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The Morrow Plots: A Landmark for Agriculture

The Morrow Plots, which are located in the heart of the Urbana-Champaign campus of the University of Illinois, are the oldest continuous agricultural research fields in the United States. Established in 1876, they are predated only by the Rothamsted Field in England, which was started in 1843. The site was designated a National Historical Landmark by the Federal Government on Sept. 12, 1968.

A 1992 view of the Morrow Plots, showing oats, corn and soybeans

A 1992 view of the Morrow Plots, showing oats, corn and soybeans.

During the dedication ceremony held in 1968, Professor M. B. Russell, then director of the Illinois Agricultural Experiment Station, noted that “it is of interest to observe that the Morrow Plots were established in 1876, the centennial year of one of the greatest proclamations of free men of all time, the Declaration of Independence.” He emphasized that “it is now clear that the lesson of the Morrow Plots represents a new kind of declaration of independence—not of political independence but independence from one of the fears that man has had since the dawn of time, the fear of hunger.”

David D. Henry, then U of I President, said that “this historic marker to be placed here is a reflection of the flowering of a magnificent concept upon which universities have been built and which today lies at the very essence of our own survival . . . I refer to the research function of universities, which results in the advancement of knowledge. I also refer to the precept of the land-grant university movement—to carry knowledge, old and new, into the field, the home, the office, and the community.”

Unlike most historic landmarks, the Morrow Plots remain today a working research site that promises to enhance our knowledge far into the future. Located in the heart of campus, the site reminds all visitors of the timeless truth of former U of I President Andrew Sloan Draper’s soil and her strength lies in its intelligent development.”


No one can answer the question of who actually started the Morrow Plots. The impetus most likely came from agricultural chemist C. W. Silver, who visited the Rothamsted Field while on-route to study for an advanced degree in Germany. Upon his return in 1875, he wrote of this experience in the campus newspaper. He concluded his write-up with a proposed layout for a long-term field study on corn.

At the time, considerable controversy existed about the need for fertilizer in the soil. At least one leading USDA scientist believed that the soil in the Midwest was so high in total nutrients that it would never be necessary to add fertilizer if a crop rotation could be found that would “liberate” nutrients from the soil.

Cyril Hopkins and James H.Pettit take a soil sample from

Figure 1. Cyril Hopkins (right), head of the Department of Agronomy, and James H.Pettit (left),
assistant in Soil Analysis at the Ag Experiment Station, take a soil sample from
the Morrow Plots circa 1900. This photo may have been taken on April 11,1904.

When the U of I was founded in 1868, Regent John Milton Gregory assumed responsibility for assembling the faculty. Manly Miles from Michigan State University, who was acknowledged as one of the most eminent agriculture professors in the country, was hired as Professor of Agriculture in 1875. On June 10, 1876, Miles wrote a letter to Prairie Farmer magazine describing a long-term experiment with corn that he had started. He also submitted a written proposal to Regent Gregory for experimental plots similar to those originally proposed by Professor Silver in the campus newspaper. The nature of the treatments described by Miles, however, were totally different from what is known about the early years of the Morrow Plots.

The first study at that site was known as the “Experiment 23 Rotation Study.” No crop yield data from the plot were reported until 1888. The first published yields from Experiment 23 for both 1888 and 1889 appeared in the Agricultural Experiment Station Bulletin for 1890. The 1888 date also coincides with the founding of the Illinois Agricultural Experiment Station. The report indicated that 10 half-acre plots had been planted during the previous 14 years, that the cropping systems were maintained as originally planned, and that no manure or fertilizers had been applied. Based on that record, the starting date for the Morrow Plots has been placed in 1876.

While Professors Silver and Miles both contributed to the founding of the experiment, the plots are named for George E. Morrow, appointed as Chair of Agriculture in 1876.

New Directions

Only three of the original 10 plots remain in place today. Two plots were lost for construction of the observatory in 1895 and five others were seeded back to lawn in 1903. The remaining three plots were reduced in size to 1/10th acre, subdivided, and separated by permanent borders at that time. The physical size and configuration of the three main plots has not changed since 1903.

