Fertilizing Hard Red Spring Wheat and Durum

Nitrogen recommendations for spring wheat and durum have been revised completely.

Nitrogen (N) management is a key to successful wheat production. Recommendations include consideration of wheat yield and protein response to added N within three major regions, and the use of wheat price and N cost in determining N rate. These recommendations are based on the concept that identifies an optimal N rate for greatest net income, not greatest yield.

For the interactive North Dakota Spring Wheat and Durum Nitrogen Calculator, go to https://www.ag.ndsu.edu/temp/cnc/.

Nitrogen fertilizer costs are much higher and more volatile than in the past. Using site-specific technologies, growers have the ability to vary fertilizer rates on different areas of fields to manage their input risks. Government policies and regulations increasingly push growers toward more judicious use of plant nutrients.

These N-rate recommendations are the result of compiling archived N-rate studies from 1970 to 2004, and include data from a statewide N-rate research program conducted from 2005 to 2021. Studies contained yield and protein data, location, fertilizer N-rate and residual soil nitrate to 2 feet in depth. Approximately one-third of the data for the recommendations come from archived data and the other two-thirds were generated since 2005.

Wheat response to N fertilizer is closely linked to wheat protein concentration. Growers rely on higher protein markets to maintain their profitability. A protein of 14% or greater is necessary to avoid discounts at the point of sale. Sometimes premiums are available to growers for protein greater than 14%.

North Dakota data on analysis segregated into three regions: western, eastern and the Langdon region.

The western region is composed mostly of long-term no-till fields, with no-till continuous for at least six years in most fields, either pure no-till using only an opener for seed/fertilizer, or one-pass seeding, which only disturbs a couple inches at the soil surface at planting time. The western region is also typified by only sediment soils, a drier and warmer climate compared to conditions in the eastern region. The Langdon region segregates from the rest of the eastern region due to the shale pieces found commonly through the soil. The shale pieces contain high amounts of mineralizable ammonium, making the Langdon region soils essentially a slow-release natural fertilizer. The Langdon region requires less N for similar yields compared to the eastern region.

Higher-than-recommended N rates in the Langdon region results in pre-anthesis lodging. The amount of N required per bushel in the west was higher than in the east. Therefore, for the purposes of N recommendations for spring wheat and durum the state have been divided into three regions as shown in Figure 1.

Data from each zone were segregated and the relationships between wheat yield and available-N, and wheat protein and available-N, were established. Using the concept of “Return to N” from Sawyer and Nafziger (2005), the economic optimal N rate for wheat prices between between $3/bushel and $15/bushel and N costs from 20 cents/pound of N to $2/pound of N were developed using wheat price and protein discount or premium. The protein discount varies with grain elevator and the year.

The calculations used in developing these relationships used a 50 cent per point discount if protein were less than 14%, and a 50 cent per point premium from 14% to 15%, with no additional premium for greater protein than 15%. The gross N recommendations on the regional tables (Tables 1-9) contain the regional economic data for wheat yield and protein in the model.

Within each region, the optimal available N for three different productivities are defined as low, medium and high. The yield potential within each productivity category is defined for each region. This is done entirely for economic reasons, not for differences within region of yield/protein responses to N.

1. Find the region of the farm and look up the gross optimal available-N from the appropriate region/productivity table (Tables 1-9).
2. Subtract the soil test nitrate-N from the 0- to 2-foot depth.
3. Subtract any previous crop N credits (Table 10).
4. Subtract or add no-till system N credits:
   – If field has been in no-till less than five consecutive years, add 20 pounds of N/acre.
   – If field has been in no-till greater than five consecutive years, subtract 50 pounds of N/acre.
5. Organic matter credit for soils greater than 5 percent organic matter – Subtract 50 pounds of N/acre for each full percent organic matter above 5 percent.

From these optimum rates, the grower and adviser may choose to adjust plus/minus up to 30 pounds of N/acre. This adjustment may be used to anticipate a host of issues, including the following:

• Subtract N for high protein varieties
• Add N for lower protein varieties
• Subtract N for areas with a history of early lodging
• Add N for soils with denitrification issues
• Add N for N application practices that are not ideal
• For wheat after small grains, we assume about 2,000 pounds/acre of straw residue. For every 2,000 pounds/acre of straw greater than this, add 30 pounds of N/acre.

As N costs increase and wheat price decreases, optimum N will not be highest yield or protein. However, from our database, these rates will provide the greatest net income.

