Two UNL NebGuides, Fertilizing Winter Wheat I: Nitrogen, Potassium, and Micronutrients (G1460) and Fertilizing Winter Wheat II: Phosphorus (G1461) by Jurg M. Blumenthal and Donald H. Sander do an excellent job of presenting information on how to manage nutrients for winter wheat production.

The following information and tables were developed from these NebGuides and allow you to see how the nitrogen and phosphorus change with the various soil test results, as well as with wheat and fertilizer prices. If you have questions about or suggestions for improving these tables, contact the authors.

Table 1. Nitrogen fertilizer recommendation for rainfed wheat. (Source: NebGuide G1460) Wheat Price ($/bu) $3.00 $4.00 Fertilizer Price ($/lb N) 0.20 0.30 0.20 0.30 Soil Test N* (ppm) Nitrogen Application Rate (LB N/A) 1 111 87 124 105 2 101 77 113 95 4 80 56 92 74 6 59 35 71 53 8 38 13 50 32 10 16 0 29 10 12 0 0 7 0 *Average at 3 feet. Use 9 ppm if no soil test was taken. For yields of 70 bu/ac and more, add another 20 lbs of nitrogen.

Nitrogen

While research results have generally shown that high yields require higher nitrogen application for most crops, research data for winter wheat in Nebraska does not consistently show any effect of yield level on optimum nitrogen required for maximizing profits from fertilizer nitrogen. Generally, one rate is adequate regardless of yield level unless the producer expects yields above 70 bushels per acre. In this case, the wheat may require an additional 20 pounds of nitrogen per acre.

The optimum fertilizer nitrogen rate for winter wheat (with a maximum rate of 100 pounds of nitrogen per acre for dryland, 150 pounds of nitrogen per acre irrigated) can be calculated with Equation 1 or by using Table 1.

These recommendations should produce a grain protein of about 12%. About 20 pounds per acre of additional nitrogen will need to be top dressed in the spring for each 1% increase in grain protein desired.

Equation 1. Nitrogen Rate (lbs/ac) = ( (N Price/Wheat Price) + 0.014558xNO₃-N - 0.235)/-0.00138

Where

N Price = the price of nitrogen fertilizer in dollars per pound of nitrogen;
Wheat Price = the price of wheat in dollars per bushel (includes actual selling price and yield-bound government subsidies); and
NO₃-N = the average parts per million (ppm) nitrate-nitorgen in three feet of soil.

Figure 1. Effect of Seeding Date on Performance of Seed and Dual Placement Methods of P Application at three locations.

Phosphorus

The method of application and phosphorus source determine the most profitable phosphorus rate. Phosphorus recommendations are different for wheat planted late such as after a crop harvested in the fall, delayed because of planting conditions or replanted. Late planted wheat is usually classified as wheat planted 10 or more days later than optimum. Late planted wheat should have row applied phosphorus even if soil tests do not call for phosphorus (see Figure 1). Use a minimum of 20 lbs where no phosphorus was called for and increase the other rates 20%. Due to reduced tillerting, seeding rates should be increased to 90 lbs in dryland and 120 lbs in irrigated cropland, based on a rate of 15,000 seeds per pound. Adjust seeding rate for larger or smaller seed size. Narrow rows — 7.5 inches for dryland and 6 inches in irrigated — are preferred.

Use Table 2 to compare phosphorus application rates in various pricing and yield scenarios.

Zinc

For winter wheat, soil zinc levels need to be below 0.5 ppm (DTPA Test) to expect a response from zinc. With a soil low in zinc and the crop producer applying 10-34-0, adding 1 lb of zinc per acre should be adequate. Sources of zinc include zinc oxide, zinc sulfate, and zinc-ammonia complexes.

Sulfur

Sandy soils with irrigation water are the most likely to respond to sulfur. On irrigated sandy soils check the water for sulfur in addition to the soil. Most fine textured soils have adquate amounts of orbanic matter and/or residual sulfate sulfur deeper in the soil. Do not apply ammonium thiosulfate (12-0-0-26S) in the fow as it can severely injure wheat seedlings. Sulfur in the sulfate form does not cause injury.

Chloride

Research conducted in Nebraska failed to give a response to the addition of potassium chloride fertilization even though 14 out of 22 locatiosn were classified as low in the soil chloride concentrations.

Robert N. Klein
Extension Cropping Systems Specialist
David D. Tarkalson
Extension Soil Fertility and Nutrient Management Specialist
Both at the West Central REC, North Platte

