a balanced approach to crop nutrition, as well as influencing crop quality.

Potassium is fundamental to many metabolic processes through the activation of a large number of enzymes required for chemical reactions. These include the synthesis of proteins and sugars required for plant growth. Only a relatively small proportion of the plant’s total potassium requirement is needed for this. The majority is required for the essential role of maintaining the water content of plant cells. These roles are discussed below. Many are interlinked.

Protein Synthesis and Nitrogen Utilisation

Protein synthesis is the production of proteins required for plant growth. Nitrogen is another nutrient that is also required by plants for protein synthesis and, where potassium levels in the plant are low, protein synthesis can be reduced, despite an abundance of available nitrogen. Potassium helps improve both the uptake of nitrogen from the soil, and the conversion of nitrogen in the plant to amino acids and ultimately protein. Maintaining adequate potassium levels is therefore very important for maximising the use of nitrogen within the plant.

As with nitrogen, potassium is taken up in large quantities by most crops during the rapid growth phases in spring and early summer, with peak uptake reaching up to 10kg/ha/day.

Turgor Pressure and Lodging Resistance

Potassium is an important nutrient for helping plants resist lodging. This is achieved through its influence on osmosis and turgor pressure, and by cell wall construction.

The process of osmosis is responsible for the movement of water within the plant and also the uptake of water from the soil by roots. This movement of water occurs as a result of the differences in the concentration of salts within the plant cells, which is largely a function of potassium as the K+ cation.

Turgor pressure is caused by the osmotic flow of water into cells causing them to swell, putting pressure on the cell walls to help maintain a rigid and upright structure for plants.

Potassium is also involved in the synthesis of cellulose, a component of cell walls. An adequate supply of potassium is therefore required for increasing the thickness and strength of cell walls, hence reducing the likelihood of lodging.

Water balance and Drought Tolerance

Plants also rely on potassium to regulate the opening and closing of the stomata. These are the tiny apertures on leaves, mainly found on the underside, surrounded by guard cells which control their opening and closing. The stomata are important for allowing the movement of carbon dioxide into the plant, as well as the release of oxygen and the loss of water vapour. The plant regulates the opening and closing of the stomata through the movement of potassium into or out of the guard cells.

When water supply is short, the cells close the stomata to prevent water loss to the atmosphere. If potassium levels within the plant are low the stomata become slow to respond and they do not close as quickly, resulting in the wasteful loss of water vapour. As a result, plants with an insufficient potassium supply are more susceptible to drought.

Frost Tolerance

Potassium promotes a high concentration of sugars in cells. This increase in sugar content in cells helps to lower the sap’s freezing point, acting as antifreeze agents, and resulting in improved frost tolerance. This is particularly helpful for potatoes.


The effect of turgor pressure in cells has a knock on impact on photosynthesis. This is the critical process for plants to convert energy from the sun into chemical energy, in the form of sugars, required for growth and ultimately yield. These sugars contain carbon derived from carbon dioxide from the atmosphere that enters the plant through the stomata. So, the role of potassium in the regulation of stomatal opening is also important for efficient photosynthesis by controlling the movement of carbon dioxide into the leaf. Low levels of potassium can result in inefficient stomatal activity, reducing the level of photosynthesis.

Turgid, swollen cells also have a larger surface area which increases their photosynthesis. Drought stressed leaves tend to roll, reducing the surface area, and reducing photosynthesis.

Potassium also has an impact on the production of ATP, the plant’s energy source. When plants are deficient in potassium the rate of photosynthesis is reduced and hence the rate of ATP production is also reduced.

Transport of water sugars and nutrients

Osmosis is needed in plants, not just for effective water movement round the plant in the xylem, but also for the transport of sugars and proteins required for growth. This is of particular importance late in the plants life for building high yields.

These sugars are produced by photosynthesis in the leaves, but are required in the grains, roots or tubers of the plant. They are transported around the plants in the phloem, and require energy in the form of ATP. When plants are low in potassium, less ATP is available and the transport system slows down. This causes photosynthates to accumulate in the leaves and so the rate of photosynthesis reduces.

Disease and Pest Resistance

Potassium has an essential role in plant disease and pest resistance, probably the most effective of all the nutrients. It is a regulator of enzyme activity, and therefore involved in nearly all cellular functions that influence disease severity.

As already mentioned, potassium is required for the synthesis of proteins, starch and cellulose. The function of cellulose on cell wall thickness not only impacts on the plant’s standing power, but also acts as a mechanical barrier to invasion and infection. Potassium deficiency reduces cellulose production, leading to thinner cell walls with less resistance to infection.

