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University of Minnesota Extension

Fertilizing wheat in Minnesota

With 1.5 million acres planted annually, wheat is the fourth largest crop in Minnesota’s agriculture. When diseases and other crop pests are not limiting, average yields continue to increase steadily. Adequate and efficient use of fertilizer is a major contributor to this increase.

Nitrogen guidelines

fall soil nitrate
The soil nitrate test should be used for nitrogen guidelines in the counties that are shaded.

Nitrogen use generates the largest net return of any nutrient used in wheat production. It is important to use this nutrient as efficiently as possible.

In Minnesota, fertilizer N suggestions are determined using two strategies that depend on the area of the state in question. For the western portion of the state, where most of the wheat is grown, the soil nitrate test (soil samples collected to 2 feet) is the best and most accurate management tool for predicting the amount of fertilizer N to use. This soil test is recommended if wheat is grown in the shaded area of the state shown on the map.

If the soil nitrate test is used, the amount of fertilizer N required to meet the yield goal is calculated from the following equation:

NRec = [(2.5) x YG] - STN(0-24 in.) - NPC

  • YG = yield goal, bushels per acre
  • STN = nitrate-nitrogen (NO3--N) measured to a depth of 2 feet, pounds per acre
  • NPC = amount of N supplied by the previous crop, pounds per acre

If wheat is grown in the second year following any of the crops in Table 1 use the N credit listed in Table 2. For situations where the soil nitrate test is not used, suggestions for fertilizer N are based on a consideration of previous crop, yield goal and soil organic matter content.

The soil nitrate test is not used for making nitrogen fertilizer guidelines for wheat grown in eastern Minnesota (the area not shaded on the map). Nitrogen fertilizer guidelines for these situations are summarized in Table 3. Use the fertilizer N guidelines for soils having a high organic matter content when wheat is grown in southeast Minnesota. This recommendation applies in Goodhue, Wabasha, Olmsted, Winona, Fillmore and Houston counties.

Table 1: Suggested nitrogen credits for crops that might precede wheat in a crop rotation*

Previous crop First year N credit lbs. N/acre
Soybean 20
Edible beans, field peas 10
Harvested sweet clover 10
Harvested alfalfa** or non-harvested sweet clover
4-5 plants/ft2 75
2-3 plants/ft2 50
1-2 plants/ft2 25
1 or fewer plants/ft2 0
Harvested red clover 35
Sugar beet
Yellow leaves at harvest 0
Light-green leaves at harvest 15-30
Dark-green leaves at harvest 60-80

*Use these credits when the soil nitrate test is used.

**If the 3rd or 4th cutting of alfalfa was not harvested, add 20 lbs. N/acre to the N credits listed.


Table 2: Suggested nitrogen credits when wheat is grown two years after a legume crop

Previous legume crop Second year N credit lbs. N/acre
Alfalfa (4+ plants/ft2), non-harvested sweet clover 35
Alfalfa (2-3 plants/ft2), Birdsfoot trefoil 25
Red clover 20

The nitrogen supplied by legume crops can also be used by the wheat crop planted 2 years after the legume. The nitrogen credits for these situations are summarized in Table 2. Subtract these values from the N guidelines that are listed for crops in Group 2 (Table 3) when wheat is planted 2 years after a legume crop.

Nitrogen from the decomposing sugar beet tops can be used by the wheat crop following sugar beet. These N credits are based on the overall color of the sugar beet tops at harvest and are listed in Table 1. If the soil nitrate test is used for nitrogen guidelines, the value for the appropriate color should be used as the nitrogen credit from the previous crop (NPC) in the N recommendation equation. If the N guidelines are taken from Table 3, subtract the value for the appropriate leaf color in Table 1 from the appropriate N recommendation listed in Table 3.

Nitrogen guidelines, whether calculated from the equation or obtained from Table 3, should also be used for winter wheat production. For this crop, 15 to 30 lbs. N per acre should be applied in the fall either before or at the time of seeding. The remainder of the fertilizer N needed should be top-dressed early the following spring.

Managing nitrogen

Research has shown that most of the total amount of nutrients used by wheat is absorbed from the soil between the growth stages of tillering and heading. So it is important to have an adequate supply of all nutrients in the root zone early in the growing season.

