Lessons of Morrow Plots: Historic fields featured at Agronomy Day

CHAMPAIGN, Ill. — The nation’s oldest agricultural research field continues to provide answers to crop production questions at the University of Illinois.

The historic Morrow Plots in the heart of campus that was designated a National Historic Landmark in 1968 was among the virtual stops at Department of Crop Sciences’ Agronomy Day.

“Before Red Grange and Dick Butkus ever set foot on the field, we had Manley Miles and George Morrow out in these fields,” said Allen Parrish, Crop Sciences Research and Education Center director.

The Morrow Plots were begun in 1876 by Miles, an agriculture professor, who established three half-acre fields with different crop schemes. These were expanded to 10 plots in 1879 by Morrow, the first dean of agriculture at the university.

The number of plots and their size was reduced over time in order facilitate expansion of the university facilities, but the original Miles plots remain.

Early Findings

“They originally started in 1876 as a rotational study. It was understood that our prairie soils were so fertile that they would never be fertilized. Eventually they realized that was not the case,” Parrish said.

Plots 3, 4 and 5 remain from the original 10 plots. Plot 3 has been in continuous corn since 1876. Plot 4 had a corn/oats rotation from 1876 to 1966 and has been a corn/soybean rotation since 1967. Plot 5 now includes alfalfa/soybeans/corn into what has been a three crop rotation plot since 1876.

“Synthetic fertilizer was applied on the west side of the plots and manure was applied on the east side. We do a lime fertility treatment as needed to reach the desired pH,” Parrish explained. “This was a really big year of preparation when all of the plots were in corn, so this fall we’ll be applying manure which is that sweet aroma of research all of the undergrads get to enjoy.”

Parrish noted several lessons learned from the Morrow Plots over time.

Lessons from the first 30 years, from 1876 to 1903, included highly fertile prairie soil could be depleted with cropping; crop rotations can decrease the rate of depletion.

Lessons learned from 1904 to 1955 were that manure, limestone and phosphorus additions increased crop yields, but did not completely replace rotations; and rotations did not completely replace fertilization.

During 1955 to 1975 the lessons noted from the plots were that fertilization can restore productivity to unproductive soil in a short time if topsoil has not been lost; corn following soybeans has out-yielded continuous corn, even when fertility is higher; and soybean yields are affected less by soil treatment than are corn yields.

Organic Matter

Monitoring soil quality continues to be the cornerstone of the Morrow Plots research today as it was in 1876.

“When we look at the soil fertility of the Morrow Plots that have been in production for over 140 years, soil organic matter is one of those indications of the importance of rotation,” Parrish said.

The continuous corn plot had an average soil organic matter of 3.2% where no nitrogen was added; 3.8% on plots where manure was applied; and 3.7% where synthetic fertilizer was used.

In Plot 4 with the corn/soybean rotation the average soil organic matter was 3.7% with no fertility added, 3.8% in the standard fertility plots, and 4.7% in the manure plots.

Soil organic matter in the three crop rotation plots was 4.6% where no fertility was applied, 4.6% with synthetic fertilizer, and 5.5% where manure was applied.

“So, you can see how the importance of applying manure is to improving soil organic matter. But also one of the things we see, especially in the three-crop rotation, is the additional rotation allows for different root and plant growth, especially with the alfalfa being allowed to grow for almost a year and a half, it allows for soil organic matter to build over time,” Parrish said.

Parrish noted some changes that have occurred at the historic plots over time.

“Most of these plots started out as unfertilized plots. Manure was the primary fertilizer through 1955 and in 1955 they added synthetic fertilizer along with manure,” he explained. “Another thing to note is the change in genetics. All of the corn prior to 1937 was open pollinated and after 1937 it was hybrid corn that was more common. In 1967 soybeans replaced oats at the site.”

Corn yields of 26 bushels per acre was the norm in the United States when the sod was first turned on this historic site 144 years ago. The U.S. Department of Agriculture estimates Illinois’ 2020 average yield at 200 bushels per acre.

But while agriculture has come a long way since Miles and Morrow collected the first data from the plots, the lessons have not changed.

“Rotations always tend to yield higher than the continuous corn plots no matter the year and also the fertilized plots always out-yield the unfertilized plots. The lessons of the Morrow Plots continue to hold true today just as much as they did when they first started,” Parrish said.