America's Oldest Agricultural Experiment Turns 150, Still Producing Data Worth Farming By

Most scientific experiments end. Funding runs out, equipment fails, the graduate students graduate and move on. The Morrow Plots, a modest strip of land near the south quad at the University of Illinois Urbana-Champaign, have been running continuously since 1876. That makes them 150 years old in 2026, the oldest continuously operating agricultural experiment in North America and the second oldest in the world. The data they have generated stretches across a period in which American agriculture transformed from largely intuitive practice to evidence-based science - and the plots themselves helped drive that transformation.

What was there to prove in 1876

When the experiment began, farming was not a particularly systematic activity. Soil fertility was largely managed by intuition and tradition. Whether rotating crops mattered, whether adding fertilizer improved yields in measurable ways, whether depleting soil could be reversed - these were practical questions with no controlled answers. The Morrow Plots were designed to provide them.

The original experimental design tested continuous corn planting against corn rotated with oats and clover, and later with other crop combinations. Over the following decades, the plots accumulated data on how yield responded to rotation, how soil organic matter changed under different management regimes, and how fertilization altered long-term productivity.

The findings were not subtle. Plots growing continuous corn without fertilization showed dramatic yield declines over decades. Rotation with legumes - which fix atmospheric nitrogen - maintained fertility. Fertilization could compensate for some of the nutrient depletion from continuous monoculture but could not fully substitute for the soil structure benefits of rotation. These results, replicated and refined across a century and a half, helped establish crop rotation as standard agronomic recommendation across the Corn Belt.

What 150 years of data provides that no other experiment can

The irreplaceable value of the Morrow Plots is not any single finding but the continuity of the record. Long-term agricultural experiments are rare because they are difficult to maintain - changes in management, funding interruptions, and institutional priorities tend to break the data record. The Morrow Plots have maintained consistent enough methodology over their 150-year history to allow researchers to compare soil and yield conditions across radically different eras of agricultural practice.

Modern researchers can now ask questions that could not have been formulated in 1876. How have soil carbon stocks changed over 150 years of different cropping systems? What does 150 years of continuous corn do to soil microbial communities compared to rotated plots? How did the introduction of synthetic nitrogen fertilizer in the mid-twentieth century affect the long-term trajectory of soil fertility that the earlier record established?

These questions require the kind of time depth that the Morrow Plots uniquely provide. Newer experiments, however well designed, simply do not have the record length to answer them.

A landmark preserved in an active university

The Morrow Plots are a National Historic Landmark - an unusual designation for an agricultural field. They are surrounded by the University of Illinois campus, which has grown around them over a century and a half. Buildings have been sited to preserve them; underground infrastructure routes around them. The university treats them as both an active research asset and a physical symbol of its land-grant mission.

German Bollero, dean of the College of Agricultural, Consumer and Environmental Sciences at Illinois, frames the plots in terms of that mission: "The Morrow Plots are a huge part of our story in the College of ACES. They're a direct example of how we live out our land-grant mission, providing evidence-based recommendations that serve the public."

The 150th anniversary in 2026 is being marked with events and activities organized through the college, but the plots themselves continue operating as they have since Ulysses S. Grant's first term in office - generating data that future researchers will use to ask questions not yet imagined.

The second oldest, not the first

The Rothamsted Experimental Station in England holds the distinction of running the world's oldest continuous agricultural experiment, the Broadbalk Winter Wheat Experiment, which began in 1843. The Morrow Plots, started 33 years later, are the oldest in North America. The comparison is instructive - both experiments have survived because the institutions housing them recognized that continuous long-term data has a compounding value that no amount of short-term experimentation can replicate.