Difference Between Potash and Potassium: Labels and Prices

The difference between potash and potassium is simple: potassium (K) is the plant nutrient, and potash is the fertilizer salt that carries it. The U.S. Geological Survey defines potash as mined and manufactured salts that hold potassium in water-soluble form, such as potassium chloride (USGS, 2026). On a bag, potash is rated by K₂O, so 0-0-60 means 60% K₂O. Phosphate is a different nutrient source: it supplies phosphorus (P), the middle number on the label.

This guide puts the terms side by side, shows the label math, charts where each nutrient is mined, and gives dated US prices. It ends with a calculator that turns a price per ton into a cost per pound of nutrient.

Potash vs potassium vs phosphate, side by side

Many mix-ups come from a few habits: farmers say “potash” and “potassium” for the same thing, soil labs report elements, and bags report oxides. The table separates the four words you will meet most often.

The grades for DAP, MAP and 0-0-60 potash come from Ohio State University Extension. The two triple superphosphate grades are listed in a USDA technical review. So potash is not phosphorus, and phosphate is not potassium. They are two different nutrients, and a crop needs both. One cannot stand in for the other. The USGS notes that no substitute exists for potassium as an essential plant nutrient.

Why fertilizer labels show K2O and P2O5

The labels follow an old convention. Penn State Extension explains that P₂O₅ and K₂O are the traditional way to state phosphorus and potassium, although those compounds do not exist in fertilizer. To get the real element share, Penn State gives two factors: percent P₂O₅ times 0.44 gives percent P, and percent K₂O times 0.83 gives percent K.

• Potash 0-0-60: a 60% rating is about 50% elemental potassium (60 x 0.83 = 49.8). A 100 lb bag holds 60 lb of the oxide form.
• DAP 18-46-0: 46% P₂O₅ is about 20% elemental phosphorus (46 x 0.44 = 20.2). A 100 lb bag holds 46 lb of P₂O₅ and 18 lb of nitrogen.

Penn State adds that you rarely need to convert, because fertilizer advice is almost always given in pounds of P₂O₅ and K₂O. The one mistake to avoid is mixing the two systems. If a soil report gives a rate in pounds of K₂O, divide by the K₂O share of your product to find how much product to buy. A 60 lb recommendation is 100 lb of 0-0-60 (60 divided by 0.60).

Types of potash fertilizer

“Potash” covers several products. In agriculture, the USGS lists potassium chloride (KCl), potassium sulfate (sulfate of potash, SOP) and potassium magnesium sulfate (langbeinite) as the potassic fertilizers. Muriate of potash (MOP) is an agriculturally acceptable mix of KCl, at least 95% pure, and sodium chloride. In the United States, the fertilizer industry used about 85% of potash sales, and more than 60% of the potash produced was SOP or potassium magnesium sulfate, which chloride-sensitive crops need (USGS, 2026). Our guide to muriate of potash and its types covers the common grades in more detail.

The practical rule: MOP is the standard choice for most field crops, and a sulfate form suits crops that react badly to chloride. Check the crop’s guidance from your local extension service before you choose.

Types of phosphate fertilizer

Phosphate fertilizers are made by treating phosphate rock with acid. In the United States, more than 95% of mined rock goes into wet-process phosphoric acid, which is then turned into granular and liquid ammonium phosphate fertilizers such as DAP and MAP. About 25% of that acid was exported as DAP, MAP, merchant-grade acid and other products (USGS phosphate rock summary, 2026). Triple superphosphate is a third common form and carries no nitrogen.

The choice often comes down to what else you need. DAP and MAP carry nitrogen with the phosphate, while triple superphosphate gives phosphate alone. As with potash, compare them by cost per pound of P₂O₅, and remember that the nitrogen in DAP and MAP has value if your crop needs it.

Where potash and phosphate come from

Both nutrients start in the ground. Potash comes from underground salt deposits or brines, and the largest producer is Canada. The USGS estimates world potash mine output at 49 million tons of K₂O equivalent in 2025, with Canada at 15 million. The United States imports most of its supply: net import reliance was 92% of apparent consumption in 2025, and Canada supplied 79% of imports in 2021-24 (USGS, 2026). Our overview of Saskatchewan potash mining looks at the Canadian side.

