Progress 10/01/05 to 09/30/10
Outputs
OUTPUTS: The activities of this project focused on vegetable production systems in California's Central Valley. Typically, these are intensively managed agroecosystems, with high inputs of irrigation, fertilizers, pesticides, and tillage. The project has shown promising results for alternative management options that reduce environmental impacts, improve soil quality and support sustainable agriculture. Overall, the most effective set of practices for improving nitrogen cycling, increasing carbon storage and minimizing greenhouse gas emissions while maintaining viable vegetable production was organic production. Almost all work involved on-farm research. Initial activities were on reduced tillage, cover crops, organic fertilizers, efficient irrigation methods and recycling of irrigation water. Later on, the project placed greater emphasis on the role of the soil biota in carbon and nitrogen transformations (e.g., microbial communities, mycorrhizae and nematode communities) especially in organic production systems. More recently, the project expanded to include farmscaping with hedgerows, restoration of waterways in vegetable farming areas as well as landscape analysis of biodiversity and indicators of ecosystem functions. As the project progressed more emphasis was placed on how agrobiodiversity affects ecosystem functions, and how site-specific interventions (as related to soil and water quality) may improve the adaptive capacity to climate change for horticultural crops. More than 25 presentations were made at regional and statewide meetings, e.g., on soil quality, organic agriculture, agriculture and air quality, climate change and agriculture, master gardeners and biodiversity in agricultural landscapes. At the national level, presentations were made to the National Council for Science and the Environment; the American Institute of Biological Sciences; symposia and workshops on root research, agricultural biodiversity, and land use change; and at meetings of the Soil Science Society of America, the American Horticultural Society, and the Ecological Society of America. Interviews for several news or newsletter articles were provided, mainly as relevant to agricultural adaptation to climate change. Much of the research was participatory in approach, and thus disseminated information to farmer-cooperators, farm advisors, high-school classes, local governmental and non-governmental organizations, as well as to state (such as California Dept. of Food and Agriculture and California Energy Commission) and federal agencies (such as NRCS). A website has been maintained on soil and root ecology, and has continually changed as new work is produced http://groups.ucanr.org/jacksonlab/. Seven graduate students and eight postdocs contributed to the more than 20 scientific publications that were produced by the project. In addition to primary research, review articles addressed the plant-soil nitrogen cycle and its provision of ecosystem services; changes in soil processes during land use change; and utilization of agrobiodiversity. PARTICIPANTS: Individuals from the Univ. of California system who were working on the project included undergraduate (12) and graduate students (8), postdoctoral scholars (8), farm advisors (4), extension specialists (3), and professors (5). Most of the projects took place on farmers' fields; six different companies were involved. Work was also conducted with organizations such as a resource conservation district. Training and development occurred through meetings organized by farming organizations, stakeholder groups, environmental stewardship groups, UC Cooperative Extension, and federal programs such as Western SARE program. TARGET AUDIENCES: The main target audience was farmers in central California counties who grow cool- and warm-season vegetables. Particular attention was paid to organic producers due to their greater reliance on soil biology for nutrient cycling. During the period of the project, direct interaction with more than 100 producers and industry personnel occurred through either on-farm research or training workshops. The project developed their awareness for the processes that retain and cycle nutrients and for practices that improve soil quality in their specific types of vegetable production. In addition to audiences for local/regional outreach and education, there were opportunities to deliver presentations to statewide and national groups involved in either stewardship or academic issues related to agriculture and environmental quality (see outputs section). PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Outcomes focused on the following five aspects of soil biology in vegetable crop systems in California. 1) Soil biota and soil transformations that regulate the production, flow, and loss of nutrients: Ammonia-oxidizer (AOB) diversity and population sizes showed little response to high vs. low N inputs, but large differences between cropping systems. An organic farm soil supported a diverse yet stable AOB community, with no effect of mycorrhizal colonization or N and P addition. Mycorrhizal tomatoes increased nutrient uptake (N, P and Zn) and soil respiration, compared to a mutant non-mycorrhizal genotype, with little effect on nematodes, fungi and microbial biomass. In a greenhouse with a continuous soil CO2 monitoring system, mycorrhizal roots had higher respiration per unit dry weight than nonmycorrhizal roots, and higher nutrient uptake per unit C expenditure belowground. 2) Ecophysiology of tomato with respect to nutrient and water use: Mycorrhizae increased N uptake by tomato from 15N pulses and resulted in substantial differences in gene expression in microarrays and with quantitative PCR. Tomato cultivars showed increased water use efficiency and productivity during 70 years of breeding in California. 3) Alternative tillage and organic matter management to improve soil quality and production: No tillage with continuous cropping altered the nematode soil food web and the depth stratification of labile C pools, but required improved management solutions to reduce high weed biomass and uneven water availability during furrow irrigation of tomatoes. Transition to organic production on two ranches resulted in changes in crop species, seasonal cropping patterns and management inputs, but without increases in pests or diseases. Nitrate leaching potential was low. Mycorrhizae increased, as did soil microbial biomass. A four-year on-farm trial compared yard waste-based vs. manure-based composts showing few changes in yield, soil parameters, or weeds. 4) Soil biology across farmscapes and landscapes dominated by vegetable production: A two-year study monitoring different habitats at an organic farm showed practices important for recycling nutrients and sediment, e.g. tailwater ponds and a tailwater return system, hedgerows, and cover crops. Across the farmscape, plant biodiversity was more important in increasing ecosystem functions than microbial or nematode communities. Along a slough, planting woody species along levee benches increased carbon stocks, reduced flooding risks, and improved wildlife habitat. A study of plant and soil biodiversity in a 150 km2 landscape used GIS as a basis for sampling, and showed that biodiversity was related to indicators of ecosystem functions such as nutrient pools, soil properties, and riparian health. 5) Planning for climate change impacts and developing adaptation strategies: Interdisciplinary analysis of climate change impacts on California agriculture, especially horticultural crops, was conducted, along with mitigation and adaptation strategies in a case study for a county in the Central Valley.