Table 1a. Langdon region, conventional tillage low productivity (less than 40 bushels per acre), $0.20 - $1.00 N cost/lb.

Table 1b. Langdon region, conventional tillage low productivity (less than 40 bushels per acre), $1.10 - $2.00 N cost/lb.

Table 2a. Langdon region, conventional tillage medium productivity (41-60 bushels per acre), $0.20 - $1.00 N cost/lb.

Table 2b. Langdon region, conventional tillage medium productivity (41-60 bushels per acre), $1.10 - $2.00 N cost/lb.

Table 3a. Langdon region, conventional tillage, high productivity (greater than 60 bushels per acre), $0.20 - $1.00 N cost/lb.

Table 3b. Langdon region, conventional tillage, high productivity (greater than 60 bushels per acre), $1.10 - $2.00 N cost/lb.

Table 4a. Eastern region, conventional tillage, low productivity (less than 40 bushels per acre), $0.20 - $1.00 N cost/lb.

Table 4b. Eastern region, conventional tillage, low productivity (less than 40 bushels per acre), $1.10 - $2.00 N cost/lb.

Table 5a. Eastern region, conventional tillage, medium productivity (41-60 bushels per acre), $0.20 - $1.00 N cost/lb.

Table 5b. Eastern region, conventional tillage, medium productivity (41-60 bushels per acre), $1.10 - $2.00 N cost/lb.

Table 6. Eastern region conventional tillage, high productivity (greater than 60 bushels per acre), $0.20 - $1.00 N cost/lb.

Table 6b. Eastern region conventional tillage, high productivity (greater than 60 bushels per acre), $1.20 - $2.00 N cost/lb.

Table 7a. Western region, conventional tillage, low productivity (less than 30 bushels per acre), $0.20 - $1.00 N cost/lb.

Table 7b. Western region, conventional tillage, low productivity (less than 30 bushels per acre), $1.10 - $2.00 N cost/lb.

Table 8a. Western region, conventional tillage medium productivity (31-50 bushels per acre), $0.20 - $1.00 N cost/lb.

Table 8b. Western region, conventional tillage medium productivity (31-50 bushels per acre), $1.10 - $2.00 N cost/lb.

Table 9a. Western region conventional tillage high productivity (greater than 50 bushels per acre), $0.20 - $1.00 N cost/lb.

Table 9b. Western region conventional tillage high productivity (greater than 50 bushels per acre), $1.10 - $2.00 N cost/lb.

Half of credit given for the first year for sweet clover and alfalfa; none for other crops.

Where acceptable, fall application of ammonia is a preferred method of N application. Fall application is acceptable on loam soils or heavier in areas not prone to spring flooding after snowmelt. Fall application of ammonia should not begin before Oct. 1, and then only after soil temperatures measured at the 4-inch depth fall to 50 degrees Fahrenheit between 8 a.m. and 10 a.m. Banded urea may be applied a week after this date, and broadcast and incorporated urea should wait two weeks after the ammonia-safe date.

For greatest efficiency, urea should be applied below the soil surface. In no-till management, this can be accomplished with seeding tools that spread the urea at or near seed-depth if rate is sufficiently low, or in a band with seed to fertilizer separation of at least 1 inch. If urea is applied to the soil surface, it should be applied using a urease inhibitor. The urease inhibitor shown most effective is NBPT, which is marketed under a number of trade names. The proper NBPT rate is 1.78 pounds active ingredient per ton of urea (3 quarts per ton, 26.7% a.i., density 8.9 pounds per gallon). The NBPT at the proper rate almost completely renders soil urease inactive for about 10 days, during which time rainfall usually moves the urea into the soil, preventing ammonia volatilization. For additional information about urease inhibitors, see Nitrogen Extenders and Additives for Field Crops at https://www.ndsu.edu/agriculture/extension/publications/nitrogen-extenders-and-additives-field-crops.

Liquid N sources, including UAN/ 28-0-0, are also best applied below the surface. If spring conditions prevent below-surface application, banding the 28% on the surface may delay volatilization several days, compared with broadcast application.