Chart

World potash mine output, leading producers

million tons of K2O equivalent, 2025 estimate; countries with 1.8 million or more

Phosphate starts as phosphate rock. World marketable output was 250 million tons in 2025, and China produced 110 million of them, followed by Morocco at 36 million and the United States at 20 million. Morocco also holds about 50 of the 73 billion tons of world reserves in the USGS table (USGS phosphate rock summary, 2026). The Fertilizer Institute adds that phosphate fertilizer needs more than rock: it also depends on sulfur and ammonia, so its cost chain differs from potash (TFI, 2026).

Chart

World phosphate rock output, leading producers

million tons of marketable rock, 2025 estimate; top five of the USGS table

What phosphorus and potassium do in the plant

Phosphorus. Iowa State University Extension describes phosphorus as part of sugar phosphates, as involved in respiration and energy transfer through ATP, and as part of DNA, RNA and cell membranes (Iowa State, Phosphorus Basics). The same source says phosphorus reaches roots mainly by diffusion and root interception, and diffusion works only over very short distances, so a large and active root system matters. Low phosphorus shows as stunting and reddish growth (Iowa State soil test guide).

Potassium. Potassium is the most abundant cation in plants and a major osmolyte that helps regulate the stomata, the leaf pores that control water use (Plant Cell Physiology, 2013, rice study). Iowa State’s lawn and garden soil-test guidance lists stunted growth and brown leaf edges as deficiency signs and notes that sandy soils lose potassium easily through leaching while clay and organic soils hold it better.

Potash and phosphate prices

DTN collects fertilizer price bids from US retailers each week. For the week of 12 to 16 October 2026, the national averages were US$937 per ton for DAP, US$981 for MAP and US$503 for potash. DAP was 2% and potash 3% higher than a year earlier (DTN, 21 October 2026). These are retail averages per ton of product, not what your dealer will quote.

Chart

US retail fertilizer prices, DAP and potash

US$ per ton of product, DTN national retail averages, 14 snapshots about four weeks apart, from 13 Oct 2025 to 12 Oct 2026

Per ton of product is not the fair comparison, because the products hold different amounts of nutrient. At 60% K₂O, a ton of potash holds 1,200 lb of K₂O, so US$503 is about US$0.42 per pound. At 46% P₂O₅, a ton of DAP holds 920 lb, so US$937 is about US$1.02 per pound (our arithmetic; DAP also carries nitrogen, so this overstates the cost of phosphorus alone). Over the 14 snapshots in the chart, potash stayed between US$484 and US$503, while DAP moved between US$847 and US$937.

How much phosphate and potash do crops remove?

Crops carry nutrients off the field in the grain. Ohio State measured this in more than 300 on-farm trials across 39 counties: 180 bu/acre corn removed 62 lb of P₂O₅ and 36 lb of K₂O per acre, while 60 bu/acre soybean removed 47 lb of P₂O₅ and 68 lb of K₂O. A corn-soybean rotation removed roughly 100-120 lb of each per acre (Ohio State Extension, 2019). Soybean takes more potash than phosphate; corn is the other way round.

Chart

Grain removal of P2O5 and K2O by crop

lb per acre removed in grain at 180 bu corn, 60 bu soybean, 80 bu wheat

Removal is not the same as need. In Iowa trials, yield gains from phosphorus were small and near zero in the higher soil-test categories, and gains from potassium were small and on average zero in the high and very high categories. At very low phosphorus tests, corn gained about 10 to 100 bu/acre (Iowa State, 2023). So a soil test decides whether to add, hold back or build up.

A worked example for a corn-soybean rotation

Ohio State converts its removal figures into products: about 210 lb of MAP, 240 lb of DAP or 180 lb of potash per acre to replace what a 180 bu corn and 60 bu soybean rotation removes. At the DTN national averages above, 180 lb of potash costs about US$45 per acre (180 lb x US$503 per ton, divided by 2,000), and 240 lb of DAP costs about US$112 per acre. Your price, rate and soil test will differ, so use the calculator below with your own numbers.

How much does a pound of K2O or P2O5 cost you?

Enter your own prices, grades and rates. The calculator gives the cost per pound of each nutrient, the product you need per acre and the total bill.

Try the numbers for your own farm below.

Seven ways to manage phosphate and potash

These steps apply to US, Canadian, UK and Australian row crops and pastures. Always follow the product label and local rules, which can limit phosphorus use in some regions, and ask a certified crop adviser for rates that fit your fields.

1. Soil test before you buy

Sample by field or by zone, and keep the sampling depth and method the same each time so results can be compared. Iowa State’s guidance builds its advice on soil tests taken to a 6-inch depth and notes that the Bray P1 test is not recommended for soils with pH 7.3 or higher (Iowa State PM 1688). Ask your lab which test suits your soil.