Susceptibility to disease decreases in response to potassium in the same way that the growth of a plant responds to increasing potassium supply.

As a rule, susceptibility to disease decreases in response to potassium in the same way that the growth of a plant responds to increasing potassium supply (as shown in the graph). Beyond optimal supply for growth, there are no further benefits from additional potassium in terms of plant health. So if the soil supply is adequate for growth (index 2-) then the supply for defence against diseases and pests is adequate.

Recent analytical results from Lancrop Laboratories have shown 87% of wheat crops and 85% of oilseed rape crops being below the guideline tissue levels in the Spring, and nearly a third of UK soils, over the last few years, have been below the target index (2-). The level of potassium deficiency may not have been enough to show any visible symptoms of disease or the effect of pests, but it could be leading to an increase in susceptibility of the plants, and putting more strain on the other methods of control.

Potassium uptake is greatest during the period of most rapid growth as plants reach the stem extension stage. Applications of potassium early in the Spring, help supplement the supply from the soil, whether it is at or below target level. Foliar applications can help to target a small quantity of potassium directly to the plants, however this cannot be relied on where the level of deficiency is too great.

Just as humans produce antibodies after infection, plants also have a similar defence mechanism when infected by a pathogen. The infection causes increased production of certain chemicals that form part of the plant’s defence mechanism. The potassium status of a plant is important for both the production and the transport of these compounds to the site of infection. Shortages reduce the amount of natural antifungal compounds, increasing the plant’s susceptibility to disease, once it has penetrated the cells.


Potassium is an essential nutrient for crop growth, being fundamental to many plant processes that impact on crop yield, quality and plant health. It is required in very large quantities, with peak potash uptake in cereals reaching more than 250kg/ha by the end of flowering. The importance of balanced nutrition is clearly evident with potassium, due to its close interactions with nitrogen, both in uptake through the roots and utilisation within the plant. A shortage of potash will not only result in lower nitrogen use efficiency, but will also lead to greater drought susceptibility, increased lodging, a reduction in photosynthesis and restricted movement of water, nutrients and sugars around the plant.

Fertilizer potassium is sometimes called “potash”, a term that comes from an early production technique where potassium was leached from wood ashes and concentrated by evaporating the leachate in large iron pots (“pot-ash”). Clearly, this practice is no longer practical and is not environmentally sustainable. In food production, potassium is removed from the soil in harvested crops and must be replaced in order to maintain future crop growth.

Over 350 million years ago, the huge Devonian Sea was slowly drying up in the area of Central Canada and northern U.S., leaving behind concentrated salts and minerals. This process continues today in places such as the Great Salt Lake and the Dead Sea.

These ancient marine salts are now recovered and used in a variety of useful ways, with the majority being used as potassium fertilizer. Potassium is a natural plant food because fertilizers such as potassium chloride and potassium sulfate are widely found in nature. Fortunately, there are huge reserves of potash in the earth that can meet our need for this nutrient for many centuries to come. This fertilizer is clearly not an artificial or manufactured chemical, since it comes directly from the earth and is simply recycled through very long geological processes.

Potassium is an important mineral required for human health. Since potassium is not stored in the body, it is necessary to continually replace this nutrient on a regular basis with potassium-rich foods. Diets high in potassium and low in sodium have been shown to be beneficial for avoiding high blood pressure.

Potassium is essential for plant health and there must be an adequate supply in the soil to maintain good growth. When the potassium supply is limited, plants have reduced yields, poor quality, utilize water less efficiently, and are more susceptible to pest and disease damage.

In many parts of the world, agricultural soils are gradually becoming depleted of potash. Some soils were high in potassium when they were first cultivated long ago. However, after many years of intensive cropping and repeated nutrient removal during harvest, many fields now require regular inputs of potash to maintain their productivity.

High yielding crops remove large amounts of potassium in the harvested portion of the crop. For example, harvesting 9 ton alfalfa/A will remove over 450 lb K2O. Similarly, a potato yield of 450 cwt/A removes 500 lb K2O, and harvesting 40 ton/A of tomatoes will take off over 450 lb K2O/A. But these high rates of nutrient removal are not usually being matched with fertilization. For example, In Idaho an average of four pounds of potash are removed in crops for every pound that is added back. In the Pacific coast states, over two pounds of potash are removed on average for every pound returned to the field as fertilizer. It’s little wonder that K deficiency is becoming a more common occurrence in agricultural fields.

There are many excellent sources of potassium that can be used to sustain a productive and healthy ecosystem and replenish the soil’s nutrient reserve. So which one should you use? Some of the most popular include:

The potassium in all these fertilizers is identical and this nutrient will be rapidly available to the plant regardless of the source. The primary difference is in the companion nutrients that come along with the potassium.

