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Fertilizing Hard Red Spring Wheat and Durum (SF712 Revised)

Nitrogen management is a key to successful wheat production. Recommendations include consideration of wheat yield and protein response to added N within three major state agri-climatology zones, 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.

D.W. Franzen, NDSU Extension Soil Specialist


Spring Wheat

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

Nitrogen management is a key to successful wheat production. Recommendations include consideration of wheat yield and protein response to added N within three major state agri-climatology zones, 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.

Previous N recommendations were straightforward yield potential formulas based on the assumption that N costs are cheap and stable. Research from the 1950s and 1960s has been the foundation for recommendations for the past 30 years in spring wheat and durum. Since the previous recommendations were established, wheat varieties have changed, and no-till and conservation tillage have been adopted.

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 2009. Studies contained yield and protein data, location, fertilizer N-rate and residual soil nitrate to 2 feet in depth. Approximately half of the data for the recommendations come from archived data and the other half were generated since 2005. The statewide data are shown in Figure 1.

Figure 1

Figure 1. Statewide N-rate data and wheat yield from 1970 to 2008. Available-N includes soil test nitrate-N to 2 feet in depth, fertilizer N rate and any previous crop N credit.

Wheat response to N fertilizer is closely linked to wheat protein concentration. Growers rely on higher protein markets to maintain their profitability. Currently, a protein of 14 percent or greater is necessary to avoid dockage at the point of sale. Sometimes substantial premiums are available to growers for protein greater than 14 percent. The relationship between wheat yield and protein statewide is shown in Figure 2.

Figure 2

Figure 2. The relationship between available-N and wheat protein from studies in North Dakota conducted from 1970 to 2008. Available N includes soil test nitrate-N to 2 feet in depth, fertilizer N rate and any previous crop N credit.

If nitrogen fertilizers were very inexpensive and other factors were not important, the statewide optimal N rate would be a flat 225 pounds of N/acre less N credits. However, in examining the data, what became clear is that certain parts of the state reacted differently to N fertilizer.

High rates of N in the Langdon region resulted 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 agri-climatology zones as shown in Figure 3.

Productivity category definitions:

Langdon Region

Low = less than 40 bushels/acre
Medium = 41-60 bushels/acre
High = greater than 60 bushels/acre

Eastern Region

Low = less than 40 bushels/acre
Medium = 41-60 bushels/acre
High = greater than 60 bushels/acre

Western Region

Low = less than 30 bushels/acre
Medium = 31-50 bushels/acre
High = greater than 50 bushels/acre

Figure 3

Figure 3. Agri-climatology zones used to segregate N-rate data and develop agri-climatology zone N recommendations.

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 $3/bushel and $10/bushel and N costs from 20 cents/pound of N and $1/pound of N were developed using wheat price and protein dock/premium. The protein dock varies with grain elevator and the year.

The figures used in developing these relationships used a 50 cent/point dockage if protein were less than 14 percent, and a 50 cent/point premium from 14 to 15 percent, with no additional premium for greater protein. 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.

To determine recommended N rate

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 1-3

Table 4

Table 5-6

Table 7-8

Table 9

Table 10

Second-year N Credits

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

Nitrogen Application

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 never should begin before Oct. 1, and then only after soil temperatures measured at the 4-inch depth fall to 50 degrees between 8 and 10 a.m. Banded urea can be applied a week after this date, and broadcast and incorporated urea should wait two weeks after the ammonia date.

Surface application of urea to no-till acres should be avoided in the spring. The risk of volatility of ammonia is too great if rain does not fall for several days. No-till wheat growers should explore ways to apply urea beneath the soil surface for greatest efficiency.

Liquid N sources, such as 28 percent, also should be applied below the surface. If spring conditions prevent below-surface application, banding the 28 percent on the surface may delay volatilization several days, compared with broadcast application.

Protein Enhancement

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/acre of 28 percent (30 pounds of N/acre) mixed with 10 gallons/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 has been reduced.

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 50 percent 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.

Phosphate

The phosphate (P) recommendation currently is related to soil test P and yield potential. 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.

Table 11

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

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 12-13

Potassium

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 levels are adequate and other crops in the rotation regularly receive K fertilizer, then fertilizer rates in the high range of soil tests may not be needed.