Plot 3 has grown continuous corn since the beginning of the Morrow Plots. The two-year crop sequence study that started in 1876 continues today in plot 4, with soybeans having replaced oats in rotation with corn during 1976. Plot 5 was planted in a three-year rotation of corn, oats with alfalfa seeding, and a forage crop of alfalfa hay starting in 1904.

Over the years, the main plots have been further subdivided as selected practices have been updated to reflect changes in agronomic practices on Illinois farm fields. The first fertility treatment was added to the plots in 1904, in response to declines in crop yields that had occurred in all rotational sequences.

Before the start of the growing season that year, each of the main rotation plots were divided into four 1/20th-acre subplots. The north half of each plot remained untreated, while the southern halves were treated with agricultural limestone, manure, and either rock phosphate or bone phosphate. Crop yields increased in the southern halves of all plots in response to liming and fertilization.

In keeping with practices of the day, underground tiles were added to provide supplemental soil drainage. The soil on the Morrow Plots is classified as Flanagan silt loam. This nearly level, dark-colored soil developed over loam glacial till under prairie vegetation and has somewhat poor natural drainage without added tiles.

By 1955, nearly all growers in the state were using fertilizers as part of their normal planting practices. Concerns were raised at that time about whether unfertilized soil had been permanently damaged. As a result, the north and south plots were divided into quarters, with one subplot treated as agronomists would recommend that Illinois growers treat their fields. The crop yields immediately jumped to the same rate as most high-yielding fields in the state.

Beginning in the 1960s, corn plant populations were also changed each year to take full advantage of the fertility levels in the various subplots. Another major adjustment occurred in 1967 with a shift in plot 4 from a corn-and-oats rotation to a corn-and-soybean rotation. This rotation better reflected the change in farming practices taking place across the state of Illinois during that period.

The Key to Higher Yields

Corn was the leading crop in Illinois at the time the Morrow Plots were started. Today, the corn crop planted in the state has increased to more than 12 million acres and information on how to maintain high yields in corn is more important than ever for Illinois corn producers. Growing concerns about the impact of fertilizer use on the environment have also become a major focus of attention in recent years. Once again, the Morrow Plots are uniquely placed to help answer pressing concerns.

The long-term studies underway at the Morrow Plots on the impact of both fertilizer treatment and crop rotation on corn yield have proved particularly instructive in helping to shape agricultural practices. Comparison of corn yields in the Morrow Plots in relation to the crop sequence is possible only every six years, when all the plots are planted with corn. The most recent available data come from 1997.

In that year, continuous corn that had never been fertilized yielded only 54 bushels per acre. The two-year sequence of corn and soybean that had never been fertilized yielded 94 bushels per acre, and the three-year sequence of corn, oats, and hay reached 110 bushels per acre. The subplots treated with the “recommended” soil test level of fertilizer since 1955 jumped to 151 bushels per acre in continuous corn, to 191 bushels per acre in the two-year sequence, and to 200 bushels per acre in the three-year sequence. Yields were consistently the lowest in continuous corn and the highest in the three-year sequence, whether or not the soil was fertilized.

The results from crop sequence and fertilization are even more dramatic when compared with the average corn yield in the state over time. In the first few years of the experiment, the corn yield in the unfertilized subplots ranked close to the average yield in the state. Since then, the corn yield in those plots has remained well below the statewide average.

On the plots that were treated with fertilizer starting in 1904, corn yields increased steadily through the 1970s. By 1978, the yields were approximately three times those of 1904 in all three cropping systems. On the other plots that received “recommended” levels of fertilizer starting in 1955, the yields almost immediately rose above the Illinois average and have remained so until today. Evidence accumulated since also indicates that larger differences in corn yield are caused by the soil treatments than by the cropping sequence.

During the last 30 years, yields have held fairly constant in all except the plots receiving both the manure and lime treatments and the recommended nitrogen, potassium, and phosphorus treatment. Weather patterns of the region may have contributed to these trends. Wet spring weather and cool temperatures in the 1990s reversed a trend toward earlier planting that began in the 1940s. Since 1967, yield has increased during years with warm spring weather and cool moist summers.