The importance of chloride is frequently overlooked, but it is an essential nutrient for plant growth. Recent research has demonstrated that many crops respond favorably to chloride applications with greater yield and quality. Like any soluble fertilizer, salt-induced damage can result if large amounts are placed in close proximity to seeds or seedlings. Potassium chloride is usually the least expensive source of potash.

All crops require an adequate supply of sulfur to develop proteins and enzymes. Sulfur-deficient plants appear light green and have reduced yields and quality. Sulfate that is present in potash fertilizers is immediately available for plant uptake.

Because its vital role in chlorophyll, magnesium deficiency is first exhibited by yellow leaves in the lower part of the plant. Magnesium requirements vary considerably, with legumes generally containing more of this element than grasses.

An abundant supply of nitrogen is essential for all high-yielding crops. For crops that prefer a nitrate source to an ammonium source of nitrogen, this potash source can be a good option.

There are many excellent potash sources available for meeting the nutrient requirements of crops. When making a decision on which source to use, choose the one that meets your needs and provides the accompanying anion that will help keep your high-yielding crops in top shape.

About the Author

Dr. Rob Mikkelsen is the Vice President of Communications and North American Program Director for the International Plant Nutrition Institute (IPNI). Prior to his work with IPNI, he served as the Professor of Soil Science at North Carolina State University in Raleigh and Soil Chemist at the National Fertilizer Development Center in Muscle Shoals, Alabama.

Dr. Mikkelsen is well known for his research and expertise in nutrient management, and has authored and co-authored numerous publications. His research has focused on basic agronomic and fertilizer technology, as well as nutrient interactions with the environment, animal waste management, and nutrient budgets.

Dr. Mikkelsen received his B.S. degree in Agronomy/Soils at Brigham Young University, and his Ph.D. in Soil Science at the University of California, Riverside. He currently resides in Merced, California.

What’s the Difference Between Potash and Phosphate?

Potash and phosphate are both used to produce fertilizers, which are becoming increasingly important as demand for food grows.

However, their roles in crop growth are different, and they cannot be used interchangeably. That’s because potash and phosphate are often precisely applied to meet the specific requirements of a particular crop, climate, soil type or topography.

For investors interested in fertilizer companies, it’s worth being aware of the difference between potash and phosphate. Having that knowledge can help guide investment decisions and ultimately lead to increased profitability. On that note, here’s a basic breakdown of the difference between potash and phosphate.


Potash is a potassium-based product that is often bonded to other chemicals. It is predominantly used as a fertilizer to encourage water retention in plants, increase yields, improve taste and help plants resist disease. The two most common potash fertilizers are sulfate of potash (SOP) and muriate of potash (MOP).

The extraction and refinement of potash ore is a complex process as many companies are focused on removing it from ancient underground oceans of potassium salts. These are often located hundreds of feet or more below the surface.

Potash ore is extracted in two ways. In conventional underground mining, ore is dug out by large machines and transported to the surface. This method is expensive, but is also the most common. Solution mining is less common, and involves injecting hot brine (a salt water solution) below the surface and into the ore body. The potash-brine solution is then pumped back to the surface for cooling and separation on surface ponds.

There are two predominant varieties of potash ore: sylvinite and carnallite. Sylvinite typically has a higher value than carnallite as it requires less energy to separate the potassium chloride it contains than it does to separate the magnesium in carnallite.

Canada is the world’s top producer of potash, and also holds the largest reserves. Other top producers include Russia, China and Belarus.


Phosphate is critical for all living organisms, and a whopping 90 percent of it is used for crop applications in support of plant growth. Its primary function is to support strong cell development and water retention.

Phosphate rock, or “phos-rock,” is ore that contains phosphorus. It is located at various depths, and extraction typically requires the use of large drag-line buckets, which scoop up the material for refinement. The phos-rock is then beneficiated, or refined, with small phosphate pebbles being left behind.

Those phosphate particles are coated with hydrocarbons during flotation, and then float to the surface for further separation. The resulting product is beneficiated phosphate rock. Its phosphorus pentoxide content is suitable for phosporic acid or elemental phosphorous production.

Beneficiated phosphate rock is often upgraded into granular diammonium or monoammonium phosphate (DAP and MAP, respectively), both of which are high-grade, water-soluble fertilizers that can be applied to crops. Single super phosphate is a cheaper alternative to the popular DAP, and is obtained through a chemical reaction between rock phosphate and sulfuric acid.

The world’s top producer of phosphate rock by a wide margin is China. The US, Morocco and Western Sahara and Russia are also key phosphate rock producers.


