The Transition from Conventional to Low-Input or Organic Farming Systems: Soil Biology, Soil Chemistry, Soil Physics, Energy Utilization, Economics, and Risk
Final Report - November 2000
Principal Investigator:
Steve Temple
Department of Agronomy & Range Science
University of California
One Shields Avenue
Davis, CA 95616
(530) 752-2023,
Email: srtemple@ucdavis.edu
Other Investigators:
Steve Temple, Agronomy
Karen Klonsky, Economics
Howard Ferris, Nematology
Ariena van Bruggen, Plant Pathology
Bruggen, University of Wageningen, Netherlands
Kate Scow, Soil Microbiology
Willi Horwath, Soil Fertility
Tom Lanini, Weed Management
Jeff Mitchell, Water Relations
Peter Livingston, Economics
Rich Demoura, Economics
Leisa Huyck, Research Manager
Peter Brostrom, Crop Production Manager
Durga D. Poudel, Former Research Manager
Lynn Epstein, Plant Pathology
Bruce Rominger, Farmer
Jim Durst, Farmer
Ed Sills, Farmer
Tom Kearney, Farmer Advisor
Gene Miyao, Farm Advisor
Wes Wallender, Water Relations
Funding:
FY 1989-90: $50,000
FY 1995-96: $37,000
FY 1990-91: $50,000
FY 1996-97: $45,661
FY 1991-92: $50,000
FY 1997-98: $46,671
FY 1992-93: $50,000
FY 1998-99: $47,712
FY 1993-94: $37,000
FY 1999-00: $24,393
FY 1994-95: $50,000
Objectives
1. Over a twelve-year period encompassing three, four-year rotation cycles, compare four farming systems with different levels of reliance on non-renewable resources with regard to:
a. Crop growth, yield, and quality as influenced by different pest management, agronomic and rotational schemes of the four farming systems.
b. Abundance and diversity of weed, pathogen, arthropod, and nematode populations and their impact on crop growth, yield, and quality.
c. Changes in soil biology, physics, chemistry, and water relations and their impact on soil quality and productivity.
d. Cost of production inputs, value of production, economic risk, energy budgets for agricultural production under the four farming systems.
2. Compare and evaluate existing and/or novel low-input and organic farming tactics, with emphasis on innovations that correct deficiencies, enhance profitability or decrease risk in each farming system.
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 in 1988 by a multidisciplinary group of researchers, farmers, and farm advisers, to study the transition from conventional to low-input and organic systems. The SAFS project has compared four farming systems: organic, low-input, and conventional 4-yr rotations, and a conventional 2-yr rotation. Cash crops in the 4-yr rotations include processing tomatoes, safflower, dry beans, wheat, corn. The 2-yr rotation is tomatoes and wheat. Conventional management is based on current farming practices in the region. In the low-input and organic systems, use of synthetic fertilizers and pesticides was reduced or eliminated primarily through cover cropping, addition of organic amendments, mechanical cultivation and residue management, and modifications of irrigation and planting schedules.
The first 12-year rotation was recently completed. Among the most important findings from the SAFS project are the following:
- Among the four-year rotations in the SAFS study, the organic system with premium prices is the most profitable. However, the two-year conventional rotation is more profitable than any of the four-year rotations, due to the doubled frequency of rotation to high-value processing tomatoes.
- Pesticide use in corn, bean, and safflower grown in a four-year rotation could be reduced by 50% or more with little or no reduction in yield or increase in cost. In processing tomatoes, total pesticide use could be reduced by 50% without yield or quality loss but premium prices are needed to compensate growers for increased weed management costs.
- Arthropods, pathogens, and nematodes have had little influence on crop yields. Weeds have resulted in small but detectable yield loss, and higher production costs in some years, particularly in the organic system.
- The conventional farming systems have been least efficient at storing excess N while the organic farming system has been the most efficient. Thus, N losses have been greatest from the conventional, intermediate from the low-input, and least from the organic farming system. However, nitrogen availability has been an occasional problem in the organic corn and tomato systems. A study examining possible solutions to this problem indicated that summer cover crops and fall irrigations promote bacteria-feeding nematode populations and N mineralization which leads to higher tomato yields.
- Infiltration rates are over 50 percent higher in the organic and low-input systems. Less than 15 percent of winter rainfall in these systems was lost as runoff, compared to 43 percent in the conventional systems.
- Soil organic carbon was doubled in 10 years in the organic system, increasing by 10 t/ha. These results were obtained despite additional tillage operations in the organic plots due to cover crop considerations.
- Based on output-input ratios, the low-input system is the most energy-efficient farming system, while the conventional 2-year rotation is the least efficient.
Results from SAFS have been presented in over 65 peer-reviewed journal articles, 7 newsletters, numerous popular press articles, a home page (http://agronomy.ucdavis.edu/safs/home.htm), and at more than 80 national and international conferences. SAFS has hosted more than 1500 visitors from around the U.S. and 30 other countries at its eleven annual field days, six workshops, tours, and individual group visits. Future research needs include conservation tillage, weed management, and water use optimization.
Introduction
The Sustainable Agriculture Farming Systems (SAFS) Project was established in 1988 to study agronomic, economic and biological aspects of conventional and alternative farming systems in California's Sacramento Valley. The study consists of 4 treatment systems: organic, low-input, conventional-4 year rotation (conv-4), and conventional-2 year rotation (conv-2) which differ primarily in crop rotation and use of external inputs (Table 1). The systems include 4-year rotations under conventional (conv-4), low-input, and organic management, and a 2-year rotation under conventional management (conv-2). The four-year rotations include tomato, safflower, bean, and corn. In the conv-4 treatment, beans are double-cropped with a winter wheat crop, while in the low-input and organic treatments, beans typically follow a cover crop of oats and vetch. The conv-2 treatment is a tomato and wheat rotation. All systems use "best farmer management practices" which are determined by researchers, farmers, and farm advisors cooperating on the project. This report summarizes the accomplishments of the first 10 years, emphasizing findings from the last year.
Table 1. Farming-system treatments of the SAFS
Project.
| Farming System | Crop Rotation | Description |
| Organic | Tomato; safflower; corn; oats/vetch, bean | Four-year, five-crop rotation using composted and aged animal manures and cover crops; no synthetic pesticides or fertilizers are used. |
| Low-input | Tomato; safflower; corn; oats/vetch, bean | Four-year, five-crop rotation using legume and grass cover crops and synthetic fertilizer at about one-half the conventional rate; pesticide use is reduced. |
| Conventional 4-year (conv-4) | Tomato; safflower; corn; wheat, bean | Four year, five crop rotation using synthetic fertilizer and pesticides used at conventionally-recommended rates |
| Conventional 2-year (conv-2) | Tomato wheat | Two-year, two-crop rotation using synthetic fertilizer and pesticides used at conventionally-recommended rates |
Data collection
The SAFS project has generated several valuable datasets, including data on soil fertility, plant growth, nutrient accumulation, water relationships, product quality, crop yields, pests and diseases, and environmental risks. Data are collected on stand establishment, crop growth rates, biomass, and the yield and quality of crops. Crop yields are determined by both hand and machine harvest. Soil mineral N levels are monitored by frequent sampling at various depths in different crops and farming systems. Plant nutrient status is determined by leaf petiole, or other tissue analysis. Soil water content is measured by neutron probe to monitor water usage by plants and the supply, uniformity of distribution, and depth of penetration of irrigation water. Deep soil cores are taken at several times during the year for determination of nitrate and ammonium and to assess the potential for leaching of nitrate into the ground water. An assessment of changes in selected soil characteristics is made after each four-year rotation cycle. Samples are archived for future evaluation.
Microbial measurements include microbial biomass C and N, potentially mineralizable N, and community composition (as measured by phospholipid fatty acid analysis). The impact of plant-parasitic nematode populations on growth and yield of crops is assessed by measuring population densities under each crop and farming system at key times of the year. Community structures of non-parasitic nematodes are also monitored to assess their impact on nutrient cycling and soil fertility. Above and below-ground populations of economically and ecologically significant arthropods are monitored, and their damage and impact on crop yield and quality is quantified. Plant pathogen populations, and the onset, progress and the severity of plant disease, are monitored. The diversity and abundance of weed populations are quantified by recording species composition, diversity, and biomass at regular intervals.
A daily log is maintained to record all field activities and farming operations, the rates of materials applied, and the equipment used for each operation. Price data for materials and equipment are obtained from local suppliers. Data are analyzed using Budget Planner microcomputer software (Klonsky and Cary, 1990). Information is carefully evaluated for quality before accession into core data sets. Core data are available to all participants in the project.
Results
Objective 1. Over a twelve-year period encompassing three, four-year rotation cycles, compare four farming systems with different levels of reliance on non-renewable resources with regard to:
- Crop growth, yield, and quality as influenced by different pest management, agronomic and rotational schemes of the four farming systems.
Yields. Comparable crop yields are obtained from the organic, low-input, and conventional farming systems (Table 2). Tomato and corn yields in the organic system are generally lower than those of the low-input and conventional systems, mainly due to N limitation; however, differences between years are generally much greater than are yield differences between systems (See Appendix A).
