Experiment 502: Wheat Grain Yield Response to Nitrogen, Phosphorus and Potassium Fertilization, Lahoma, OK

PS
Coordinates:
36.388267, -98.108654
E502_15.xls (long-term data base) (Lahoma site Pictures)
PLOT PLAN 502
Experiment 502, Lahoma OK Experiment 502, looking east 502, looking east
Experiment 502, NUE with time
502 Long Term Wheat Experiment


Experiment 502, Mean Deviations over time

Abstract

Response of wheat grain yields to fertilization with nitrogen (N), phosphorus (P) and potassium (K) has been determined in numerous soil fertility experiments around the world.  Experiment 502 was established in 1971 to evaluate the effect of long-term N, P and K fertilization in continuous winter wheat.  Yield increases due to applied N (80 pounds N/acre) have averaged between 15 and 20 bushels/acre/year.   No response to applied P or K has been seen in any year, since soil test P and K levels were high when this experiment was initiated in 1970.  Soil test P levels have declined somewhat where no P has been applied, however, sufficiency levels still exceed 100%.  Soil organic C levels have increased with increasing N applied when compared to the check.  Grain yields were maximized at the 80 lb N/ac/yr rate.  In the first ten years of the experiment, N applied preplant and incorporated had no effect on grain %N.  However, in the last 20 years, grain %N increased linearly up to 100 lb N/ac. 

Materials and Methods

Experiment 502 was established in the fall of 1970 under conventional tillage on a Grant silt loam (fine-silty, mixed, thermic Udic Argiustoll).  Wheat has been planted for 28 continuous years in 10 inch rows at seeding rates of 60 pounds per acre.  The variety 'Nicoma' was planted from 1971-74, 'Triumph 64' from 1975-1976, 'Osage' in 1977 and 1979, 'Triumph 64' in 1978, 'TAM W-101' from 1980-91, Karl 92 from 1993 to 1994 and Tonkawa from 1995 to present.  Changes in management, application dates and fertilization are reported in Table 1.  The experimental design employed is a randomized complete block with four replications.  Fertilizer treatments used in this experiment and average grain yield means for selected periods are reported in Table 2.  Results from surface (0-6 inches) soil samples collected in 1995 are reported in Table 3.  Individual plots at this site are 16 feet wide and 60 feet long.  The center 10 feet of each plot was harvested for yield using a conventional combine.  In addition to wheat grain yield measured every year (exception was 1973 where crop failure resulted due to lack of rainfall), periodic soil and grain samples were taken for further chemical analyses.

Results

In the first ten years of the experiment, grain yields increased by an average of 14 bushels/acre/year when 80 pounds of N as ammonium nitrate was applied preplant.  Similarly, applied N over the last twenty years of the experiment resulted in yield increases up to 20 bu/ac.  No increase in grain yield could be attributed to P or K in any year of the experiment.  Soil test P levels have declined somewhat where no P has been applied, but sufficiency levels still exceed 100%.  Soil organic C levels increased with increasing applied N when compared to the check (Table 3).  Soil pH and K have changed very little over the 28 years that these treatments have been evaluated.  In the first ten years of the experiment N applied preplant and incorporated had no effect on grain %N.  However, in the last 20 years, grain %N increased linearly up to 100 lb N/ac. 

Table 1. Treatment  applications and experimental management for continuous winter wheat Experiment 502, Lahoma, OK, 1971-2015.

Year Variety Fert App Date Planting Date Harvest Seeding Rate, lb/ac
1971          
1972          
1973          
1974          
1975          
1976          
1977          
1978       6/13/1978  
1979 TAM W-101     6/28/1979  
1980 TAM W-101     6/24/1980  
1981 TAM W-101   10/31/1980 6/18/1981 65
1982 TAM W-101     6/28/1982  
1983 TAM W-101   10/18/1992 7/1/1983  
1984 TAM W-101     6/21/1984  
1985 TAM W-101   10/30/1984 6/13/1985 75
1986 TAM W-101   10/21/1985 6/11/1986 74
1987 TAM W-101   10/28/1986 6/18/1987 68
1988 TAM W-101 8/31/1987 10/2/1987 6/20/1988 67
1989 TAM W-101 10/10/1988 10/14/1988 6/19/1989 70
1990 TAM W-101   10/13/1989 6/20/1990 65
1991 TAM W-101 8/2/1990 10/15/1990 6/6/1991 65
1992 TAM W-101 9/9/1991 9/26/1991   63
1993 Karl 8/24/1992 10/1/1992   76
1994 Karl 9/14/1993 9/28/1993   75
1995 Tonkawa 8/5/1994 10/28/1994 6/19/1995 62
1996 Tonkawa 8/31/1995 10/10/1995 6/21/1996 69
1997 Tonkawa 9/4/1996 10/3/1996 6/13/1997 66
1998 Tonkawa 9/11/1997 10/17/1997 6/12/1998 70
1999 Tonkawa 9/3/1998 10/9/1998 6/30/1999 73
2000 Custer 9/8/1999 10/12/1999 6/13/2000 75
2001 Custer     6/15/2001  
2002 Custer   11/21/2001 6/25/2002  
2003 Custer   10/8/2002 6/17/2003  
2004 Custer   10/15/2003 6/11/2004  
2005 Overley   9/24/2004 6/15/2005  
2006 Overley        
2007 Overley   10/2/2006 6/26/2007  
2008 Overley        
2009 Endurance 9/23/2008 9/30/2008 6/18/2009  
2010 Bullet 9/15/2009 10/7/2009 6/11/2010  
2011 Bullet 10/1/2010 10/6/2010 6/6/2011  
2012 Billings 9/27/2011 10/24/2011 5/22/2012 90
2013 Billings 10/4/2012 10/11/2012 6/24/2013  
2014 Ruby Lee 10/9/2013 10/24/2013 6/17/2014 70
2015 Iba 10/3/2014 10/21/2014 6/22/2015 70