Potash is a generic term for various Potassium (K) salts. Over 90% of Potash is used as fertiliser and is one of the three primary agricultural nutrients (N-P-K).

The end product is sold in fertiliser markets and can take a number of forms, all of which include the critical nutrient Potassium.

Potash can be used on all plants to boost plant health and nutrition as well as to increase crop yields.


While all Potash fertilisers contain Potassium there are a number of different forms. The two most common forms are Muriate of Potash (MOP) and Sulfate of Potash (SOP).

Sulfate of Potash (SOP) is a premium Potash fertiliser free of Chloride (unlike MOP) which is harmful to plants).

SOP is used primarily on high value crops, usually leafy plants, such as fruits and vegetables. MOP is commonly used on carbohydrate type crops such as wheat. SOP may be applied to carbohydrate crops however the use of MOP on leafy plants will typically burn and harm them while also affecting taste.

As a premium product, SOP attracts a premium price to MOP which is currently well above historical premiums of approximately 50%.

The premium has widened in recent times due to instability in the MOP market through the split of Uralkali, a major Potash producer, from the Belarusian Potash Company. Throughout this period the price of SOP has remained stable.

The SOP price is underpinned by the rarity of sizeable primary deposits and the high cost of the Mannheim production process through which approximately 50% of SOP is created. There are no viable substitutes and demand continues to steadily increase, unaffected by the instability in the MOP market.


SOP is produced via primary or secondary processing methods. Primary processing is the lowest cost production method however the rarity of primary deposits means less than 30% of SOP production is via this method.

Reward Minerals will be a primary producer of SOP via its brine deposits in Western Australia.

Around 50% of SOP is produced via the Mannheim process, an energy intensive conversion process whereby MOP is combined with sulfuric acid to create SOP and a hydraulic acid by-product. Not only is the process highly capital intensive, it is predicated on the availability of markets to sell both of the resulting products. It is this supply of SOP which creates a price floor for the commodity well above the marginal production costs for any primary deposits.

‘Potash’: How to Get the Right Kind of K in your N-P-K

‘Potash’: How to Get the Right Kind of K in your N-P-K
Q: Is ‘muriate of potash’ safe to use as an additive in the raised bed gardens I’ll be planting next spring? And if so, do you recommend it? I used it very sparingly along with bone meal and blood meal in an ‘in-ground’ garden I had in St. Louis, where the clay content of the soil was very high. The garden seemed to have no problem producing tomatoes, cucumbers, summer squash, and cantaloupe—although the cantaloupe was not very flavorful.
I plan on filling my new raised beds with premium topsoil and my own compost—which started out as a mix of fall leaves and food waste in a tumbler. The beds will be planted with the same kinds of vegetables as in St. Louis. I’ve purchased the blood meal and bone meal, but none of the garden/hardware/superstores around me carry muriate of potash. An internet search yielded plenty of results, but some sites had warnings that muriate of potash ‘is known by the state of California to cause cancer’, which led me to seek your advice.
—Jack; “originally from St. Louis but currently residing in Richboro, PA.”
A: Centuries ago, true Potash was made by boiling wood and other plant ashes in a pot, which would concentrate the naturally-occurring potassium from the plants into the ashes, hence ‘pot-ash’: potassium in the form of ashes in a pot. But the term became so popular that, despite being archaic and specific, the word ‘potash’ is used to describe pretty much any form of potassium that’s used as a fertilizer.
(Science Sidetrack: Potassium is the “K” in the ‘big three’ of N-P-K; the initials used to indicate the relative amounts of the primary plant nutrients Nitrogen, Phosphorus and Potassium on the labels of all commercial fertilizers, whether synthetic, organic or anything in between
Nitrogen (N) grows big plants, but can inhibit flowering and fruiting if used at high levels. Phosphorus (P) is ‘the flowering nutrient’; it encourages plants to produce more flowers and fruits—and stronger roots. Potassium (K) pretty much does just about everything else: it increases water retention, vigor, yields, nutrient content, color and flavor.)
Now back to our discussion at hand. Are the words ‘potassium’ and ‘potash’ equivalent?
That’s almost a religious discussion. Virtually all of the potassium fertilizers sold today are mined from what used to be prehistoric oceans that are now inland, while a true ‘potash’ would have to have been made from plant ashes. Our listener’s “muriate of potash” is technically a contradiction in terms, because it refers to a specific form of potassium—potassium chloride—that’s mined (along with salt) from those old oceanic deposits and never saw a pot or ashes. (The word ‘muriate’ even refers to brine, or salt.) But old-timers love the word, so ‘potash’ will always be in the N-P-K lexicon.
Now let’s cut to the chase and answer the question. Jack is using blood meal to add nitrogen to his garden and bone meal for phosphorus—both are slaughterhouse by-products that some people might oppose ethically but they’re about as natural as it gets. “Muriate of potash”, aka potassium chloride, is just the opposite; it’s a man-made chemical that’s generally available in what I consider to be crazy high concentrations. So if he really wants to add the big three individually, I’m going to recommend that he stick to the natural path and look for greensand instead.
New Jersey is the site of the biggest known deposit of greensand—an area that was an ocean shore 80 million or so years ago. The material looks like its name—a green-colored sand. Although the bag will say that it only contains one percent potassium, its actually seven percent. (This form of potassium is released slowly over time, and labeling laws only allow you to use the number that’s available to plants the first season.).
Greensand also contains a lot of important and hard to find trace minerals. AND it’s said to improve the structure of both clay and sandy soils. But I would be remiss if I didn’t add that compost and composted manures naturally contain a good amount of potassium—in a form that should be more immediately available to plants. (Hardwood ashes are also a good source of potassium as long as you confine yourself to small amounts and don’t use them anywhere near acid-loving plants like blueberries, azaleas and rhododendrons.)
But even though I have a wood stove (used almost exclusively for fun and power failures) compost is where my garden gets its ‘K’. As we always stress, adding two inches of fresh high-quality compost to your beds every season will satisfy all your plants’ nutritional needs.
Now, what about this “California Cancer” warning?
Back in 1986, California voters adopted what’s known as “Proposition 65” by a wide margin. The Act requires anything that can potentially cause cancer or birth defects to carry the scary warning that you see on a lot of everyday objects. The list is updated every year; and a quick scan of the 800 currently listed chemicals includes a lot of truly bad actors—like arsenic, creosote, the nasty seed treatment captan and virtually every chemical herbicide I’ve ever heard of.
But I also see the warning on things like clothing and plumbing fixtures. Why?
Two possibilities.
&nbsp&nbsp 1) The thresholds for getting on the list are very low, and many people do feel that the warnings lack potency because they seem so ubiquitous.
&nbsp&nbsp 2)Then again, maybe our blithe use of a lot of seemingly harmless everyday objects might explain why we don’t seem to be winning the war on cancer.