Table 2. Average crop yields (Mg ha-1) at the SAFS project, 1989-1999.
| Crop | Organic | Low-input | Conv-4 | Conv-2 |
| Tomato | 67.2 | 74.5 | 77.2 | 73.1 |
| Safflower | 2.4 | 2.3 | 2.7 | n/a |
| Corn | 10.5 | 11.9 | 11.2 | n/a |
| Wheat | - | - | 5.6 | 5.6 |
| Beans | 1.9 | 1.9 | 1.7 | n/a |
Quality. A study of the impacts of farming systems on tomato product quality was conducted in 1998 (Colla, 2000). Soluble solid concentration of tomato fruit is an important quality parameter evaluated by processing industries in determining crop prices. Fruit soluble solids for the organic (4.45 brix) and low-input (4.72 brix) tomatoes were found to be below the average fruit soluble solids for the state (5.31 brix), while tomatoes from the conventional system had higher soluble solids (5.85 brix) than the average value for the state. The soluble solid concentrations of the tomato crop in each system was inversely proportional to the amount of irrigation water applied to that farming system. The higher infiltration rate and corresponding amount of water that percolated through the soil profile in the organic and low-input systems appear to have a negative impact on fruit quality in the alternative systems. Current research involves fine-tuning irrigation management to solve this problem.
- Abundance and diversity of weed, pathogen, arthropod, and nematode populations and their impact on crop growth, yield, and quality.
Weeds. Weed species and abundance changed during the transition from conventional to low input or organic farming systems (Lanini et al., 1994; Clark et al., 1998; Poudel et al., 2000). Weeds are most abundant and most problematic in the organic farming system and least abundant in the conventional systems where chemical intervention is used. Weed seed densities have almost doubled in low input and organic plots (10,000/m2) compared to conventionally managed systems. Weed seed density is similar for the two conventionally managed systems, however, the species composition varies. In conv-2 plots, winter weeds have increased, particularly annual bluegrass (Poa annua) and chickweed (Stellaria media). In the conv-4 plots, summer weeds predominate, with redroot pigweed (Amaranthus retroflexus) and lambsquarters (Chenopodium album L.) having the greatest seed increases. The seed banks of redroot pigweed, barnyardgrass (Echinochloa crus-galli), and chickweed have increased three-to ten-fold in the low input and organic plots compared to the conventional. By 1999, nightshade (Solanum sp.) and field bindweed (Convolvulus arvensis), resistant to the common herbicides, had become prevalent in the conventional system. Frequent cultivation in the organic and low-input systems prevented these weeds from becoming established, but did not deter the rapidly growing barnyardgrass. The general trends are for the weed community to shift from annual to predominantly perennial species under conventional management and from broadleaved weeds to grasses under low-input and organic management. These changes reflect the management in different systems, including escapes from herbicides in the conventional systems and from cultivation in the organic system.
Microbial communities. The farming systems influence the composition of soil microbial communities (Gunapala and Scow, 1998; Gunapala et al., 1998; Jaffee et al., 1998). Phospholipid fatty acid analysis (PLFA) provides an assessment of the total microbial biomass, as well as information about community composition. Microbial community structure was assessed throughout the 1997 growing season, following tillage and fertilization, at different spatial locations within the field, and within different farming systems. Microbial biomass was usually higher (up to 2x) in the organic and low-input systems than in the conventional systems; microbial activity, when measured, showed the same pattern (Gunapala and Scow, 1998). The PLFA fingerprints for microbial communities in the organic- and conventionally-managed plots, though significantly different on most dates, indicated substantial microbial diversity in both systems (Bossio et al., 1997). Microbial communities in low-input plots were intermediate in composition between the conventional and organic communities.
Fungi were greater in relative abundance in organic than in conventional soils yet made up a very small portion of the detritivore community in any farming system. On a single date in the latter part of the growing season in 1997, the communities associated with some crops could be distinguished from the others (e.g., wheat, beans from others) while others were similar to one other (e.g., tomatoes, safflower and corn). Communities in the conv-2 plots were distinctly different from those in the three four-year rotation plots. Soil respiration and organic matter decomposition rates after addition of cover crops were measured in soil samples collected four times from conv-4 and organic plots and incubated in the lab. There was no consistent difference between the organic and four-year conventional communities. This suggests that, despite differences in microbial biomass, the conventional communities are not substantially different from the organic communities with respect to their potential for cover crop decomposition.
Pathogens. Symptoms of corky root disease in tomato are significantly more severe in plots with a two-year rotation than in plots with a four-year rotation (van Bruggen 1995; van Bruggen and Semenov, 1999). Microsclerotia of the causal organism, Pyrenochaeta lycopersici, are similar in their formation to those of Verticillium dahliae. Consequently, we infer that the break-down of P. lycopersici microsclerotia will take more than two, but less than four, years, accounting for the increase in disease severity in the two-year rotation (Mol et al., 1996). Soft root tips caused by Pythium or Phytophthora sp. and red root rot caused by Fusarium sp. are generally also more severe in the two-year rotation than in the four-year rotations. Apparently the short, intense rotation reverts to host crops too frequently to allow for natural regulation of root diseases. The system is not sustainable in that regard and pesticide intervention will likely be necessary. In the other systems, levels of plant-parasitic nematodes and fungal root pathogens are being regulated by the length and diversity of the four-year rotation.
Nematodes. Statistically significant differences in root-knot nematode (Meloidogyne spp.) population levels in tomato plots were found only in 1994. In that year, higher densities were found in the conventional compared to the alternative tomato systems, suggesting that the soil management practices used in the low-input and organic systems may have suppressed this pest. However, the degree of galling due to root-knot nematodes in these soils has always been very low and there was no significant difference among treatments (Clark et al., 1998).
Our research on nematode communities has shown that nematode faunal analysis can provide a powerful tool for diagnosis of the complexity and status of soil food webs (Ferris et al, 1999). Nematodes include component taxa of the soil food web at several trophic levels. Since related taxa, with similar morphological, anatomical and physiological attributes, have similar feeding habits, useful faunal analyses can be obtained by identification to the family level (Bongers, 1990; Bongers, 1999, Bongers and Ferris 1999). They can be categorized into functional guilds whose members respond similarly to food web enrichment and to environmental perturbation and recovery.
Graphical representations of food web structure, based on nematode faunal analyses, allow diagnostic interpretation of its condition. Simple ratios of the weighted abundance of representatives of specific functional guilds provide useful indicators of food web structure, enrichment, and decomposition channels. We have developed guidelines for interpretation of graphical representations of food web condition (Ferris et al, 2000).
Using faunal analysis (Fig. 1), we have found that by creating conducive conditions for microbial activity in the early fall (adjusting soil moisture and enhancing carbon levels) we can enhance the abundance of grazers on the microbial biomass the following spring. That, in turn, increases mineralization rates in the spring to meet nutritional requirements during the vegetative growth period of the summer crop (Ferris et al, 1998; 1996).
Fig. 1 Progression of changes in nematode faunal analyses
from dry soil in late August in plots where the soil was irrigated and summer
and winter cover crops were grown (dark symbols) or were not irrigated and had
no cover crop (light symbols). The star indicates the time at which organic
material was incorporated into both plots (April). The soil food web of the
dry plots was unable to respond rapidly to the enrichment, while that in the
irrigated plots responded immediately. The differences were reflected in availability
of soil nitrogen in May and in yields of the subsequent tomato crop.
- Changes in soil biology, physics, chemistry, and water relations and their impact on soil quality and productivity.
Soil Carbon and Organic Matter. A commonly held, but largely untested, belief is that it is difficult to increase organic matter content in California agricultural soils due to the warm arid climate. There is considerable evidence, however, that carbon dynamics and soil organic matter differ between the organic and conventional systems of the SAFS project (Table 3). After 8 years of differential management, levels of soil organic matter in the organic and the low-input farming systems were 20 and 10% greater, respectively, than in the conv-2 system. The changes in organic matter content are consistent with rates of organic inputs into each system.
Table 3. Average carbon inputs1, soil organic matter (SOM)2 and humic acids (MHA)3 in the organic, low-input and conventional farming systems at SAFS.
|
Total C inputs
(Mg ha-1) |
SOM
(%) (Mg ha-1) |
MHA
(Mg ha-1) |
||
|
Organic
|
97.8
|
1.83
|
34.9
|
14.5
|
|
Low-input
|
90.8
|
1.69
|
32.2
|
13.4
|
|
Conv-4
|
51.2
|
1.54
|
29.3
|
12.7
|
|
Conv-2
|
40.2
|
1.53
|
29.1
|
11.7
|
1Carbon inputs over 8 years (1989 - 1996).
2Soil organic matter at 0-15 cm soil depth averaged across all crops
(1996).
3Mobile humic fraction at 0-15 cm soil depth averaged for all crops
(1998).
Humic acids were measured to assess the more stable pools of soil C. Within humic substances, the mobile humic acid (MHA) fraction is among the most dynamic components of SOM, and is directly involved in short-term nutrient cycling. Assessments of nutrient dynamics based on MHA analysis are considered to be more precise than those based on bulk soil analysis. Differences among farming systems in the mass of the MHA fraction were highly significant for the organic, low-input, and conventional soils in 1998 (Table 3). MHA accumulation was greatest in the organic system. It was intermediate in the low-input and conv-4, and least in the conv-2 system. These results, combined with data on total soil organic matter, reveal the potential for sequestering C and N in this Mediterranean environment. Carbon levels were doubled, with 10 t/ha being sequestered over an eight-year period (Horwath et al., 2000; Poudel et al., 2000).
