Timing of Nitrogen Fertilization for Winter Wheat
The following is a synopsis of several recent trials investigating the use of fall nitrogen applications for winter wheat. Spring ammonium nitrate application is considered the standard treatment that other yields and protein are indexed to. Some comments are added.
Traditional timing for N application has been spring broadcast application. Spring nitrogen should be applied as soon as soil conditions permit in April. Early nitrogen encourages tillering, which is especially important to improve productivity of thin stands. However, if wet conditions do delay field operations, N application is still profitable at the stem elongation stage.
A) Effects of N and P on the Winter Hardiness, Yield and Protein Content of Zero Till Winter Wheat. C.A. Grant, 1983. Manitoba Soil Science Society proceedings.
Table 1. Influence of N timing on winter wheat yield.
Timing |
Yield bu/ac |
Check (no N) |
13 |
At seeding |
27 |
At freeze up |
28 |
On snow |
21 |
Spring |
33 |
B) Field scale evaluations of nitrogen sources, timing and placement for zero-tilled winter wheat. J Heard, B Fraser and R Gares, 2001. MAC
Table 2. Influence of N timing on winter wheat yield and protein.
Yield bu/ac |
Protein content % | |||||
N Timing |
1999a |
1999b |
2000 |
1999a |
1999b |
2000 |
spring urea |
59.2 |
89.9 a |
12.4 |
12.6 a | ||
fall urea |
54.8 |
83.6 b |
12.2 |
12.2 ab | ||
spring UAN |
53.1 |
89.7 a |
11.8 |
12.8 a | ||
fall UAN |
48.0 |
82.0 b |
11.3 |
11.9 b | ||
split UAN |
47.5 |
86.5 a |
11.3 |
12.2 ab | ||
Different letters beside values indicate significant differences at the 5% probability level.
Fall applied N was always inferior to spring applications in yield (7% less for urea and 6% less for UAN) and protein (Table 2).
In fall 1999 (site 2000) it remained warm and dry after application on Nov 2, which may have permitted volatilization loss of urea portions of urea and UAN. Split N applications (1/2 in fall + 1/2 in spring) were intermediate in yield and protein between fall and spring applications.
C) Timing of nitrogen application on winter wheat: Fall vs spring, recommended practices and current research. D. Poison, R. Karamanos, n Flore and J. Harapiak (Westco). MAC 2003
Yield bu/ac |
Protein % | ||
N Timing |
S Alberta
(dark brown, black soil zones) |
MB 2002-3 |
MB 2002-3 |
Control (no N) |
34 |
70 |
11.3 |
Fall band urea |
96 |
13.4 | |
Fall sideband urea |
60 |
93 |
13.4 |
Spring broadcast AN |
52 |
97 |
13.2 |
Spring broadcast urea |
52 |
90 |
12.6 |
Spring broadcast urea & Agrotain |
52 |
94 |
13.1 |
Spring broadcast UAN |
52 |
||
Spring dribble UAN |
52 |
||
Comments:
In environments with dry falls and springs (AB) there is a distinct advantage to nitrogen application in the fall. At the study in MB fall and spring treatments performed similarly, except for some reduction in yield and protein where broadcast urea was not treated with Agrotain.
In environments with dry falls and springs (AB) there is a distinct advantage to nitrogen application in the fall. At the study in MB fall and spring treatments performed similarly, except for some reduction in yield and protein where broadcast urea was not treated with Agrotain.
High rates of N were used resulting in high yields and high protein. The N rate may have been sufficiently high that differences in efficiency are not apparent (when protein exceeds 11.5%, it means full yield potential was reached).
More WESTCO studies have been conducted since this time.
D) Winter wheat fertilization: Post ammonium nitrate. B. Irvine, G. Lafond, R. Kutcher, B. May. MAC 2006.
% of AN |
Yield bu/ac | |||||||
Site |
Melfort* |
Indian Head |
Brandon* | |||||
Yr |
2005 |
06 |
04 |
05 |
06 |
03 |
06 | |
Control |
75 |
42 |
48 |
50 |
54 |
24 |
51 |
33 |
Urea @ Seeding |
96 |
57 |
68 |
53 |
73 |
39 |
43 |
55 |
UAN late fall band |
93 |
56 |
75 |
54 |
58 |
28 |
54 |
52 |
UAN late fall coulter |
93 |
54 |
72 |
57 |
58 |
30 |
51 |
55 |
UAN spring band |
99 |
57 |
72 |
54 |
69 |
31 |
60 |
58 |
UAN spring coulter |
99 |
55 |
72 |
56 |
71 |
32 |
52 |
62 |
Urea spring broadcast |
99 |
55 |
76 |
57 |
72 |
39 |
52 |
52 |
AN spring broadcast |
100 |
54 |
72 |
58 |
74 |
39 |
52 |
55 |
* There was not a significant response to N at Melfort in 2003 or Brandon in 2004.
Comments: N rates were applied at 70% of maximum yield potential at that site – so that efficiency differences would be more apparent.
- There was a small negative effect of the coulter.
- Urea side-or mid-row banded at seeding was equal to spring ammonium nitrate in 4/7 instances and yielded less in 3/7.
- Late N fall applications were similar to spring ammonium nitrate in 5/7 instances but inferior in Indian Head in 2005 and 2006.
E) Other field studies
Often the suggestion is made to growers to compare some fall treatments to the standard spring application. I have not been able to compile any of these experiences, due to a lack of data. Studies that were implemented include:
- WADO field trial in mid 2000’s
- PESAI at Stonewall in 2006-7
If you are aware of any documented results, please forward to me. The MB Soil Fertility Advisory Committee will want to develop a provincial recommendation based on the previous research and any practical lessons from producer experiences.