The Numbers on Fertilizer Labels, What They Mean

A hallmark of good gardening is providing your plants with fertilizer, right? Well, not necessarily. Let’s take a look at some fertilizer facts and review not just the do’s and don’t of fertilization but, more importantly, the “why’s” behind it all.

Fertilizer is sometimes seen as a gardening “bandage.” Many gardeners are under the false impression that – if their plants look unhealthy or don’t produce – adding fertilizer will fix the problem. In fact, inappropriately adding fertilizer can be the reason for unhealthy or unfruitful plants.

Two Basic Types of Fertilizer

Fertilizer can be synthetic or natural (oftentimes, organic). Natural, or organic-based, fertilizer is derived from plant, animal, microbe, or mineral origin. Examples of organic-based fertilizers (or ingredients) include:

  • Plant-derived: alfalfa, cottonseed meal or seaweed
  • Animal-derived: bone meal or manure
  • Microorganisms derived: heat-dried microbes
  • Mineral-derived: green sand or rock phosphate

Nutrient ratios should be easy to find on fertilizer packaging, as seen here on this 12-55-6 fertilizer high in phosphorus.

Synthetic (also called non-organic) fertilizers are manufactured chemically. They are engineered to deliver nutrients rapidly. The faster the better, right? Well – as with all things, there are benefits and drawbacks to those quick-release nutrients.

Synthetic fertilizers deliver nutrients in a form that can be immediately taken up by plant roots. Quick release = immediate availability = fast results

It’s this immediate availability that can “burn” your plants when too much fertilizer is applied. The plant roots take up too much too quickly, and the plant can be damaged or even die as a result. (Even surrounding soil can be damaged by an over-application of synthetic fertilizer.)

Any synthetic nutrients not taken up by the plants are very susceptible to leaching out of your garden beds or landscape. To put it another way: Synthetic fertilizers stay on the move. They are, essentially, a foreigner in the natural soil ecosystem. As a water soluble product, they’re designed to be readily-available for root uptake. If they aren’t taken up, they travel on out into the environment at large to be taken up by other flora – or, ultimately, into watersheds or aquifers.

For all of these reason, careful and proper application of synthetic fertilizer is key.