Soil Fertility. Despite its greater SOM and MHA pools, the organic system is highly variable in N availability on annual basis (Cavero et al., 1998; Clark et al., 1999). Nitrogen availability is a function of current and historical N inputs, and activity and structure of the soil food web (Ferris et al., 1996). Nitrogen is released slowly from organic pools in the organic and low-input systems. Available mineral N in the soil solution differs during the growing season in the organic and conventional plots (Cavero et al., 1997); the organic plots have lower mineral N levels from mid-season to late-season while, due to sidedressing (the application of synthetic fertilizers alongside the developing crop rhizosphere), the conventional plots have greater mid-season to late-season mineral N levels. The organic and low-input systems have larger pools of stored nutrients than the conventional systems (Clark et al., 1998; Poudel et al., 2000).
Interesting difference are emerging in extractable cation ratios, with the Ca:Mg ratio in the upper 15 cm of the soil profile at 0.73 in the conventional soils, 0.79 in the low-input, and 0.83 in the organic soils (Clark et al., 1998) The low Ca:Mg ratios of the conventional soil may be contributing to the development of restrictive layers. Comparing 1996 values with baseline data taken in 1988, 1996 values for soil pH, soluble P, and SOM were greater for all the four management systems, while EC values, except for conv-4 system, were lower. The organic system showed a greater increase in soluble P, K and SOM than other systems. In 1996, the organic system, on average, had 91% greater soluble P, 21.5% greater soluble K, and 14.1% greater SOM than in 1988. There was only a 3% increase in the conv-2 SOM in 1996 from that of 1988. Salt levels in the organic system have increased over the course of the experiment, presumably associated with the use of composted animal manures. However, there were no detectable differences in the electrical conductivity of the soil solution among systems in 1996. Continued increase in soil salt concentration is neither ecologically or agronomically sustainable and will require future management intervention.
Soil physics and water relations. Clear differences in soil physical properties among farming systems have emerged. The soil in the low-input and organic systems has better tilth and is easier to work than that of the conventional systems. The proportion of water-stable aggregates which varies seasonally is generally greater in the organic and low-input than in the conventional soils. Due to these changes in soil structure, water infiltration rates are greater in the low-input and organic systems (Table 4). The proportion of winter rainfall that is lost as runoff is less than 15 percent in the organic and low-input systems, compared to 43 percent in the conventional systems (Figure 2). Volumetric water content is correspondingly higher in the organic and low-input systems (Figure 3) (Joyce et al., 2000). The differences in water percolation rates among the farming systems are amplified by a restrictive layer that develops at 20-30 cm depth in the conventional systems. The long-term effects of these differences, in totality, has resulted in yield losses in the conventional system due to difficulties with water penetration; while in the organic and low-input systems, the amount of irrigation water that must be applied for the water to reach the end of a furrow is substantially higher than in the conventional system (Table 5) (Colla et al., 2000).
Table 4. Cumulative water infiltration rate (m3/m) after 180 min. for conventional, low-input and organic system by irrigation events of 1998.
| Irrigation date Organic | Conv-2 | Conv-4 | Low-input | |
| 17 June | - | 0.019e | 0.062a | 0.071a |
| 29 June | - | 0.037d | 0.050b | 0.049ab |
| 17 July | 0.047c | 0.035d | 0.072a | 0.073a |
| 27 July | - | 0023e | 0.064a | 0.068a |
Means with the same letter are not significantly different at the 0.01 probability level.
Figure 2. Percent of precipitation lost as runoff at SAFS project, winter 1999-2000.
Figure 3. Seasonal volumetric soil water content for four depth intervals of the soil profile to 2.85m.
Table 5. Average amount of water applied (mm) through furrow irrigation in tomato and corn production in a cropping season (1995-1998). (n = 16)
|
Organic
|
Low-input
|
Conv-4
|
Conv-2
|
|
| Tomato |
752a
|
703a
|
467b
|
465b
|
|
(78)1
|
(75)
|
(38)
|
(54)
|
|
| Corn |
829a
|
720ab
|
576b
|
-
|
|
(65)
|
(51)
|
(45)
|
-
|
Different letters within a row are significantly different at
0.5 probability.
1 Standard errors of mean.
- Cost of production inputs, value of production, economic risk, energy budgets for agricultural production under the four farming systems
Economic viability. Although they vary annually as a reflection of supply and demand, premium prices are available for the organically-produced commodities grown in the SAFS project. The net return for the organic system is calculated two ways, one using conventional prices and the other with premium organic prices. Prices and costs are obtained from local growers and input suppliers annually. Analysis of the whole farm performance of each system, measured as average cumulative net income per hectare (Fig. 4), reveals that the economic viability of the organic system has depended on premium prices. While the organic system with premium prices has performed better than the conv-4 or low-input systems, large increases in organic production within the region would likely result in a depression of the premium prices. Assessed under a conventional price structure, the organic system has not been profitable. The cumulative net return for the conv-2 system has always been higher than that for any other system due to the greater frequency of high-value tomato crops in this rotation. However, the economic and environmental viability of that system are threatened by the greater prevalence of pests and diseases, and the greater reliance on pesticides.
Figure 4. Whole farm cumulative net return (1989-99) at SAFS project. Organic (P) represents organic system with premium prices.
Pesticide inputs. Cumulative pesticide usage over the course of the project has been greatest in the conv-2 system, followed by the conv-4 system, the low-input system and finally the organic system (Table 6). Total usage is related to the philosophy and protocols of the farming systems, and the crop rotation. The major uses of pesticides are in the management of weeds in the conventional and low-input systems.
A large proportion of cumulative pesticide use in the organic, low-input, and conventional tomatoes was from the application of sulfur (Thiolux) to control russet mites in 1989, 1990, and 1991. A cumulative amount of 20 kg ha-1 (active ingredient) of sulfur was applied to each of these farming systems during the three-year period. Potassium salts (Safer soap), neem oil (Trilogy 90EC), and Bacillus thuringiensis (Dipel) are applied to organic tomatoes, while glyphosate (Round-up Ultra), trifluralin (Treflan), and napropamide (Devrinol) are commonly applied to the low-input and conventional tomatoes. Glyphosate, metolachlor (Dual) and 2,4-D (Weedar) are major pesticides used in corn, whereas glyphosate and trifluralin are frequently applied to safflower. Trifluralin, sethoxydim (Poast), and dicofol (Kelthane) are the major pesticides used in beans. In wheat, diclofop (Hoelon), bromoxynil plus MCPA (Bronate), and MCPA (Rhomene) are common pesticides applied.
Table 6. Cumulative pesticide use (kg ha-1 active ingredient) at the SAFS project, 1989-1999.
| Crop | Organic | Low-input | Conv-4 | Conv-2 |
| Tomato | 25.2 | 24.7 | 49.5 | 49.4 |
| Corn | 0 | 7.2 | 28.6 | - |
| Safflower | 0 | 0.9 | 12.2 | - |
| Bean | 0 | 1.4 | 8.9 | - |
| Wheat | - | - | 18.3 | 19.1 |
| Oats/vetch | 0 | 0 | - | - |
| Total2 | 25.2 | 34.2 | 117.5 | 137.0 |
1Not applicable.
2Pesticide use multiplied by 2 in the Conv-2 system to account for
two-year rotation (area in tomato and wheat is twice that of the other farming
systems).
Energy. Based on output-input ratios, the low-input system is the most energy-efficient farming system, while the conventional 2-year rotation is the least efficient. The organic system is less efficient than the low-input system because of the great distance that many organic fertilizers (such as dried seaweed) are shipped before arriving at the field, and because of energy requirements for mechanical weed control (Livingston, 1995).
In summary, the SAFS project has demonstrated the potential to reduce synthetic fertilizer and chemical inputs and to maintain yields in irrigated agricultural systems in northern California (Clark et al., 1999). The costs and challenges differ dramatically among crops and farming systems. Fertility management in the alternative systems has been more expensive than for the conventional systems because of the cost of producing, irrigating and incorporating cover crops.
In addition, the use of composted manure, kelp and fish emulsion on tomatoes, and composted manure on corn, in the organic system have been sizeable expenses. The move to transplanted tomatoes in 1992 added about $741 per hectare in costs to the alternative systems, but has allowed a delay in planting so that the cover crop can grow for a longer period of time before incorporation. This has in turn increased nitrogen and biomass production, reduced weed pressure through competition, and consequently has reduced hand-hoeing costs.
Objective 2. Compare and evaluate existing and/or novel low-input and organic farming tactics, with emphasis on innovations that correct deficiencies, enhance profitability or decrease risk in each farming system.
