Crops and Conservation

Winter Wheat, Nitrogen, Amount and Timing

It’s imperative for Northern Plains winter wheat producers to get a grasp on the yield potential of their winter wheat crop, and adjust nitrogen rates accordingly. The best time to apply nitrogen can vary by year and location.

 Let’s take a closer look at the need for adequate nitrogen to meet the higher winter wheat yield potential, nitrogen timing, and nitrogen and fungicide interaction. 

The USDA Agricultural Statistics Service average yield data for North Dakota indicates that winter wheat has yielded approximately 24% more than spring wheat in the last eight years. NDSU winter wheat and spring wheat variety trials at Lisbon, N.D. averaged 96 bu/ac and 63 bu/ac, respectively, in 2006 when treated with fungicide. These numbers clearly point out the increased yield potential of winter wheat.

It is imperative that new winter wheat producers get a grasp on the yield potential and adjust their nitrogen rates accordingly. Ask current growers about their yields and fertility program. University research and extension staff, and industry agronomists are also great resources to draw upon.

A long term study by USDA’s Agricultural Research Service stations in Mandan, N.D. and Sidney, Mont. indicated that it requires 2.3 pounds of actual nitrogen per bushel of wheat to attain 12% protein winter wheat.  This is in contrast to the more commonly used value of 2.5 lbs of N/bu for spring wheat and durum.

Nitrogen Timing
DU, in cooperation with NDSU (Dr. Joel Ransom) and SDSU (Dr. Martin Draper), has recently completed a 3-year study at two sites, Ellendale, N.D. and Andover, S.D.  Treatments consisted of a nitrogen check (N-Check); nitrogen applied in a deep band with Anderson openers at seeding (N-Seed); nitrogen early (March 29 to April 12 ~ N-Early); nitrogen late (April 27 to May 3 ~ N-Late); nitrogen split (one-half rate applied at each the early and late dates of application ~ N-Split).  The spring nitrogen treatments were applied with stream bars provided by Amity Technology.

The early treatment at Andover in 2004 was significantly lower in yield than the N-Seed, N-Early and N-Late nitrogen treatments (Figure 1). In contrast to Figures 2 and 3, N -Early was the highest yielding in 2005 and N-Early and N-Late were the highest yielding in 2006.  The N-Early treatment was likely lower yielding in 2004 because of inadequate rainfall to incorporate the nitrogen following the early treatment application. The first significant rainfall came after the late nitrogen application.

The N-Early treatment was the highest yielding in 2006 at Andover. There was substantial visual winter injury and stand loss and the early nitrogen application stimulated plant growth and tillering. This was similar to a response at Ellendale in 2003.

The three year average shown in Figures 4 and 5 indicate there are no differences in yield between the nitrogen timing treatments at both sites.  However, the best time to apply nitrogen may be different each year, depending on winter injury to the winter wheat and the timing of precipitation.

Figure 1.

Figure 2.

Figure 3.

Figure 4.

Figure 5.

Figure 6.

Figure 7.

Figure 8.

Nitrogen & Protein
Figures 6 compares the protein levels for each nitrogen treatment for Ellendale for each year and the 3-year average. The protein trends are in line with expectations in that the later you apply the nitrogen the higher your protein will be.  The protein levels for the N at seeding appear to be trending slightly lower than the spring treatments.  The protein levels in 2004 are a reflection of the inverse relationship between yield and protein. The winter wheat yields were from 102 to 107 bu/ac at Ellendale in 2004.

Nitrogen & Fungicide
Figure 7 is data from a DU winter wheat trial near Ellendale, N.D. in 2004 that demonstrates an interesting relationship between nitrogen and fungicide. There are eight treatments included in the bar chart.  All the treatments had nitrogen applied for an 80 bu/ac yield goal at seeding with Anderson openers in a deep band. 

The treatments represented by the yellow bars did not receive a fungicide treatment, while the treatments represented by the green bars received a one-half rate fungicide treatment with the herbicide and an early flower fungicide treatment.  The Check bars received only the nitrogen at seeding.

The Early, Late and Split N treatments received the nitrogen at seeding, and a second application in the spring with stream bars equal to the amount at seeding. The potential yield goal was 80 bu/ac for the Check treatments and 133 bu/ac for the Early, Late and Split N treatments.

The Check treatment yields were substantially above the 80 bu/ac fertility yield goal. Fungicide application only increased yield by 4.4 bu/ac in the nitrogen short environment of the Check treatment. 