Publications
- Jackson, L.E., S.M. Wheeler, A.D. Hollander, A.T. O'Geen, B.S. Orlove, J. Six, D.A. Sumner, F. Santos-Martin, J.B. Kramer, W.R. Horwath, R.E. Howitt, and T.P. Tomich. Adaptation to climate change in an agricultural landscape in the Central Valley of California. In press, Climatic Change. Smukler, S.M., L.E. Jackson, A.T. OGeen, and H. Ferris. Environmental tradeoff assessment for best management practices on an organic farm in a Mediterranean-type climate. In press, Journal of Soil and Water Conservation. Barrios-Masias, F.H. and L.E. Jackson. Cultivar mixtures of processing tomato in an organic agroecosystem. In press, Organic Agriculture. Smukler, S.M., S. Sanchez-Moreno, S.J. Fonte, H. Ferris, K. Klonsky, A.T. OGeen, K.M. Scow, K.L. Steenwerth, and L.E. Jackson. 2010. Biodiversity and multiple ecosystem functions in an organic farmscape. Agriculture, Ecosystems and Environment 139:80-97. Culman, S.W., A. Young-Mathews, A.D. Hollander, H. Ferris, S. Sanchez-Moreno, A.T. O'Geen, and L.E. Jackson. 2010. Biodiversity and soil ecosystem functions over a landscape gradient of agricultural intensification in California. Landscape Ecology 25:1333-1348. Young-Mathews, A., S.W. Culman, S. Sanchez-Moreno, A.T. O'Geen, H.Ferris, A.D. Hollander, and L.E. Jackson. 2010. Plant-soil biodiversity relationships and nutrient retention in agricultural riparian zones of the Sacramento Valley, California. Agroforestry Systems 80:41-60. Suddick, E.C., K.M. Scow, W.R. Horwath, L.E. Jackson, D.R. Smart, J.P. Mitchell, and J. Six. 2010. The potential for California agricultural crop soils to reduce greenhouse gas emissions: a holistic evaluation. Donald L. Sparks, editor. Advances in Agronomy 107:123-162. Ruzicka, D.R., F.H. Barrios-Masias, N.T. Hausmann, L.E. Jackson and D.P. Schachtman. 2010. Tomato root transcriptome response to a nitrogen-enriched soil patch. BMC Plant Biology 10:75. Jackson, L.E., M. van Noordwijk, J. Bengtsson, W. Foster, L. Lipper, M. Said, J. Snaddon, and R. Vodouhe. 2010. Biodiversity and agricultural sustainagility: from assessment to adaptive management. Current Opinion in Environmental Sustainability 2:80-87.
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: During the past year, several avenues have been utilized for outputs and outreach. Presentations were made on use of biodiversity in agriculture at the National Council for Science and the Environment in Washington DC, at the American Institute of Biological Sciences annual meeting on sustainable agriculture, and a symposium on root research (Univ. of Missouri). Talks were given at statewide cooperative extension meetings, e.g., the Organic Soil Fertility Management Symposium, and on Agriculture and Air Quality (both in Davis, California), and at California state agency meetings, such as for the California Dept of Water Resources and the California Energy Commission. Other presentations were made at conferences on sustainable agriculture in California (CalCan, the wine industry, and Western Sustainable Agriculture Research and Education program). Other presentations were given at international conferences on sustainability and organic farming. Interviews for several news or newsletter articles were provided, mainly as relevant to agricultural adaptation to climate change. Much of the research was participatory in approach, and thus disseminated information to farmer-cooperators, local agencies, local non-governmental organizations, as well as to statewide agencies through the discussion and adaptive management process. More than ten scientific publications were produced or revised, demanding a great deal of time and effort. The main emphasis of this year's outputs was to show how alternative management practices (e.g., hedgerows, farmscaping, organic production) can improve nitrogen cycling, the role of agrobiodiversity (particularly in the root and soil context) affects ecosystem functions, and how diversification of agricultural management (particularly as related to soil and water) may improve the adaptive capacity to climate change for horticultural crops. PARTICIPANTS: Postdocs on the project were Dr. Steve Culman and Dr. John Williams. Graduate students were Felipe Barrios-Masias, Anna Young-Williams, and Sean Smukler. As noted in the publications, collaborations exist with many other scientists both within and outside the University of California system. Partner organizations were state and local agencies, non-governmental organizations. These, along with training and professional development, area are described in the output section above. International organizations to which this project has directly contributed are DIVERSITAS and the International Centre for Organic Food Systems. TARGET AUDIENCES: The main target audiences include: 1) local farmers and ranchers in Yolo County, California; 2) state agencies involved in implementing climate change policy; 3) agricultural industry members working on sustainability issues. As stated in both the output and outcome sections above, the emphasis on multi-scale, participatory research, is directly conveying soil and water management options to landowners, and to agencies involved with policy. In addition, the work is reaching a scientific audience through peer-reviewed publications. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
The main focus of this year's work has been to 1) synthesize data sets that describe the effects of high-input agricultural intensification in vegetable crop systems in California; 2) conduct new experiments on water and nutrient use by tomatoes using ecophysiological and genetic techniques; and 3) write proposals to fund new research on soil biology, agrobiodiversity, nutrient cycling, and climate change. Submitted and published research papers emphasized ecosystem and landscape scales. New research showed that there is considerable genetic variation in tomatoes for traits that improve nutrient and water use efficiency, thus serving as a model system for our new grant proposals. These three types of work can be summarized as a set of interrelated projects: a) A two-year study monitoring different habitats at an organic farm showed that various types of interventions were important for increasing and recycling nutrients and sediment, such as tailwater ponds and a tailwater return