The Transition from Conventional to Low-input or Organic Farming Systems: Soil Biology, Soil Chemistry, Soil Physics, Energy Utilization, Economics and Risk

Project Overview

Project Type: Research and Education
Funds awarded in 1994: $186,666.00
Projected End Date: 12/31/1996
Matching Non-Federal Funds: $513,844.00
Region: Western
State: California
Principal Investigator:
Steven Temple
University of California

Annual Reports


  • Agronomic: corn, safflower, wheat
  • Vegetables: beans, tomatoes


  • Energy: energy use
  • Farm Business Management: risk management
  • Production Systems: organic agriculture, transitioning to organic
  • Soil Management: soil chemistry, soil microbiology


    [Note to online version: the original report contained tables and appendices which it was not possible to include in full here. The regional SARE office will be happy to send a hard copy of the complete report. Just contact Western SARE at (435) 797-2257 or]

    The Sustainable Agriculture Farming Systems (SAFS) project was established to evaluate the biological, agronomic, and economic performance of conventional and alternative farming systems in California’s Sacramento Valley. The study consists of 4 treatment systems which differ primarily in crop rotation and dependence on non-renewable resources. These include a conventional 2-year rotation (conv-2) and three different 4-year rotations: conventional (conv-4), low-input, and organic. The main crops are tomato, corn, wheat, beans, and safflower. All systems have used “best farmer management practices,” determined with the assistance of growers who cooperate on the project. Nitrogen in the organic system is derived from winter legume cover crops and animal manure while that in the low-input system comes from cover crops and supplemental inorganic fertilizer.

    Crop yields in the organic system have been comparable to somewhat less than those of the conventional systems. Nitrogen has commonly been the limiting factor in the organic corn and tomato crops due to unpredictible mineralization from cover crops and animal manure. Nitrogen availability in the low-input system has been less problematic because of the limited use of mineral fertilizer. Developing cover crop management strategies to optimize nitrogen availability is an ongoing focus of the project but has been complicated by the influence that cover crops have on insect pest and weed abundance, soil water maintenance, and ultimately, farm operating expenses and profits. Disease, insect, and pathogen pressures have usually not been a significant limitation in any of the systems although there are differences in pest abundance across the treatments. Among these pest classes, weeds have been the most difficult to manage in the organic system because of the absence of herbicides.

    Current research efforts are underway in the companion area of the SAFS project to improve the cover crop management practices of the low-input and organic systems for improved nitrogen availability for the following cash crop and more effective weed control. An additional experiment is being used to test the effect of late-summer/fall cultural and cropping practices on levels of bacterial-feeding nematodes in the spring, and to determine the effect of those practices on nitrogen availability to transplanted tomatoes. Research findings from the project are being disseminated through a quarterly newsletter, workshops, and a video, as well as through scientific meetings and publications.

    Project objectives:

    A. Compare four farming systems, with differing levels of dependence on external resources over a twelve year period, with respect to:
    1. Abundance and diversity of weed, pathogen, arthropod and nematode populations.
    2. Changes in soil biology, physics, chemistry, and water relations.
    3. Crop growth, yield and quality as influenced by different pest management, agronomic and rotational schemes.
    4. Economic viability.

    B. Evaluate existing and/or novel sustainable and organic farming tactics.

    C. Distribute and facilitate adoption of information generated by this project to all interested parties as it becomes available.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.