"The wealth of Illinois is in her soil, and her
strength lies in its intelligent development."-Andrew Sloan Draper, President,
University of Illinois, 1894-1904
When Andrew Sloan Draper paid that tribute to Illinois agriculture in 1894, the Morrow Plots already were as old as his freshman students. Established in 1876 by men of vision who sought answers to agricultural questions, the Morrow Plots are the oldest agronomic experiment fields in the United States. They include the longest-term continuous corn plot in the world. In 1968, the Morrow Plots became a National Historic Landmark. Located near the center of the University of Illinois' Urbana campus, they are a living reminder of the purpose for which this university and the land-grant system were established.
FIG. 1. These two ears of corn demonstrate vividly the difference between adequate and inadequate soil management and crop production.
When the Morrow Plots were established in 1876, the United States was celebrating, its 100th birthday. Farm wage rates in Illinois were $15 a month and corn sold for 30 cents a bushel. The state's average corn yield was 30 bushels an acre, about one-quarter what it is today. Fewer than 40 million people lived in the United States - over two-thirds of them on farms. Only 388 attended the nine-year-old Illinois Industrial University, whose name would be changed in another nine years to University of Illinois.
George E. Morrow, who was to become the first dean of the College of Agriculture, and Manley Miles, a professor of agriculture, were the visionaries behind the Morrow Plots. They planned to conduct experiments that would yield results "suggestive to the practical farmer." Three years after they established the original 10 half-acre plots, Morrow paid a visit to the experimental farm of John Bennet Lawes at Rothamsted, England. Continuous agricultural experiments had been conducted at this farm for over 40 years, and Morrow became convinced that continuous experiments should be maintained on the plots in Urbana.
Illinois was already famous for its deep, black prairie soils that were so admirably suited to corn production. But Morrow and Miles wanted to find out whether this productivity could be sustained and how various cropping-systems would affect yield and soil properties. If corn were grown year after year on the same field, would yields decline? How soon would this decline come and how severe would it be? If corn were alternated or rotated with other crops, would that help to maintain the soil's productivity?
FIG. 2. Sampling soil from the Morrow Plots around 1904: At left is James H. Pettit, an assistant in soil analysis at the Agricultural Experience Station; at right, Cyril G. Hopkins, head of the Department of Agronomy from 1900 to 1919.
As the growing university expanded, the plots were reduced in both size and number. The Observatory now stands where Plots 1 and 2 were located. Mumford Hall, as well, was built on land that once was part of the Morrow Plots. Only three plots, totaling six-tenths of an acre, remain of the 10 original half-acre plots. The north plot - Number 3 - has been planted to corn every year since 1876. The middle plot - Number 4 - was in a two-year rotation of corn-oats until 1968, when soybeans replaced oats. The south plot - Number 5 - originally was in a six-year rotation of corn-corn-oats-meadow-meadow-meadow, but this was changed in 1901 to a three-year rotation of corn-oats-clover. In 1953, the south plot's rotation was changed again - to corn-oats-alfalfa.
No soil treatment was applied to the plots until they were 29 years old. By then, two lessons already had been learned: the highly fertile prairie soil could be depleted with cropping, and depletion could be postponed by using crop rotations. Beginning in 1904, manure, lime and phosphorus (MLP) were added to the south half of each plot. Fifty years later, the unfertilized continuous corn was yielding an average of less than 25 bushels per acre. In vivid contrast., the fertilized corn in the three-year rotation that included legume hay was averaging well above 100 bushels!
Although hybrid corn, introduced into the experiment in 1937, was a factor in increasing yields on the fertilized plots, the untreated plots were so low in plant nutrients that they were unable to take full advantage of this new development. Another turning point came in 1955. Limestone, nitrogen, phosphorus and potassium (LNPK) were added to a plot that had received no prior treatment and to another that had been getting MLP since 1904.
FIG. 3. Soil treatments and cropping systems for the Morrow Plots: M = manure, L = limestone, P = phosphorus, N = nitrogen, K = potassium. Some plots have received no soil treatment.
FIG. 4. Response of soybeans to soil treatments. In this corn-soybeans rotation, nitrogen is added only to the corn. Soybeans were first grown on the Morrow Plots in 1968
These new LNPK treatments increased corn yields on the plots that had earlier received MLP. On the previously unfertilized plots, the results indicated dramatically how soon productivity could be restored. In the first year, the LNPK treatment more than doubled the yield of continuous corn on the plots that had not been fertilized before. The following year, 1956, the yield for untreated continuous corn was 29 bushels per acre, compared with 113 for the continuous corn that had received LNPK. Nevertheless, the long history of growing corn every year has taken its toll on the soil. Yearly tillage and organic matter loss are breaking down the structure of the soil, making it difficult for water to penetrate. Even with adequate fertilizer, continuous corn appears to be more vulnerable to moisture stress in dry -rowing seasons than is rotation corn.
Reflecting the rapidly changing technology in agricultural production, the Morrow Plots were modified again in 1967. Another section of each plot from all three cropping systems was treated with higher levels of LNPK. Plant populations also were increased. Corn yields of more than 200 bushels per acre were produced on three subplots during 1982. The highest corn yield that year was 215 bushels on the subplot which had received LNPK 1955 to present, but previously had received no limestone or fertilizer treatment. During 1985, this same subplot produced 205 bushels of corn per acre.
Soybeans, now the second most important crop in Illinois but unknown in the state when the plots began, were introduced into the cropping system in 1968 as part of a corn-soybeans rotation. Without soil treatment, the average soybean yield has been 35 bushels an acre (Fig. 4). With limestone and fertilizer added, soybean yields have increased to 48 bushels an acre.
From the story of the Morrow Plots comes both a warning and a promise. The warning is symbolized by the top ear of corn in Fig. 1. This ear grew on a plot whose soil was once productive. Year after year, the land was plowed and planted to corn. Year after year, the corn removed nutrients from the soil that were never returned. The result: pale, stunted plants and a small yield of low-quality nubbins.
The other ear of corn, however, reminds us that, with good rotation and adequate soil treatment, we can reap the benefits of the soil ourselves and still keep it productive for our children.
Persons interested in more details about the Morrow Plots can write to the Department of Crop Sciences, University of Illinois, 1102 South Goodwin, Urbana, Illinois 61801.
FIG. 6. Corn yields on the Morrow Plots, 1904-1986: Crop yields have been influenced
by both soil treatment and cropping systems. LNPK treatments were started in 1955