Oakes Irrigation Research Site
Carrington Research Extension CenterNorth Dakota State University
P.O. Box 531, Oakes, ND 58474-0531, Voice: (701) 742-2744, FAX: (701) 742-2700, E-mail: Walter.Albus@ndsu.edu

 

FARM EXTENSION ACTIVITIES

W. Albus, L. Besemann and H. Eslinger

 

Corn Response to Fertilizer N Rate in Ten Farm Fields, 2006

Table 1.  The effect of fertilizer N rate on irrigated corn in five producer fields at Oakes ND, in 2006.

Corn Response to Fertilizer N Rate in Six Farm Fields, 2007:

Table 2.  The effect of fertilizer N rate on irrigated corn in three producer fields at Oakes ND, in 2007.

 

Corn N Rate Studies in Producer Fields

 

            Corn Response to Fertilizer N Rate in Ten Farm Fields, 2006:  The effect of fertilizer nitrogen‑rate on yield and plant-soil nitrogen relationships was studied in ten irrigated corn fields (fields a-j), on five farms at Oakes ND, in 2006.  Historically, low fertilizer nitrogen prices and less precise methods of fertilizer application resulted in higher than required applications of N to manage risk.  With current technology and soaring nitrogen prices this strategy in no longer relevant.  In this study producers applied 50 lb/acre less N than the field rate in a strip across their field and in a second strip applied 50 lb N/acre more than the field rate.  These strips and the field rate were than compared by yield, soil nitrate-N content (spring and fall), end of season nitrate-N stalk test, grain protein, starch and oil content as well as test weight.  The return to fertilizer N applied above the lowest N rate for each field was also calculated for a corn price of $4.50/bu and a fertilizer N price of $0.50/lb of actual N. 

 

            Spring nitrate-N at the 0-24” soil depth exceeded 68 lb/acre in three of the fields.  There was little or no yield response to fertilizer N applications above the low rate in these high testing fields.  This is supported by the nitrate-N content in stalk samples (8” stalk sections taken at 6” above soil surface) from mature corn stalks.  Stalk nitrate-N was very high, 3,900 ppm, at the lowest N rate in these fields.  Stalk test criteria states that N is deficient at nitrate-N contents of 0-250 ppm, marginal at 250-700 ppm, adequate at 700-2,000 ppm and excessive when over 2,000 ppm.  Stalks tested less than 611 ppm nitrate-N in fields where spring soil tests were less than 41 lb N/acre and N was applied at the low rate.  Data from the 10 fields indicated that when stalk tests exceeded 1,000 ppm yields were maximized or very close.  Stalk nitrate-N contents of more than 2,000 ppm indicated excess N application resulting in elevated soil N in the fall sampling.  Grain protein tended to increase with increasing N rate to the point yields were maximized.  Starch content tended to decrease as grain protein increased.  The fertilizer N rate that was 50 lb N/acre less than the field rate gave the highest returns in eight farm fields.  Field j which was corn on corn, returned $15.19 more per acre at the 185 lb/acre N rate than at the 135 lb/acre N rate.  Field f which was corn on potato ground returned $4.38 more at the 170 lb/acre N rate than at the 120 lb/acre N rate.

 

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Table 1.  The effect of fertilizer N rate on irrigated corn in five producer fields at Oakes ND, in 2006.

Field

Fertilizer

Spring-2006

Yield

Y/Ymax1

Stalk

Fall-2006

Grain

Test

Return to

Crop

Soil

Soil

N Above

N Rate

Nitrate-N

Nitrate-N

Nitrate-N

Oil

Protein

Starch

Weight

Low N Rate2

2005

 

lb/ac

lb/ac

bu/ac

 

ppm

lb/ac

%

%

%

lb/bu

$

 

i

135

36

207

0.97

511

24

2.8

8.2

74.0

58.6

 