2. Match rates to removal where soil tests are in range

Ohio State’s “build up and maintain” approach says that once soil is in the maintenance range, you apply about what the grain removes. The Ohio figures above turn a yield goal into a pounds-per-acre starting point.

3. Pick the right potash type

Use MOP for most crops and a sulfate form for chloride-sensitive crops, as the USGS describes. Compare products by the cost per pound of nutrient, not per ton.

4. Watch sandy soils for potassium loss

Because sandy soils lose potassium by leaching, Iowa State’s garden guidance suggests working potassium into the soil rather than only spreading it on the surface. Ask your adviser whether a split rate suits your soil and crop.

5. Protect fields from phosphorus runoff

Phosphorus is strongly adsorbed by soil particles, as Iowa State notes, so erosion and runoff can carry it off the field. The EPA lists right amount, right time, right method and right placement, plus year-round ground cover, field buffers and conservation tillage, as ways to reduce nutrient losses.

6. Map the field, then vary the rate

Fields are rarely uniform. Zone or grid sampling shows where soil tests differ, and a spreader with variable-rate control can follow the map. Satellite vegetation maps help you choose where to sample first, but they show crop vigor, not the nutrient behind it, so confirm with a soil or tissue test.

7. Count manure and compost as nutrient sources

Manure holds both phosphorus and potassium. The USGS notes that manure is a low-potassium material that is practical to haul only short distances. Test manure for its nutrient content and credit it against your plan, as Iowa State advises for manure nutrients.

Keeping phosphate and potash out of the water

Good nutrient management is also water management, and the same steps that protect your soil protect the stream beside the field.

Phosphorus is the nutrient that matters most for water. The EPA says excess nitrogen and phosphorus can wash from fields in rain and snowmelt and cause eutrophication, which can lead to low-oxygen “dead zones” and harmful algal blooms (EPA). The EPA Watershed Academy summary of the scientific literature states that in the United States and many other nations, fertilizer inputs of phosphorus and nitrogen to agriculture exceed what is removed in products (EPA Watershed Academy). Applying more potash than the crop and soil need also wastes money.

▶ Seven green farming technologies that save water, fuel and fertilizer, explained by a cow farmer. · 2:24

Where satellite maps help

Farmonaut Satellite + AI Farm Monitoring System shows field-by-field vegetation change from satellite passes, which can point you to the weaker zones to test for phosphorus, potassium or other limits. It cannot name the cause on its own, so treat the map as a way to decide where to look.

▶ A demo-account apple block where satellite passes show crop stress before it is visible on foot. · 1:42

How we checked the numbers

Production, reserve, import and definition figures come from the USGS Mineral Commodity Summaries for potash and phosphate rock, published in 2026. Price figures come from the DTN retail fertilizer survey of 21 October 2026, which reports retailer bids as national averages. Removal figures come from Ohio State University Extension. The per-pound costs and the per-acre costs are our own arithmetic from those sources. Prices change weekly, so check a local quote before you buy.

FAQ

What is the difference between potash and potassium?

Potassium is the element and plant nutrient. Potash is the group of potassium salts sold as fertilizer, such as potassium chloride, and its label number is K₂O. Potash 0-0-60 holds 60% K₂O, about 50% potassium by weight (Penn State factor of 0.83).

Is potash the same as phosphorus or phosphate?

No. Potash supplies potassium, the third number on the label. Phosphate fertilizers such as DAP, MAP and triple superphosphate supply phosphorus, the middle number. A crop needs both, and neither replaces the other.

Is phosphate the same as potassium?

No. Phosphate carries phosphorus (P, as P₂O₅), and potassium (K, as K₂O) comes from potash. They do different jobs in the plant, and they are mined in different places and priced differently.

Can I use DAP instead of potash, or the other way round?

No, because they supply different nutrients. DAP 18-46-0 gives nitrogen and phosphate and no potassium, and potash 0-0-60 gives only potassium. A soil test shows which one your field needs.

Is muriate of potash safe for every crop?

Not every crop. Muriate of potash contains chloride, and the USGS says sulfate forms are used for chloride-sensitive crops. Check the label and your local extension advice for the crop.

How do I turn a K2O recommendation into pounds of product?

Divide the recommendation by the K₂O share of the product. For 90 lb of K₂O per acre from 0-0-60, divide 90 by 0.60 to get 150 lb of potash per acre. The calculator above does the same sum for phosphate.

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