system, hedgerows, and cover crops. Across the farmscape, plant biodiversity was more important in increasing ecosystem functions than soil biodiversity (nematode counts, and microbial communities assessed by phospholipid fatty acid analysis (PLFA)). Specific 'best management practices' were outlined for California irrigated row-crop agriculture, based on both field and farmscape level measurements. b) An analysis of multiple functions along a restored stream corridor (beside an intensively managed row-crop ecosystem) showed the ecosystem benefits of planting woody species along levee benches for carbon stocks, reducing flooding risks, and wildlife habitat. c) A landscape study of plant and soil biodiversity (nematode counts and PLFA) along waterways in Yolo County, California, was analyzed for its methodological approach and as a context for restoration management. Statistical analysis showed that the approach of the project was robust, i.e., geographic information system as a basis for engaging with farmers, participatory research and a rigorous sampling scheme provided a good inventory of biodiversity and indicators of ecosystem functions related to nutrient pools, other soil properties, and riparian health. It also showed how waterways in rangeland and cropland differed in management needs. e) Current research during the summer field season was focused on detailed analysis of differences in tomato genotypes for water use efficiency and nutrient acquisition, using stable isotopes and gene expression differences for crops grown in the field. d) An analysis of climate change adaptation potential, also in Yolo County, used an interdisciplinary approach (ecology, agronomy, pedology, economics, anthropology, and landscape architecture) to determine commodities and sub-regions most vulnerable to change. Agrobiodiversity and water use were targeted as two of the most necessary factors to adapt and mitigate to climate change over the next 50 years. e) Several review-type articles were completed on agrobiodiversity and ecosystem functions, in some cases using detailed literature review, or on meta-analysis and multivariate comparisons of large data sets.
Publications
- Drenovsky, R.E., K.L. Steenwerth, L.E. Jackson, and K.M. Scow. 2009. Land use and climate factors structure regional patterns in soil microbial communities. Global Ecology and Biogeography 19:27-39.
- Wright, J., A. Symstad, J.M. Bullock, K. Engelhardt, L.E. Jackson, and E. Bernhardt. 2009. Restoring biodiversity and ecosystem function: will an integrated approach improve results Chapter 12. In: Biodiversity and Human Impacts (S. Naeem, D. Bunker, A. Hector, M. Loreau and C. Perrings, eds.). Oxford University Press, Oxford, UK. pp. 167-177.
- Jackson, L.E., F. Santos-Martin, A.D. Hollander, W.R. Horwath, R.E. Howitt, J.B. Kramer, A.T. O'Geen, B.S. Orlove, J.W. Six, S.K. Sokolow, D.A. Sumner, T.P. Tomich, and S.M. Wheeler. 2009. Potential for adaptation to climate change in an agricultural landscape in the Central Valley of California. Report from the California Climate Change Center. CEC-500-2009-044-D. 170 pp.
- Potthoff, M., L.E. Jackson, S. Sokolow, and R.G. Joergensen. 2009. Responses of plants and microbial communities to litter addition and annual lupines in perennial California grassland restored with the bunchgrass, Nassella pulchra. Restoration Ecology 42:124-133.
- Jackson, L.E., T. Rosenstock, M. Thomas, J. Wright, and A. Symstad. 2009. Managed ecosystems: biodiversity and ecosystem functions in landscapes modified by human use. Chapter 13. In: Biodiversity and Human Impacts (S. Naeem, D. Bunker, A. Hector, M. Loreau and C. Perrings, eds.). Oxford University Press, Oxford, UK. pp. 178-194.
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: Many outputs have been produced during the past year: >10 seminars, oral talks and posters at scientific meetings and workshops; 5 extension presentations (e.g. Master Gardeners, UC Cooperative Extension meetings) and newsletters regarding soil biology, biodiversity, nutrient cycling, and carbon sequestration; direct communication with >10 farmers about soil management; a high-school field project for students to learn about carbon sequestration in soil and plants in farm restoration; presentations and field trips for governmental (e.g. NRCS) and non-governmental agencies (e.g. Audubon California) about soil and plants in farm restoration; collaborative work with state agencies on agricultural mitigation and adaptation to climate change (e.g. California Dept. of Food and Agriculture and the California Energy Commission); and interaction with international groups involved in climate change and biodiversity conservation (e.g. DIVERSITAS and the CGIAR). Outcomes/Impact Vegetable crop systems in California require a great deal of attention to nutrient management, especially for organic farms. Managing soil fertility using renewable inputs, soil biology and ecological processes is the focus of this project. Intensive vegetable production systems represent a significant challenge, because they rely on high inputs of fertilizers and irrigation, and are often associated with nutrient loss through leaching, runoff, and greenhouse gas emissions. Alternatives are being studied in this project are reduced tillage, cover crops, organic matter amendments, cultivar selection, and farmscape management. PARTICIPANTS: This project provided training opportunities for two graduate students and three postdocs during the past year. Many (>15) farmers and ranchers in Yolo County, California were involved in on-farm research. The international program on biodiversity science, DIVERSITAS, supported the work that generated some of the review articles. The California Energy Commission supported the project on agricultural adaptation to climate change in Yolo County, California. TARGET AUDIENCES: Target audiences were diverse, ranging from growers (especially organic growers), to non-governmental organizations and governmental agencies involved in farm restoration projects. There was a strong commitment to presentations and publications for solely scientific audiences as well. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