corn

i

185

36

212

0.99

1459

32

3.0

8.4

73.3

59.1

-2.05

corn

i

235

36

213

1.00

4057

68

3.1

8.4

73.1

59.4

-22.10

corn

j

135

28

198

0.95

610

16

3.4

7.8

73.6

59.3

 

corn

j

185

28

207

0.99

1161

32

3.2

8.4

73.8

58.3

15.19

corn

j

235

28

209

1.00

1868

32

3.4

8.6

73.1

59.4

-1.09

corn

k

100

60

196

1.00

1018

36

2.8

8.7

72.8

60.0

 

corn

k

150

60

194

0.99

2724

60

2.6

8.2

73.4

59.2

-35.31

corn

k

200

60

190

0.97

1894

68

2.6

8.2

73.6

58.7

-76.91

corn

c

90

68

237

0.97

214

16

3.2

8.5

73.1

61.3

 

pinto

c

150

68

242

0.99

1134

36

3.2

8.8

72.8

61.1

-7.50

pinto

c

200

68

244

1.00

1449

88

3.2

9.0

72.7

61.5

-23.50

pinto

c

250

68

244

1.00

1955

160

3.1

9.2

72.6

62.2

-48.50

pinto

e

90

136

225

0.97

3931

176

3.1

8.7

72.5

59.1

 

pinto

e

190

136

231

1.00

4104

112

2.7

8.6

73.6

58.9

-22.55

pinto

e

190

136

220

0.95

4477

200

2.8

8.7

73.1

59.9

-72.05

pinto

e

230

136

226

0.98

4113

164

2.6

8.4

73.6

59.2

-65.05

pinto

a

100

40

180

0.98

82

52

3.2

8.2

72.8

58.9

 

potato

a

150

40

175

0.96

380

52

3.1

8.6

73.4

61.3

-43.45

potato

a

200

40

183

1.00

313

160

3.0

8.8

73.0

61.1

-35.60

potato

f

120

104

194

0.97

7982

52

2.7

8.2

73.4

59.8

 

potato

f

170

104

201

1.00

6398

100

2.6

8.6

73.6

60.2

4.38

potato

f

230

104

195

0.97

9078

140

3.1

8.7

72.6

59.9

-51.36

potato

g

120

60

202

0.98

1880

20

3.2

7.7

72.8

59.9

 

potato

g

170

60

205

1.00

6752

76

2.8

7.9

73.2

60.1

-10.82

potato

g

230

60

202

0.99

8337

92

3.0

7.8

73.1

59.7

-52.66

potato

h

170

64

214

1.00

5270

88

3.0

8.2

73.4

58.9

 

potato

h

220

64

211

0.99

5378

196

3.1

8.2

73.4

59.8

-36.83

potato

h

270

64

209

0.98

8774

168

2.9

8.3

73.7

60.2

-70.75

potato

b

165

106

203

1.00

4043

84

3.7

7.9

72.6

59.4

 

soybeans

b

200

106

201

0.99

3499

192

3.5

7.7

73.3

58.4

-24.70

soybeans

1Y/Ymax = yield for each N rate in a field divided by the highest yield for a N rate in that field.

2Return to fertilizer N above the low rate in each field was calculated using $4.50 per bushel corn and $0.50 per lb of actual N.

 

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            Corn Response to Fertilizer N Rate in Six Farm Fields, 2007:  The effect of fertilizer nitrogen-rate on yield and plant-soil nitrogen relationships was studied in six irrigated corn fields (fields lp), on three farms at Oakes ND, in 2007.  The goal in this study was to compare the results of the field N rate to a strip within the each field where 40 lb/acre less N was applied.  The reduced N rates actually ranged from 30-86 lb/acre less than the field rates.  These strips and the field rate were than compared by yield, soil nitrate-N content (spring and fall), chlorophyll meter readings at silking, leaf N at silking, end of season nitrate-N stalk test, grain protein, starch and oil content as well as test weight.  The nitrate-N content in mature corn stalks was determined on 8-inch stalk sections taken at 6 inches above the soil surface.  Stalk test criteria states that N is deficient at nitrate-N contents of 0-250 ppm, marginal at 250-700 ppm, adequate at 700-2,000 ppm and excessive when over 2,000 ppm The return to fertilizer N applied above the lowest N rate for each field was also calculated for a corn price of $4.50/bu and a fertilizer N price of $0.50/lb of actual N. 