The second comparison (adding nitrogen without fungicide) indicates the average yield for the Early, Late and Split N treatments without fungicide (yellow bars averaged) was 110.4 bu/ac or 5.8 bu/ac more than the Check treatment without fungicide (104.6). 

The third comparison made from Figure 7 is the average yield of the Early, Late and Split N fungicide treated plots (green bars averaged) is 128.2 bu/ac.  This is an increase of 23.6 bu/ac compared to the Check without fungicide (104.6).

In a nut shell, adding fungicide in a high yield/nitrogen short environment gave us an additional 4.4 bu/ac, and adding nitrogen in a high yield/nitrogen short environment without fungicide gave us 5.8 bu/ac. However, adding both the nitrogen and fungicide provided a 23.6 bu/ac yield increase.  It required adding both nitrogen and fungicide to capture the yield potential in this high yield environment.

Figure 8 reflects the three-year average winter wheat yield increase from fungicide application to the nitrogen check, early, split and late treatments. The late nitrogen treatment (5 to 6 leaf stage) winter wheat yields trended lower when fungicide was not applied, but were similar to the early and split nitrogen treatments when fungicide was applied. Starter fertilizer was applied at seeding in all the treatments.

If a producer is delaying or is unable to apply their first nitrogen to winter wheat until the 5 leaf stage, it may be a wise investment to include a half-rate of fungicide with your herbicide. There appears to be a pretty good chance for a yield response. The plants may be more susceptible to disease infection if they are short of nitrogen and plant health is less than desirable.

Summary and Conclusions
The best time to apply nitrogen can vary by year and location. The variation can be caused by rainfall timing and amount following nitrogen application and by the extent of winter injury to the winter wheat. Applying some nitrogen early is highly recommended to increase tillering to compensate for loss of stand, tillers and vigor when winter injury is obvious. This also applies to fields that have had their nitrogen applied at seeding. If winter injury is severe, the winter wheat roots will have to redevelop from the winter wheat crown. The roots will then be a distance from the deep-banded nitrogen.

The slightly depressed yields from the early nitrogen treatment in 2004 show how important rainfall timing, temperature, residue levels and surface moisture are in determining the success of surface applied nitrogen. Most University soils specialists do not recommend the use of surface applied nitrogen in no-till fields with heavy surface reside cover.  The data does indicate that surface applied liquid nitrogen with stream bars can be an effective method to apply nitrogen in the appropriate conditions.

It is encouraging that the deep banded nitrogen application with the drill at seeding is yielding the same as the three stream bar-post applied nitrogen treatments in the spring when comparing the three year average yields.  However, there is a trend toward slightly lower protein content in the winter wheat from the nitrogen at seeding treatment. 

The research may suggest that a grower’s management strategy could be to place a majority of his nitrogen in a band at seeding, and then stream apply the balance at the 5 to 6 leaf stage when working with loam soils.  This would give the grower an opportunity to adjust nitrogen rates to capture added yield potential and improve protein.

There can be fall or early spring moisture events in individual years that cause leaching. Important factors such as soil type, organic matter, flooding or ponding of water, and water table distance from the soil surface, are items to consider when determining when and by what method to apply your nitrogen to winter wheat. However, it is encouraging to have yields from the nitrogen applied in a band with the drill at seeding to equal the spring nitrogen treatment yields in these silt loam soils with organic matter levels between 3% and 4%.

The million dollar questions are:  Is your nitrogen program in line with your winter wheat’s yield potential? Is nitrogen or fungicide limiting the yield response of one another?

Vander Vorst is regional agronomist with Ducks Unlimited, Inc., Bismarck, N.D. Find more information about DU’s agronomy program, including winter wheat performance data and production information, online at
www.ducks.org/agronomy. 

Acknowledgements:
The research at the two sites was supported in part by grants from Ducks Unlimited, BASF Corporation, Bayer Crop Science, Syngenta Crop Protection, ND Natural Resources Trust, ND Game and Fish Department, SD Game, Fish & Parks. Others providing material support were the Bristol and Oakes Wheat Growers, Agriliance of Ellendale, NDSU Foundation Seed, SD Foundation Seed, Horsch Anderson, AgriPro Seeds, UAP Northern Plains, David Kinzler, TJ Technologies, Dakota Crop Services, K&S Soil Analysis, Amity Technology, Dickey Co. and Day Co. CIA, NDSU and SDSU Extension Service, Conservation Districts and NRCS.