There is an emphasis on understanding how soil biodiversity can increase nutrient cycling, productivity, and carbon sequestration. During this fourth year of the project, the following topics have been studied. 1) A paper was published on the three-year transition to organic production systems on two farms in the Salinas Valley, California. The huge data set required a great deal of synthesis. The results demonstrate that organic production can be highly productive, as well as environmentally sound, e.g. low nitrate leaching potential, higher soil carbon pools, and lack of synthetic pesticide use and thus no detrimental off-farm effects. 2) An on-farm research station trial compared standard tillage / standard conventional management with alternative strip tillage / organic practices. The results were that the alternative practices produced lower and more variable crop yields, higher soil bulk densities, and slightly higher soil carbon and nitrogen retention than in conventionally-farmed soils. 3) An ecophysiological comparison of tomato cultivars was conducted to understand changes in water use efficiency and productivity during the past 70 years of breeding processing tomatoes in California. 4) For tomatoes, an experimental set-up was developed to compare N uptake with the stable isotope, 15N, with microarray analysis. The upregulation of specific genes under inorganic N is now being analyzed. 5) Other projects are focusing on farmscape management, such as using perennial grasses, shrubs and trees in farm hedgerows and along riparian corridors, by measuring carbon sequestration and greenhouse gas emissions in relation to biodiversity in different farm habitats. There are two types of approaches: landscape analysis using a GIS-based sampling design, and seasonal monitoring on long-term farmscapes in Yolo County. These projects depend on on-farm participatory research with farmers. 5) A review article was published, describing the role of root biology and soil nitrogen transformations on ecosystem services, and the potential for improving the biological basis of soil fertility in crop systems. 6) Other review articles discuss agrobiodiversity, its provision of ecosystem services, and the prognosis for increasing socioeconomic benefits. These results are being used in outreach through scientific publications, on-farm participatory research, and interactions with various agencies. 7) An analysis of climate change impacts on agriculture in Yolo County, and mitigation/adaptation potential was produced through interdisciplinary cooperation. One of the central focal points was the feasibility of adopting reduced tillage and reduced N inputs for vegetable crops, in order to reduce greenhouse gas emissions, and possibly receive credit for farmers through California's cap and trade policy (AB32).
Publications
- Drenovsky, R.E., K.L. Steenwerth, L.E. Jackson, and K.M. Scow. 2008. Land use and climate factors structure regional patterns in soil microbial communities. Global Ecology and Biogeography. In press.
- Gaskell, M. R. Smith, L. Jackson, and T.K. Hartz. 2008. Nitrogen fertility management. Section 6. In: Cover Cropping for Vegetable Production: A Grower's Handbook. (R. Smith, R. Bugg, O. Daugovish, M. Gaskell, and M. Van Horn, eds.). DANR Publication #xxxx. In press.
- Jackson, L.E., F. Santos-Martin, A.D. Hollander, W.R. Horwath, R.E. Howitt, J.B. Kramer, A.T. O'Geen, B.S. Orlove, J.W. Six, S.K. Sokolow, D.A. Sumner, T.P. Tomich, and S.M. Wheeler. 2008. Potential for adaptation to climate change in an agricultural landscape in the Central Valley of California. Report from the California Climate Change Center. CEC-500-2008-xxx. 170 pp. In press.
- Cavagnaro, T.R., L.E. Jackson, K. Hristova, and K.M. Scow. 2008. Short-term population dynamics of ammonia oxidizing bacteria in an agricultural soil. Applied Soil Ecology 40:13/18.
- Brodt, S., K. Klonsky, L.E. Jackson, S.B. Brush, S.M. Smukler. 2008. Factors affecting adoption of hedgerows and other biodiversity-enhancing features on farms in California, USA Agroforestry Systems. DOI 10.1007/s10457-008-9168-8.
- Drinkwater, L.E., M. Schipanski, S.S. Snapp, and L.E. Jackson. 2008. Ecologically based nutrient management. Chapter 6. In: Agricultural Systems: Agroecology and Rural Innovation for Development. (S. Snapp and B. Pound, eds.). Academic Press, Elsevier, Burlington, MA, USA. pp. 161/210.
- Cavagnaro, T.R., J.A. Langley, L.E. Jackson, S.M. Smukler, and G.W. Koch. 2008. Growth, nutrition, and soil respiration of a mycorrhiza-defective tomato mutant and its mycorrhizal wild-type progenitor. Functional Plant Ecology 35:228/225.
- Smukler, S.M., L.E. Jackson, L. Murphree, R. Yokota, S.T. Koike, and R.F. Smith. 2008. Transition to large-scale organic vegetable production in the Salinas Valley, California. Agriculture, Ecosystems and Environment 126:168/88.
- Jackson, L.E. 2007. Using biophysical information in policies for agroecosystem services in California. Agroecosystem Brief #1. Workshop and Policy Round Table Proceedings. California Agroecosystem Services: Assessment, Valuation and Policy Perspective. University of California Agricultural Issues Center. 19 pp.
- Sanchez-Moreno, S., S. Smukler, H. Ferris, and L.E. Jackson. 2007. Nematode diversity, food web condition, and chemical and physical properties in different soil habitats of an organic farm. Biology and Fertility of Soils 59:341/63.
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: The following outputs have been produced: seminars, oral talks and posters at scientific meetings; extension presentations and newsletters regarding soil biology, biodiversity, nutrient cycling, and carbon sequestration; direct communication with farmers about soil management; high-school field projects for students to learn about carbon sequestration in soil and plants in farm restoration; presentations and field trips for non-governmental agencies about soil and plants in farm restoration; collaborative work with state agencies on agricultural mitigation and adaptation to climate change; and interaction with international groups involved in climate change and biodiversity conservation.
PARTICIPANTS: This project provided training opportunities for five graduate students and two postdocs. Several farmers and ranchers in Yolo County, California were involved in on-farm research. The international program on biodiversity science, DIVERSITAS, supported the work that generated some of the review articles.
