Magruder Plots:  Long-Term Application of N, P, K, Lime and Manure, 1892-2005
Magruder Plots, Oldest Long-Term Winter Wheat Experiment in the World
Dr. A.C. Magruder, 1867-1924

LATITUDE: 36, 7.1844, N
LONGITUDE: 97, 5.3190, W

Annual Rainfall:  33 inches per year (825 mm)
Mean Annual Temp:  59F,  15.5C
Kirkland silt loam (fine, mixed, thermic Udertic Paleustolls)

Publications

Nitrogen Balance in the Magruder Plots Following 109 Years in Continuous Winter Wheat  J. Plant Nutr.  26:1561-1580. (pdf)

Use of Stability Analysis for Long-Term Soil Fertility Experiments.  Agron J. 85:159-167

The Magruder Plots:
Environmental Production History 1892-2004


In 1892, A.C. Magruder initiated a soil fertility experiment which would be continued for more than 100 years. The Magruder plots were initially established to evaluate wheat production on native prairie soils without fertilization. Although several changes have been made to the initial trial, the Magruder plots remain the oldest continuous soil fertility wheat experiment west of the Mississippi River. One of the key findings of the Magruder Plots has been the sustained wheat production of more than 16 bu/ac, following more than 100 years without any fertilization.  Not until the last 5-10 years have we seen any benefit of K fertilization.  Early on, the response to P fertilization was notable (P-only versus the check).  As issues of sustainability and environmental safety become increasingly more important, trials such as the Magruder Plots will be further explored. 

Procedures

Initially only one plot was established to evaluate native wheat production without the application of organic or inorganic fertilizers from 1893 to 1898. From 1899 to 1929, half of the experimental area was fertilized with barnyard manure while the other half received no fertilization. In 1930, Dr. H.J. Harper established ten separate fertilization treatments on these plots which would continue to 1947. Due to a university construction decision for a new dormitory, plots from six of the ten treatments were moved (surface 0- 16") following wheat harvest in 1947 to its present location on the Agronomy Research Station (Figure 1). The subsoil at the new location was noted to be very similar to that of the original site located just west of present day Stout Hall.

Table 1. Changes in location and treatment modifications for Magruder plots,1892-present.

Year

Trts.

Nitrogen source

N rate, lb. N/ac

N rate, manure lb. N/ac

P source

Row spacing inches

Seed Rate lb/ac

Loc.

Seed Type

1892-1898

1

-

-

-

-

7

75

Old

SRWW

1899-1912

2

Manure only

-

-

-

7

75

Old

SRWW

1913-1929

2

Manure only

-

120**

-

7

75

Old

HRWW

1930-1933

10

NaNO3 (16-0-0)

33

120**

OSP (0-20-0-12S)

7

75

Old

HRWW

1934-1945

10

NaNO 3(16-0-0)

33

120**

OSP (0-20-0-12S)

14

50

Old

HRWW

1946-1947

10

NH4NO3(33.5-0-0)

33

120**

OSP (0-20-0-12S)

14

50

Old

HRWW

1948

6

NH4NO3(33.5-0-0)

33

120**

OSP (0-20-0-12S)

7

75

New

HRWW

1949-1957

6

NH4NO3(33.5-0-0)

33

120**

OSP (0-20-0-12S)

14

50

New

HRWW

1958-1967

6

NH4NO3(33.5-0-0)

33

120**

OSP (0-20-0-12S)

10

60

New

HRWW

1968-1993

6

NH4NO3(33.5-0-0)

60

240**

TSP (0-46-0)

10

60

New

HRWW

1994-pres

6

NH4NO3(33.5-0-0)

60

240**

TSP (0-46-0)

7.5

60

New

HRWW

 

Table 2. Soil fertility treatment effects on Magruder Plot wheat grain yields, Stillwater, OK, 1930-2004

 

Treatment
N-P2O
5
       K2O

lb/ac/yr

1930-37

1938-47

1948-57

1958-67     

1968-77

1978-87

1988-97

1998-04

1.  Manure  only +

 

24.1

17.5

18.0

29.9

30.2

34.1

28.0

39.5

2.

0

0

0

16.6

9.5

13.3

18.9

18.0

19.6

15.1

18.6

3.

0

30

0

21.2

15.9

19.1

21.5

18.8

22.4

14.7

20.4

4.

33*

30

0

22.6

17.2

19.8

31.7

36.0

30.5

27.4

41.7

5.

33*

30

30

23.4

17.4

19.9

29.4

33.9

30.9

32.4

44.6

6.

33*

30

30+ lime

22.3

17.3

22.5

33.0

37.6

33.0

32.9

45.6

 

 

 

 

 

 

 

 

 

 

 

 

 

Mean

 

 

 

21.7

15.8

18.8

27.4

28.9

28.4

25.1

35.1

SED

 

 

 

2.6

1.8

1.8

2.0

2.6

1.9

2.6

3.7

* N rate increased to 60 lbs N/ac in 1968.  + Beef manure applied at a rate of 120 and 240 lb N/ac every fourth year for periods 1930-1967 and 1967-present, respectively.  Lime (L) applied when soil analysis indicated a pH of 5.5 or less. 

Magruder Plots

Figure 1. Physical location and treatment structure of the Magruder Plots, 1947-present,
Agronomy Experiment Station, Stillwater

 

Figure 2.  Changes in soil organic matter (%) in the Magruder Plots, 1892-present.