REMINISCENCES ABOUT
WALT WISCHMEIER, DWIGHT SMITH, AND THE USLE EFFORT
at the
Dedication of an ASAE Historic Landmark
Honoring
THE UNIVERSAL SOIL LOSS EQUATION
Purdue University April 25, 2003
Don Meyer
This is very special occasion for me for many reasons, including seeing many of you that I haven’t seen for a long time and being back on the Purdue campus where I worked 18 years and where all three of our sons graduated. Thanks for the invitation to participate.
Also, the persons and work we are honoring are very special to me. When I was an undergraduate student at the University of Missouri, Dwight Smith challenged me with a hydraulic problem that led to my first professional publication on the sliced inlet for tube structures; he was a major resource when I was conducting my MS thesis research on parallel terraces; Dwight recommended me for hiring by ARS; and he was my NPS leader for many years while I worked at Purdue. During those student years, Walt Wischmeier was a clerk in Dwight’s office and then was my supervisor the 18 years I was here at Purdue. And, of course, improved erosion prediction and control was a goal of all of us who worked here under Walt’s supervision, and certainly the USLE is the most renowned result of these efforts. So, this truly is a very special day for me!
The background and work that led to the development of the USLE is an intriguing story. I will focus on it for my part of this talk; however, it really deserves hours rather than a few minutes, so there will only be time to hit some of the high spots.
The USLE is based largely on results from runoff and erosion plot research. The first such plots were established in 1917, eighty-six years ago, by Professor M. F. Miller at the University of Missouri, just a short walk from my dorm. They are now a National Historical Monument in the midst of the MU campus. If you haven’t, I hope you can visit them someday.
In the 1920s, Hugh Hammond Bennett and others who were horrified by the terrible erosion that was taking place in many parts of the United States became evangelists for soil conservation. They published and spoke extensively, urging action to deal with this menace.
As a result, in the 1930s, 10 erosion research stations were authorized by Congress and established in various parts of the US. Dwight Smith began his career at one of these, the Bethany MO station. Also during the 30s, several researchers began efforts to identify and evaluate the major factors that cause erosion.
In the 1940s, the first erosion equations were proposed. Austin Zingg (also located at the Bethany station and later a foremost authority on wind erosion) published his extensive analysis of the effect of slope length and steepness on soil loss in 1941. The following year, Dwight Smith added factors for cropping method and supporting conservation practice, and he also added the concept of soil loss limits. However, these equations were based on midwestern data and applicable only to the Midwest. A few years later, George Browning added soil erodibility and management factors, and these and other researchers prepared tables and graphs to simplify the application of these relationships.
The USDA Soil Conservation Service (SCS, now NRCS) recognized the great potential of a soil loss equation for land management planning, and the Milwaukee office began asking for an equation suitable for application throughout the Cornbelt. This approach was called the “slope-practice method”. About the same time, Dwight Smith and Darnell Whitt proposed a “rational” equation for claypan soils with factors for cropping method, slope steepness, slope length, soil type, and supporting practice.
Then, in the late 40s, a meeting of experts was held and the result was the Musgrave equation, which added a rainfall factor. (This prediction equation with accompanying factor values was used for many years; in some cases, even long after the USLE was introduced.)
In the early 1950s, SCS recognized and pushed for one equation for all of the U.S. Dwight Smith and others lead a concerted effort toward a nationwide soil-loss prediction equation. This resulted, in 1954, with the establishment of the National Runoff and Soil Loss Data Center here at Purdue, with Walt Wischmeier as the leader. Several clerks were hired to help Walt with data assembly and analysis. In 1955, Don McCune and I were hired to work on gaps in the data. We were given the goal of designing a rainfall simulator that could apply rainstorms with the important characteristics of natural rainfall for use on field plots to evaluate erosion variables for which there were no or inadequate data from erosion plot and watershed studies.