Since N is mobile in soils and can move to the roots with soil moisture, there is considerable flexibility in the management of this nutrient. For wheat production in most of Minnesota, fertilizer N can be applied in the fall after soil temperatures have stabilized at or below 50°F, or in the spring. In southeast, south-central, and central Minnesota, fertilizer N should be applied in the spring and incorporated before planting.

Because of the potential for losses due to leaching, fertilizer N should be applied in the spring when soils are sandy. Split N applications are encouraged for very sandy soils. For these situations, the first application can be made before planting followed by the remainder between tillering and jointing.

In northwest and western Minnesota, N applications at tillering may be justified if you suspect loss of previously applied N from leaching or denitrification. Applying N at this time would also be appropriate where a yield goal established in the fall was conservative and projected weather plus available soil moisture suggests there is a good probability for a higher yield. For these situations, added N at tillering may also increase the protein content of hard red spring wheat.

Table 3: Nitrogen fertilizer suggestions for wheat where the soil nitrate test is not used

Crop grown last year Organic matter level* Yield goal below 40 bu/acre Yield goal 40-49 bu/acre Yield goal 50-59 bu/acre Yield goal 60-69 bu/acre Yield goal 70-79 bu/acre Yield goal 80+ bu/acre
Alfalfa (4+plants/ft2), non-harvested sweet clover Low 0 lbs N/acre 0 lbs N/acre 30 lbs N/acre 55 lbs N/acre 80 lbs N/acre 95 lbs N/acre
Alfalfa (4+plants/ft2), non-harvested sweet clover Medium/High 0 0 0 35 60 75
Soybeans Low 35 60 85 110 135 150
Soybeans Medium/High 0 40 65 90 115 130
Edible beans, field peas, harvested sweet clover Low 45 70 95 120 145 160
Edible beans, field peas, harvested sweet clover Medium/High 25 50 75 100 125 140
Any crop in Group 1 Low 0 30 55 80 105 120
Any crop in Group 1 Medium/High 0 0 35 60 85 100
Any crop in Group 2 Low 55 80 105 130 155 170
Any crop in Group 2 Medium/High 35 60 85 110 135 150
Organic soil 0 0 0 0 30 35

* Low = less than 3.0%; Medium (Med.) and High = 3.0% or more.
Crops in Group 1: Alfalfa (2-3 plants/ft2), Alsike Clover, Birdsfoot Trefoil, Grass/legume hay, Grass/legume pasture, Fallow, Red Clover.
Crops in Group 2: Alfalfa (0-1 plants/ft2), Millet, Rye, Sweet corn, Barley, Corn, Mustard, Sorgum-sudan. Triticale, Buckwheat, Flax, Oat, Sugar beet, Wheat, Canola, Grass/hay/pasture, Potato, Sunflower, Vegetables.

If applied properly, all the common N fertilizers will have an equal effect on wheat yields. Some precautions in the application of some N sources are necessary. With anhydrous ammonia (82-0-0), there is concern for loss during application. If there is a strong ammonia odor emanating for the field, further application is discouraged since significant losses are likely occurring with application.

There is also a potential for N loss if urea (46-0-0) or urea-ammonium nitrate (28-0-0) is broadcast on the soil surface without incorporation when soil pH is higher than 7.3, air temperatures are 50 degrees F or greater and there is residue on the soil surface. Shallow incorporation of urea or fertilizers containing urea within 48 hours of application is encouraged when these N sources are used for wheat production. Fall application of 28-0-0 or 32-0-0 UAN is strongly discouraged due to a portion of the N in the fertilizer already in the nitrate form at application.

Late season applications of 30 lbs. N/ acre as Urea-ammonium nitrate solution (28-0-0) 2 to 5 days after anthesis (flowering) has been shown to increase hard red spring wheat grain protein 0.5 to 1.0%, 80% of the time. This rate will cause some leaf burn but will not harm grain yield. The economics of this application depend on the cost of the 28-0-0 and the protein premium of the wheat market. Do not apply during the heat of the day; instead apply either in early morning or evening application to limit the leaf burn by the 28-0-0. Do not tank mix N with any fungicides — wait 2 to 5 days after anthesis.