1. Niche-specific cover crops. During the first SAFS rotation cycle, the LI and Organic systems relied heavily on winter cover crops that were lana vetch or mixtures of lana vetch with oats. We began to observe a general reduction in stands, performance, and early spring decline (often with diseases that included Alternaria and Phoma species) some 3-5 years after the SAFS began. It became clear that, even though the lana vetch crop was a) a winter precursor to summer annuals, and b) not always carried through to a seed harvest, the heavy use of this single species, renowned as it was for high biomass and N production, represented an unacceptable violation of agronomic precepts favoring longer rotations. We therefore adjusted the cover crop rotations by 1) diversifying the vetch species, 2) adding Austrian winter pea to the oat/vetch mixture, and 3) incorporating late summer cover crops in niches following the harvest of tomatos in late July/early August. For the summer CC mix, we have used a sorghum-sudan hybrid, which is a very fast-growing scavenger of available N following tomato, and also experimented with a number of legumes, searching for components that compliment the SS. We settled on a combination of vegetative cowpea and Dolichus lablab. The cowpea is quick to germinate and provide substantial ground cover and weed competition, but slows growth early in the fall and winter kills relatively easily, while the Lablab cv "Highworth" is slower-starting but more persistent through fall and early winter.
Specific studies were conducted early in the SAFS, which examined several novel means of using cover crops in the LI and Organic rotations. Results may summarized as follows: Attempts to intercrop a range of low-growing, shade-tolerant legumes under corn and sunflower were generally disappointing (economically unacceptable decreases in cash crop densities are required to encourage legume biomass commensurate with seed and management costs). In another experiment, evaluating the potential of several Mediterranean annual and perrenial legumes planted in the fall-winter CC niche preceding transplanted tomatos, we identified interesting species of medics, but concluded that much more detailed studies of residue management, CC persistence and competition with the tomatos (N and water), and effective weed management, are required to make this a viable option at the commercial level. Uncertainties of spring weather is also a factor.
1994-95 studies had shown that summer cover crops, planted following the harvest of early field tomatos, would recycle free soil N and produce large amounts of biomass, if the cover crop could be established no later than Sept 1st. A large 1997 trial demonstrated the great potential of mixtures containing sorghum-sudan, the excellent compatibility of lablab with sorhum-sudan, and the potential to choose cowpea genotypes less sensitive to photoperiodic effects, to Lygus attack, and to root knot nematodes. Based on 1997 data, 10 cowpea genotypes were tested in a 1998 study which specifically examined the compatibility of cowpea genotypes with the sorghum-sudan and lablab components of the planned CC mixture. Cowpea candidates were further narrowed to the 3 genotypes planted in 1999 and 2000 tests, and for which data for component biomass and N are still being analyzed. We anticipate that, in spite of relatively atypical temperatures those two growing seasons, it should be possible to determine the most effective and economical combination of CC species for the late summer niche, and (if indicated) to choose the optimal cowpea genotype for release as a component of that species mixture.
2. Fall management practices to enhance activity of bacterial- and fungal-feeding nematodes. We have conducted several studies on fall management practices to enhance activity of bacterial- and fungal-feeding nematodes in cover crop decomposition and soil fertility. The bacterial-feeding nematode species fall predominantly into two groups, those that are "enrichment opportunists" and respond rapidly to increase in their food source, and those that increase more gradually and may be more persistent, the "general opportunists". In fact, our research has indicated that the "general opportunists" constitute the basal nematode community that occurs in all soils. Both groups have a higher C:N ratio than their bacterial prey and mineralize N that is in excess of their growth requirements.
We have attempted to increase numbers of these nematodes by enhancing soil biological activity the previous fall. Manipulations have included an irrigated late-summer cover crop, fall irrigation alone, and/or a winter cover crop. Nematode and microbial communities were measured, as well as soil nitrogen and performance of the following tomato crop. Generally, the ratio of bacterial:fungal-feeding nematodes was greater when the soil was irrigated in the fall. Dry soil in the fall selected for fungal-feeding nematodes and the so-called general opportunists, perhaps reflecting the prevalence of fungal-mediated decomposition under those conditions and the lower ability of enrichment opportunists to exploit the conditions. Fall irrigation only and fall irrigation plus a late summer cover crop provided significantly greater available N in the following spring and yield enhancement of the subsequent tomato crop.
We conclude that "feeding and activating" the soil foodweb during the early fall when soil temperatures are conducive to biological activity, increases the bacterial-grazing community the following spring. A consequence for the farming system is measurably greater amounts of soil mineral N during the early growth of the subsequent tomato crop and increased tomato yields. (Ferris et al., 1994, 1996, 1998, 1999, 2000).
3. Reduced-tillage tomato production. A series of recently organized farmer/scientist focus sessions by UC-SAREP indicated strong growers' interest in testing reduced/no-till practices in the field row-crops production system in Sacramento Valley (Mitchell, 2000). General concerns that farmers brought up in relation to reduced tillage were: (1) how to deal with fertilizer/herbicide inputs? (2) furrow irrigation which is very different from Mid-west reduced-tillage practices, (3) crop rotation and cover crops are difficult to find to combat weeds, and (4) economics of reduced tillage. Farmers are considering evaluating several types of no-till equipment, including Buffalo planter, Sub-surface tiller transplanter, Ferguson strip till machine, and 5-ft cover crop seeder. Reduced tillage appears to be an opportunity to increase the sustainability of production systems in the Sacramento Valley. Current SAFS research in the companion area is evaluating the feasibility of reduced- and no-tillage methods of tomato production. SAFS researchers are now developing a reduced-tillage tomato system which uses nonchemical or reduced-chemical cover crop management, transplanting, and cultivation under high-residue conditions.
Objective 3. Distribute and facilitate adoption of information generated by this project to all interested parties as it becomes available.
In addition to over 65 peer-reviewed journal articles, 7 popular press articles (see Appendix B for complete list), and a home page (http://agronomy.ucdavis.edu/safs/home.htm), results from SAFS have been presented in more than 80 national and international conferences. A video and an audiotutorial slide set developed by the project have been used by PI's, the UCD Campus Visitors Center, and sold to UC and non-UC visitors. Over the twelve-year life of the project, SAFS has hosted more than 1500 visitors at its eleven annual field days, six workshops, tours, and individual group visits. Visitors have included farmers from throughout the U.S. and indeed from throughout the world; leaders from UC, the state and nation (political, agribusiness, and academic); and numerous international political and research guests representing at least 26 countries. Members of the SAFS team have been invited to speak throughout the world, often to provide advice on how to initiate a comparable project at the host institution. The SAFS project has benefited from collaborations with visiting scholars from numerous countries including Italy, Spain, Brazil, Mexico, South Africa, Peru, France and Israel whom have chosen to spend periods varying from several weeks to two years at UCD working on the project. The SAFS plots serve as a living laboratory for field trips, as well as provide lab samples, for numerous UC Davis classes and Cooperative Extension courses in soils, agronomy and the pest sciences.
In a survey of USDA-funded research pertaining to organic agriculture, the Organic Farming Research Foundation lauded three SAFS-associated projects as the "state-of-the-art of university-based organic farming systems research" throughout the entire U.S. The SAFS project has positively impacted farming practices and agricultural communities in the Sacramento Valley, the state, the nation, and many countries around the world (see above section on Objective 3). These changes include: a greater interest in cover crops, legumes and crop rotations; increased organic acreage of field crops; increased monitoring by growers of water use/efficiency, pest thresholds and soil and crop nitrogen requirements; a growing recognition of the importance of soil ecology; and heightened interest in a more holistic view of soil quality.
After attending SAFS field days, agricultural equipment dealers have shown an interest in developing or modifying equipment, specifically for reduced tillage and non-chemical weed management. A multinational food conglomerate, Unilever, wishing to ensure that its suppliers grow food using sustainable practices, has recently expressed a desire to partner with the SAFS project to help provide tomato growers with information on alternative systems.
The SAFS project has specifically demonstrated that it is profitable to grow tomatoes organically; that pesticide use can be reduced by half with little or no decrease in yields; and that cover-cropping can provide multiple important benefits, including sequestration of carbon, decreased nitrogen leaching, increased infiltration and decreased runoff, and improved soil quality. The project has also served to demonstrate a need for more and continued research on sustainable agricultural practices. Areas that need particular attention include:
- Weed management. While other pest species are generally regulated by the
rotations and associated cultural practices, the combination of high soil
nutrient levels, irrigation and frequent tillage provides environments for
specific communities of weed competitors in each farming system.
- Fertility management for organic and low input systems. The basic design
of the rotations, repeatedly using Vicia spp. as a cover crop, is of
concern. In recent years, cover crop biomass and associated N input at SAFS
plots has decreased markedly compared to early years, and weed severity has
increased. Optimization of cover crop decomposition through timing of incorporation
and the management of microbial and nematode communities continues to be a
challenge.
- Reduction in the frequency and intensity of tillage operations. The intensive
tillage currently practiced in the area, among other consequences, (i) is
a major source of fugitive dust, (ii) stimulates exponential increases in
soil respiration and the consequent loss of sequestered carbon to the atmosphere
as CO2, (iii) degrades soil structure, (iv) increases soil compaction, and
(v) disrupts soil biological activity. However, skepticism in relation to
the adoption of reduced tillage exists primarily due to practical difficulties
such as fertilizer/herbicide application, furrow irrigation, and effective
weed control in cover crop based-systems. In addition, the economic viability
of reduced tillage, especially in irrigated field row-crop production systems
in the Western US, is unknown. ·
- Water-use efficiency. Increasing demands for non-agricultural uses of very scarce water resources, and drought-induced limitations of good quality water, are strong public concerns in the Sacramento Valley. An important future challenge for the SAFS project is to improve irrigation management so as to optimize water use.