Most often, organic nutrients are not in a form that can be taken up immediately. Nutrients in organic-based or natural fertilizers rely on microorganisms in the soil to digest and break those nutrients down into a form that is – then – available to be taken up by plants. Natural fertilizers are slower to take effect in cooler weather, because the microorganisms in the soil are less active.

This break down process means that organic-based nutrients are very resistant to leaching and contain a very low salt index. The nutrients remain in the soil until utilized by plants, and there is very little risk of burning or dehydration – even in periods of extreme drought or over-application.

In a sense, organic-based fertilizers make themselves at home in your garden beds. They remain in the soil and provide ongoing effects.

As illustrated here, organic-based nutrients rely on microorganisms in the soil. Synthetic fertilizers are engineered to be taken up by plant roots immediately.

A Stanford University study performed an experiment on apple trees. They used synthetic fertilizer on some trees, organic fertilizer on other trees, and on a final group of trees, both organic and synthetic were applied. The study determined that approximately five times the nitrate leached from the synthetic fertilizer than the organic, and the combined approach leached the equivalent of half that of the full synthetic applications.

Why does that matter? First, the money you spend on a synthetic fertilizer is, to some degree, washing away in the leaching process. Organic fertilizers are more expensive, but they will remain longer to provide additional benefits that I’ll touch on more in a moment.

Second, those leached nutrients impact our environment. One example of this is when leached nutrients migrate into waterways. The additional nutrients cause increased algae growth, which sets off a chain reaction of impact on the environment at large. There’s a lot written on the impact of fertilizer migration into the environment if you are interested in learning more.

The bottom line: Synthetic and natural fertilizers both have their place in the garden. My job is to help you understand how to use them effectively, efficiently and safely.

Worm castings are an amendment staple at the GardenFarm.

Natural fertilizers will have far-reaching benefits in your garden, but they will be more expensive and results will be slower in coming. Synthetic fertilizers will provide quick results, but the package directions must be followed carefully and nutrient levels must be chosen wisely to prevent leaching. More is definitely not better when it comes to synthetic fertilizer.

Fertilizer Nutrient Ratios

When buying fertilizer, nutrient levels will usually be indicated on the packaging. The levels are often indicated as a ratio – for example 10-10-10

What exactly do those nutrient ratios mean? The numbers represent the percentage, by weight, of Nitrogen (N¹ – always the first number), Phosphorus (P²O5 – always the second number) and Potassium (K²O – always the third number).

A common way of describing the purpose behind each chemical is to think “up, down, and all around.”

Applying this simple phrase will help you remember that Nitrogen helps with plant growth above ground. Nitrogen does a great job of promoting the green, leafy growth of foliage; and it provides the necessary ingredients to produce lush green lawns. Lawn fertilizers will frequently have a high first number – a high level of nitrogen.

Nitrogen fosters foliage and is the top pick for spring lawn fertilization. However, I get these great results with a layer of compost and an application of Milorganite once each year.

Phosphorus is very effective at establishing growth below ground, in the form of healthy root systems. It is also the component most responsible for flower blooms and fruit production. You’ll notice that fertilizers designed for flower production, or starter-type fertilizers for your lawn, have a high middle number – high phosphorus.

Potassium is considered important for overall plant health. This is primarily due to its ability to help build strong cells within the plant tissue. In turn, the plants withstand various stresses; such as heat, cold, pests, and diseases. For example, winterizer fertilizers will have a high third number – high component of potassium.

A common type of all-purpose fertilizer is referred to as 10-10-10. This is a balanced blend of equal portions of nitrogen, phosphorus and potassium. If you purchased a 50-pound bag; five pounds (or 10%) would be nitrogen (N¹), five pounds would be phosphorus (P²O5), and five pounds would be potassium (K²O). The remaining 70% is simply filler, or inert ingredients, which are there mostly to help disperse the chemicals.

So what do these fertilization ratios really mean to the home gardener? If you are a beginning gardener, are not opposed to using synthetic fertilizers, and you just want to provide your plants a good all-around fertilizer; a balanced 10-10-10 ratio would be a common recommendation.

If you have wisely obtained a soil test, the test results may direct you to add a specific fertilizer ratio, like 1:1:3.

This part might require a bit of math on your part – I know, it’s not my favorite subject either.

A side-by-side comparison of synthetic and organic fertilizer traits.

A 1:1:3 would be the same as 10-10-30 or 20-20-60 or 5-5-15. You may not be able to find any fertilizer available at a matching ratio, but don’t sweat it. These are guidelines. If all you can find is a 10-5-15 or a 10-10-20, that ratio will still get your soil going in the right direction.