TARGET AUDIENCES: Farmers, ranchers, government agencies involved in resource management and energy use, and non-governmental agencies involved in biodiversity conservation are the public target audiences. The work is also aimed at scientific audiences in biogeochemistry, plant ecology, and sustainable agriculture.
Impacts
This project focuses on managing soil fertility using renewable inputs, soil biology and ecological processes. This is a particular challenge for intensive vegetable production systems, which typically rely on high inputs of fertilizers and irrigation, and are often associated with nutrient loss through leaching, runoff, and greenhouse gas emissions. Alternatives are being studied in this project are reduced tillage, cover crops, organic matter amendments, cultivar selection, and farmscape management. There is an emphasis on understanding how biodiversity can increase nutrient cycling, productivity, and carbon sequestration. During this third year of the project, the following topics have been studied. 1) The transition to year-round/organic/no-till cropping systems in California showed variable crop yields, higher soil bulk densities, and higher soil carbon and nitrogen retention than in conventionally-farmed soils. 2) To better understand the availability of
inorganic N, ammonia-oxidizing bacteria were studied. In high-input conventional agriculture soils, N fertilizer addition had little effect on the diversity and population sizes of ammonia-oxidizing bacteria. Likewise, in organic tomato production, there were no effects of arbuscular mycorrhizae on ammonia-oxidizing bacteria. These results indicate diverse but stable communities of ammonia-oxidizing bacteria in relation to short-term environmental factors. 3) Using a mycorrhizal mutant and its mycorrhizal progenitor, mycorrhizal colonization increased uptake of P and Zn, and nutrient uptake per unit carbon expenditure by roots. These results were obtained in a controlled microcosm experiment with continuous monitoring of soil respiration. Overall the two genotypes differed little in their effect on total soil respiration, soil microbial biomass, or soil microbial communities based on phospholipid fatty acid (PLFA) analysis were similar across all treatments. 4) Other projects are
focusing on farmscape management, such as using perennial grasses, shrubs and trees in farm hedgerows and along riparian corridors, by measuring carbon sequestration and greenhouse gas emissions in relation to biodiversity in different farm habitats. On-farm participatory research with farmers is a key element in this research. 5) A review article was written to describe the role of root biology and soil nitrogen transformations on ecosystem services, and the potential for improving the biological basis of soil fertility in crop systems. 6) Other review articles discuss agrobiodiversity, its provision of ecosystem services, and the prognosis for increasing socioeconomic benefits. These results are being used in outreach through scientific publications, on-farm participatory research, and interactions with various agencies.
Publications
- Sanchez-Moreno, S., S. Smukler, H. Ferris, and L.E. Jackson. The soil nematode fauna reflects aboveground farmscape patterns. In press 2007, Biology and Fertility of Soils.
- Jackson, L.E., M. Burger, and T.R. Cavagnaro. Roots, nitrogen transformations, and ecosystem services. In press 2007, Annual Review of Plant Biology.
- Cavagnaro, T.R., S.K. Sokolow, and L.E. Jackson. Mycorrhizal effects on growth and nutrition of tomato under elevated atmospheric carbon dioxide. In press 2007, Mycorrhiza.
- Minoshima, H., L.E. Jackson, T.R. Cavagnaro, and H. Ferris. Short-term fates of 13C-depleted cowpea shoots in no-tillage and standard tillage soils. Soil Science Society of America Journal 2007 71:1859-1866.
- Cavagnaro, T.R., L.E. Jackson, K.M. Scow, and K.R. Hristova. Effects of arbuscular mycorrhizas on ammonia oxidizing bacteria in an organic farm soil. In press 2007, Microbial Ecology.
- Minoshima, H., L.E. Jackson, T.R. Cavagnaro, S. Sanchez-Moreno, H. Ferris, S.R. Temple, and J.P. Mitchell. 2007. Soil food webs and carbon dynamics in response to conservation tillage in legume rotations in California. Soil Science Society of America Journal. 71:952-963.
- Jackson, L.E., M. Potthoff, K.L. Steenwerth, A.T. O Geen, M.R. Stromberg, and K.M. Scow. 2007. Soil biology and carbon sequestration. Chapter 7. In: Ecology and Management of California Grasslands (Corbin, J., C. d'Antonio, and M.R. Stromberg, eds.). University of California Press, Berkeley, CA.
- Jackson, L.E., L. Brussaard, P.C. de Ruiter, U. Pascual, C. Perrings, and K. Bawa. Agrobiodiversity. In press 2007, Encyclopedia of Biodiversity. Elsevier Inc.
- Cavagnaro, T.R. and L.E. Jackson. 2007. Isotopic fractionation of zinc in field grown tomato. Canadian Journal of Botany 85:230-235.
- Jackson, L.E., K. Bawa, L. Brussaard, U. Pascual, and P. de Ruiter. 2007. Biodiversity in agricultural landscapes: saving natural capital without losing interest. Agriculture, Ecosystems, and Environment 121:193-195.
- Jackson, L.E., U. Pascual, and T. Hodgkin. 2007. Utilizing and conserving agrobiodiversity in agricultural landscapes. Agriculture, Ecosystems, and Environment 121:196-210.
