Summer 1993 (v5n4)
Farming Systems Comparison Project
by David Chaney SAREP
To facilitate the transition to
sustainable agriculture, farmers need accurate information about
the benefits, costs and risks associated with "conventional"
and "alternative" systems. To generate this information,
research must eventually be conducted at the whole-farm level.
By broadening the boundaries of investigation, researchers are
able to critically evaluate the success of farming practices and
their effects on the environment, as well as the special requirements
for adapting these practices to farms in various locations. A
SAREP-funded research project comparing conventional, low-input
and organic farming systems is an excellent example of this research.
The goal of this 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 (members listed at the end of the article),
and participating farmers and farm advisor 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 28 acres at the UC Davis Agronomy Farm.
Rotations and Experimental Design
The main experiment occupies about
20 acres and compares four cropping systems: 1) a conventional
two-year rotation; 2) a conventional four-year rotation; 3) a
low-input four-year rotation; and 4) an organic four-year rotation.
The four systems are arranged in plots with four replicates of
each system. All the cropping systems include processing tomatoes,
a high-value commodity grown on approximately 310,000 acres in
California (1990 data). Other cash crops grown include wheat,
safflower, field corn, and beans. In addition, winter-spring cover
crops are grown in the low-input and organic systems. The specific
rotations used in the different management systems are shown in
Table 1.
Table 1. Summary of Crop Rotations Used in Four Management Systems. | ||||||||
| Year 1 | Year 2 | Year 3 | Year 4 | |||||
| Management | Fall | Spring | Fall | Spring | Fall | Spring | Fall | Spring |
| System | ||||||||
| Conventional (2 yr) | fallow | tomato | wheat | fallow | tomato | wheat | ||
| Conventional (4 yr) | fallow | tomato | fallow | safflower | fallow | corn | wheat | beans |
| Low-Input | cover1 | tomato | cover | safflower | cover | corn | oat+vetch | beans |
| Organic | cover | tomato | cover | safflower | cover | corn | oat+vetch | beans |
| 1 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
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 some 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 or not 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 is a key objective as experimentation and analysis continue.
Specific Research Objectives
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 2-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?
Funding Sources
In addition to funding from SAREP ($50,000/yr through FY 1991/92,
$12,500 FY 1992/93), this project is supported by the USDA Sustainable
Agriculture Research and Education program and the HJ. Heinz Foundation.
For more information, contact Steve Temple, Agronomy
and Range Science, University of California, Davis, CA 95616,
(916) 752-8216 or Tom Lanini, Botany
Extension, University of California, Davis, (916) 752-0612.
A Comparison of conventional, Low-Input and Organic Farming Systems: The Transition Phase and Long-Term Viability
Investigators (all at UC
Davis): Steve Temple, agronomy and range science; Howard
Ferris, nematology; Karen Klonsky, agricultural economics
Extension; Tom Laini, botany Extension; James J. Marois,
plant pathology; Frank Zalom, entomology; Carol Shennan,
vegetable crops; Bob Miller, DANR Analytical lab; Kate
Scow, land, air and water resources; Larry Schwankl,
land, air and water Extension.
Cooperators: Tony Turkovich,
farmer, Winters, Yolo County; Ed Sills, farmer, Pleasant
Grove, Sutter County; Bruce Rominger, farmer, Winters,
Yolo County; Jim Durst, farmer, Esparto, Yolo County;
Tom Kearney and Gene Miyao, UC Cooperative Extension
farm advisors, Yolo County.
Other: Don Stewart,
crop production manager; Diana Friedman, research manager;
Tomaz Ripoli, visiting professor; Miriam Volat,
student assistant. E
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