Dissemination of results
See above section on Objective 3.
References
Bossio, D.A., K.M. Scow, N. Gunapala, and K.J. Graham. 1998. Determinants of soil microbial communities: Effects of agricultural management, season, soil type on phospholipid fatty acid profiles. Microbial Ecology 36:1-12.
Cavero, J., R.E. Plant, C. Shennan and D.B. Friedman. 1997. The effect of nitrogen source and crop rotation on the growth and yield of processing tomatoes. Nutrient Cycling in Agroecosystems 47: 271-282.
Cavero, J., R.E. Plant, C. Shennan, J.R. Williams, J.R. Kiniry and V.W. Benson. 1998. Application of EPIC model to nitrogen cycling in irrigated processing tomatoes under different management systems. Agricultural Systems 56(4):391-414.
Clark, M. S., H. Ferris, K. Klonsky, W.T. Lanini, A.H.C. van Bruggen, F.G. Zalom, S. Temple. 1997. Pesticide use reduced by 50-100% in low-input and organic cropping systems. Sustainable Agriculture Farming Systems Project Bulletin 1 (3): 1-3.
Clark, M. S., W. R. Horwath, C. Shennan, K. M. Scow. 1998. Changes in soil chemical properties resulting from organic and low-input farming practices. Agronomy Journal. 90: 662-671.
Clark, M. S., H. Ferris, K. Klonsky, W.T. Lanini, A.H.C. vanBruggen, & F.G. Zalom. 1998. Agronomic, economic, and environmental comparison of pest management in conventional and alternative tomato and corn systems in northern California. Agriculture, Ecosystems & Environment. 68:51-71.
Clark, S., K. Klonsky, P. Livingston, and S. Temple. 1999. Crop-yield and economic comparisons of organic, low-input, and conventional farming systems in California's Sacramento Valley. American Journal of Alternative Agriculture 14: 109-121.
Clark, M.S. 1999. Ground beetle abundance and community composition in conventional and organic tomato systems of California's Central Valley. Applied Soil Ecology 11:199-206.
Clark, M.S., W.R. Horwath, C. Shennan, K.M. Scow, W.T. Lanini, and H. Ferris. 1999. Nitrogen, weeds and water as yield-limiting factors in conventional, low-input, and organic tomato systems. Agriculture, Ecosystems & Environment 73:257-270.
Colla, G., J.P. Mitchell, B.A. Joyce, L.M. Huyck, W.W. Wallender, S.R. Temple, T. C. Hsiao, and D.D. Poudel. 2000. Soil physical properties, tomato yield and quality in alternative cropping systems. Agronomy Journal (in press)
Devêvre OC and WR Horwath. 1999. Soil Humic Fractions as Indicators of the Transition from Conventional to Low-Input-Organic Farming Systems: Evaluation of SOM Maintenance. Proceedings of the International Humic Society, Brisbane, Australia. September 1998.
Ferris, H., T. Bongers, R. G. M. de Goede. 2000. A framework for soil food web diagnostics: extension of the nematode faunal analysis concept. Applied Soil Ecology. In Press.
Ferris, H., Bongers, T. De Goede, R.G.M., 1999. Nematode faunal indicators of soil food web condition. J. Nematol. 31, 534-535.
Ferris, H., R.C. Venette, and S.S. Lau. 1996. Dynamics of nematode communities in tomatoes grown in conventional and organic farming systems, and their impact on soil fertility. Applied Soil Ecology 3:161-175.
Ferris, H., K. Scow, S. Temple, M. Espley, R. Venette. 1996. Introduction to the SAFS Project. Sustainable Agriculture Farming Systems Project Bulletin 1 (1): 1-3.
Ferris, H., R. C. Venette, H. R. van der Meulen and K. M. Scow. 1998. Nitrogen fertility and soil food web management. Journal of Nematology 30:495-496.
Ferris, H., R. C. Venette and S. S. Lau. 1996. Dynamics of nematode communities in tomatoes grown in conventional and organic farming systems, and their impact on soil fertility. Applied Soil Ecology 3: 161-175.
Ferris, H., R. C. Venette, S. A. Lau, K. M. Scow, and N. Gunapala. 1994. Bacterial -feeding nematodes in organic and conventional farming systems. Journal of Nematology 26:544 (abstr.).
Gunapala, N. and K.M. Scow. 1998. Dynamics of soil microbial biomass and activity in conventional and organic farming systems. Soil Biology and Biochemistry 30:805-816.
Gunapala, N., R.C. Venette, H. Ferris, and K.M. Scow. 1998. Effects of soil management history on the rate of organic matter decomposition. Soil Biology and Biochemistry 30:1917-1927.
Horwath, W.R., O.C. Devevre, T.A. Doane, and D.D Poudel. 2000. Defining changes in soil organic matter quality during the transition from conventional to organic and low-input systems to identify sustainable farming practices. Submitted.
Jaffee, B.A., H. Ferris, and K.M. Scow. 1998. Nematode-trapping fungi in organic and conventional cropping systems. Phytopathology 88:344-349.
Joyce, B.A., W.W. Wallender, J.P. Mitchell, L.M. Huyck, S.R. Temple, P.N. Brostrom and T.C. Hsiao. Seasonal changes in infiltration and soil water storage in conventional and alternative agricultural systems. Submitted.
Kaffka, S. 1994. Scientists and farmer try new approach to research. California Agriculture. 48(5): 11-14.
Klonsky, K. and D. Cary. 1990. Budget Planner Overview. Department of Agricultural Economics, University of California, Davis.
Klonsky, K. and P. Livingston. 1994. Alternative systems aim to reduce inputs, maintain profits. California Agriculture. 48(5): 34-42.
Klonsky, K., M. S. Clark, P. Livingston. 1997. Economic viability of organic and low-input farming systems in Sacramento Valley. Sustainable Agriculture Farming Systems Project Bulletin 1 (4): 1-3.
Lanini, W.T., F. Zalom, J.J. Marois, and H. Ferris. 1994. Researchers find short-term insect problems, long-term weed problems. California Agriculture 48(5):27-33.
Livingston, P.L. 1995. A comparison of economic viability and measured energy required for conventional, low-input, and organic farming systems over a rotational period. Unpublished M.S. thesis, California State University, Chico, CA. 324 pp.
Mitchell, J.P., W.T. Lanini, S.R. Temple, P.N. Brostrom, E.V. Herrero, E.M. Miyao, T.S. Prather, B. Fouche, R.J. Mullen, and K.J. Hembree. 2000. Conservation tillage initiatives in California. In Mitchell, J. P.(Ed.): Proceedings of Conservation Tillage 2000: Conservation Tillage Success Stories from around the U.S. Feb. 10-11, 2000. Kearney Agricultural Center, University of California Cooperative Extension, Parlier, CA.
Mol, L, Huisman, O. C., Scholte, K., and Struik, P. C. 1996.Theoretical approach to the dynamics of the inoculum density of Verticillium dahliae in the soil: First test of a simple model. Plant Pathology (Oxford) 45: 192-204.
Poudel, D.D., W.R. Horwath, J.P. Mitchell, and S.R. Temple. 2000. Impacts of farming systems on soil mineral nitrogen levels in irrigated processing tomatoes. Submitted.
Poudel, D.D., W.R. Horwath, J.P. Mitchell, S.R. Temple. 1999. Impacts of Farming System on Soil Mineral Nitrogen Levels of Irrigated Processing Tomatoes: A Case Study from the UC Davis Sustainable Agriculture Farming Systems Project. Sustainable Agriculture Farming Systems Project Bulletin 3 (1): 1-3.
Temple, S.R., D.B. Friedman, O. Somasco, H. Ferris, K. Scow, and K. Klonsky. 1994. An interdisciplinary, experiment station-based participatory comparison of alternative crop management systems for California's Sacramento Valley. American Journal of Alternative Agriculture 9: 64 -71.
