NDSU Crop and Pest Report
Soils


ISSUE 4   May 27, 2004

SUPPLEMENTAL N TO SPRING WHEAT

Growers in some areas of the state were conservative on N rates this spring due to lack of soil moisture, high N prices or both. In some of these areas, soil moisture is much improved and the cool temperatures suggest that higher yield potential is possible this season. Supplemental N for spring wheat can be applied from seeding through the 6-leaf stage. Rainfall within a few days of application will help the efficiency of the application and decrease volatility of the urea portion of the fertilizer. Rainfall within a few days is especially crucial if the fertilizer is applied at the 6-leaf stage. If the N is not utilized until jointing, yield increases due to supplemental N will decrease substantially compared to earlier applications.

Supplemental N to emerged wheat is best applied using liquid N sources, such as 28-0-0, with streamer bars or streamer nozzles. These tools result in much less leaf burn potential than broadcast applications. The streamers also concentrate the N in surface bands, where the urea portion of the liquid is less subject to immediate volatilization compared with a broadcast application. These applications, however, should not be referred to as a foliar application. They are soil applications that need rainfall to incorporate them. A good inch of rain is necessary to receive full benefit from these applications. Nitrogen applications should not be mixed with herbicides or fungicides. They should be applied in a separate application.

Rates of N applied depend on the additional yield that might be realized. Common rates tend to be in the 10-20 gpa range. One gallon per acre of 28-0-0 is equivalent to 3 lb N per acre.

Rates studies of supplemental N were conducted last year by NDSU Extension and Experiment Station scientists at Carrington, Langdon and Minot in 2003. The results from Carrington (Table 1) show that when significant precipitation falls within 24 hours of application, there are no differences in yield whether the application was made at the 3, 4, 5, or 6 leaf stage. However, results from Minot and Langdon show yield reductions at the 6 leaf stage to jointing stage.

Table 1. Supplement N to dryland wheat at Carrington, P. Hendrickson, 2003.

Growth stage

Rate of N lb/acre

Yield, bu/acre

Protein, %

No suppl. N

0

45.5

11.0

3-leaf

90

60.7

13.0

4-leaf

90

59.5

12.7

5-leaf

90

61.7

14.4

6-leaf

90

59.7

14.2

6-leaf

135

65.4

14.3

LSD 5%

 

8.6

1.2

About 1 inch of rain fell within 48 hours of application.

Table 2. Supplemental N, Minot (Garrison), K. McKay, 2003.

Preplant N

Post N, Timing

Yield

Protein

90

----------

67

12.0

45

45, 2.5 leaf

66

12.2

-------

90, 2.5 leaf

64

12.0

-----

90, jointing

58

12.4

LSD 5%

 

7

NS

Only 0.23 inches rainfall over a two day period within 72 hours of the jointing application. Rainfall totals for 2.5 leaf application were about 0.5 inches within four days. Spring soil N, 31 lb/acre.

Table 3. Supplemental N, Langdon, J. Lukach, 2003. Soil test N, 35 lb/acre.

Preplant N, lb/acre

Post N,  Timing

Yield, bu/acre

Protein, %

135

0

74.1

13.6

45

90, 3 leaf

71.5

12.6

45

90, 6 leaf

74.5

14.0

0

135, 3 leaf

72.0

12.4

0

135, 6 leaf

64.5

12.2

LSD 5%

 

4.1

0.5

The streamer bar application should be made when it is not windy. Wind will break up the stream pattern and turn the application into one similar to broadcast. Significant leaf burn will then result. Keep alert for stream pattern break-up and stop the application if the pattern is compromised.

Dave Franzen
NDSU Extension Soil Specialist
dfranzen@ndsuext.nodak.edu


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