Historic Landmark of Agricultural Engineering

To commemorate the Development of the Universal Soil Loss Equation

Comments by Maurice J. Mausbach

Natural Resources Conservation Service

April 25, 2003

It is an honor and a privilege to represent Chief Bruce Knight and the Natural Resources Conservation Service at this historic event to commemorate the development of the USLE. For those of you who don’t know me, I am a soil scientist who has, in one way or another, been associated with USLE for most of my career, especially the ‘K’ factor part of the equation. I even wrote a PhD thesis dealing with soil erosion and its control along secondary road cuts and had the privilege to work with Bill Moldenhauer and Howard Taylor while both were at Iowa State University. I vaguely recall a National Conference on Soil Erosion that was held here at Purdue about 27 years ago in May 1976 in honor of the work of Walt Wischmeier. I was a new research soil scientist at our National Soil Survey Laboratory and was asked by my supervisor, Steve Holzhey, to co-author a paper entitled “Using Soil Taxonomy to Estimate K values in the Universal Soil Loss Equation.”

Others more knowledgeable than me will have covered the history of the USLE, but I can not help but mention that our agency the Soil Conservation Service, now the Natural Resources Conservation Service, was formed because of the erosion menace of our nation. Through the efforts of our first Chief, Hugh Hammond Bennett, a soil scientist/soil surveyor, he was able to obtain funding to investigate soil erosion and water conservation. He worked with Agricultural Experiment Stations and others to establish the first soil erosion experimental farms. Through the standardized experimental design of the unit plot, these farms generated much of the data that were used to develop the USLE. I think that much of the success in developing the USLE was the close relationship that the research scientists had with the professional field staff in developing a tool that addressed their needs.

The use of the USLE has been phenomenal and has been a unifying approach to management of our nation’s private lands. In the early 1960s, SCS staff implemented the USLE in local field offices for use in conservation planning on cropland east of the Rocky Mountains. In the early 1970s, we began to apply the USLE to idle and similarly undisturbed lands. By the mid-1980s, interest in public policy in soil conservation had increased dramatically and the USLE coupled with data from our National Resource Inventory (NRI) was used to formulate the Food Security Act of 1985. Use of the USLE became part of the farm bill regulations, first in the determination of highly erodible land, and then in the planning process to enable farmers and ranchers to be in compliance of the requirements of the law. I know that the use of an erosion model in determining producers eligibility for farm programs made some people nervous (maybe some of you in this room) but it has with stood the test of time and that in itself is no small feat.

In 1992, the Revised Universal Soil Loss Equation (RUSLE) was adopted by NRCS as its erosion prediction tool. We implemented RUSLE in ‘paper form’ maintaining the structure of the USLE, thus applying the new technology much as we had been doing since the 1960s. Changes in the model have occurred in response to changes in farming systems. It is a credit to the developers that they have balanced the power and sophistication of advanced, complex science with the need for the user to understand and feel comfortable with the model and its output. USLE and now RUSLE and RUSLE2 have provided a wealth of benefits to private landowners on working lands throughout this country and the world to address natural resources of concerns, especially soils. These tools have been the basis of our conservation planning efforts for nearly a half-century.

In February of this year, we began implementing RUSLE2 nationwide. This time we are using the full power of computer technology to implement the model.

Previously, I mentioned coupling the USLE with our NRI to monitor the trends in our natural resources, particularly soil erosion. Our NRI has shown that since the implementation of the 1985 Farm Bill, erosion has decreased by 38%, or from 3.1 billion tons to 1.9 billion tons per year. That’s the good news. Since 1995, when conservation compliance plans had to be fully implemented, erosion has leveled off at 1.9 billion tons per year. This may partially indicate that the impact of the 1985 and subsequent farm bills has reached their limit in effectiveness. Or, it could also be related to the fact the 1.9 billion tons distributed over all cropland acres is about 5 tons/ac/yr soil loss. Most of our crop land soils have a soil loss tolerance value of 5 tons/ac/yr! Maybe we need to set a new goal!

So what does the future hold for soil loss prediction? I would like to mention a couple of items for thought.

We are presently looking at adding a carbon goal to our quality criteria for conservation planning. This would be in addition to our existing soil loss tolerance goal. Our staff tells me that if we work with farmers and ranchers to improve their soil organic matter input, soil loss can be lowered to around 2 or 3 tons/ac/yr, and the health of the soil will be increased at the same time. Enhancements in RUSLE2 can be made as part of a planning tool for managing C much like it is currently used for erosion prediction! Managing for C would further decrease the total soil loss by about 1.29 billion tons per year. At $28.48 for a ton of soil, that is $15 billion dollars saved annually.

The other item for thought is how to best deal with the issue of climate change. A recent paper published by the Soil and Water Conservation Society entitled “Conservation Implications of Climate Change: Soil Erosion and Runoff from Cropland” addresses possible impacts on agriculture from climate change – specifically on soil erosion and surface runoff. The paper forecasts the increase in more extreme precipitation events and suggests that increases in soil erosion (ranging from 4 to 95 %) and increases in runoff (from 6 to 100%) may become evident in some locations. One of the three recommendations for dealing with the increased risk from extreme weather events is to develop a conservation planning tool that evaluates the risk of damage from severe rainstorms and placing the risk into the conservation planning systems and environmental outcomes. In addition to planning for average annual soil loss RUSLE2 could be used as a planning tool that provides soil erosion thresholds levels tied to frequency and intensity of storm events. This would be much like we do today with hydrologic planning for dams and flood prevention. Designing for storm frequency and intensity would require tools such as RUSLE to be adapted to handle extreme storm events in addition to predicting average annual soil loss.

This lab is to be commended on your long history in developing erosion prediction technology. We in NRCS have utilized the products evolved here for nearly a half-century. We continue to make erosion predictions each and every day we visit farm fields and create conservation plans with our clients, using the instruments of conservation planning developed here in West Lafayette. Our agency, our field staffs, and the operators of working lands appreciate what we have been served.