Experiment 501: Sorghum Grain Yield Response to Nitrogen, Phosphorus and Potassium Fertilization, Lahoma, OK

Abstract

Sorghum grain yield response to long-term applications of nitrogen (N), phosphorus (P) and potassium (K) remains extremely important relative to maximum yields and the potential for environmental risk.  Experiment 501 was established in 1971 to evaluate fertilizer applications on grain sorghum grown in western Oklahoma.  This experiment has now been conducted for 30 years.  Response to applied N was not seen until the second decade of the experiment.  In the last 20 years of the experiment, sorghum grain yields have been maximized at an average annual N rate of 60 lb N/ac.  Grain % N levels were generally maximized at the same N rate as that noted for maximum yields.  To date, no response to applied P and/or K has been found in this long-term grain sorghum experiment. 

Materials and Methods

In the spring of 1971, Experiment 501 was established under conventional tillage on a Grant silt loam (fine-silty, mixed, thermic Udic Argiustoll) at the North Central Research Station near Lahoma, Oklahoma. Grain Sorghum has been planted for 20 continuous years in 36 inch rows at seeding rates of 4.3 pounds per acre.  The variety 'ACCOR1019' was planted from 1971-79, 'DKC42Y+' from 1980-1994, SG-822 from 1995-1998 and SG-753 from 1999 to present.  Experimental methods, application dates and changes over time are reported in Table 1. The experimental design employed is a randomized complete block with four replications.  Fertilizer treatments and average grain yield means over selected periods are reported in Table 2.  Individual plots at this site are 20 feet wide and 60 feet long.  The center 2 rows of each plot were harvested for yield using a conventional combine the entire 60 feet in length.  In addition to grain sorghum yield measured every year (exception was 1973 where crop failure resulted due to lack of rainfall for most experiments at the North Central Research Station), periodic soil and grain samples were taken for further chemical analyses.  Results from surface (0-6 inches) soil test analyses from samples collected in 1988 are reported in Table 3.

Table 1.  Treatment  applications, and experimental management  for continuous sorghum Experiment 501, Lahoma, OK, 1971-2000.

Year

Variety

Fertilizer Application Date

Planting Date

Harvest Date

Seeding Rate

Harvest Area

1972

 

 

 

 

 

2rows*60ft

1973

 

 

 

11-15-73

 

180sqft

1974

ACCO R1019

5-22-74

6-24-74

12-4-74

10lb/A

10'*60'

1975

 

 

 

11-14-75

 

3row*60ft

1976

 

 

 

11-9-76

 

10'*60'

1977

 

 

 

11-18-77

 

10'*60'

1978

 

 

 

12-5-78

 

10'*60'

1979

 

 

 

12-3-79

 

2row*60ft

1980

DKC42Y+

 

6-12-80

11-10-80

 

3row*60ft

1981

DKC42Y+

 

7-12-81

12-4-81

4.3#/A

 

1982

DKC42Y+

 

6-14-82

11-9-82

5#/A 85%germ

 

1983

DKC42Y+

5-26-83

6-17-83

11-16-83

4.5#/A

3row*60ft

1984

DKC42Y+

 

6-22-84

11-14-84

 

 

1985

DKC42Y+

 

 

12-6-85

 

3row*60ft

1986

DKC42Y+

6-18-86

 

11-14-86

 

 

1987

DKC42Y+

6-23-87

6-24-87

 

 

 

1988

DKC42Y+

 

6-7-88

 

3#/A

 

1989

DKC42Y+

 

 

10-26-89

 

10'*60'

1990

DKC42Y+

 

6-5-90

10-26-90

 

10'*60'

1991

DKC42Y+

 

6-21-91

11-8-91

6#/A

10'*60'

1992

DKC427

5-1-92

5-7-92

 

6#/A

10*60

1993

DKC427

5-28-93

5-28-93

 