Taken together, this data from the Morrow Plots represents more than 100 years of accumulated knowledge on the effect of both sound and unsound crop management practices on corn yield. Most importantly, it has helped to establish the importance of crop rotation and fertilizer treatments in the modern agricultural system that has allowed us to so successfully feed an ever-increasing world population.

Changes in the Soil

A glass jar of soil from

Figure 2. A glass jar of soil from the Morrow Plots that was given to college donors in 1994.

Besides crop yield, the other major item of interest for the Morrow Plots is the changing level of soil organic matter in relation to the cropping sequence and fertilizer application. In dark-colored soils, such as Flanagan silt loam, cropping reduces soil organic matter. Organic matter, which is derived from plant and, to a lesser extent, animal residues, is composed of carbon, oxygen, hydrogen, and trace amounts of minerals.

Unfortunately, there are no archival soil or chemical data showing the conditions that existed when the study started in 1876. The earliest surviving soil samples, which date from 1904, were stored in glass jars. The study had already been underway for 28 years by the time these samples were taken.

The grass borders, however, may well approximate the original soil organic matter content of the plots. Values range from 5.5 percent organic matter on the west border to 6.5 percent on the east border. With an assumed starting level of about 6.0 percent organic matter, the soil in the continuous corn plot had dropped to 4.1 percent by 1904. The two-year rotation of corn and oats measured about 4.5 percent organic matter, and the three-year sequence of corn, oats, and hay was measured at about 5.9 percent, indicating a differential drop in organic matter related to the crop sequence.

Soil samples have been collected at least at 10-year intervals since 1904. Soil organic matter contents have been consistently higher in plots under the corn, oats, and hay sequence than in soils under the other two cropping systems. In plots where no fertilizer has been applied, the organic matter content first declined rapidly and then continued to decline at a slower rate under all cropping systems.

Organic matter level losses have generally occurred more slowly in south plots treated with manure. The only plots that no longer appear to be losing organic matter are the two- and three-year rotation plots that are treated with both the manure and inorganic fertilizer. Those trends in organic matter are difficult to assess statistically because none of the fertilizer treatments is replicated within the main rotation treatment and organic matter levels are known to vary within the experimental area.

A comparison of selected soil test data for 1997 and archival samples from 1913 show an overall decline in soil test phosphorus level, which is probably due to crop removal. A slight corresponding increase in soil pH and soil potassium levels has probably resulted from weathering.

Results from the Morrow Plots clearly demonstrate the positive relationship between crop yield response and soil organic matter levels. The composition or characteristics of organic matter may contribute more to soil quality than the quantity of organic material in the soil. In the Morrow Plots, the size and metabolic function of the microbial communities, as well as the amount and composition of particulate organic matter and of amino sugars, has been influenced by the crop rotation and fertility treatments. Ongoing investigations may succeed in relating some of these characteristics to specific aspects of soil performance

A Century of Knowledge

The need to protect this invaluable source of data stretching back more than 120 years has been well recognized over the years. The Undergraduate Library, which is located directly to the west of the plots, was built underground so as not to disturb the physical setting of the plots. In 2000, the efforts of Ted Peck, then professor of soil fertility, resulted in the considerable modification of plans for a nearby facility so as to minimize the impact on the Morrow Plots.

Despite its world renown, the Morrow Plots has operated without a designated director and has been open to all faculty within what today is the College of Agricultural, Consumer and Environmental Sciences. Over the years, it has been closely associated with a long list of eminent researchers from the College. To them and to C. W. Silver, Manley Miles, and George E. Morrow, the agricultural community owes a debt of gratitude for making possible the many lessons that have been learned from the Morrow Plots. Future generations will benefit from these lessons and hopefully from new, updated, and improved long-term experiments that the Morrow Plots have inspired.

Back to Agronomy Day 2001 Index

Department of Crop Sciences
College of Agricultural, Consumer and Environmental Sciences
University of Illinois Extension
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