The Century Experiment

We are exploring the effects of agricultural management on resource use, economics, and the environment over the course of 100 years

The Century Experiment

We are exploring the effects of agricultural management on resource use, economics, and the environment over the course of 100 years

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The Century Experiment

by Laura Crothers last modified May 15, 2018 04:16 PM
Changes in the soil and the environment happen gradually, so we started our flagship 100-year experiment—the Century Experiment—in 1993 to understand the real impacts of agricultural management on resource use, economics, and the environment in the long term.

“The study of [soil is] really a study of biotic memories, of how living things, whether bacteria or people, reshape and are themselves reshaped by their habitat, through many generations….

One way of fostering this long view is through “listening places”—places set aside for patient and oft-repeated measurements, where our observations are melded into those of our predecessors, then handed off as heirlooms to those who follow us. In that way, we bequeath a lengthening legacy—a library expanding with time—from which to read the soil’s memory and elicit portents of what is yet to be.”     —H. Henry Janzen

The philosophy of the Century Experiment is a simple one: studying how farm management practices impact the ecology of the farm over the seasons, years, and decades will help us figure out how to make agriculture and food production more sustainable.

On the 72 one-acre plots of the Century Experiment, we measure these trends by regularly observing:

    • crop yield
    • soil quality and biodiversity
    • profitability
    • water and energy use
    • other environmental impacts


The Experimental Design

  • Long-term Experiment in a Mediterranean Climate

    Regions characterized by a hot-summer Mediterranean climate are in blue, and by a warm- or cool-summer Mediterranean climate in orange. Map adapted from a figure by Adam Peterson, from data provided by PRISM Climate Group at Oregon State University (source:; CC 4.0 license).
    Unlike most other long-term agricultural cropping systems studies, Russell Ranch is located in a region with a Mediterranean climate, meaning that most of the rain falls between November and April and little rain is received during the summer, a drought period accompanied by high temperatures. The Mediterranean climate type stretches across the western U.S., all the way north through central Washington State and Montana, south to southern CA and New Mexico.

    The Mediterranean climate provides prime conditions for production of many crops, as the dry period limits disease and pest damage, but also stresses crop plants during the summer and necessitates irrigation to grow healthy crops. We use irrigation systems at a large scale similar to those used by field crop growers in California, so that our findings scale up and are applicable to large farms throughout the state of California and the western United States.
  • Cropping Systems of the Century Experiment

    The cropping systems in the long-term experiment include rainfed and irrigated systems, organic and conventional systems, and different forms and quantity of nitrogen inputs. The study began in 1993 with a uniform sudangrass crop to evaluate inherent soil differences and the original cropping systems were first planted in 1994.

    The cropping systems at the Century Experiment are designed to fall along a gradient of increasing irrigation and fertilization intensity, and a gradient of crop management philosophies (i.e., conventional to organic to a hybrid system) mirroring typical crop rotations common to the Sacramento valley. Currently, the Century Experiment contains ten systems that are:

    • two-year corn/tomato rotations (started in 1994)
    • two-year wheat/tomato rotation (started in 1994)
    • two-year wheat/fallow rotations (started in 1994)
    • two-year wheat/legume rotation (started in 1994)
    • six-year alfalfa-tomato-corn rotation (started in 2012)
    • a perennial native grass system

    Each system is repeated on six one-acre plots, featuring three plots for each of the two phases (for the two-year rotations).

  • Current Design of the Century Experiment

    • Changes in the Century Experiment since 1993

        • In 1999, a new transitional system was added to the Century experiment, which converted conventional plots to an organic corn/tomato rotation
        • In 2003, the “Legume” Corn–Tomato system was altered to receive cover crop each winter (instead of every other winter)
        • From 2003–2007, all one-acre plots of the Corn–Tomato systems were split in half and reduced tillage treatments were compared to standard tillage treatments (see tillage results here)
        • In 2007, the Irrigated Wheat–Legume system was discontinued
        • Wheat replaced corn from 2010-2012
        • In 2012, two systems, a six-year rotation (alfalfa–alfalfa–alfalfa–tomato–corn–tomato) and perennial native grass mix including nodding needlegrass (Nassella cernua), pine bluegrass (Poa secunda), three week fescue (Vulpia microstachys), squirreltail (Elymus multisetus), California oniongrass (Melica californias), and purple needlegrass (Nassella pulchra), were added to the Century Experiment
  • The Future of the Century Experiment

    • Long-term experiments are dynamic and need to respond to changing farming practices, as well as address evolving scientific priorities. For example, as subsurface drip tape became available to reduce water use in agroecosystems, we invested in conversion from flood irrigation to subsurface drip in most of our corn-tomato systems. Following this change, UC Davis scientists are leading research into optimizing irrigation efficiency with subsurface drip, while also working to understand the effects of this large-scale irrigation change on soil health. New innovations are always being explored to keep the Century Experiment on the cutting edge of crop management methodologies and technologies.

      The cropping systems of the long-term project are being evaluated to be more flexible and responsive to current trends, while maintaining the integrity of the long-term experiment.

      Additional new projects being discussed include:

      • integrated nutrient management systems
      • animal forage systems
      • rotations with pulse crops (grain legumes, e.g., garbanzo beans)
      • woody perennials (orchards and vineyards)
      • reduced tillage rotations
      • restoration ecology

Event Details


One Shields Drive
UC Davis
Davis, CA

(530) 752-3915