Potassium Recommendations

Soils with smectite-to-illite clay chemistry ratio of 3.5 or less (Figure 5)

• 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/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 5)

• 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)

Figure 5

 Figure 5. Smectite-to-illite clay chemistry for soils in North Dakota from soil sampling survey conducted in 2017.

Sulfur

Sulfur is becoming more important than potassium or chloride in the state as a third major nutrient. Environmental regulations on fossil fuel emissions have put more stringent restrictions on sulfur emissions in recent years. This has resulted in less sulfur through rainfall (Franzen 2015b).

The sulfur soil test is not a good predictor of possible sulfur deficiency. Sulfur deficiency has become so prevalent in small grains and corn that for spring wheat/durum, a base application of 10 pounds of S/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 percent organic matter on higher landscape positions are most at risk, but most 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/acre or gypsum at 20 pounds of S/acre would be excellent sources of sulfur.

Elemental sulfur, even premium bentonite-blended forms, would not be nearly as useful in correcting a deficiency. 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/acre needed as the ammonium sulfate portion of the fertilizer, or the application should be supplemented with a sulfate containing fertilizer.

Copper

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 percent 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 percent organic matter, provides no benefit. An application of copper sulfate at a rate of 5 pounds of Cu/acre will last many years.

Chloride

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

Other Nutrients

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.

Acknowledgments

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.

References

Bauer, A. 1970. Nitrogen uptake by irrigated wheat under varying fertilizer nitrogen application rates. p. 95-99. In. NDAA 22nd Annual Fertilizer Conference. Soil Management for Crop Production and Environmental Protection Short Course. Dec. 3-4, 1970, Fargo, N.D. North Dakota Plant Food Association and NDSU Extension Service.

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.

Dahnke, W.C. 1981. Department memo. Jan. 29, 1981.

Etchevers, J.D. 1970. Effect of CCC and nitrogen on two cereals. M.S. thesis, NDSU.

Franzen, D.W., M. McMullen and D.S. Mossett. 2008. Spring wheat and durum yield and disease responses to copper fertilization of mineral soils. Agronomy Journal 100:371-375.

Franzen, D.W. 2015a. Fertilizer application with small grain seed at planting. NDSU Extension publication EB62 (revised).

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.

Goos, R.J., B. Johnson and F. Sobolik. 1982. Fertilizer studies on recropped small grain in western N.D., 1981. p. 200-202. 1982 North Dakota Crop Production Guide. NDSU Extension Service, Fargo, N.D.

Goos, R.J., B.E. Johnson, E.J. Deibert and F.J. Sobolik. 1981. The effects of N rate, N source, P, and K on the yield and protein content of spring wheat. p. 191-194. In 1981 North Dakota Crop Production Guide. NDSU Extension Service, Fargo, N.D.

Goos, R.J. 1983. Small grain soil fertility investigations, 1979-1983. p. 27-30. In North Dakota Farm Research. Vol. 4, No. 1. North Dakota State University Agricultural Experiment Station, Fargo, N.D.

Halvorson, A.D. 1986. Phosphorus management for MEWY and quality. 12 p. Presented at Hands-On Workshop for Implementing Maximum Economic Wheat Yield Systems. July 8-11, 1986. Bismarck, N.D.

Sawyer, J., and E. Nafziger. 2005. Regional approach to making nitrogen fertilizer rate decisions for corn. p. 16-24. In Proceedings of the North Central Extension-Industry Soil Fertility Conference, Nov. 16-17, 2005, Des Moines, Iowa. Potash & Phosphate Institute, Brookings, S.D.

Schneider, R.P. 1980. N Sources and N-Serve in North Dakota spring wheat production. p. 216-221. In 1980 North Dakota Crop Production Guide. NDSU Extension Service, Fargo, N.D.

Sobolik, F. Nitrogen use on fallow and re-cropped land in northwest North Dakota. p. 243-244. In 1977 North Dakota Crop Production Guide.
NDSU Extension Service, Fargo, N.D.

Vanden Heuvel, R.M. 1980. Effect of time of residue incorporation, time of N application, N rate and N source on HRS wheat (Triticum aestivum L.). NDSU M.S. thesis.

January 2018

 

 

 

 

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