With 1.5 million acres planted annually, wheat is Minnesota’s fourth largest crop.
Average yields increase steadily as long as diseases and other crop pests are not limiting. Adequate and efficient fertilizer use is a major contributor to this increase.
Nitrogen guidelines
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
For situations where the soil nitrate test is not used, suggestions for fertilizer N are based on previous crop, yield goal, and soil organic matter content.
The soil nitrate test is not used to make nitrogen fertilizer guidelines for wheat grown in eastern Minnesota (the area not shaded on the map). Use the fertilizer N guidelines for soils that have high organic matter content when wheat is grown in southeast Minnesota. This recommendation applies in Goodhue, Wabasha, Olmsted, Winona, Fillmore, and Houston counties.
Use these credits for crops that might precede wheat in a crop rotation when the soil nitrate test is used. First-year N credit applies to all crops.
- Soybean: 20 lb N/acre
- Edible beans and field peas: 10 lb N/acre
- Harvested sweet clover: 10 lb N/acre
- Harvested red clover: 35 lb N/acre
- Harvested alfalfa or non-harvested sweet clover (if the third or fourth cutting was not harvested, add 20 lb N/acre to the N credits):
- 4-5 plants/sq. foot: 75 lb N/acre
- 2-3 plants/sq. foot: 50 lb N/acre
- 1-2 plants/sq. foot: 25 lb N/acre
- 1 or fewer plants/sq. foot: 0 lb N/acre
- Sugar beet:
- Yellow leaves at harvest: 0 lb N/acre
- Light-green leaves at harvest: 15-30 lb N/acre
- Dark-green leaves at harvest: 60-80 lb N/acre
Nitrogen from 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.
If the soil nitrate test is used for nitrogen guidelines, the value for the appropriate beet leaf color should be used as the nitrogen credit from the previous crop in the N recommendation equation. If the N guidelines are taken from the following table, subtract the value for the appropriate leaf color from the appropriate N recommendation.
Suggested nitrogen credits when wheat is grown two years after a legume crop
The nitrogen supplied by legume crops can be used by the wheat crop planted two years after the legume.
- Alfalfa (4+plants/sq. foot), non-harvested sweet clover: 35 lb N/acre
- Alfalfa (2-3plants/sq. foot), Birdsfoot trefoil: 25 lb N/acre
- Red clover: 20 lb N/acre
Subtract these values from the N guidelines for crops listed in the table below when wheat is planted two years after a legume crop.
Nitrogen guidelines, whether calculated from the equation or the table, should also be used for winter wheat production. For this crop, 15 to 30 pounds 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.
Nitrogen fertilizer suggestions for wheat where the soil nitrate test is not used
Crop grown last year | Organic matter level* | Goal <40 bu/ac | Goal 40-49 bu/ac | Goal 50-59 bu/ac | Goal 60-69 bu/ac | Goal 70-79 bu/ac | Goal 80+ bu/ac |
---|---|---|---|---|---|---|---|
Alfalfa (4+plants/ft2), non-harvested sweet clover | Low | 0 lbs N/ac | 0 lbs N/ac | 30 lbs N/ac | 55 lbs N/ac | 80 lbs N/ac | 95 lbs N/ac |
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 | High | 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, Sorghum-Sudangrass. Triticale, Buckwheat, Flax, Oat, Sugar beet, Wheat, Canola, Grass/hay/pasture, Potato, Sunflower, Vegetables.
Research has shown that most of the nutrients used by wheat are 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 nitrogen is mobile in soils and can move to the roots with soil moisture, you can be flexible when managing this nutrient. For wheat production in most of Minnesota, you can apply fertilizer N in the fall after soil temperatures have stabilized at or below 50°F, or in the spring. In southeast, south-central, and central Minnesota, apply fertilizer N in the spring and incorporate it 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 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.
If applied properly, all the common N fertilizers will have an equal effect on wheat yields. Take precautions when applying some N sources. With anhydrous ammonia (82-0-0), there is concern for loss during application. If there is a strong ammonia odor coming from the field, stop application to avoid significant losses.
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 pounds N per acre as Urea-ammonium nitrate solution (28-0-0) two to five days after anthesis (flowering) have 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. Apply either in the early morning or evening application to limit the leaf burn by the 28-0-0 solution. Do not tank mix N with any fungicide; wait two to five days after anthesis.
Phosphate and potash
In Minnesota, we test the phosphorus (P) status of soil using either the Bray or Olsen test. These tests are 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, however, values from the Olsen tests will be lower for the same soil test classification range since the Bray and Olsen tests extract P out of different pools of available P in the soil.