Crop yields from the four SAFS farming system treatments, 1989-1999.
| Year | Organic | Low-input | Conv-4 | Conv-2 | Yolo Co. Ave. |
|
Tomato (tons/acre) |
|||||
| 1989 | 24.50 b 1 | 30.92 a | 34.33 a | 34.18 a | 30.20 |
| 1990 | 30.70 c | 36.28 b | 36.82 ab | 39.56 a | 28.79 |
| 1991 | 28.20 c | 34.85 b | 45.58 a | 37.42 b | 30.50 |
| 1992 | 42.66 | 42.87 | 47.70 | 41.25 | 33.84 |
| 1993 | 28.10 | 32.60 | 26.60 | 25.68 | 29.17 |
| 1994 | 24.39 b | 27.97 b | 41.49 a | 37.95 a | 33.66 |
| 1995 | 28.80 b | 35.83 a | 33.66 a | 30.02 b | 32.58 |
| 1996 | 35.40 | 31.20 | 31.60 | 29.70 | 33.41 |
| 1997 | 34.10 | 33.80 | 36.70 | 36.60 | 33.93 |
| 1998 | 27.11ab | 29.56a | 22.13b | 23.89b | 29.16 |
| 1999 | 26.19ab | 30.04a | 22.36b | 22.61b | - -2 |
|
Safflower (lbs/acre) |
|||||
| 1989 | 1,358 | 1,343 | 2,058 | - - | 2,320 |
| 1990 | 2,070 | 2,350 | 2,160 | - - | 2,100 |
| 1991 | 1,990 | 1,879 | 2,155 | - - | 1,740 |
| 1992 3 | - - | - - | 2,575 | - - | 1,920 |
| 1993 | 2,373 | 2,011 | 2,455 | - - | 1,820 |
| 1994 | 2,308 | 2,266 | 2,567 | - - | 2,100 |
| 1995 | 2,389 | 2,076 | 2,682 | - - | 1,680 |
| 1996 | 2,408 | 2,400 | 2,828 | - - | 1,880 |
| 1997 | 2,865 | 2,495 | 2,757 | - - | 2,600 |
| 1998 | 2,476b | 2,094b | 3,212a | - - | 1,820 |
| 1999 | 1,122 | 1,106 | 1,307 | - - | - -2 |
|
Corn (tons/acre) |
|||||
| 1989 | 4.18 | 5.21 | 5.08 | - - | 4.51 |
| 1990 | 5.20 | 5.00 | 4.91 | - - | 4.87 |
| 1991 | 4.07 b | 4.09 b | 5.06 a | - - | 4.59 |
| 1992 | 4.92 b | 5.92 a | 4.76 b | - - | 4.90 |
| 1993 | 3.87 b | 5.72 a | 4.76 ab | - - | 5.21 |
| 1994 | 6.38 a | 6.55 a | 5.16 b | - - | 5.21 |
| 1995 | 4.00 b | 6.19 a | 5.66 a | - - | 4.52 |
| 1996 | 5.19 | 5.38 | 4.68 | - - | 4.49 |
| 1997 | 4.73 | 5.39 | 5.40 | - - | 5.07 |
| 1998 | 5.21 | 4.52 | 4.58 | - - | 4.99 |
| 1999 | 3.57 | 4.66 | 4.68 | - - | - -2 |
|
Wheat (lbs/acre) |
|||||
| 1989 | - - | - - | 4,507 b | 4,916 a | 5,200 |
| 1990 | - - | - - | 4,615 | 4,961 | 4,660 |
| 1991 | - - | - - | 5,273 | 5,485 | 5,380 |
| 1992 | - - | - - | 4,694 | 4,498 | 4,440 |
| 1993 | - - | - - | 5,335 a | 4,811 b | 4,780 |
| 1994 | - - | - - | 6,837 | 6,789 | 5,740 |
| 1995 | - - | - - | 4,181 | 4,734 | 3,760 |
| 1996 | - - | - - | 5,438 a | 4,485 b | 4,520 |
| 1997 | - - | - - | 4,889 | 5,003 | 4,620 |
| 1998 | - - | - - | 4,839 | 4,180 | 3,960 |
| 1999 | - - | - - | 4,437 | 4,959 | - -2 |
|
Beans (lbs/acre) 4 |
|||||
| 1990 | 2,218 a (Y) | 2,330 a (Y) | 1,934 b (S) | - - | 1,980 |
| 1991 | 1,592 (RK) | 1,457 (RK) | 1,140 (RK) | - - | 1,780 |
| 1992 | 2,830 (Y) | 2,716 (Y) | 2,442 (Y) | - - | 1,780 |
| 1993 | 1,473 (MB) | 1,584 (MB) | 1,529 (MB) | - - | 1,660 |
| 1994 | 1,929 (MB) | 1,687 (MB) | 1,717 (MB) | - - | 1,820 |
| 1995 | 1,014 b (RK) | 1,173 b (RK) | 1,454 a (MB) | - - | 1,720 |
| 1996 | 1,070 (MB) | 1,848 (MB) | 1,689 (MB) | - - | 1,220 |
| 1997 | 2,100 a (P) | 1,923 a (P) | 1,501 b (P) | - - | 1,320 |
| 1998 | - - | - - | - - | - - | 1,140 |
| 1999 | 830 (RK) | 644 (RK) | 528 (RK) | - - | - -2 |
|
Oats/Vetch (lbs/acre) |
|||||
| 1991 | 1,783 | 2,093 | |||
| 1992 | 659 | - -5 | |||
| 1993 | 1,870 | 2,364 | |||
| 1994 | 1,692 b | 3,112 a | |||
| 1995 | 5,007 | 4,534 | |||
| 1996 | - -6 | - -5 | |||
| 1997 | - -6 | - -5 | |||
| 1998 | - -6 | 10,341 | |||
| 1999 | 6,2337 | 5,6667 | |||
1 Means within a row followed
by different letters indicate significant statistical differences among systems
at P £ 0.05 (N=4).
2 Not available at printing time.
3 Organic and low-input safflower in 1992 were plowed under early
in the season and Yolano beans were planted. Bean yields were 2,193 and 2,273
lbs/acre for the organic and low-input systems respectively.
4 Varieties of beans as follows: Y=Yolano; S=Sutter; RK=Red Kidney;
MB=Midnight Blacks; P=Pinto.
5 Low-input oats/vetch harvested for green chop in 1992 and removed
as hay in 1996 , 1997, and 1998; no seed yield.
6 Oats/vetch crop was incorporated into soil.
7 Yield calculated from hand harvest (biomass sampling) data. Removed
as hay in both treatments.
Appendix B
Publications and presentations
1. Publications
Peer-Reviewed Publications through June 2000
Bongers, T., and H. Ferris. 1999. Nematode community structure as a bioindicator in environmental monitoring. Trends in Evolution and Ecology 14:224-228.
Bossio D. A. and K.M. Scow. 1997. Management changes in rice production alter mirobial community. California Agriculture 51(6), 33-40.
Bossio, D.A., and K.M. Scow. 1995. Impact of carbon and flooding on the metabolic diversity of microbial communities in soil. Appl. Environ. Microb. 61:4043-4050.
Bossio, D.A., K.M. Scow, N. Gunapala, and K.J. Graham. 1998. Determinants of soil microbial communities: Effects of agricultural management, season, soil type on phospholipid fatty acid profiles. Microbial Ecology 36:1-12.
Bossio, D.A., and K.M. Scow. 1998. Impact of carbon and flooding on PLFA profiles and substrate utilization patterns of soil microbial communities. Microb. Ecol. 35:265-278.
Bruns, M.A., and K.M. Scow. 1999. DNA fingerprinting as a means to identify sources of soil-derived dust: problems and potential. p. 193-205. In: Scow et al. (eds) Integrated assessment of ecosystem health. Lewis Publishers, Boca Raton, FL.
Bruns, M., K.J. Graham, K.M. Scow, and T. VanCuren. 1998. Biological markers to characterize potential sources of soil-derived particulate matter. Air Waste Manag. Assoc. Proc.
Cavero, J., R.E. Plant, C. Shennan and D.B. Friedman. 1997. The effect of nitrogen source and crop rotation on the growth and yield of processing tomatoes. Nutrient Cycling in Agroecosystems 47: 271-282.
Cavero, J., R.E. Plant, C. Shennan, J.R. Williams, J.R. Kiniry and V.W. Benson. 1998. Application of EPIC model to nitrogen cycling in irrigated processing tomatoes under different management systems. Agricultural Systems 56(4):391-414.
Chen, J and H. Ferris. 1998. Mineralization of nitrogen by Aphelenchoides composticola. Journal of Nematology 30:490 (abstr.)
Chen, J. and H. Ferris. 1999. The effects of nematode grazing on nitrogen mineralization during fungal decomposition of organic matter. Soil Biology and Biochemistry 31:1265-1279.
Chen, J. and H. Ferris. 2000. Growth and nitrogen mineralization of selected fungi and fungal-feeding nematodes on sand amended with organic matter. Plant and Soil 218:91-101.
Chen, J., H. Ferris, K. M. Scow and K. J. Graham. 1999. The effect of fungal-feeding nematodes on fungal biomass during decomposition of organic matter . Journal of Nematology 31:517.
Chen, J. and H. Ferris. 1997. Nitrogen mineralization by Aphelenchus avenae associated with Rhizoctonia spp. and barley straw. Journal of Nematology 29: 572 (abstr.)
Clark, M. S., W. R. Horwath, C. Shennan, K. M. Scow. 1998. Changes in soil chemical properties resulting from organic and low-input farming practices. Agronomy Journal. 90: 662-671.
Clark, M. S., H. Ferris, K. Klonsky, W.T. Lanini, A.H.C. vanBruggen, & F.G. Zalom. 1998. Agronomic, economic, and environmental comparison of pest management in conventional and alternative tomato and corn systems in northern California. Agriculture, Ecosystems & Environment 68:51-71.
Clark, S., K. Klonsky, P. Livingston, and S. Temple. 1999. Crop-yield and economic comparisons of organic, low-input, and conventional farming systems in California's Sacramento Valley. American Journal of Alternative Agriculture 14: 109-121.
Clark, M.S. 1999. Ground beetle abundance and community composition in conventional and organic tomato systems of California's Central Valley. Applied Soil Ecology 11:199-206.