Phosphate guidelines

Suggestions for phosphate use are summarized in Table 4. The phosphorus (P) status of Minnesota soils is determined by using either the Bray or the Olsen analytical procedure. These tests are intended to be an index of crop response and not a direct measure of the amount of P in the soil. The Bray soil test uses a strong acid to extract P from the soil. In situations where carbonates are present in the soil, the acid in the Bray solution can be neutralized reducing the amount of P extracted and the effectiveness of the test. The Olsen test provides more accurate results if the soil pH is 7.4 or higher as it is not affected by carbonates in the soil. Both tests can be accurately used in situations where high soil pH is not an issue but values obtained from the Olsen tests will be lower for the same soil test classification range since the Bray and Olsen test extract P out of different pools of available P in the soil.

Table 4: Broadcast and drill phosphate fertilizer guidelines*

Expected yield Bray-P**
Expected yield Olsen
Broadcast/Drill 0-5 ppm
0-3 ppm
6-10 ppm
4-7 ppm
11-15 ppm
8-11 ppm
16-20 ppm
12-15 ppm
21+ ppm
16+ ppm
Less than 40 bu/acre Broadcast 40 lbs/acre 30 lbs/acre 15 lbs/acre 0 lbs/acre 0 lbs/acre
Less than 40 Drill 20 15 20 15-Oct 0
40-49 Broadcast 40 30 15 0 0
40-49 Drill 20 15 20 15-Oct 0
50-59 Broadcast 50 35 20 0 0
50-59 Drill 25 20 15 15-Oct 0
60-69 Broadcast 60 45 20 0 0
60-69 Drill 30 25 15 15-Oct 0
70-79 Broadcast 70 50 25 0 0
70-79 Drill 35 25 20 15-Oct 0
80 or more Broadcast 80 55 25 0 0
80 or more Drill 40 30 20 15-Oct 0

*Pounds of P2O5 suggested to apply per acre for wheat production based on either the Bray-P1 or Olsen soil methods test reported in parts per million (ppm).

**Use one of the following equations if a phosphate recommendation for a specific soil test and a specific yield goal is desired.

  • P2O5 Rec =
    • [1.071 - (.054) (Bray P, ppm)] (yield goal)
    • [1.071 - (.067) (Olsen P soil test, ppm)] (yield goal)

No phosphate fertilizer is suggested when the Bray P test is 21 ppm or higher or the Olsen P test is 16 ppm or higher.

The phosphate fertilizer suggestions change with soil test level and placement. At very low, low, and medium soil test levels, the needed phosphate can be broadcast and incorporated before planting or applied with the drill at planting in a narrow band near or with the seed Rates can be reduced by as much as 50% if the phosphate is applied with the drill.

No broadcast phosphate is suggested when the soil test for P is high (Bray P = 16 to 20 ppm; Olsen P = 12 to 15 ppm). A small amount of P2O5 applied with the seed is suggested for these situations. No phosphate will be needed when the soil test for P is in the very high range (Bray P = 21+ ppm; Olsen P = 16+ ppm) unless soils are cold and wet at planting time. On soils with high P fixing capacity such as soils with pH greater than 7.5, though soil test P is high or very high, some phosphate fertilizer (10 lbs. P2O5 per acre) placed in a band with or near the seed at planting may improve wheat yields.

Previous research has shown advantages to banding fertilizer in these situations as it reduces the amount of soil in contact with fertilizer which reduces the risk for fixation of P.

Potash guidelines

Suggestions for potash use are summarized in Table 5. As with phosphate, the soil test represents and index of availability and is not a direct measure of potassium in the soil. Suggestions vary with placement and soil test level for K. No broadcast potash will be needed when the soil test for K is 121 ppm or higher. No potash fertilizer (either drilled or broadcast) is suggested when the soil test for K is 161 ppm or higher.

It may not be practical to broadcast some of the low rates of suggested phosphate and potash. When low rates are suggested for a broadcast application, it is probably more practical to double the suggested broadcast rate and apply in alternate years if the grain drill or air seeder is not equipped to apply fertilizer with the seed.

Any phosphate and/or potash that is broadcast should be incorporated before seeding. These nutrients do not move in most soils and will have very little effect on production if they are top-dressed to an established stand. Application prior to a primary tillage operation is preferred.