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Progress 01/01/06 to 12/31/06
Outputs
In intensive production systems, soil fertility is often supplied in the form of inorganic fertilizers, rather than through nutrient cycling mediated by soil biology. Intensive vegetable production systems are particularly dependent on high inputs of fertilizers and irrigation, which are often associated with nutrient loss through leaching, runoff, and greenhouse gas emissions. Alternatives are being studied in this project including reduced tillage, cover crops, and organic matter amendments. The emphasis is on understanding soil biota, their activity, and their influence on retention of carbon and nitrogen in intensively managed soils. During this second year of the project, the following topics have been studied. 1) Field and microcosm experiments tested effects of no-tillage and continuous cropping rotations, compared with standard tillage and intermittent fallow. No tillage + continuous cropping resulted in significant changes in the surface layer (0-5 cm),
compared to the other treatments: higher microbial biomass C, more fungi as indicated by ergosterol and phospholipid fatty acid analysis, and higher nutrient availability. Total soil C was least with standard tillage + fallow, which is the typical cropping system. The soil food web, as indicated by the nematode fauna, did not become more complex with no tillage + continuous cropping, possibly due to the lack of colonization by higher trophic level organisms. Plant aboveground biomass, except for weeds, was reduced by no tillage, and it will be necessary to improve management to increase crop yields in this Mediterranean-type climate. 2) Responses to elevated CO2 were studied in pot studies using a mycorrhiza defective tomato mutant and its mycorrhizal wild-type progenitor, showing that growth initially increased with mycorrhizae but then declined, probably resulting from a carbon drain from the fungal symbiont with time. 3) Zinc (Zn) deficiency is a common public health problem. Using
the 68Zn isotope, Zn uptake by mycorrhizal plants was shown to be greater than for non-mycorrhizal plants. 4) Other projects are focusing on nitrogen cycling, and the role of ammonia oxidizing bacteria and mycorrhizae in organic production systems. On-farm participatory research with farmers is a key element in much of this research.
Impacts
Presentations have been given on the project to farmer audiences and at the International Conference on the Future of Agriculture: Science, Stewardship and Sustainability. Sacramento. Newsletters from the Sustainable Agriculture Farming Systems Project at UC Davis have highlighted the results from the tillage research.
Publications
- Gaskell, M. R. Smith, J. Mitchell, S.T. Koike, C. Fouche, T. Hartz, W. Horwath, and L. Jackson. 2006. Soil fertility management for organic crops. DANR Publication 7249. 8 pp. http://anrcatalog.ucdavis.edu/pdf/7249.pdf
- Sanchez-Moreno, S., H. Minoshima, H. Ferris, and L.E. Jackson. 2006. Linking soil properties and nematode community composition: effects of soil management on soil food webs. In press, Nematology.
- Cavagnaro, T., L.E. Jackson, J. Six, H. Ferris, S. Goyal, D. Asami, K.M. Scow. 2006. Arbuscular mycorrhizas, microbial communities, nutrient availability, and soil aggregates in organic tomato production. Plant and Soil 282:209-225.
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Progress 01/01/05 to 12/31/05
Outputs
Vegetable production systems in the Central Valley of California are the main focus of this project. Although these are intensively managed agroecosystems, with high inputs of irrigation, fertilizers and pesticides, several new management options are now being adopted to reduce environmental impacts and increase economic viability. Projects on reduced tillage, cover crops, organic fertilizers, efficient irrigation methods, and recycling of irrigation water are now underway. This research emphasizes understanding of soil biota, their activity, and their influence on retention of carbon and nitrogen in intensively managed soils. During this initial year of the project, the following topics have been studied. 1) Soil food webs and carbon cycling were compared between no tillage and standard tillage treatments, with either a continuous rotation of crops or intermittent fallow in a legume-vegetable rotation. Plant aboveground residue C was more readily lost as CO2 in soils
under conservation tillage, as demonstrated by fates of 13C-depleted residue in microcosms. No tillage with continuous cropping altered the soil food web and the depth stratification of labile C pools, but required improved management solutions to reduce problems such as high weed biomass and uneven water availability during furrow irrigation. 2) Ammonia oxidizers are being quantified in different types of vegetable production systems, showing that their population size varies in response to N inputs. 3) Arbuscular mycorrhizal (AM) fungi were shown to be important nitrogen uptake for tomato, using the stable isotope, 15N, but AM fungi did not reduce the emissions of nitrous oxide, a potent greenhouse gas, from soil. 5) Other field and greenhouse experiments are testing the conditions in which mycorrhizae increase the uptake of zinc, a nutrient that is limiting in many areas of the developing world. On-farm participatory research with farmers is a key element in much of this
research.
Impacts
Several presentations have been given on the project: at the California Agriculture Symposium in Sacramento, CA (March 23-24, 2005), at a symposium of the annual American Society for Horticultural Science meeting in Las Vegas, NV (July 20, 2005), at the annual Soil Science Society of America meeting in Salt Lake City, Utah (November 9, 2005), at the DIVERSITAS Open Science Conference in Oaxaca, MX (November 11, 2005), at the San Joaquin Valley Conference on Organic Farming in Reedley, CA (December 16, 2005), and to other farming-related groups in Northern California.
Publications
- Cavagnaro, T., L.E. Jackson, J. Six, H. Ferris, S. Goyal, D. Asami, K.M. Scow. 2005. Arbuscular mycorrhizas, microbial communities, nutrient availability, and soil aggregates in organic tomato production. In press, Plant and Soil.
- Steenwerth, K.L., L.E. Jackson, F.J. Calderon, K.M. Scow, and D.R. Rolston. 2005. Response of microbial community composition and activity in agricultural and grassland soils after a simulated rainfall. In press, Soil Biology and Biochemistry.