Have you wondered why this Data Center was established at Purdue? Missouri would have been the obvious location; both Dwight and Walt were there, the longest history of plot research and the outstanding McCredie research station were there, and much of the foremost soil and water research had been and was being conducted there. However, at that time, the Missouri Agricultural Extension Service was promoting their Balanced Farming program that was very antagonistic toward SCS, so Missouri was out as a possibility.
What about locating it in Iowa, where productive soil was being lost at tremendous rates, or in other states in the Midwest or elsewhere with major erosion problems? Probably Purdue was chosen for several reasons, but most likely because of the close friendship between Lewie Nelson, the head of the Eastern Branch of ARS-SWC, and J. B. Peterson, the head of the Purdue Agronomy Department. “Doc Pete” had worked at one of the early erosion stations, was a strong promoter of soil conservation, and had a department of interested and capable staff members. George Spencer, head of Purdue Agricultural Engineering, was also supportive and had space to house the new ARS project.
Thus, this pioneering ARS project was established at Purdue, using the method of attack conceived by Dwight Smith. Walt Wischmeier focused on assembling the available data with guidance from Dwight, and Russ Uhland was detailed from Beltsville to Purdue for a short time to assist Walt.
Think of the challenges facing this new project: researchers at the various field locations that had the needed runoff and erosion data resisted providing “their” data to the Data Center; the data that were submitted came in all conditions and forms, often without important needed information; digital computers were new to all of the persons working on the project (therefore, much of the early work was done using mechanical calculators); the new clerks were unfamiliar with agricultural terminology and research methodology; and extensive interaction with researchers and SCS users was necessary. Yet, by early 1956, about 7000 plot-years and 500 watershed-years of data had been assembled at the Data Center, a tremendous accomplishment!
In 1956, two meetings that made great advances toward the USLE were held at Purdue. Leading soil conservation specialists from ARS, SCS, and several universities were invited to attend. At the February meeting, participants struggled with decisions about the type of relationship to be used in the USLE, which factors to include, how to quantify the factors, and what soil-loss tolerance limits to use. They also identified priorities for Walt and others to work on before the next meeting.
The second meeting was held in July to resolve many issues and to decide what factor values to use for conditions where insufficient or no data existed. Also, the need for a nationwide rainfall erosion index was emphasized as a priority for Walt to study. Subsequently, Walt made an extensive analysis of rainfall and erosion data from fallow erosion plots and Weather Bureau rainfall records to derive an erosion index for the R factor in the soil-loss prediction equation.
In 1958, Jerry Mannering was hired to replace Don McCune who took a position with the Rockefeller Foundation, and Tam Olson was hired to work with Walt on K-factor values from 1960-62.
By 1960, progress was sufficient to hold regional workshops at sites throughout the US where Walt and Dwight introduced the USLE to SCS and other user groups. Those persons attending these workshops from SCS depended on which group was to take the lead in applying it – soil scientists, agronomists, or engineers.
In 1961, ARS Special Report 22-66 was distributed as the first published information on the complete USLE. Then in 1965, Agricultural Handbook 282, the “bible” for USLE users, was published. It was based on more than 10,000 plot-years of data from 47 locations in 24 states. It was the crowning achievement of Walt Wischmeier, Dwight Smith, and all the other persons who had worked so hard and long in its development.
The USLE was the culmination of many years of effort by many persons. This effort had involved assembly and analysis of tremendous amounts of data, cooperation by numerous groups and agencies, input from many researchers, and publication of dozens of technical reports and papers, all based on the foresighted vision of Dwight Smith and dedicated work by Walt Wischmeier.
So, the USLE was not a sudden development, but a logical result of several decades of innovative research by talented researchers, then an outstanding effort by Walt, Dwight, and many others, some of whom are here today.
I’m so pleased personally that ASAE is honoring the USLE and recognizing the accomplishments of Dwight and Walt in this way. They were fine men and outstanding researchers, and I feel privileged to have known and worked with both of them.
And, this saga does not end in 1965; there is still more to tell about Dwight Smith and Walt Wischmeier and the USLE. Mat Romkens, Director of the National Sedimentation Laboratory in Oxford, MS is here to tell the rest of the story.