Table 2. Phosphorus rates for dual or row application. For late seeding always put at least 20 lbs of P2O5/acre in row and narrow row spacing. (Source: NebGuide G1461, Blumenthal and Sander)* Yield Goal 40 Bushel  50 Bushel  60 Bushel  70 Bushel  Wheat Price $3.00 $4.00 $5.00 $3.00 $4.00 $5.00 $3.00 $4.00 $5.00 $3.00 $4.00 $5.00 Fertilizer Price $0.30 $0.40 $0.30 $0.40 $0.30 $0.40 $0.30 $0.40 $0.30 $0.40 $0.30 $0.40 $0.30 $0.40 $0.30 $0.40 $0.30 $0.40 $0.30 $0.40 $0.30 $0.40 $0.30 $0.40 WPrice FPrice Factor 10 7.5 13.33 10 16.66 12.5 10 7.5 13.33 10 16.66 12.5 10 7.5 13.33 10 16.66 12.5 10 7.5 13.33 10 16.66 12.5 Bray P1 Olsen     5 3.3 ROW 24 18 32 24 40 30 34 25 45 34 56 42 42 31 55 42 69 52 48 36 65 48 81 61 BRD 33 24 43 33 54 41 39 29 52 39 65 49 44 33 59 44 74 55 49 37 65 49 81 61 10 6.7 ROW 7 5 10 7 12 9 17 13 28 17 28 21 25 19 33 25 42 31 32 24 43 32 53 40 BRD 10 8 14 10 17 13 17 13 23 17 28 21 22 17 29 22 37 28 27 20 35 27 44 33 15 10 ROW 0 0 0 0 0 0 7 6 10 7 12 9 15 12 21 15 26 19 22 17 30 22 37 28 BRD -3 -2 -4 -3 -4 -3 4 3 5 4 6 5 9 7 12 9 15 11 14 10 18 14 22 17 20 13.3 ROW 0 0 0 0 0 0 1 0 1 1 1 1 9 6 11 9 14 11 15 12 21 15 26 19 BRD -12 -9 -16 -12 -20 -15 -6 -4 -7 -6 -9 -7 0 0 0 0 1 0 4 3 6 4 7 5 25 16.7 ROW 0 0 0 0 0 0 0 0 0 0 0 0 3 2 4 3 5 4 10 8 13 10 17 13 BRD -19 -14 -25 -19 -32 -24 -13 -9 -17 -13 -21 -16 -7 -6 -10 -7 -12 -9 -3 -2 -4 -3 -5 -4 30 20 ROW 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 6 4 8 6 10 7 BRD -25 -19 -33 -25 -42 -31 -19 -14 -25 -19 -31 -23 -13 -10 -18 -13 -22 -17 -9 -7 -12 -9 -15 -11   Yield Goal 80 Bushel 90 Bushel  100 Bushel 120 Bushel  Wheat Price $3.00 $4.00 $5.00 $3.00 $4.00 $5.00 $3.00 $4.00 $5.00 $3.00 $4.00 $5.00 Fertilizer Price $0.30 $0.40 $0.30 $0.40 $0.30 $0.40 $0.30 $0.40 $0.30 $0.40 $0.30 $0.40 $0.30 $0.40 $0.30 $0.40 $0.30 $0.40 $0.30 $0.40 $0.30 $0.40 $0.30 $0.40 WPrice FPrice Factor 10 7.5 13.33 10 16.66 12.5 10 7.5 13.33 10 16.66 12.5 10 7.5 13.33 10 16.66 12.5 10 7.5 13.33 10 16.66 12.5 Bray Pl Olsen   5 3.3 ROW 54 41 72 54 90 68 59 45 79 59 99 74 64 48 85 64 107 80 72 54 96 72 120 90 BRD 53 39 70 53 87 66 56 42 75 56 93 70 59 44 79 59 98 74 64 48 86 64 107 80 10 6.7 ROW 38 28 50 38 63 47 43 32 57 43 71 54 48 36 63 48 79 60 56 42 74 56 93 70 BRD 30 23 41 30 51 38 34 25 45 34 56 42 37 28 49 37 61 46 42 32 56 42 70 53 15 10 ROW 28 21 37 28 47 35 33 25 44 33 55 42 38 28 51 38 63 47 46 34 61 46 76 57 BRD 17 13 23 17 29 22 21 16 28 21 34 26 24 18 32 24 40 30 29 22 39 29 48 36 20 13.3 ROW 21 16 28 21 35 27 26 20 35 26 44 33 31 23 41 31 52 39 39 29 52 39 65 49 BRD 8 6 11 8 13 10 11 9 15 11 19 14 15 11 19 15 24 18 20 15 26 20 33 25 25 16.7 ROW 16 12 21 16 27 20 21 26 28 21 35 26 26 19 34 26 43 32 34 25 45 34 56 42 BRD 1 1 1 1 1 1 4 3 6 4 7 5 7 6 10 7 12 9 13 10 17 13 21 16 30 20 ROW 12 9 16 12 19 15 17 13 22 17 28 21 22 16 29 22 36 27 30 22 39 30 49 37 BRD -5 -4 -7 -5 -8 -6 -2 -1 -2 -2 -3 -2 2 1 2 2 2 2 7 5 9 7 11 9   *For broadcast application, use pH adjustment for pH above and below 7.2   pH 6 6.2 6.4 6.8 7.0   pH 7.4 7.6 7.8 8 8.2 8.4 8.6   Factor 1.79 1.47 1.16 0.56 0.28 Factor 0.26 0.53 0.78 1.03 1.27 1.51 1.74 For these soil pH's add factor multipled times WPFP factor For these soil pH's subtract the factor multipled times WPFP factor Example for pH of 6.2, 70 bushel wheat, Bray 10 ppm, $4.00 wheat and $0.30 P2O5 35 + (1.47 x 13.33 = 20) = 55 lb P2O5 Example for pH of 7.8, 70 bushel wheat, Bray 10 ppm, $4.00 wheat and $0.30 P2O5 35 - (0.78 x 13.33 = 10) = 25 lbs P2O5

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Published by University of Nebraska-Lincoln Extension in the Institute of Agriculture and Natural Resources Cooperating with the counties and the U.S. Department of Agriculture.

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