North Dakota research has shown that the best chance of protein enhancement of spring wheat and durum is accomplished by waiting until the end of flowering (post-anthesis) and broadcasting 10 gallons per acre of UAN/28-0-0 (30 pounds of N per acre) mixed with 10 gallons per acre of water over the wheat in the cool of the day. Some leaf burning will result. The use of an equivalent N rate of urea solution also has been effective, and if the urea is low in biuret content, the addition of water dilution is not necessary and leaf burn is reduced. For research studies on protein enhancement in spring wheat, see https://www.ndsu.edu/agriculture/ag-hub/publications/post-anthesis-n-application-studies-north-dakota-region-and-elsewhere

The addition of some herbicides, fungicides and insecticides may increase the intensity of leaf burn and limit the efficacy of the pesticide application. About a 0.5% grain protein increase has been achieved using this method. The use of low rates of slow-release N products before or after anthesis has not been shown to increase grain protein effectively. For more information regarding the use of low rates of specialty N products for protein enhancement see https://www.ndsu.edu/agriculture/ag-hub/publications/studies-slow-release-liquid-fertilizers-applied-low-rates-foliar-application

The phosphate (P) recommendation in North Dakota currently is based on the Olsen P soil test. The broadcast recommendations appear in Table 11.

If the fertilizer is applied as a band, rates in Table 11 can be reduced by one-third. Reducing rates in low-testing soils will result in soil test levels that do not increase through time.

Reducing rates is suggested when P costs are high. At P costs of 30 cents/pound of P2O5 and less, the profitability of applying P to wheat is positive at soil test values indicated in Table 11. However, when 11-52-0 sells for more than $350/ton, using more than a minimum amount of P as a starter becomes unprofitable at a wheat price of $6/bushel. As wheat prices increase above $6/bushel, the grower can apply P at higher cost profitably (Figure 2).

Wheat benefits greatly from banded fertilizer placement near the row or in the row at seeding, provided that rates are moderate. Yield increases of several bushels per acre due to banded P are common in P banding vs. broadcast studies in wheat.

The rate of fertilizer that can be applied safely with wheat seed is more dependent on the N content of the fertilizer than the P content. Maximum N fertilizer rates that can be used with the seed are provided in Tables 12 and 13.

Reducing rates is suggested most when P costs are relatively high. At 30 cents/pound of P2O5 and below, the profitability of applying P to wheat is positive at soil test levels indicated in Table 11. However, when 11-52-0 sells for more than $350/ton, using more than a minimum amount of P as a starter becomes unprofitable at a wheat price of $6/bushel. As wheat prices increase above $6/bushel, the grower can apply P at higher cost profitably (Figure 4).

Figure 4. Profitability of using P for $6/bushel wheat at 30 cent/pound of P2O5, 50 cent/pound P2O5, and $1/pound P2O5. From Halvorson (1978).

Wheat benefits greatly from banded fertilizer placement near the row or in the row at seeding, provided that rates are moderate. Yield increases of several to many bushels are common in P banding vs. broadcast studies in wheat.

The rate of fertilizer that can be applied safely with wheat seed is more dependent on the N content of the fertilizer than the P content. Maximum N fertilizer rates that can be used with the seed are provided in Tables 12 and 13.

Table 12. Maximum N fertilizer rates with wheat seed at planting based on row spacing, planter opener type and seedbed utilization (From Franzen, 2015a). SU = seedbed utilization.

Table 13. Maximum N fertilizer rates with wheat at planting based on soil texture and seedbed utilization. From Franzen, 2015a.

The potassium (K) recommendations have changed. Finding responses to K is difficult when soil test K levels are greater than 100 parts per million (ppm). Nearly all of the higher K responses are related to a chloride response.

Most soils in North Dakota have high enough potassium (K) levels to support excellent wheat production. Exceptions might be sandier soils or soils with a history of many years of continuous soybean.

Current K fertilizer recommendations are based on a soil test critical level of 100 ppm. The recommendation in higher-testing soils is provided to replace K that the crop will remove and to provide chloride if necessary. If chloride (Cl) values are adequate and other crops in the rotation regularly receive K fertilizer, then KCl application when K and Cl are in the high range category are not necessary.

Potassium Recommendations

Soils with smectite-to-illite clay chemistry ratio of 3.5 or less (Figure 3)

• Soil test K > 150 ppm, no additional K required.

• KCl (0-0-60-50Cl) may be applied if soil Cl levels are less than 40 pounds of Cl in a 2-foot depth.

• Soil test K 150 ppm or less, apply 50 pounds/acre KCl (25 pounds/acre K2O)

Soils with smectite-to-illite clay chemistry ratio more than 3.5 (Figure 3)

• Soil test K > 100 ppm, no additional K required.