Broadcast and drill phosphate fertilizer guidelines*
Yield Bray-P1 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/ac | Broadcast | 40 lb/ac | 30 lb/ac | 15 lb/ac | 0 lb/ac | 0 lb/ac |
Less than 40 | Drill | 20 | 15 | 20 | 10-15 | 0 |
40-49 | Broadcast | 40 | 30 | 15 | 0 | 0 |
40-49 | Drill | 20 | 15 | 20 | 10-15 | 0 |
50-59 | Broadcast | 50 | 35 | 20 | 0 | 0 |
50-59 | Drill | 25 | 20 | 15 | 10-15 | 0 |
60-69 | Broadcast | 60 | 45 | 20 | 0 | 0 |
60-69 | Drill | 30 | 25 | 15 | 10-15 | 0 |
70-79 | Broadcast | 70 | 50 | 25 | 0 | 0 |
70-79 | Drill | 35 | 25 | 20 | 10-15 | 0 |
80 or more | Broadcast | 80 | 55 | 25 | 0 | 0 |
80 or more | Drill | 40 | 30 | 20 | 10-15 | 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 for a phosphate recommendation for a specific soil test and a specific yield goal.
- 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 pounds 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.
As with phosphate, the soil test represents an 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 (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 broadcast phosphate or potash 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 before a primary tillage operation is preferred.
Broadcast and drill potash guidelines
Yield (bu/ac) | Broadcast/Drill | 0-40 ppm | 41-80 ppm | 81-120 ppm | 121-160 ppm | 161+ ppm |
---|---|---|---|---|---|---|
Less than 40 | Broadcast | 95 lb/ac | 70 lb/ac | 40 lb/ac | 0 lb/ac | 0 lb/ac |
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 for a potash guideline for a specific soil test value and a specific expected yield.
- 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.
Applying fertilizer
Since most of the wheat acreage in Minnesota is planted in early spring when soil conditions are cold and wet, applying some fertilizer with the drill should be a routine management practice to increase nutrient availability in the root zone.
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 depends on the moisture content of the soil at planting. Damage can be substantial if soils are dry at planting. If soils are dry at planting, keep the amount of urea in contact with the seed to 10 pounds 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 pounds 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.
Many air 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 pounds per acre as urea can reduce germination if applied with the wheat using an air seeder when soils are dry. By contrast, 75 pounds 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 the tables below summarize the maximum rates of N that can be applied, assuming that soils are not dry at seeding. If soils are dry at planting, reduce seeding rates to decrease the risk of damage.
Maximum suggested nitrogen fertilizer rates with small grain seed at planting for air seeder
Seed spread (inches) | 6 in. - % seedbed used | 6 in. - lb N/acre | 7.5 in. - % seedbed used | 7.5 in. - lb N/acre | 10 in. - % seedbed used | 10 in. - lb N/acre | 12 in. - % seedbed used | 12 in. - lb N/acre |
---|---|---|---|---|---|---|---|---|
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 | n/a | n/a | 94 | 76-90 | 70 | 58-74 | 58 | 50-64 |
8 | n/a | n/a | n/a | n/a | 80 | 66-83 | 67 | 56-71 |
9 | n/a | n/a | n/a | n/a | 90 | 73-92 | 75 | 62-78 |
10 | n/a | n/a | n/a | n/a | 100 | 80-100 | 83 | 68-86 |
11 | n/a | n/a | n/a | n/a | n/a | n/a | 92 | 74-93 |
12 | n/a | n/a | n/a | n/a | n/a | n/a | 100 | 80-100 |
Maximum suggested nitrogen fertilizer rates with small grain seed at planting for double disc and hoe
Planter type | Seed spread (inches) | 6 in. - % seedbed used | 6 in. - lb N/acre | 7.5 in. - % seedbed used | 7.5 in. - lb N/acre | 10 in. - % seedbed used | 10 in. - lb N/acre | 12 in. - % seedbed used | 12 in. - lb 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 |
Hoe | 3 | 50 | 44-58 | 40 | 37-48 | 3o | 30-40 | 25 | 26-34 |
Tables adapted from Deibert, E.J. 1994. Fertilizer Application with Small Grain Seed at Planting. N Dakota State Univ. Ext. Publ EB-62.
The maximum nitrogen rate applied with the air seeder must be adjusted based on soil texture. 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.
Maximum suggested rates of N for soils with differing textures based on application method
Soil texture | Sand particle size % | Silt particle size % | Clay particle size % | Seedbed use: 10-20%, double disc, 1 in. | Seedbed use: 30-50%, hoe, 1 in. | Seedbed use: 60-100%, airseeder, 4-12 in. |
---|---|---|---|---|---|---|
Loamy sand | 80 | 10 | 10 | 5 lb/acre | 10-20 lb/acre | 25-40 lb/acre |
Sandy loam | 60 | 35 | 15 | 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 92 pounds 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, the rates of both nutrients should be reduced.
Other nutrients
The 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.
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 are for organic (peat) soils only. We do not recommend Cu in a fertilizer program when wheat is grown on mineral soils.
Guidelines for copper (lb/acre) for wheat grown on organic soil
Copper, ppm | Broadcast, copper | Broadcast, copper sulfate | Foliar spray, copper | Foliar spray, copper sulfate |
---|---|---|---|---|
0-2.5 (low) | 6-12 lb/acre | 24-48 lb/acre | 0.3 lb/acre | 1.2 lb/acre |
2.6-5.0 (marginal) | 6 | 24 | 0.3 | 1.2 |
More than 5.0 (adequate) | 0 | 0 | 0 | 0 |
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.
Reviewed in 2024