Table 5: Broadcast and drill potash guidelines*

Expected yield (bushels/acre) Broadcast/Drill 0-40 ppm 41-80 ppm 81-120 ppm 121-160 ppm 161+ ppm
Less than 40 Broadcast 95 lbs/acre 70 lbs/acre 40 lbs/acre 0 lbs/acre 0 lbs/acre
Less than 40 Drill 50 35 20 15-20 0
40-49 Broadcast 105 75 45 0 0
40-49 Drill 55 40 25 15-20 0
50-59 Broadcast 130 95 55 0 0
50-59 Drill 65 50 30 15-20 0
60-69 Broadcast 155 110 65 0 0
60-69 Drill 80 55 35 15-20 0
70-79 Broadcast 180 125 75 0 0
70-79 Drill 90 65 40 15-20 0

*Pounds K2O/acre for wheat production in Minnesota based on K soil test reported in parts per million.

Use one of the following equations if a potash guideline for a specific soil test value and a specific expected yield is desired.

  • K2O suggested = [2.710 - .017 (K soil test, ppm)] (yield goal)
  • No potash fertilizer is suggested when the K test is 161 ppm or higher.

Fertilizer in contact with the seed

Since most of the wheat acreage in Minnesota is planted in early spring when soil conditions are cold and wet, the application of some fertilizer with the drill should be a routine management practice to increase nutrient availability in the root zone.

But there is some need for caution when placing fertilizer with the seed.

  • Do not place ammonium thiosulfate (12-0-0-26) in direct contact with the seed.
  • Do not place boron fertilizers in direct contact with the seed.

Damage from nitrogen and urea (46-0-0) placed in contact with the seed is dependent on the moisture content of the soil at planting. Damage can be substantial if soils are dry at planting. If soils are dry at the time of planting, keep the amount of urea in contact with the seed to 10 lbs. N per acre or less. Higher rates can be used if the soil is wet at planting. The suggested rates for this use, however, are not well defined.

High rates of potash in contact with the seed can cause problems if soils are dry at planting. Under typical moisture conditions, rates of K2O up to 60 lbs. per acre in contact with the seed should not cause problems with emergence.

Phosphate has no negative effect on seed germination and seedling growth. Therefore, ample amounts of phosphate can be applied in contact with the seed.

Fertilizer applied with air seeders

The use of air seeders has increased in popularity in recent years. Many seeders are equipped to apply a mixture of seed and dry fertilizer at the time of planting. The amount of fertilizer that can safely be applied with the air seeder will depend on the seeder spacing, the spread width of the fertilizer and seed mixture, and soil texture. Less fertilizer can be safely applied when the fertilizer and seed are placed within a narrow band or when air seeders are used on coarse textured soils.

The amount of nitrogen that can be used with the air seeder is related to soil moisture content at planting. Recent trials showed that N rates over 25 lbs. per acre as urea can reduce germination if applied with the wheat using an air seeder when soils are dry. By contrast, 75 lbs. N per acre as urea caused no emergence problems when soils were wet.

Urea fertilizer can present a significant risk of seedling damage when placed in contact with the seed. Data in Table 6 summarizes maximum rates of N that can be applied, assuming that soils are not dry at seeding. If soils are dry at planting, seeding rates should be reduced to decrease the risk of seeking damage.

Table 6: Maximum suggested nitrogen fertilizer rates with small grain seed at planting*

Planter spacing
Planter type
Seed spread 6 inch
Seedbed used
6 inch
lbs. N/acre
7.5 inch
Seedbed used
7.5 inch
lbs. N/acre
10 inch
Seedbed used
10 inch
lbs. N/acre
12 inch
Seedbed used
12 inch
lbs. N/acre
Double disc 1 inch 17% 20-30 13% 19-28 10% 17-23 8% 15-20
Hoe 2 33% 32-44 27% 27-38 20% 23-31 17% 20-27
3 50% 44-58 40% 37-48 30% 30-40 25% 26-34
Air seeder 4 66% 56-72 53% 46-58 40% 37-48 33% 32-42
5 83% 68-86 68% 56-68 50% 44-57 44% 38-49
6 100% 80-100 80% 66-79 60% 51-55 50% 44-56
7 94% 76-90 70% 58-74 58% 50-64
8 80% 66-83 67% 56-71
9 90% 73-92 75% 62-78
10 100% 80-100 83% 68-86
11 92% 74-93
12 100% 80-100

 *based on planter spacing, planter type, and seedbed use. Table adapted from E.J. Deibert, 1994. Fertilizer Application with Small Grain Seed at Planting. North Dakota State Univ. Ext. Publ EB-62.