Table 2.  Treatment structure of long-term wheat Experiment 502, wheat grain yield and percent N in the grain for selected periods, Lahoma, OK, 1971-2000.

Trt.

N

P2O5

K2O

1971-1980

1981-1990

1991-2000

1971-2000

 

             

lb/ac applied

 

bu/ac

%N

bu/ac

%N

bu/ac

%N

bu/ac

%N

1

0

0

0

25.6

2.07

25.8

2.06

23.5

2.26

24.9

2.10

2

0

40

60

25.3

1.88

25.9

1.97

23.1

2.29

25.3

2.10

3

20

40

60

31.0

1.94

34.4

1.94

31.6

2.23

32.8

2.08

4

40

40

60

33.4

1.88

36.0

2.17

35.8

2.37

35.9

2.21

5

60

40

60

37.4

1.99

39.7

2.33

39.7

2.45

39.6

2.33

6

80

40

60

40.1

1.88

41.2

2.47

43.0

2.53

41.9

2.41

7

100

40

60

38.5

2.04

38.4

2.62

43.6

2.73

41.3

2.58

8

60

0

60

35.0

2.11

34.5

2.55

40.5

2.60

37.6

2.46

9

60

20

60

37.0

1.98

38.6

2.38

40.7

2.50

39.3

2.31

10

60

60

60

36.9

2.05

38.8

2.31

40.5

2.43

39.9

2.28

11

60

80

60

38.6

2.03

41.2

2.29

40.4

2.47

41.0

2.27

12

60

60

0

37.2

1.84

38.6

2.35

41.7

2.48

40.3

2.27

13

100

80

60

39.2

2.18

38.4

2.43

40.3

2.76

40.0

2.45

14

60

40

60*

39.3

1.98

41.3

2.40

42.3

2.43

41.1

2.31

SED

 

 

 

3.1

0.17

3.1

0.12

2.7

0.09

2.9

0.13

CV

 

 

 

12

12

12

7

10

6

11

8

N, P2O5, and K2O applied as ammonium nitrate (34-0-0), triple superphosphate (0-46-0) and potassium chloride (0-0-60), respectively. * K2O applied  as sul-po-mag (0-0-22). SED - standard error of the difference between two equally replicated means, CV - coefficient of variation.

Table 3.  Treatment structure of long-term wheat Experiment 502, and surface (0-6 inches) soil test analyses from samples collected in the summer of 1995, Lahoma, OK.

Trt.

N

P2O5

K2O

pH

Total N

Organic C

P

K

 

lb/ac applied

 

%

%

ppm

ppm

1

0

0

0

5.69

0.085

0.89

45

423

2

0

40

60

5.81

0.083

0.88

69

481

3

20

40

60

5.69

0.083

0.91

71

456

4

40

40

60

5.60

0.088

0.91

69

458

5

60

40

60

5.47

0.086

0.96

79

478

6

80

40

60

5.38

0.088

0.92

76

453

7

100

40

60

5.23

0.089

0.98

83

443

8

60

0

60

5.59

0.089

1.04

38

487

9

60

20

60

5.65

0.090

1.09

63

472

10

60

60

60

5.63

0.091

1.12

96

525

11

60

80

60

5.65

0.093

1.16

103

472

12

60

60

0

5.52

0.090

1.12

92

387

13

100

80

60

5.44

0.095

1.17

129

535

14

60

40

  60*

5.59

0.089

1.10

64

460

 

 

 

 

 

 

 

 

 

SED

 

 

 

0.16

0.005

0.10

14

47

CV, %

 

 

 

4

8

14

27

15

N, P2O5, and K2O applied as ammonium nitrate (34-0-0), triple superphosphate (0-46-0) and potassium chloride (0-0-60), respectively. * K2O applied  as sul-po-mag (0-0-22). SED - standard error of the difference between two equally replicated means, CV - coefficient of variation.