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

1996 Annual Report for SW96-012

Project Type: Research and Education
Funds awarded in 1996: $100,000.00
Projected End Date: 12/31/1998
Matching Non-Federal Funds: $320,537.00
Region: Western
State: California
Principal Investigator:
Steven Temple
University of California

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



1. Compare four farming systems (organic, low-input, and conventional two- and four-year rotations) with differing levels of dependence on external resources over a twelve year period, with respect to a) abundance and diversity of weed, pathogen, arthropod and nematode populations, b) changes in soil biology, physics, chemistry, and water relations, cover crop growth, yield and quality as influenced by different pest management, agronomic and rotational schemes, and d. economic viability.
2. Evaluate existing and/or novel sustainable and organic farming tactics.
3. Distribute and facilitate adoption of information generated by this project to all interested parties as it becomes available.


The Sustainable Agriculture Farming Systems (SAFS) Project was established to study the transition from conventional to low-input and organic practices. Treatments include three four-year rotations under conventional (conv-4), low-input, and organic management and a conventionally-managed, two-year rotation (conv-2). Crop yields in all systems have been near or above Yolo County averages throughout the study. Nitrogen (N) availability and weed competition have been the most important factors limiting yields in the organic and low-input systems. Positive effects on soil quality resulting from low-input and organic management include increased soil organic matter, increased pools of phosphorus (P) and potassium (K), higher microbial biomass and activity, increase in mobile humic acids, increased water infiltration rates, and soil water-holding capacity. Pesticide use in the low-input cropping system is less than 50 percent of that used in the conventional systems.

The most profitable farming system continues to be the conv-2 system due to the greater frequency of tomato in that rotation. Among the four-year rotations, the organic system with price premiums is the most profitable while the organic system without premiums is the least profitable. The low-input corn system, which combines cover crops with mineral fertilizer has emerged as an agronomically superior and economically viable alternative to conventional production.

New research efforts are focusing on developing reduced-tillage tomato production methods, and cover crop management strategies to optimize N availability following cash crops. Additional research is underway to quantify the contribution of cover crop N to the following cash crop in the low-input and organic systems and to measure the impact of farming system management on soil biota and the associated effects on soil fertility and pest management.

Information generated from SAFS research has been disseminated through a video highlighting the project results, workshops, annual field days, field tours, educational materials, peer-reviewed articles, and a Internet homepage. The project was the host site for AgTech98, the annual UC Davis showcase of important research and technology. Interest in the findings of the SAFS project by farmers, industry, researchers, and the general public continues to increase, and the SAFS plots serve as a living laboratory for graduate and undergraduate students, and provide samples for a number of soil and agronomic courses on campus.

Dissemination of Findings

In 1997 and 1998, five issues of the SAFS Newsletter were produced and distributed to over 1500 growers and agricultural professionals statewide. Presentations were given at a number of conferences in 1997 and in 1998 including those of the American Society of Agronomy, Entomological Society of America, Society of Nematologists, Soil and Water Conservation Society, and Association of Farming Systems Research and Extension. Peer-reviewed papers were published in several journals including Agriculture, Ecosystems & Environment, Nutrient Cycling in Agroecosystems, Soil Biology and Biochemistry, Plant and Soil, Agronomy Journal, Agricultural Systems, and Microbial Ecology.

Potential Benefits or Impacts on Agriculture

SAFS project research has demonstrated many of the benefits and limitations of low-input and organic farming systems in California’s Sacramento Valley. The findings with the most potential for positive benefits lie in the areas of pest management, N fertility and nutrition, and soil structural improvement.

Agronomic and economic evaluations of pest management systems have shown dramatically different potentials for pesticide reduction in the processing tomato and field corn. The findings illustrate that pesticide reductions in tomato, while possible, are economically costly primarily because of the lack of efficient nonchemical weed management tactics. Although pesticide use could be reduced by 50 percent, premium prices are needed to compensate growers for increased pest management costs which may average 50 percent more than conventional pest management costs. By contrast, pesticide use in corn, bean, and safflower grown in a four-year rotation could be reduced by 50 percent or more with little or no reduction in yield.

The performance of the low-input and organic tomato and corn systems has demonstrated that winter legume cover crops can provide 50 percent of needed N and result in improved soil structure.

Farmer Adoption and Direct Impact

The SAFS project receives increased attention each year from farmers, industry, researchers, and the general public. Ideas that were once considered to be impractical or even radical are now gaining in popularity. As consumer demand for organic foods increases more growers are considering the transition to organic farming systems and seek out the SAFS project to get information and advice. Others are simply interested in reducing costs or improving soil quality. Information and experience generated by the SAFS project since 1989 can be incredibly valuable in informing growers of some of the agronomic, economic, and ecological consequences of their many options.

Although long-term, comprehensive records are not available, recently reported statistics indicate substantial growth in the organic farming industry in California. According to 1992-1993 records, there were 1,159 organic growers farming over 45,000 acres, with gross sales exceeding $75 million. The Sacramento Valley accounts for nearly a quarter of California’s organic acreage with most of this land in vegetable, fruit, and/or nut production and about 18 percent of the area in field crops. Industry experts, however, estimate that the number of organic growers in California increased by 25 percent per year and that gross sales doubled between 1992 and 1995.

The degree to which California farmers are adopting low-input production methods is difficult to assess. Although there is clear evidence that increasing numbers of growers are using or are planning to use low-input practices in fertility and pest management, statewide material input expenses are increasing at a much greater rate than is total gross farm income. Total material input, fertilizer and lime, and pesticide expenses increased by 40, 35, and 22 percent, respectively, from 1992 to 1995. Moreover, state records indicate that total pesticide use in California continues to increase. Thus, while there are numerous examples of farmers experimenting with or adopting more environmentally-sound practices in California, reduced dependence on purchased material inputs is not widely apparent at the state level. Clearly, there is a continued need for research, education, and extension on agricultural sustainability in California.

Reactions from Farmers and Ranchers

Bruce Rominger, Yolo County farmer, reflecting on the impact of the SAFS project over the nine years of its existence, said, .. in the first years of the project the question was, ‘Are these systems [low-input and organic] going to work?’ and now we take for granted that they do work. Many of the initial problems have been overcome and now the focus has shifted toward refining the systems...

He added, The pendulum [of conventional agriculture] has swung toward the low-input and organic farming systems.

This summary was prepared by the project coordinator for the 2000 reporting cycle.