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Progress 01/01/04 to 12/31/04
Outputs
Three projects have focused on soil biology in cool-season vegetable crop systems, which are some of the most intensively managed agricultural systems in California. The main theme has been transition to organic production from conventional vegetable production. A three-year monitoring study was conducted on 81 permanent points on two ranches. All field sampling has been completed, and data analysis is showing that the transition went smoothly, and resulted in changes in crop species, seasonal cropping patterns, and management inputs, but did not result in major changes in pests or other problems. Nitrate pools in the soil were low, indicating low leaching potential. Mycorrhizae increased, as did soil microbial biomass. A four-year on-farm compost quality trial has compared yard waste-based vs. manure-based composts since 2000. Few changes in yield, soil parameters, or weeds have occurred through time, although the final sample has not been fully analyzed. A third
project on the effects of brassica cover crops on arbuscular mycorrhizae, nutrient in crop tissue, and yield is now underway. Several on-farm trials were sampled for various types of vegetable crops, in cooperation with five organic farmers. Many farmers have recently included these cover crops in their rotations. So far, the results indicate that there is little effect of the brassica crops on yield or plant nutrition. These results indicate that specific soil amendments or species of cover crops do not have large effects on soil biology in organic production systems.
Impacts
Organic production of vegetables is growing rapidly in California. This research is demonstrating that soil biology can change rapidly during organic transition from conventional production, but that large changes in soil biology due to specific types of composts or to brassica vs. cereal cover crops are not readily discernable. These results are being presented at farmers meetings and scientific audiences.
Publications
- Jackson, L.E. 2005. Soil biology: root architecture and growth. Encyclopedia of Soils in the Environment. Elsevier Ltd. Pp. 411-421.
- Mitchell, J.P., L.E. Jackson, and E. Miyao. 2004. Minimum tillage in vegetable crop production systems in California. Publication 8231. DANR 7000 series, Division of Agricultural and Natural Resources, University of California.
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Progress 01/01/03 to 12/31/03
Outputs
The transition to organic vegetable production is being described at the whole farm scale, and data analysis is now underway to evaluate changes that occurred during a three-year period from 2000-2003. The three-year monitoring study was designed to sample 81 permanent points on two ranches in the Salinas Valley for soil (e.g., potentially mineralizable N, soil microbial biomas, nitrate, and ammonium) and plant characteristics (e.g., biomass, nutrient content, and mycorrhizal colonization), diseases and insect pests, and weeds. The grower has provided us with all information on management practices, irrigation, fertilizer, compost and other inputs used for each of the transect locations for each sampled crop. Since June, 2000, 171 transects have been sampled (516 individual plots) on 48 sampling days. A total of 25 different crop species have been sampled. As the transition progressed, there were fewer crop species, and fewer crops during the summer, due to the
growers concern for leaf miner damage in late summer crops. Nutrients, i.e, N P and K, in lettuce, as an example, were in excess of sufficient supply in all three years. Soil analyses showed surprisingly low concentrations of nitrate and ammonium throughout the three-year transition. Pest and disease damage and weeds did not increase during the transition period. Arbuscular mycorrhizal colonization increased slightly with time. Management data obtained so far indicate a slight increase in total N applied (chicken pellets, soluble fertilizer, and compost), and irrigation over the three years, also reflected in higher water content at the time of sampling. There has been no consistent increase in any products applied for pest control. More complete data analysis will be continued during the coming year. A compost trial conducted during organic transition in the Salinas Valley indicates that a compost based largely on yard waste inputs increased radicchio dry weight in 2002 compared to a
manure-based compost, but that plant N content was reduced. This suggests that the yard waste-based compost may be affecting plant growth in other ways besides N availability, and supports our early findings in the study, when higher lettuce yields were observed after one year, compared to the manure-based. Other possibilities are being explored by taking samples for bulk density, moisture holding capacity, and organic matter constituents.
Impacts
Organic transition is attracting interest among many mainstream vegetable growers. Based on our recent results, organic transition by large conventional growers is feasible, although it requires many management changes. More research is needed to refine management practices so that organic production is financially lucrative, as well as environmentally sound. Research on soil management for organic systems can also be useful to conventional farmers who wish to improve soil quality and minimize inputs of inorganic fertilizer.
Publications
- Jackson, L.E., I. Ramirez, R. Yokota, S.A. Fennimore, S.T. Koike, D.M. Henderson, W.E. Chaney, K.M. Klonsky. 2003. Scientists, growers assess trade-offs in use of tillage, cover crops and compost. California Agriculture 57:48-54.
- Fennimore, S.A. and L.E. Jackson. 2003. Effects of organic amendments and reduced tillage on weed emergence and seedbanks in a California vegetable field. Aspects of Applied Biology 69:107-112.
- Jackson, L.E., I. Ramirez, R. Yokota, S.A. Fennimore, S.T. Koike, D. Henderson, W.E. Chaney, F.J. Calderon, and K. Klonsky 2003. On-farm assessment of organic matter and tillage management on vegetable yield, soil, weeds, pests, and economics in California. Agriculture, Ecosystems, and Environment, in press.
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Progress 01/01/02 to 12/31/02
Outputs
Cover crops, compost, and the transition to organic farming are being evaluated in intensive vegetable production systems. On a growers' field that was in transition to organic production, cover crops, organic fertilizers and compost were used. Compost derived largely from municipal yard waste increased lettuce yields after one year, compared to a compost made from manure and a lower percentage of yard waste, especially in plots that had a small rather than large amount of cover crop biomass in the previous season. There were no effects on assays for soil carbon and nitrogen availability, and no effects of one vs. two applications of compost per year. Soil microbial biomass and potentially mineralizable N increased across all treatments throughout the 1.5 year period. Another trial on a Metz silt soil comparing winter bare, cover crop, cover crop+compost, and compost treatments showed higher lettuce yields in the treatments with compost, but with no consistent effect
of these amendments on soil carbon and nitrogen availability. Since this trial was flooded temporarily, the experiment is being repeated on an Antioch loam soil. Preliminary results show that lettuce yields were similar in all three compost or cover crop treatments, and these were higher than the winter bare treatment. Economic analysis of cover crop+compost use in relation to all other management costs for vegetable production on a Salinas silt loam soil showed that these amendments increased yield with acceptable net economic returns during a two-year period. The additional cost of cover crop+compost treatments paid off in terms of net returns for a broccoli crop, due to a high yield response but less so for lettuce crops. Thus, use of cover crop+compost inputs was economically viable, and when compared to non-amended soils. These inputs also improved some aspects of soil quality. In a project to document the transition from conventional to organic cool-season vegetable production,
numerous samples were taken to document the third year of the transition from conventional to organic production on a large-scale farming operation, which is being documented by monitoring many points for yield, crop nutrient content, soil microbial biomass, soil organic matter, diseases, pest damage, and weeds. A transect from these vegetable fields though grassland ecosystems has been studied to determine the rates of changes in soil C, soil quality parameters, and soil biology. Total soil C, N, and phospholipid ester-linked fatty acid (PLFA) levels were higher in the grassland than cultivated soils. A given land use category could by identified by soil microbial community structure, based on PLFA profiles, as well as similar soil characteristics and management factors.