Now that you have a deeper understanding of the benefits produced by each nutrient, you might choose to fertilize based on specific needs or goals. Here are some examples:

  • To boost lawn growth at the beginning of the growing season, a fertilizer with a high nitrogen ratio is your best option. The nitrogen will foster the growth of lawn foliage. In fact, many commercially-available lawn fertilizers provide a high nitrogen ratio and indicate zero as the phosphorus ratio (phosphorus is most likely to be unused and to leach into the environment).
  • To amp up bloom power of your shrubs and perennials, a fertilizer with a higher phosphorus ratio is most appropriate. This is the main reason you often see fertilizer with high phosphorus labeled as a “bloom” fertilizer.
  • To increase production of your favorite tomatoes, a fertilizer with higher phosphorus and potassium ratios (low on nitrogen) is your best option.
  • To toughen up your plants or lawn for environmental stresses – like drought or cold, you’ll want a fertilizer with a higher ratio of phosphorus and potassium. During periods of stress, plants naturally enter a dormancy – they slow down or stop foliage growth. So adding nitrogen in this case may not be appropriate – you don’t want to fertilize for new foliage when the plant is trying to go dormant.

Instead, your goal should be to promote cell structure and strong roots which continue to grow through those times of environmental stress – strengthening your plant to be more vigorous once environmental conditions are less extreme.

When buying synthetic fertilizer, those ratios will be front-and-center on the package, making it easy to customize according to your needs. But what about natural fertilizers? When buying commercially-available natural fertilizers, those ratios may also be provided.

When you are wistful for more bloom and color in your garden, seek out a fertilizer with a higher phosphorous ratio.

Oftentimes, you are purchasing an organic ingredient, like fish emulsion or bone meal, to be used as fertilizer. Nutrient ratios aren’t always as clear when relying on natural fertilizers. Here are some good basics:

Nitrogen providers: Dried blood, blood meal, cottonseed meal, fish emulsion, and seaweed extract

Phosphorus providers: Bone meal, rock phosphate

Potassium providers: Greensand, sulfate of potash

Organic-based fertilizers – because they are natural – release their nutrients at different rates. So when I say natural fertilizers are released “slowly” – that is intentionally vague. Here are some examples of organic nutrient release rates:

  • Blood meal and many types of manure – which can be available to plant roots within two to six weeks
  • Alfalfa, clover and rye – which can be available to plant roots within two to six months
  • Eggshells and fish emulsion – which can be available to plants quickly but are often used up within two weeks
  • Heat-dried microorganisms’ slow release nitrogen – which can be available to the plant up to 8-10 weeks.
    • What are heat-dried microorganisms? These organisms have consumed nutrients in another environment and have died once all available nutrients have been consumed. The organisms are, then, preserved in a drying process to be added back to your garden environment to provide nutrients to the living microorganisms there. It’s similar to the process of leaves falling from trees in fall, to break down and be absorbed by the soil food web of the forest floor.

In addition to nitrogen, phosphorus and potassium, there are 12 other elements considered essential for plant growth that are absorbed from the surrounding soil. Organic soil amendments are ideal for providing all of these elements as well. There’s more on that in my soil “recipe.”

My journey with soil has brought occasional heartbreak – but years of experience have culminated into these gorgeous results with the development of my perfect “soil recipe” of organic ingredients. This rich soil isn’t achieved through fertilization. It’s enriched year over year with proper care and amendment.

It’s worth noting that natural and organic-based fertilizers will not have an impact on your soil pH – at least not a significant impact. Soil pH is another topic altogether, and there are specific steps you can take to alter your pH. That said, virtually all organic ingredients will help to balance your soil to a neutral (6.5-7.0) pH. Compost is a great example of that.

As you add compost, your soil pH will tend toward neutral.

Fertilizer Forms

Fertilizers are most commonly-available in liquid or granular forms, spikes, or pellets.

Liquid form can be a good option when you are in need of quick results. However, remember that liquid fertilizer is most likely to have a higher leach rate. What isn’t taken up immediately by plant roots will be washed away.

I don’t recommend using spikes. They don’t provide an even distribution of nutrients.

For a slow and steady feeding, I prefer granular or pelletized organic-based or natural fertilizer. They are the easiest forms to distribute evenly, and they are taken up more slowly by plant roots.

If I’m looking for a quick boost to supplement the organic matter I apply to the soil, I use an organic or natural liquid fertilizer, usually a fish emulsion product to provide the nitrogen infusion I’m after.

Adding nitrogen to tomato plants is a common gardening mistake. When added at the wrong time, nitrogen hinders fruiting – meaning fewer luscious tomatoes for your kitchen.