The maximum nitrogen rate applied with the air seeder also must be adjusted based on soil texture. Table 7 summarizes maximum suggested rates of N for soils with differing texture based on method of application. Loamy sands and sandy loams present the greatest risk for seedling damage as these soils contain less available water than clay loams and clays. Extreme care should be taken when applying fertilizer with the seed on sandy soils when fertilizer is banded in a narrow band with the seed.

Table 7: Maximum suggested nitrogen fertilizer rates with small grain seed at planting based on soil texture and seedbed use*

Soil texture Sand particle size Silt particle size Clay particle size Seedbed use: 10-20%, Double disc, 1 inch Seedbed use: 30-50%, Hoe, 1 inch Seedbed use: 60-100%, Airseeder, 4-12 inch
Loamy sand 80% unit? 10% 10% 5 lbs/acre 10-20 lbs/acre 25-40 lbs/acre
Sandy loam 60 35 15 ?100% 10 15-25 30-45
Sandy clay loam 55 15 30 15 20-30 35-50
Loam 40 40 20 20 25-35 40-55
Silt loam 20 65 15 25 30-40 45-60
Silty clay loam 10 55 35 30 35-45 50-70
Clay loam 30 30 40 35 40-50 55-80
Clay 20 20 60 40 45-55 60-100

* Table adapted from Deibert, E.J. 1994. Fertilizer Application with Small Grain Seed at Planting. North Dakota State Univ. Ext. Publ EB-62.

Recent trials have shown that rates of phosphate of 92 lbs. P2O5 per acre or less have not hindered germination if mixed with wheat seed planted with an air seeder. The amount of K2O that can be applied in contact with the seed using an air seeder is not known at this time. If N and K are applied together, rates should be reduced of both nutrients.

Other nutrients needed

Major emphasis in wheat production should be directed to efficient and effective management of nitrogen, phosphate, and potash fertilizers. Sulfur (S) and copper (Cu) can be important in certain situations. These special cases are described in the paragraphs that follow.


Sulfur fertilization can increase wheat yields when the crop is grown on sandy soils. Research trials have shown that there is no need to add S to a fertilizer program for increasing grain yield and protein when wheat is grown on fine-textured soils in Minnesota. However, it is possible that in some years medium textured soils (loam and silt loam soils) with organic matter levels less than 3.0% may have limited S mineralization and may need small rates of sulfur to maximize yield. In these cases, a smaller broadcast rate of 10-15 lbs. of S per acre may be applied on a trial basis.

The broadcast application of 25 lbs. S per acre in the sulfate form will be adequate for growing wheat on sandy soils. For more efficient applications, use 10 to 15 lbs. S per acre with the drill or air seeder at planting.


Copper (Cu) may be required in a fertilizer program when wheat is grown on organic soils. Suggestions for Cu use are summarized in Table 8. The suggestions in Table 8 are for organic (peat) soils only. The use of Cu in a fertilizer program is not currently suggested when wheat is grown on mineral soils.

Table 8. Guidelines for use of copper for wheat grown on an organic soil

Copper, parts per million Broadcast application, Copper Broadcast application, Copper sulfate Foliar spray application, Copper Foliar spray application, Copper sulfate
0-2.5 (low) 6-12 lbs/acre? 24-48 lbs/acre 0.3 lbs/acre 1.2 lbs/acre
2.6-5.0 (marginal) 6 24 0.3 1.2
More than 5.0 (adequate) 0 0 0 0

Other micronutrients

Research from throughout Minnesota has shown that magnesium, calcium, iron, boron, zinc, and manganese are not needed in fertilizer programs. Most soils can supply ample amounts of these nutrients to a high-yielding wheat crop.

Authors: Daniel E. Kaiser, Extension soil and plant nutrient management specialist, and Keith Piotrowski, director of the soil testing laboratory

Reviewed in 2023

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