Clark, M.S., W.R. Horwath, C. Shennan, K.M. Scow, W.T. Lanini, and H. Ferris. 1999. Nitrogen, weeds and water as yield-limiting factors in conventional, low-input, and organic tomato systems. Agric. Ecosyst. Environ. 73:257-270.
Colla, G., J.P. Mitchell, B.A. Joyce, L.M. Huyck, W.W. Wallender, S.R. Temple, T. C. Hsiao, and D.D. Poudel. 2000. Soil physical properties, tomato yield and quality in alternative cropping systems. Agronomy Journal (in press)
Devêvre OC and WR Horwath. 1999. Soil Humic Fractions as Indicators of the Transition from Conventional to Low-Input-Organic Farming Systems: Evaluation of SOM Maintenance. Proceedings of the International Humic Society, Brisbane, Australia. September 1998.
Ferris, H., T. Bongers, R. G. M. de Goede. 2000. A framework for soil food web diagnostics: extension of the nematode faunal analysis concept. Applied Soil Ecology. In Press.
Ferris, H., R. C. Venette, H. R. van der Meulen and K. M. Scow. 1998. Nitrogen fertility and soil food web management. Journal of Nematology 30:495-496.
Ferris, H., T. Bongers and R. G. M. de Goede. 1999. Nematode faunal indicators of soil food web condition. Journal of Nematology 31:534-535.
Ferris, H., R. C. Venette, H. R. van der Meulen, and S. S. Lau. 1997. Nitrogen mineralization by bacterial-feeding nematodes. Journal of Nematology 29: 577 (abstr.)
Ferris, H., R.C. Venette, H.R. van der Meulen, S.S. Lau. 1998. Nitrogen mineralization by bacterial-feeding nematodes: Verification and measurement. Plant and Soil 203:159-171
Ferris, H., R. C. Venette, and S. S. Lau. 1997. Population energetics of bacterial-feeding nematodes: Carbon and nitrogen budgets. Soil Biology and Biochemistry 29: 1183-1194.
Ferris, H., M. Eyre, R. C. Venette, and S. S. Lau. 1996. Population energetics of bacterial-feeding nematodes: stage-specific development and fecundity rates. Soil Biology and Biochemistry 28: 271-280.
Ferris, H., R. C. Venette and S. S. Lau. 1996. Dynamics of nematode communities in tomatoes grown in conventional and organic farming systems, and their impact on soil fertility. Applied Soil Ecology 3: 161-175.
Ferris, H., S. Lau, and R. Venette. 1995. Population energetics of bacterial-feeding nematodes: respiration and metabolic rates based on carbon dioxide production. Soil Biology and Biochemistry 27:319-330.
Ferris, H., R. C. Venette, S. A. Lau, K. M. Scow, and N. Gunapala. 1994. Bacterial -feeding nematodes in organic and conventional farming systems. Journal of Nematology 26:544 (abstr.).
Fuller, M.E., and K.M. Scow. 1997. Impacts of trichloroethylene (TCE) and toluene on nitrogen cycling in soil. Appl. Environ. Microbiol. 68:120-129
Fuller, M.E., K.M. Scow, S.S. Lau and H. Ferris. 1997. Trichloroethylene (TCE) and toluene effects on the structure and function of the soil community. Soil Biology and Biochemistry 29:75-89.
Gaskell, Mark, Benny Fouche, Steve Koike, Tom Lanini, Jeff Mitchell and Richard Smith. 2000. Organic vegetable production in California - Science and practice. HortTechnology. 10(4);699-713.
Gristina, L., D. Friedman and S. Temple. 1994. Yield stability analysis during the transition from conventional to organic farming systems in the Sacramento Valley - California. Proceedings from the 3d ESA Conference, Abano-Padova, Italy. pp. 702-703.
Grünwald, N. J., S. Hu and A. H. C. van Bruggen. 2000. Short-term cover crop decomposition in organic and conventional soils; Characterization of soil C, N, microbial and plant pathogen dynamics. European Journal of Plant Pathology 106:37-50.
Grünwald, N. J., S. Hu and A. H. C. van Bruggen. 2000. Short-term cover crop decomposition in organic and conventional soils: Soil microbial and nutrient cycling indicator variables associated with different levels of soil suppressiveness to Pythium aphanidermatum. European Journal of Plant Pathology 106:51-65.
Gunapala, N. and K.M. Scow. 1998. Dynamics of soil microbial biomass and activity in conventional and organic farming systems. Soil Biology and Biochemistry 30:805-816.
Gunapala, N., R.C. Venette, H. Ferris, and K.M. Scow. 1998. Effects of soil management history on the rate of organic matter decomposition. Soil Biology and Biochemistry 30:1917-1927.
Horwath, W.R., O.C. Devevre, T.A. Doane, and D.D. Poudel. 2000. Defining changes in soil organic matter quality during the transition from conventional to low-input and organic systems to identify sustainable farming practices. Submitted.
Hu, S.J., van Bruggen, A.H.C., and Grunwald, N.J. 1999. Dynamics of bacterial populations in relation to carbon availability in a residue-amended soil. Appl. Soil Ecol. 13:21-30.
Jaffee, B.A., H.Ferris, and K.M. Scow. 1998. Nematode-trapping fungi in organic and conventional cropping systems. Phytopathology 88:344-349.
Johnson, C.R., and K.M. Scow. 1999. Effect of nitrogen and phosphorus addition on phenanthrene biodegradation in four soils. Biodegradation 10:43-50.
Joyce, B.A., W.W. Wallender, J.P. Mitchell, L.M. Huyck, S.R. Temple, P.N. Brostrom and T.C. Hsiao. Seasonal changes in infiltration and soil water storage in conventional and alternative agricultural systems. Submitted.
Klonsky, K. and P. Livingston. 1994. Alternative systems aim to reduce inputs, maintain profits. California Agriculture. 48(5): 34-42.
Lanini, W.T., F. Zalom, J.J. Marois, and H. Ferris. 1994. Researchers find short-term insect problems, long-term weed problems. California Agriculture 48(5):27-33.
Lau, S.S., M.E. Fuller, H. Ferris, R.C. Venette, and K.M. Scow. 1997. Development and testing of an assay for soil-ecosystem health using the bacterial-feeding nematode Cruznema tripartitum. Ecotoxicology and Environmental Safety 36:133-139.
Lundquist, E.J., L.E. Jackson, and K.M. Scow. 1999. Wet-dry cycles affect dissolved organic carbon in two California agricultural soils. Soil Biol. and Biochem 31:1031-1038.
Lundquist, EJ; Scow, KM; Jackson, LE; Uesugi, SL; Johnson, CR. 1999. Rapid response of soil microbial communities from conventional, low input, and organic farming systems to a wet/dry cycle. Soil Biology and Biochemistry 31:1661-1675.
Lundquist, E.J., L.E. Jackson, K.M. Scow, and C. Hsu. 1999. Changes in microbial biomass and community composition, and soil carbon and nitrogen pools after incorporation of rye into three California agricultural soils. Soil Biol. and Biochem. 31:221-236.
Mitchell, J.P., W.T. Lanini, S.R. Temple, P.N. Brostrom, E.V. Herrero, E.M. Miyao, T.S. Prather and K.J. Hembree. 1999. Reduced-disturbance agroecosystems in California. In Proceedings Congress for Ecosystem Health. Sacramento, CA August 1999. In press.
Poudel, D.D., W.R. Horwath, J.P. Mitchell, and S.R. Temple. 2000. Impacts of farming systems on soil mineral nitrogen levels in irrigated processing tomatoes. Submitted.
Poudel, D.D., H. Ferris, K. Klonsky, W.R. Horwath, K.M. Scow, A.H.C. van Bruggen, W.T. Lanini, J.P. Mitchell, S.R. Temple. 2000. The Sustainable Agriculture Farming Systems Project in California's Sacramento Valley. Outlook on Agriculture. In Press.
Poudel, D.D., W.R. Horwath, S.R. Temple, W.T. Lanini, and A.H.C. van Bruggen. 1999. Using plant tissue nitrogen as an indicator of crop yield and soil nitrogen availability in organic, low-input, and conventional farming systems. ASA Proc. (abstr.)
Scow, K.M., E. Schwartz, M. Johnson, and J.L. Macalady. 2000. Measurement of microbial diversity. In: Encyclopedia of Biodiversity. (in press)
Scow, K.M. 1999. Soil microbiology. In: Encyclopedia of Microbiology. Academic (in press)
Scow, K.M., O. Somasco, N. Gunapala, S. Lau, R. Venette, H. Ferris, R. Miller, and C. Shennan. 1994. Transition from conventional to low-input agriculture changes soil fertility and biology. California Agriculture 48(5):20-26.
Scow, K.M. 1997. Soil microbial communities and carbon flow in agroecosystems, p. 361-407. In: Jackson, L.E.(ed.) Ecology in Agriculture. Academic Press, N.Y.
Scow, K. M. 1997. Interrelationships between microbial dynamics and carbon flow in agroecosystems. In: Jackson, L.E. (ed.) Agricultural Ecology.