• KCl (0-0-60-50Cl) may be applied if soil Cl levels are less than 40 pounds Cl/2-foot depth.

• Soil test K 100 ppm or less, apply 50 pounds/acre KCl (25 pounds/acre K2O)

Sulfur (S) has become more important than K or Cl in North Dakota as the third major crop nutrient. Environmental regulations on fossil fuel emissions have put stringent restrictions on sulfur emissions in recent years. Industry response to regulation has resulted in less S received in North Dakota fields from precipitation (Franzen 2015b).

The S soil test is a very poor predictor of soil S status. Sulfur deficiency has become so prevalent in small grains and corn that for spring wheat/durum, a base application of 10 pounds of S per acre would be prudent, particularly if the fall, winter or early spring before seeding has received normal to above normal precipitation. Soils with sandy loam or coarser textures and less than 3% organic matter on higher landscape positions are most at risk, but all soils are at risk in wetter seasons.

Sulfur fertilizer application is a spring operation because sulfate leaches easily beyond the rooting zone. The spring fertilizer application should consist of a soluble sulfur fertilizer. Ammonium sulfate at rates of about 10 pounds of S per acre or gypsum (calcium sulfate) at 20 pounds of S per acre would be excellent sources of sulfur. Ammonium thiosulfate (ATS) is a liquid formulation of S that is highly plant-available. However, ATS should not be applied with the seed at planting, nor should it be broadcast over wheat after emergence.

Elemental S, even premium bentonite-blended forms, are not nearly as useful in correcting a deficiency as sulfate/thiosulfate fertilizers. Composite blended granules of phosphate fertilizers that include sulfur could be used, but rates need to be high enough to supply the 10 pounds of S per acre needed as the ammonium sulfate portion of the fertilizer, or the application should be supplemented with a sulfate containing fertilizer.

Increases in yield and decreases in fusarium head blight (scab) have been documented in North Dakota (Franzen et al., 2008) with copper application. The responses to copper were seen mostly on low-organic matter, sandy soils. However, only about 15% of sites that fit these criteria in the study responded.

Predicting whether wheat grown on these soils would respond to copper is difficult. Copper application is a site-specific nutrient at best. Applying it on loam or heavier soils, or in soils between 3% and 8% organic matter, provides no benefit. An application of copper sulfate at a rate of 5 pounds of Cu/acre will last many years.

Chloride responses are well-documented for spring wheat and durum. Studies in the state and the region show that wheat tends to respond positively to chloride about half the time, with yield increases of 2 to 5 bushels/acre. Studies in consecutive years investigating varietal responses to chloride provided inconsistent results.

Yield increases from Cl arise from increased resistance to certain root and leaf diseases and an increase in kernel size. The critical soil test value of Cl is 40 pounds per acre in the surface 2-feet of soil. If the soil test is less than 40 pounds of Cl per acre, fertilizing with 5 to 10 pounds of Cl per acre with or near the seed at planting should sufficiently supply the crop for the year.

No evidence exists that supplemental zinc, iron, manganese or boron are required for spring wheat or durum wheat in North Dakota. Although numerous reports have been made in the U.S. and around the world of these nutrients being required as fertilizer, our soils apparently supply enough of these nutrients and our wheat is adapted to these soils; therefore, these nutrients do not need to be supplied artificially.

Thanks to my collaborative researchers Gregory Endres, Carrington Research Extension Center; Roger Ashley and Glenn Martin, Dickinson Research Extension Center; John Lukach, retired, Langdon Research Extension Center; James Staricka, Williston Research Extension Center; and Kent McKay, formerly Extension area specialist with the North Central Research Extension Center. Funding for studies that contributed data to these recommendations came from North Dakota SBARE-Wheat Committee, North Dakota Wheat Commission, US-NSF grant number PFI-1114363, and USDA-ARS project No. 58-6064-8-023.

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Bauer, A. 1971. Fertilizer nitrogen effects on spring wheat varieties. p. 8-21. In 1971 North Dakota Crop Production Guide. NDSU Extension Service, Fargo, N.D.

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Franzen, D.W. 2015b. Sulfur sources, chemistry, extent of deficiencies, and application considerations in the North Central Region of the USA. p. 22-43. In Proceedings of the North Central Extension-Industry Soil Fertility Conference, Nov. 4-52015. Des Moines, Iowa. IPNI, Peachtree Corners, Ga.

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