Impacts
Combined use of compost and cover crops are being studied for two reasons. 1) The two sources of organic matter provide both readily-available (plant residues) and more degradation-resistant (compost) carbon compounds, which together were hypothesized to increase and sustain the soil microbial biomass and the capacity for retaining carbon in the soil. And, 2) many organic and organic-transitional vegetable growers use both inputs in their crop rotations, and this research was aimed at providing information on these practices for this growing sector of the California agricultural industry.The management implications of this project are that composts made of municipal yard waste are recommended for vegetable production to increase yield, especially in circumstances where a cover crop is not possible, or only a short-term cover crop can be accommodated due to scheduling. The role of compost in increasing yield was not clear and cannot be simply attributed to changes in
soil carbon and nitrogen availability.
Publications
- Jackson, L.E., F.J. Calderon, K.L. Steenwerth, K.M. Scow, and D.E. Rolston. 2002. Responses of soil microbial processes and community structure to tillage events and implications for soil quality. In press, Geoderma.
- Steenwerth, K.L., L.E. Jackson, F.J. Calderon, M.R. Stromberg, and K.M. Scow. 2002. Soil microbial community composition and land use history in cultivated and grassland ecosystems of Coastal California. In press, Soil Biology and Biochemistry.
- Fennimore, S.A. and L.E. Jackson. 2002. Organic amendment and tillage effects on vegetable field weed emergence and densities. In press, Weed Technology.
- Jackson, L.E., D. Miller, and S.E. Smith. 2002. Arbuscular mycorrhizal colonization and growth of wild and cultivated lettuce in response to nitrogen and phosphorus. Scientia Horticulturae 94: 205-218
- Calderon, F.J. and L.E. Jackson. 2002. Roto-tillage, disking and subsequent irrigation: effects on soil nitrogen dynamics, microbial biomass and carbon dioxide efflux. Journal of Environmental Quality 31:752-758
- Jackson, L.E., I. Ramirez, I. Morales, and S.T. Koike. 2002. Alternative tillage practices for lettuce production. California Agriculture 56:35-39.
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Progress 01/01/01 to 12/31/01
Outputs
The effects of cover crops, compost, and crop rotation in vegetable production in the Salinas Valley were the focus of the project. 1) An on-farm study was completed that showed that organic matter inputs (compost and cover crops) increased soil microbial biomass and crop yield, decreased weeds and nitrate leaching, but had no effect on total soil carbon, nor on insect pests and diseases. Less pronounced responses occurred with reduced compared to conventional tillage. The typical practices of conventional tillage with no organic matter inputs, however, gave the highest net economic returns. 2) A two-year project on a growers' field in Salinas is showing no differences in soil quality, soil microbial activity, and crop yield between two kinds of compost, or between two input rates. 3) Numerous samples were taken to document the second year of the transition from conventional to organic production on a large-scale farming operation, which is being documented by
monitoring 81 points on 9 fields for yield, crop nutrient content, soil microbial biomass, soil organic matter, diseases, pest damage, and weeds.
Impacts
These on-farm projects are showing the optimal management regimes for organic matter inputs, i.e., compost and cover crops in an intensive cropping system that normally has little return of organic matter to the soil.
Publications
- No publications reported this period
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Progress 01/01/00 to 12/31/00
Outputs
The projects in plant and soil ecology in cool season vegetable systems focused on nitrogen cycling, soil quality, and transition from conventional to organic production systems. 1) Continuation of a study on alternative tillage and organic matter management practices showed that combining compost and cover crop inputs showed prolonged increases in soil microbial biomass, and increased broccoli and lettuce yield, but showed a similar trend of less pronounced responses with reduced rather than conventional tillage. Economic analysis of this on-farm trial is now underway. 2) A two-year project was set up on a growers' field in Salinas to compare effects of two kinds of compost, each at two input rates on soil quality, soil microbial activity, and crop yields. 3) The transition from conventional to organic production on a large-scale farming operation is being documented by monitoring 81 points on 9 fields for yield, crop nutrient content, soil microbial biomass, soil
organic matter, diseases, pest damage, and weeds. Sampling is occurring two to three times per year.
Impacts
These on-farm projects are showing the optimal management regimes for organic matter inputs, i.e., compost and cover crops in an intensive cropping system that normally has little return of organic matter to the soil.
Publications
- Jackson, L.E. (2000) Fates and losses of nitrogen from a 15N-labelled cover crop in an intensively managed vegetable system. Soil Science Society of America Journal 64:1404-1412.
- Calderon, F.J., L.E. Jackson, K.M. Scow, and D.E. Rolston (2000). Microbial responses to simulated tillage in cultivated and uncultivated soils. Soil Biology and Biochemistry 32:1547-1559.
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