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Nitrogen-on-Beans Initiative

A joint project with Dr. Tim Smith of Cropsmith

The authors are grateful for this project sponsorship by the Illinois Soybean Association

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Summary
Our goal is to develop a better understanding of nitrogen use and demand in soybeans while factoring in nitrogen fixation capability, soil supply, yield, and weather as a basis for developing nitrogen recommendations for high- yield soybeans in the future.

In 2015, we generated yield increases of 8 to 11 bushels per acre depending upon location, nitrogen source and timing of application, with applications during the reproductive stages producing the most consistant yield increases.

To increase productivity of soybeans, some farmers have applied nitrogen (N). However, the yield response of soybeans is inconsistent and unpredictable. While many methods exist to model N in the soil and plant to predict if additional N may be necessary for corn production, a similar functional model does not exist for soybean production. Through the use of plant and soil measurements, we aim to develop a prediction model and/or method to help producers determine the conditions in which N fertilizer would increase yields. We are also investigating the form of N fertilizer and the application timing that's best for optimal yields.

2015 is the first year of this project, so we are obtaining baseline data to understand nitrogen dynamics in the plant and soil.

Procedure:

  • Three locations across the state (DeKalb, Champaign, and Harrisburg)
  • Soybean varieties complimentary to location (HiSoy 31A32, 39A42, and 42A12)
  • Eight different nitrogen sources:
    • untreated control
    • Urea (46-0-0)
    • ESN controlled release urea (44-0-0) from Agrium
    • Ammonium Nitrate (AN, 34-0-0)
    • liquid Urea Ammonium Nitrate (UAN, 28-0-0)
    • Ammonium Sulfate (AMS, 21-0-0-24S) from Honeywell
    • Limus-coated Urea (contains the Urease inhibitor Limus from BASF, 46-0-0)
    • Blend of Ammonium Nitrate, Potassium Nitrate, and Ammonium Sulfate (30-0-7-2S) from Schertz Aerial
  • Four N application timings (pre-plant, V3 (three leaf), R1 (silking), and R3 (milk)
  • Applied Fungicides and insecticides at R3
  • Sampling Soil thoroughout the season
  • Samping plants and leaves for N and ureide levels throughout the season, and a final plant and yield harvest at maturity

Observations

Plants receiving pre-plant N appeared taller and greener early in the season. (see photo below)

In 2015, the plants experienced a very wet June and July, while the summer was cool and dry. Fall has been very dry, and there's been a quick dry- down.

Findings from 2015:

When averaged over all three locations, all fertilizer sources significantly increased soybean yield over the unfertilized control (of 71.7 bu/ acre), with no fertilizer at any time decreasing yield.

Among the various N sources, AN resulted in the greatest yield increases (range of 4 to 5.7 bu/ acre), followed by UAN (range of 3.1 to 4.1 bu/ acre); with both sources increasing yield regardless of application time.

All N sources increased yield when applied at the R1 or R3 growth stages.

Effect of N source and timing of N application on grain yield averaged across three Illinois locations in 2015.

 

Application Time

N Source

Preplant

V3

R1

R3

 

--------- bushels/ acre ---------

Unfertilized control

73.0

71.5

70.9

71.5

AN

77.0*

75.7*

76.2*

77.2*

AMS

75.7

73.1

74.4*

74.7*

UAN

76.5*

75.6*

74.7*

74.6*

Urea

75.3

74.4*

74.1*

74.6*

ESN

76.2*

74.2

75.2*

74.6*

Limus Urea

74.6

74.8*

74.6*

75.7*

AN+KN+AMS

75.6

72.9

75.4*

75.1*

*significantly different than unfertilized control within an application time, P 0.10.

AN is ammonium nitrate, AMS ammonium sulfate, UAN is liquid urea and ammonium nitrate, ESN is controlled release environmentally smart N, Limus Urea is urea treated with the urease inhibitor Limus, and AN+KN+ AMS is a mixture of ammonium nitrate, potassium nitrate and ammonium sulfate. 

At the individual locations, there was variation in the N source and application time that gave the greatest yield response, suggesting a large influence of soil and weather conditions on yield.

At DeKalb, applications of AN, Limus Urea, and the mixture of AN+KN+AMS at the R3 growth stage led to yield increases greater than 11 bushels/ acre.

In Champaign, applications of AN, AMS, Urea, Limus Urea, and the mixture of AN+KN+AMS at the R1 growth stage led to yield increaes of about 5-8 bushels/ acre.

In Harrisburg, applications of AN, AMS, UAN, ESN, Limus Urea, and the mixture of AN+KN+AMS at the R3 growth stage led to yield increaes of about 4-8 bushels/ acre.

The greater response from reproductive-stage applications may be due to abundant precipitation during vegetative growth at all locations in 2015, and possibly earlier fertilizer applications may be more effective in other years.

Effect of N source and timing of N application on grain yield at three Illinois locations in 2015.

 

Application Time

N Source

Preplant

V3

R1

R3

 

-------------- change in bushels/ acre ---------------

DeKalb (Unfertilized control = 63.2 bu/acre)

AN

7.9*
6.9*
11.4*
3.1

AMS

2.8
2.5
5.6*
-1.5

UAN

0.3
4.5
9.4*
0.4

Urea

0.7
2.8
5.7*
0.8

ESN

0.7
4.9*
6.8*
1.1

Limus Urea

-0.4
1.9
11.3*
-0.9

AN+KN+AMS

0.8
3.6
11.4*
-1.3
Champaign (Unfertilized control = 73.3 bu/acre)

AN

3.5
4.0
4.2
7.9*

AMS

3.7
2.0
4.3
6.5*

UAN

2.7
2.2
1.8
4.3

Urea

3.0
1.9
3.6
5.2*

ESN

2.4
2.4
3.0
3.2

Limus Urea

0.0
3.1
3.2
5.3*

AN+KN+AMS

2.7
2.7
2.7
6.9*
Harrisburg (Unfertilized control = 78.8 bu/acre)

AN

0.4

1.6

0.1

6.2*

AMS

1.4

0.2

0.3

4.8*

UAN

7.3*

5.4*

0.1

4.7*

Urea

2.9

3.9

0.2

3.5

ESN

6.3*

0.6

2.8

5.1*

Limus Urea

5.1*

4.8*

-3.6

8.4*

AN+KN+AMS

4.2

-2.1

0.7

5.4*

*significantly different than unfertilized control within an application time, P 0.10.

AN is ammonium nitrate, AMS ammonium sulfate, UAN is liquid urea and ammonium nitrate, ESN is controlled release environmentally smart N, Limus Urea is urea treated with the urease inhibitor Limus, and AN+KN+ AMS is a mixture of ammonium nitrate, potassium nitrate and ammonium sulfate. 

Yield components and quality were also measured, with yield increases from N fertilization being more associated with increases in seed weight.

Increases in grain protein and oil were sporadic, although protein concentration increases tended to occur with early N applications, and oil increased with later applications.

 

Click here for the full report.

 

soy plants with different greenness