The Morrow Plots at the University of Illinois have inspired folklore, demonstrations and even a college song or two, but the historic plots hold significant research that helped develop crop production in the Midwest across the late 19th and much of the 20th centuries.

Established in 1876, the Morrow Plots are the oldest continuous experimental crop field in America, and the second oldest in the world, behind Rothamsted research station in England. Three of the 10 original plots — developed to test crop rotation — remain and are a protected National Historic Landmark.

Andrew Margenot, soil science assistant professor, chairs the Morrow Plots Committee and offers more insight into how Illinois agriculture has benefited from research on the plots.

What were the first Morrow Plots researchers trying to learn? At the time, they were looking at corn on corn or corn rotated with oats and clover, which was commonly raised back then for livestock like horses. Within about three decades, they went from looking at how rotating crops could improve yields to studying how nutrient inputs could improve yields. People weren’t really fertilizing with concentrated inputs until the 1900s, and they weren’t available at scale until after World War II; before then, it was largely manure.

That had to really change things. Yes. In 1904, they kicked off the second of five phases of the Morrow Plots that looked beyond crop rotations. That was looking at fertilizer inputs. Phase 3 was introducing hybrids and commercial fertilizers; phase 4 introduced soybeans to replace oats in the corn-oat rotation.

But their effect has been the same? Right. Long story short, the Morrow Plots have preserved their mission of looking at long-term effects on soils since 1876 of how we grow crops and how it affects yields.

WILDLIFE REFUGE: The University of Illinois Morrow Plots are enclosed with a hedge rather than a fence — but Andrew Margenot says they’re hoping for an upgrade to a fence. Why? The current hedge works as a refuge for wildlife like squirrels, which decimated the corn crop in 2022.

Do you think the first researchers had any idea it would still be going today? From what we can tell from the notebooks of the scientists back then, there was no intention of that. I suspect they began as a medium-term study. They probably figured, oh, it’ll go for a couple decades. I don’t think they thought, “This is gonna go for 146 years and counting.”

But we know they started taking and archiving soil samples in 1904, so they started to get the idea it might be around a while. And they began to divide up the treatment plots to have sub-treatments of fertility. So today we still have those first soil samples in the archives, taken in 1904. Now we can look at how soils have changed over time.

AG CAMPUS: Just south of the Morrow Plots is Mumford Hall, which serves as home base for many offices in the College of Agricultural, Consumer and Environmental Sciences.

What have we learned from the plots? Some of the things seem kind of obvious today but were revolutionary at the time. In 1876, we didn’t know the major nutrients crops need are nitrogen, phosphorus and potassium. That wasn’t teased out until the 1910s or so.

Second, that manure can support yields as well as N, P and K synthetic inputs, but that can lead to phosphorus buildup.

Third, that hybrids can really catalyze yield increases. And that plant populations increase yield — corn used to be grown as mounds or hills spaced 3 feet apart, with two or three seeds per mound.

And fourth, we have more insight on corn on corn. There are places in the plots that have been growing corn on corn for 146 years, and there’s one treatment with no fertility inputs ever. It’s still giving 30-bushel-per-acre corn, so it shows that the fertility of our soils is pretty tremendous.

And fifth, we’ve learned that rotating crops means you can do with less inputs — like corn after a legume like soybeans or alfalfa.

What does research today look like? The plots are just 2 acres, so statistically speaking, they’re no longer significant for research. They’re a historical curiosity and good for demonstration. At the same time, I think that we’ve undercapitalized them, and part of my research program is drawing heavily on the Morrow Plots. For example, we’re taking soil samples to 3-foot depths, which has not been done since 1962. We can do a proper inventory of nutrients, called nutrient stocks. There’s a lot of lessons to be learned about the nutrient stocks. We can use isotopes as carbon and nitrogen to understand how much of the carbon the organic matter left in the Morrow Plots. We can still do some very good science with them. So stay tuned a bit for.

NO SHADE: Just west of these soybeans growing in the Morrow Plots is the underground Undergraduate Library. Andrew Margenot says it’s a myth that the library was built underground to avoid shading the corn — but it’s a fun myth.

Logistically, how do you plant and harvest 2 acres in the middle of a major college campus? It’s all hand labor, with kids from class and from my own lab. It takes about five hours to harvest with 12 people. I think that’s the fun part, when you’re stripping corncobs off the stalks and weighing them, and then we shell them and with the grain. So it’s labor intensive; for fertility, we’ve gotta get out there with shovels and apply manure by hand. It’s the only way to do it on a small plot and not get spillover.

What kind of attention do the plots get on campus? There are a couple of myths: That if you get caught in the Morrow Plots you get expelled on sight, or that the Undergrad Library was built underground to avoid casting shade. I don’t think either are true. An anti-Vietnam War protest group had a plan to destroy the crops in 1969, but that got stopped. And some crop circles showed up in 2003 from students as a practical joke. I know it’s kind of funny, but that does screw up the data pretty good. So hopefully people don’t do that!