8#/A

10*60

1994

DKC427

5-10-94

6-1-94

Hailed out

8#/A

10*60

1995

SG-822

6-13-95

6-19-95

 

6#/A

10*60

1996

SG-822

5-21-96

5-29-96

 

6#/A

10*60

1997

SG-822

5-23-97

6-19-97

 

6#/A

10*60

1998

SG-822

5-22-98

7-15-98

12-15-98

6#/A

10*60

1999

SG-753

5-26-99

5-27-99

11-11-99

 

10*60

2000

SG-753

5-12-00

6-5-00

 

6#/A

Table 2.  Treatment structure of long-term sorghum Experiment 501, sorghum grain yield and percent N in the grain for selected periods, Lahoma, OK, 1971-1999.

Trt.

N

P2O5

K2O

1971-1980

1981-1990

1991-1999

1971-1999

 

lb/ac

lb/ac

%N

lb/ac

%N

lb/ac

%N

lb/ac

%N

1

0

0

0

2071

2.16

1363

1.41

940

1.21

1473

1.60

2

0

40

40

2284

2.18

1339

1.30

1039

1.24

1567

1.54

3

20

40

40

2239

2.26

2053

1.61

1356

1.27

1908

1.75

4

40

40

40

2273

2.26

1942

1.69

1347

1.61

1875

1.84

5

60

40

40

2066

2.39

2287

1.82

1790

1.64

2066

1.95

6

80

40

40

2264

2.21

2217

1.75

1748

2.07

2093

1.93

7

60

0

40

2416

2.08

2097

1.81

1710

1.91

2088

1.90

8

60

20

40

2242

2.21

2073

1.76

1497

1.75

1957

1.89

9

60

40

0

2213

2.35

2211

1.77

1608

1.81

2032

1.95

10

60

60

40

2238

2.19

2433

1.83

1627

2.01

2129

1.96

11

60

80

40

2169

2.28

2245

1.88

1592

1.66

2026

1.96

12

60

40

40

2180

2.33

2314

1.76

1735

1.81

2097

1.93

13

60

40

40*

2070

2.30

2396

1.75

1770

1.65

2102

1.89

SED

 

 

 

422

0.22

290

0.28

366

0.15

372

0.15

CV

 

 

 

27

14

20

7

34

13

27

11

N, P2O5, and K2O applied as ammonium nitrate (34-0-0), triple superphosphate (0-46-0) and potassium chloride (0-0-60), respectively. * -K2O as Sul-po-mag,  **- 60-40-40 + Cyamid Micro charger in 0-38-10 applied to give 40# P2O5. SED - standard error of the difference between two equally replicated means, CV - coefficient of variation.

Table 3.  Treatment structure of long-term grain sorghum Experiment 501 and results from surface (0-6 inches) soil test analyses conducted in 1988, Lahoma, OK.

Treatment

N

P2O5

K2O

pH

P

K

 

lb/ac

 

ppm

ppm

1

0

0

0

5.33

25

537

2

0

40

40

5.30

64

705

3

20

40

40

5.17

41

634

4

40

40

40

5.07

40

668

5

60

40

40

4.95

43

663

6

80

40

40

4.87

44

713

7

60

0

40

4.87

24

646

8

60

20

40

4.97

35

653

9

60

40

 0

4.95

44

562

10

60

60

40

4.92

46

613

11

60

80

40

5.00

59

625

12

60

40

40*

4.92

34

593

13

60

40

40**

4.95

42

622

 

 

 

 

 

 

 

SED

 

 

 

0.05

12

47

CV, %

 

 

 

1.4

39

11

N, P2O5, and K2O applied as ammonium nitrate (34-0-0), triple superphosphate (0-46-0) and potassium chloride (0-0-60), respectively. * -K2O as Sul-po-mag,  **- 60-40-40 + Cyamid Micro charger in 0-38-10 applied to give 40# P2O5. SED - standard error of the difference between two equally replicated means, CV - coefficient of variation.