A Comparison of Conventional, Low-Input, and Organic Farming Systems: The Transition Phase and Long-Term Viability
Project Description
Rotations and Experimental Design
Preliminary Observations
Specific Research Objectives
Investigators:
Steve Temple, Department of Agronomy & Range Science, UC Davis;
Howard Ferris, Department of Nematology, UC Davis;
Karen Klonsky, Agricultural Economics Extension, UC Davis;
Thomas Lanini, Botany Extension, UC Davis;
James J. Marois, Department of Plant Pathology, UC Davis;
Frank Zalom, Department of Entomology, UC Davis;
Carol Shennan, Department of Vegetable Crops, UC Davis;
Bob Miller, DANR Analytical Lab;
Kate Scow, Department of Land, Air and Water Resources, UC Davis;
Larry Schwankl, Land, Air and Water Extension, UC Davis.
Cooperators:
Tom Kearney, UC Cooperative Extension, Yolo County;
Gene Miyao, UC Cooperative Extension, Yolo County;
Tony Turkovich, farmer, Yolo County;
Ed Sills, farmer, Sutter County;
Bruce Rominger, farmer, Yolo County;
Jim Durst, farmer, Yolo County;
Don Stewart, Crop Production Manager;
Diana Friedman, Research Manager;
Tomaz Ripoli, Visiting Professor, Brazil;
Miriam Volat, Student Assistant.
- Budget:
- FY 88/89: $50,000
- FY 89/90: $50,000
- FY 90/91: $50,000
- FY 91/92: $50,000
- FY 92/93: $37,500
- FY 93/94: $25,000
- FY 89/90: $50,000
Project Description
The goal of this long-term research project is to describe and quantify the
environmental and economic consequences of the transition from conventional to low-
input and organic farming systems typical of the southern Sacramento Valley. The
research team is multidisciplinary and participating farmers and UC farm advisors
play a key role in guiding the management decisions applied to the various production
systems. The project was initiated in 1989 and is located on the UC Davis Agronomy
Farm.
Rotations and Experimental Design
Return to the top of the page. The main experiment occupies about 20 acres and compares four cropping systems:
- a conventional two-year rotation;
- a conventional four-year rotation;
- a low-input four-year rotation; and
- an organic four-year rotation.
Summary of Crop Rotations Used in Four Management Systems.
Year 1 Year 2 Year 3 Year 4
Management System Fall Spring Fall Spring Fall Spring Fall Summer
Conventional (2 yr) fallow tomato wheat fallow tomato wheat
Conventional (4 yr) fallow tomato fallow safflwr fallow corn wheat beans
Low-Input cover** tomato cover safflwr cover corn oat+vetch beans
Organic cover tomato cover safflwr cover corn oat+vetch beans
** Cover crops used have included vetch, oats, and cowpeas, solely or in mixtures. Other species
are currently being evaluated. Both conventional systems are managed using practices typical for the southern Sacramento Valley. The two-year conventional system is practiced by farmers when short-term profit must be maximized. The low-input system includes a winter cover crop prior to planting of tomatoes, safflower, corn, and beans. While trying to reduce dependency on non-renewable resources, synthetic fertilizers or pesticides may be used in the low-input system to maintain the profitability of the operation. The organic system is managed according to the certification requirements of California Certified Organic Farmers (CCOF). Only approved fertilizers and pesticides are used. "Best farmer" management practices are used in all systems. For example, insect and disease management decisions for all systems are based on periodic monitoring of pest levels and no pesticides are applied until economic threshold levels are exceeded.
A companion research area of eight acres is being used to test alternative grain and cover crop legumes that could be used as cash crops, as winter and summer cover crops, or in intercropping systems in California. Along with this effort, investigators are evaluating various kinds of agricultural equipment for use in reduced tillage operations and innovative cover crop management.
Preliminary Observations
Return to the top of the page. Data collected during the first four years of the experiment include measurements of: crop growth, yield, and quality; soil biology; soil fertility; soil organic matter levels; soil water infiltration rates; weed biomass; disease levels; pest and beneficial insect populations; and economic performance. From these data, researchers have been able to make preliminary observations about the performance of the various cropping systems.
Soil fertility and weed management have been identified as the most important factors limiting yields in the organic and low-input systems. Researchers have altered production practices to address these constraints. Organic and low-input tomatoes, for example, are now transplanted instead of direct- seeded. This practice gives tomatoes a head start in competing against weeds and allows for the use of more efficient mechanical cultivation techniques. Supplemental manure fertilizers have also improved yields in the organic and low-input systems.
Other problems thus far have not been a major constraint for any of the production systems. However, the soil-borne pathogen Verticillium dahliae has been consistently higher in the conventional two-year system than in the others. Researchers will be collecting additional data to determine whether the disease organism will actually decrease tomato yields in this rotation.
Organic matter added through cover cropping and manuring has resulted in small increases in soil organic matter levels in the organic and low-input plots. This increase seems to be improving soil physical structure as shown by trends toward increased water infiltration rates.
Preliminary results suggest that similar crop yields may be obtained when "best farmer" management practices are used in each of the different systems. Similar yields, however, do not necessarily translate into similar profits. Year-to-year variations in production costs for each system, and the modest price premiums offered for organically-grown commodities should also be considered. During the 1991 growing season, for example, gross returns, per acre operating costs, and net returns above total costs were all highest in the conventional two-year rotation (all crops combined). The 1992 season, by contrast, showed that the organic system had the highest figures in each of these same categories. Results of this study support what other studies have found: The transition period (as evidenced by the performance of the low- input system) carries significant risk. There are no price premiums for "transitional commodities," costs of production may be high, growers are generally on the steep part of the learning curve, and the new production system can be ecologically unstable for a time. Recommendations for minimizing this risk are a key objective as experimentation and analysis continue.
Specific Research Objectives
Return to the top of the page.
Differences between the four cropping systems and the relationships among
various parameters observed during the first four years of the experiment have
suggested a number of more specific research questions to pursue. These are
listed below under the general headings of soil, pests, and economics:
SOIL
- How do seasonal changes in nitrogen availability differ among the various farming systems?
- What is the role of microbial biomass in regulating seasonal nitrate pool levels?
- How do microbivorous nematodes affect nutrient cycling?
- Can soil microbial parameters be used as indices of soil health?
- How will differences in soil organic matter levels and water infiltration rates affect the volume of soil explored by roots and the water balance of crops?
PESTS
- Will soil-borne pathogens limit yields of tomatoes under the intensive two-year tomato-wheat rotation?
- What levels of weed pressure can be tolerated in the different systems without loss of yield?
ECONOMICS
- How do the costs of cover cropping and manuring compare to those of applying chemical fertilizer?
- What are the cost differences and relative efficacy of conventional and alternative weed management strategies?
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