Scow, K.M., and M.R. Werner. 1999. The soil ecology of cover cropped vineyards. p. 69-79. In: Ingels, C. (ed.) Cover cropping in vineyards. University of California Division of Agriculture and Natural Resources. Publication 3338. DANR, Oakland, CA.
Scow, K.M. 1997. Soil microbial communities and carbon flow in agroecosystems, p. 361-407. In: Jackson, L.E. (ed.) Ecology in Agriculture. Academic Press, N.Y. Semenov, A. M., A. H. C. van Bruggen, and V. V. Zelenev. 1999. Moving waves of bacterial populations and total organic carbon along roots of wheat. Microbial Ecology 37:116-128.
Shouse, B. N. and H. Ferris. 1999. Microbe-grazer-predator community dynamics during organic matter decomposition. Journal of Nematology 31:570 (abstr.)
Song, XH; Hopke, PK; Bruns, MA; Graham, K; Scow, K. 1999. Pattern recognition of soil samples based on the microbial fatty acid contents. Environmental Science and Technology 33:3524-3530.
Song, X.H., P.K. Hopke, M. Bruns, D.A. Bossio, and K.M. Scow. 1998. A fuzzy adaptive resonance theory-supervised predictive mapping neural network applied to the classification of multivariate data Chemomet. Intell. Lab. Syst. 41:161-170.
Sudarshana, P., J.R. Hanson, and K.M. Scow. 1999. Application of random amplified polymorphic DNA (RAPD) method for characterization of soil microbial communities. In: Scow et al. (eds) Critical methodologies for the study of ecosystem health. Lewis Publishers, Boca, Raton, FL.
Temple S.R., O.A. Somasco, M. Kirk and D. Friedman. 1994. Conventional, low-input, and organic farming systems compared. California Agriculture. 48(5): 14-19.
Temple, S.R., D.B. Friedman, O. Somasco, H. Ferris, K. Scow, and K. Klonsky. 1994. An interdisciplinary, experiment station-based participatory comparison of alternative crop management systems for California's Sacramento Valley. Amer. J. Altern. Agric. 9:64 -71.
van Bruggen, A.H.C. 1995. Plant disease severity in high-input compared to reduced input and organic farming systems. Plant Disease 79:976-984.
van Bruggen, A.H.C. and A.M. Semenov. 1999. A new approach to the search for indicators of root disease suppression . Australian Plant Pathology. 28:4-10.
Venette, R.C., and H. Ferris. 1998. Influence of bacterial type and density on population growth of bacterial-feeding nematodes. Soil Biology and Biochemistry 30:949-960.
Venette, R.C., F.A. M. Mostafa, and H. Ferris. 1997. Trophic interactions between bacterial feeding nematodes and the nematophagous fungus Hirsutella rhossiliensis in plant rhizospheres to supress Heterodera schachtii. Plant and soil 191:213-223.
Venette, R. C. and H. Ferris. 1997. Thermal restraints to population growth of bacterial-feeding nematodes. Soil Biology and Biochemistry 29-63-74.
Venette, R. C. and H. Ferris. 1995. Impact of temperature on population growth rates of bacterial- feeding nematodes: implications for invasion biology. Suppl. Bull. Ecol. Soc. America 76:398.
List of SAFS Newsletters
Clark, M.S., T. Lanini, K. Klonsky. 1998. Weed Management Practices in Organic and Low-Input Farming Systems. Sustainable Agriculture Farming Systems Project Bulletin 2 (2): 1-3.
Clark, M.S., K. Scow, H. Ferris, S. Ewing, J. Mitchell, W. Horwath. 1998. Evaluating soil quality in Organic, Low-Input, and Conventional Farming Systems. Sustainable Agriculture Farming Systems Project Bulletin 2 (1): 1-3.
Clark, M. S., H. Ferris, K. Klonsky, W.T. Lanini, A.H.C. van Bruggen, F.G. Zalom, S. Temple. 1997. Pesticide use reduced by 50-100% in low-input and organic cropping systems. Sustainable Agriculture Farming Systems Project Bulletin 1 (3): 1-3.
Ferris, H., K. Scow, S. Temple, M. Espley, R. Venette. 1996. Introduction to the SAFS Project. Sustainable Agriculture Farming Systems Project Bulletin 1 (1): 1-3.
Friedman, D., R. Miller, S. Temple, T. Kearney, M. Espley. 1997. Low-input corn production yields good crop, better returns, and improved soil quality. Sustainable Agriculture Farming Systems Project Bulletin 1 (2): 1-3.
Klonsky, K., M. S. Clark, P. Livingston. 1997. Economic viability of organic and low-input farming systems in Sacramento Valley. Sustainable Agriculture Farming Systems Project Bulletin 1 (4): 1-3.
Poudel, D.D., W.R. Horwath, J.P. Mitchell, S.R. Temple. 1999. Impacts of Farming System on Soil Mineral Nitrogen Levels of Irrigated Processing Tomatoes: A Case Study from the UC Davis Sustainable Agriculture Farming Systems Project. Sustainable Agriculture Farming Systems Project Bulletin 3 (1): 1-3.
2. Conference/ Presentations in 1999
Chen, J., H. Ferris, K. M. Scow and K. J. Graham. 1999. The effect of fungal-feeding nematodes on fungal biomass during decomposition of organic matter . Annual Meeting of the Society of Nematologists.
Ferris, H., T. Bongers and R. G. M. de Goede. 1999. Nematode faunal indicators of soil food web condition. Annual Meeting of the Society of Nematologists.
Ferris, H. Nematodes and Fruit Trees: Analysis of Soil Fauna. Davis. 11/04/99
Ferris, H. 1999. The soil food web and indicators of its conditions, Southern California Turfgrass Institute, Buerna Park, 12/15
Ferris, H. Soil Sampling and Interpretation of Nematode Count Data - California Nematology Workshop, Yuba City 3/29/99
Mitchell, J.P., W.T. Lanini, S.R. Temple, G. Miyao, et al. 1999. Conservation tillage technologies in California vegetable production systems, Proceedings, 1999, CA Plant and Soil Conference, CA Chapter of American Society of Agronomy and CA Fertilizer Association, Visalia, Jan 20- 21, 1999. (35 attendance)
Poudel, D.D., W.R. Horwath, S.R. Temple, W.T. Lanini, and A.H.C. van Bruggen. 1999. Using plant tissue nitrogen as an indicator of crop yield and soil nitrogen availability in organic, low-input, and conventional farming systems. ASA 1999 annual meeting, Salt Lake City (80 attendance)
Scow, K.M. 1999. A bug's story. Invited talk in Dept. of LAWR (2/10).
Scow, K.M. 1999. Developing relationships between soil communities and soil quality in agroecosystems. Kearney Symposium. (3/23)
Scow, K.M. 1999. Role of microorganisms in the soil/atmospheric interface. Air Quality Workshop, Davis, CA. (7/27)
Shouse, B. N. and H. Ferris. 1999. Microbe-grazer-predator community dynamics during organic matter decomposition. Annual Meeting of the Society of Nematologists.
van Bruggen, A.H.C. 1999. Organic Farming and Ecosystem Health. Invited seminar at Wageningen University, the Netherlands, March 15, 1999.
van Bruggen, A.H.C. 1999. In search of indicators for soil health and disease suppression. Keynote address at the First Australian Soilborne disease Symposium at Brisbane, Australia, 10-12 February, 1999.
3. Field Days/Presentations/Outreach in 1999
Presentation to 7 Japanese visitors interested in organic farming (Feb. 2)
Presentation to 2 Egyptian scholars one from Mansora University, Mansora, Egypt, & another from National Research Center, Dokki, Giza, Cairo, Egypt (September 22)
Presentation to UC Davis FARMS field day. 30 high school students of the Farming Agriculture and Resources Management for Sustainability (FARMS). (November 6).
Field tour for three participants of a seminar on "On-farm Participatory Research" from North Carolina and Michigan States by Steve, Durga, and Peter. (February, 19).
Field tour and presentation to 25 7th graders from Bates School. (March , 2).
Field tour for Dr. Kuni Ishihara, Professor of Crop Science, Faculty of Agriculture, Utsunomiya University Mine, Utsunomiya, Japan (March, 9).
Field tour for 25 Hungarian farmers sponsored by John Deere Co. (April, 14).
Field tour for 3 Irish visitors-Dr. Liam Downey, Director of Agriculture and Food Research Ireland, Dr. Tom Thomas, Deputy Director of Agri. & Food Research Ireland, and Dr. Jim Burke. (May, 27).
Field tour for 4 Indian visitors. Morsel Agro Industries Private Ltd, Gujrat, India. (July, 21).
Field tour for Dr. Clovis Manuel Borkert, Embrapa, Brazil. (August, 13).
Field tour for 20 students from Japan. Iwate Agricultural Junior College, Iwate, Japan. (August, 23).
Field tour for Prof. David J. Midmore, Central Queensland University, Australia, and Mr. Purnendu Narayan Sing, Irrigation Engineer, Department of Irrigation, Nepal. (December, 21).
Ray Fry, an Australian Science Journalist, had a radio interview with Willi Horwath about the SAFS project. (Jan 20th)
SAFS annual field day. Guest Speaker: Prof. John Luna, Oregon State University, title: Water-plant relationships and water management to increase agricultural productivity and sustainability (80 attendance). (July 26)