Key Takeaways

• Most soils have enough K. Most Nebraska soils can supply enough potassium (K) for excellent corn yields, and EC117 suggests no K when soil-test K is 125 ppm or higher.

• K response unlikely above 100 ppm soil-test K. Above 100 ppm soil-test K, the probability of a yield response is very low, so weigh corn and potash prices before applying.

• Banding can reduce fertilizer costs. On medium-testing soils, a 10 lb K₂O/ac band beside the row is an EC117 alternative to 40 lb broadcast.

• Potash prices remain relatively stable. Potash averaged $498 per ton in late September 2026, about $0.42 per lb K₂O and only 2.5% more than a year earlier.

• Prioritize fields with the greatest need. Spend K dollars first on low-testing fields and zones, and credit K supplied by manure.

Potassium (K) fertilizer deserves a different management approach than nitrogen or phosphorus in much of Nebraska. Most Nebraska soils are capable of supplying enough K for excellent corn yields, and K is held on soil particles and moves little in most soils. Deficiency can still occur, but routine K application without soil-test information is difficult to justify, particularly when fertilizer prices are high.

The opportunity for savings is straightforward: use soil testing to distinguish fields that need K from fields where another application is unlikely to pay.

Unlike phosphorus, potash prices have changed little over the past year. According to DTN, the average retail price of potash (0-0-60) during Sept. 21–25, 2026, was $498 per ton, up about 2.5% from $486 per ton during the same week in 2025 (Quinn, 2026). Because a ton of potash contains 1,200 lb K₂O, that works out to about $0.42 per lb K₂O, compared with about $0.41 a year earlier (Figure 1). 

At that price, a 40-lb K₂O/ac broadcast application costs about $17/ac in fertilizer alone, compared with about $50/ac for the 120-lb rate recommended for very low-testing soils. Those dollars are better spent on acres where a response is likely.

Start With a 0- to 8-Inch Soil Test

Nebraska Extension recommends collecting soil samples from the surface 0–8 inches, ideally in the fall, every three to five years to determine P, K and micronutrient needs. EC117’s K categories are based on an exchangeable K test, which most labs report as ammonium acetate-extractable K. Confirm that your lab reports this test, and use the same lab and sampling season to make year-to-year comparisons more reliable.

The Nebraska Extension NebGuide EC117, “Nutrient Management Suggestions for Corn” (Iqbal et al., 2023), gives suggested K₂O rates by soil-test category (Table 1) and, as an alternative to the table, a simple equation:

K₂O rate (lb/ac) = 125 − soil-test K (ppm), when soil-test K is below 125 ppm

For example, a field with a soil-test K level of 100 ppm K would call for 25 lb K₂O/ac, while a field testing 130 ppm would need no additional K fertilizer. At lower soil-test levels, the equation gives somewhat lower rates than the table (95 lb K₂O/ac compared with 120 lb K₂O/ac at 30 ppm, and 65 lb compared with 80 lb at 60 ppm). Both are EC117 options, and the equation’s field-specific rates may suit a tight budget on medium-testing soils.

Response Is Unlikely at Higher Soil-Test K

EC117 notes that when soil-test K is above 100 ppm, the probability of a corn yield response to K fertilizer is very low, and no K₂O is suggested once soil-test K reaches 125 ppm. The 100–124 ppm range is therefore a decision zone: EC117 still lists a medium-category rate for these soils, but whether that application is profitable depends on corn and potash prices (see below).

A producer may have included potash in a standard fertilizer program every year. But if the soil test shows adequate K, repeating that application simply because it was part of last year’s program offers little chance of a profitable response. Under high fertilizer prices, that is exactly the type of expense that deserves reevaluation. Where K is skipped on high-testing fields, resampling every three to five years will show whether soil-test K is trending down.

Prioritize Low-Testing Fields

The objective is not to eliminate K fertilizer. Soil K deficiency can occur in Nebraska, and low-testing fields still need appropriate fertilization. Spend K dollars first on fields or management zones where soil tests indicate the greatest agronomic need.

EC117 groups soil-test K into five categories (Table 1). Suggested broadcast rates are:

• 120 lb K₂O/ac for very low (0 to 40 ppm).
• 80 lb for low (41 to 74 ppm).
• 40 lb for medium (75 to 124 ppm) soils.

No K is suggested for high (125 to 150 ppm) or very high (more than 150 ppm) soils.

^{Banded rates are placed beside the seed row, not with the seed. “Plus” means in addition to the broadcast rate; “or” means instead of it.}

Band to Stretch K Dollars on Medium-Testing Soils

EC117 lists 10 lb K₂O/ac banded beside the seed row as an alternative to the 40 lb broadcast rate on medium-testing soils. On very low and low soils, a band of 20 or 10 lb K₂O/ac is suggested in addition to the broadcast rate. Place the band beside the seed row, not in contact with the seed. 

At the September 2026 average potash price, 10 lb K₂O/ac costs about $4/ac in fertilizer, compared with about $17/ac for the 40 lb broadcast rate, although liquid K sources used for banding can cost more per pound of K₂O. This option requires a planter or applicator that can place fertilizer beside the row, so check equipment before counting on it.