Still – Not the Final Solution

Now that you have a better understanding of fertilizers and their impacts in the garden, remember that fertilizer is still not the ultimate answer for plant health. If your plants are suffering, fertilizer may not be your solution, so I recommend going back to the basics:

  • Are your plants receiving appropriate light? Conditions in your landscape can change – trees can grow and shade out plants you originally placed for full sun.
  • Are your plants receiving appropriate water? Watering systems can malfunction, leaving plant roots drowning or gasping for a drink.
  • Is your soil pH out of balance? If you haven’t gotten a soil test to rule out pH as your problem, I highly recommend starting there.
  • Did you over-fertilize? Improperly fertilizing (especially with a synthetic fertilizer) can cause more harm than good. Be sure to read the fertilizer label for proper application to avoid burning your plants.
  • Are there any pests or diseases at work? Yes, fertilizing can improve your plant’s resilience to stand up against pests or disease, but fertilizer won’t solve this problem. Check out some of my other resources on management of these garden foes.

Fertilizer, when applied inappropriately, can damage plant health – burning foliage with an excess of nutrients.

If this all feels like too much to think about, don’t worry! Anyone can do this, and do it like a pro. Just learn each aspect step-by-step. I have lots of additional information already available to help you, and there is much more to come.

How I Fertilize in My Garden

Now you have a better understanding of the pros and cons – the why’s of fertilizing. This will help you make the best choices for your garden and lifestyle.

You may be wondering what I prefer. I’m glad you asked.

The GardenFarm in full – and bountiful – swing. I didn’t add fertilizer to these planting holes at the beginning of the growing season. This health and vigor is the result of organic amendment to my soil.

In general, I prefer not to fertilize. If you’ve listened to my recent podcast series on raised bed gardening, you know that I build up my soil with a “recipe” of organic materials, and I keep feeding that nutrient “bank” with organic amendments once or twice each season.

Those organic amendments feed the soil, so my soil can feed the plants. All that organic material also helps my soil maintain optimal moisture balance and increases overall disease- and pest-resistance in my garden.

The higher your soil is in organic matter (5% by weight is the ideal, but even 2% is considered good) the better the structure overall – meaning improved drainage and an easier medium to plant in and work with.

I take the same approach with my lawn – using only organic-based or natural amendments – and I am rewarded with a lush, green lawn that doesn’t require much supplemental watering.

By broadcasting compost in my lawn, I am improving soil health and aeration. That fosters better development of grass roots and means my grass is naturally able to withstand extreme conditions – like drought and heat. Don’t get me wrong – it doesn’t mean my lawn is bulletproof but pretty darn close.

There are instances when I use natural fertilizers in my lawn and garden. During my seasonal garden amendment, I often add just a little kick of natural fertilizer. When growing heavy feeders like tomato plants or containers, I will add a bit of natural fertilizer two (sometimes three) times during a growing season.

For lawns and landscaped beds, my favorite organic-based fertilizer is Milorganite®. In raised beds, I also use fish emulsion and worm effluent (from my vermicompost bin) and diluted at 10 to 20 parts with water. I get amazing results from each.

Personally, I don’t use synthetic fertilizers in my landscape or garden, and I don’t add any type of fertilizer to planting holes or through my irrigation system. I prefer to make the longer-term investment of natural ingredients that have kept my gardens looking television-ready for years.

A Final Note

I’ve often been asked about disposing of fertilizer. If you have fertilizer that you no longer wish to use in your garden or landscape, don’t simply throw it in the trash or flush it away. The nutrients in that fertilizer make their way into our environment through the landfill, and they can have long-term negative effects. You’ll need to contact your county or city government and ask them when and where you can go to safely dispose of your unwanted fertilizer.

Links & Resources

Episode 008: Organic Pest Control with Jeff Gillman

Episode 009: Organic Disease Control with Jeff Gillman

Episode 043: Raised Bed Gardening, Pt. 2: Perfect Soil Recipe

GGW Episode 726: The Down and Dirty on Healthy Soil and Compost

GGW: Liquid Worm Juice; Superfood for Organic Gardens


UMass Extension Center for Agriculture: Understanding a Turf Fertilizer Label

About Joe Lamp’l

Joe Lamp’l is the creator and “joe” behind joe gardener®. His lifetime passion and devotion to all things horticulture has led him to a long-time career as one of the country’s most recognized and trusted personalities in organic gardening and sustainability. That is most evident in his role as host and creator of Growing a Greener World®, a national green-living lifestyle series on PBS currently in production of its ninth season. When he’s not working in his large, raised bed vegetable garden, he’s likely planting or digging something up, or spending time with his family on their organic farm, just north of Atlanta, GA.

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