 

            All fields in this study began the cropping season with less than 55 lb/acre of nitrate-N in 2007.  Evidently, higher corn prices in 2007 caused producers to increase their N rates as the average in-field fertilizer N rate went from 173 lb/acre in 2006 to 201 lb/acre in 2007.  In three fields, the field N rate provided higher revenue than the reduced rate and this increase averaged $21.94/acre.  In the three fields where revenue was higher at the reduced N rate, revenue averaged $36.03/acre higher than the field N rate.  Stalk nitrate-N values of 3,571 and 6,053 ppm in fields m and o at the reduced N rate, respectively, suggest the higher yields at the field rate were due to variability among sampling areas.  The $17.90 increase in revenue at the field N rate over the reduced rate in field p is substantiated by the stalk test increasing from 752 at the low rate to 1,695 ppm at the field rate. This is not surprising as field p was corn on corn with low soil N and a field N rate of 180 lb N/acre.  Grain protein tended to increase and starch content tended to decrease with increasing N rate. 

 

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Table 2.  The effect of fertilizer N rate on irrigated corn in three producer fields at Oakes ND, in 2007.

Field

Fertilizer

Spring-2007

Yield

Y/Ymax1

Chlorophyll

Chlorophyll

Leaf  N

Stalk

Fall-2007

Grain

Test

Return to

Crop

Soil

Readings

Readings

at

Soil

Weight

N Above

N Rate

Nitrate-N

At Silk

Late Aug

Silking

Nitrate-N

Nitrate-N

Oil

Protein

Starch

lb/bu

Low N Rate2

2006

 

lb/ac

lb/ac

bu/ac

 

 

 

%

ppm

lb/ac

%

%

%

 

$

 

n

180

44

202

1.00

55.9

55.7

2.3

1008

32

2.4

8.1

73.8

58.2

 

corn

n

268

44

202

1.00

58.9

59.3

2.9

5764

72

2.3

8.5

73.1

57.1

-46.43

corn

p

140

24

197

0.96

59.4

57.2

2.1

752

44

2.1

7.9

73.9

58.8

 

corn

p

180

24

205

1.00

58.7

58.7

2.0

1695

76

2.3

8.1

73.6

58.6

17.90

corn

q

140

24

192

1.00

56.8

60.6

2.1

1133

48

2.6

7.7

74.2

57.0

 

corn

q

180

24

186

0.97

59.5

58.4

2.7

2345

252

2.5

8.4

72.9

57.4

-49.58

corn

l

180

54

252

0.99

57.5

58.1

2.1

1337

24

2.8

8.2

72.7

58.6

 

potato

l

220

54

254

1.00

58.0

59.2

3.0

5746

72

2.3

8.2

74.0

58.7

-12.08

potato

m

180

44

229

0.96

55.5

53.4

2.8

3571

40

2.2

7.3

74.5

57.4

 

potato

m

224

44

240

1.00

56.9

54.9

3.1

2862

28

2.2

7.1

74.2

56.9

26.02

potato

m

268

44

231

0.96

55.0

54.3

2.7

8735

96

2.2

7.9

74.0

57.6

-36.03

potato

o

150

38

193

0.96

58.2

 

2.3

6053

44

2.5

8.2

73.6

57.7

 

potato

o

180

38

202

1.00

59.2

 

2.3

5981

64

2.0

8.2

74.3

57.4

21.90

potato

1Y/Ymax = yield for each N rate in a field divided by the highest yield for a N rate in that field.

2Return to fertilizer N above the low rate in each field was calculated using $4.50 per bushel corn and $0.50 per lb of actual N.

 

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