Include Fertilizer Price and Corn Price in the Decision

EC117 cautions producers to consider both corn value and K fertilizer cost when soil-test K is above 100 ppm, because the chance of a yield response is already low. A profitable response is unlikely when the ratio of corn price per bushel to K₂O price per pound is below 8.

To calculate the ratio, first divide the price per ton of potash by 1,200 to get the price per pound of K₂O. Then divide the corn price per bushel by that number. At the September 2026 average potash price of $498 per ton ($0.415/lb K₂O), the ratio falls below 8 when corn is below about $3.32/bu (Figure 2). For example, with corn at $4.00/bu the ratio is about 9.6, and at $3.25/bu it is about 7.8. Run the numbers with your own dealer quote and expected corn price.

Because potash prices have changed little over the past year, the ratio at current corn prices sits above 8 this year. That means the soil test, more than the price ratio, should drive most K decisions: on soils testing 125 ppm or more, no K is suggested regardless of price, and between 100–124 ppm the ratio helps decide whether the medium-category rate is worth applying.

The relevant question under high input prices is not whether K might produce some response, but “Is the expected yield response large enough to pay for the fertilizer?” Where soil-test K is already adequate, dollars are better spent on other nutrients that may provide a better return on your investment.

Use Spatial Information Where K Varies Within a Field

A single composite sample can work well in relatively uniform fields, but K can vary within a field because of soil type, landscape position, erosion, deposition, past manure applications and previous fertilizer management. A field-average test might indicate adequate K levels even when parts of the field test low enough to warrant fertilizer. Conversely, one uniform rate across the field may fertilize acres that already have enough.

Improving K management does not necessarily require new technology. Many growers already have several years of soil-test results, yield maps, soil survey and elevation data, and manure and fertilizer application records. These records can help identify which parts of a field would benefit from grid or management-zone sampling. Start with the nutrient decision, not the equipment: if better spatial information is likely to change the K rate, zone sampling and variable-rate application may pay.

Account for Potassium Supplied by Manure

Manure can supply substantial amounts of K. Fields with a history of repeated manure applications may test adequate or high in K even if no commercial potash has been applied recently, and failing to credit manure K can mean buying nutrients the soil already has. Use soil tests and manure analysis together to decide whether commercial K is needed. Nebraska Extension NebGuide G1335, “Determining Crop-Available Nutrients from Manure,” explains how to estimate the K supplied by an application. 

Evaluate What You Are Removing 

K removal varies by the crop grown (Table 2). Fields harvested for silage or that have cornstalks baled remove far more K than grain-only fields. Forage crops, such as alfalfa, also remove significant amounts of K. Keep this in mind when evaluating the economics of these practices. 

If you have soils with high soil-test K levels, extra removal is not an immediate economic concern. However, on low-testing soils, the cost of fertilizer to replace nutrients taken off may not make financial sense. Low-testing fields with significant K removal are worth testing more often, even when they receive manure.

^{Per-unit removal values are from Iowa State University PM 1688 (Mallarino et al., 2023). Example yields are illustrative; multiply the per-unit value by your own yield. Corn stover removal is in addition to grain removal. Replacement cost uses the September 2026 average potash price of $498/ton, or $0.415/lb K₂O (Quinn, 2026).}

Verify Uncertain Responses With Strips

If you are uncertain whether a particular field will respond to K fertilizer, replicated treated and untreated strips can provide useful local information, and yield monitors make it possible to compare them at field scale. The Nebraska On-Farm Research Network can help design and analyze these comparisons. Over time, these results can improve K decisions more than routinely applying K without evidence of need.

The Bottom Line

For potassium, the biggest cost-saving opportunity in many Nebraska fields may be identifying where fertilizer isn't needed. Most Nebraska soils can supply enough K for strong corn production, and the probability of a response is very low above 100 ppm soil-test K.

Use 0–8-inch soil tests. Prioritize low-testing acres. Where soil-test K is above 100 ppm, weigh fertilizer cost against corn price, and consider banding on medium-testing soils. Credit manure K, and use spatial sampling where field variability justifies it.

When K fertilizer is expensive, soil testing is a better investment than applying fertilizer to acres that are unlikely to respond.

References

• Iqbal, J., Ferguson, R. B., Maharjan, B., & Thompson, L. (2023). Nutrient management suggestions for corn (EC117). University of Nebraska–Lincoln Extension. 
• Mallarino, A. P., Sawyer, J. E., Barnhart, S. K., & Licht, M. A. (2023). A general guide for crop nutrient and limestone recommendations in Iowa (PM 1688). Iowa State University Extension and Outreach. 
• Quinn, R. (2026, September 30). Anhydrous leads fertilizer prices higher, up 25% from a year ago. DTN/Progressive Farmer. 

Additional Resources

• Determining Crop-Available Nutrients from Manure, Nebraska Extension NebGuide G1335
• Guidelines for Soil Sampling, Nebraska Extension NebGuide G1740
• Nebraska On-Farm Research Network