About the STANFORD UNIVERSITY STUDY
Below is Kimberly Cheung’s honors thesis for the Stanford University study on “Tomato Polyculture and Implications for Environmental and Human Health”
We didn't secure a grant for this study, so we're exploring alternative avenues for assistance:
- Donations of farming supplies such as compost, mulch, t-posts, agribon row covers, tomato trellis materials, irrigation systems, and farming equipment.
- Volunteer support over Memorial Weekend for transplanting, as well as on other days beforehand to help prepare the soil and administer various treatments to the tomato beds.
If you or someone you know, or a company, can offer help, it would be greatly appreciated.
Experimental examination of tomato polyculture at the local level:
Implications for environmental and human health
by Kimberly Cheung, Ecology and BioEngineering Stanford Student
A. Objective and Specific Aims
Monoculture agriculture has been shown to have considerable negative ecological and social impacts. Therefore, approaches to polyculture agriculture are becoming increasingly relevant. The intent of this research project is to measure the impacts of polyculture on environmental and human health, and examine the timeline and mechanisms of the ecological transition to polyculture in a particular study case in California. This project will be co-managed by Chef and Farmer Lan Thai, who practices traditional regenerative farming techniques in her everyday work at Fammá, a food as medicine company bridging culinary, healthcare, and agricultural industries. The implementation of polyculture agriculture at the small-scale farming level has the potential of creating more sustainable agroecosystems at the local level and, if practiced more broadly, ensuring global food security. Furthermore, documentation of the benefits of polyculture in multiple settings, should they be consistent, may lead to major advances in the field and encourage more collaboration between scientists and farmers, as well as emphasize the vital interconnections between environmental and human health through agriculture. This is the reasoning that inspires the present research.
B. Introduction
Among the multiple approaches to address sustainable food production, I choose to focus on polyculture, as this agricultural concept can be applied on a variety of sizes of farms and in many different socio-environmental contexts. There are many subtypes under the heading of polyculture, such as intercropping, mixed cropping, or permaculture guilds, but the essence of the practice is that there are two or more crop species grown at the same time (Andrews and Kassam, 1976). The idea of polyculture has been a crucial part of many cultures since agriculture began. Examples include the “milpa” practice of the Three Sisters combination (maize, bean, squash) in the Indigenous peoples of Mexico and Mesomerica (Fonteyne et al. 2023). Another example is Vuon Ao Chuong, a food production system in which a tiered intercropped garden is combined with fish and other animals (Permaculture Research Institute, 2008). I specifically use polyculture in its broadest terms because this can include, in addition to crop plants, planting species which are not intended for consumption. When intercropping species, they are chosen to represent a variety of ecological niches within an agricultural plot in order to optimize for space and nutrients; at the core, this practice emphasizes cultivating species relationships within limited resource conditions, a key component of generating diverse and well-functioning agroecosystems (Andrews and Kassam, 1976).
From the environmental perspective, researchers have been interested in polyculture for its diverse benefits like sustainability impacts (Mousavi et al. 2011), fostering of plant diversity (Brooker et al. 2014), increased crop yield (Iverson et al. 2014 & Mousavi et al. 2011), crop disease prevention (Iverson et al. 2014 & Mousavi et al. 2011), and soil fertility (Kebede 2017). Beyond these eco-benefits, there is now increased interest in how these environmental variables are interconnected with human health.
This study will focus on tomatoes as the main crop because of their widespread global importance and their health benefits related to reducing the risk of certain types of cancer, cardiovascular disease, and age-related macular degeneration (Dorais et al. 2008). Some researchers have highlighted the significant connections between tomato polyculture and nutrient quality (Hart et al. 2014, Bona et al. 2016). However, research tends to look at environmental and human health categories in siloes, and research into the ecological mechanisms which connect these variables is scant. In addition, there is a lack of farmer engagement and collaboration in the process of measuring the impacts of polyculture agricultural techniques. An increasingly accepted tenet of sustainability work is meaningful involvement of stakeholders from the academic community and on-the-ground practitioners (Yarime et al., 2012). Therefore, the goal of this research is to quantitatively examine the effects of tomato polyculture practices (tomato and a selected set of additional species; see below) on both ecological and human health variables in a small-scale agricultural setting. This research opportunity will be co-managed by an active, sustainability-motivated Chef and Farmer, Lan Thai, who opened the opportunity for me to participate in the execution and subsequent analysis of tomato-based polyculture on her Neu Mune farm.
C. Detailed Research Plan
Study Site:
Neu Mune Farm is a 19 acre farm located in Bonsall, California (33.29° N, 117.16° W, Fig. 1). This region is characterized by Mediterranean climate, which includes mild, wet winters and warm, dry summers. The farm is located in the 10A Agricultural Zone. Agriculture in these areas is significantly threatened by drought and rising temperature, therefore this research aligns with the increasing need of building resilience in agroecosystems (del Pozo et al. 2019). As agricultural techniques continue to evolve in this region, the idea of polyculture has significant implications for both environmental and human health. Neu Mune Farm used to be an avocado monoculture, but as of 2023 is now a regenerative farm owned by Chef Lan Thai, under her Fammá program.
Figure 1: The Neu Mune Farm located in north county San Diego. The left photo is the geographic coordinates of the farm and the right photo is the inset boundary of the 19 acre farm.
Selection of intercropping species:
The study consists of comparing three different polyculture treatments with tomato (Solanum lycopersicum) [protocol of Neu Mune Farm]:
i) Beneficial intercropping with plants which attract pollinators or deter pests: sage (Salvia officinalis), sweet alyssum (Lobularia maritima), yarrow (Achillea millefolium), nasturtium (Tropaeolum majus);
ii) Companion intercropping with other herbs and vegetables to maximize edible yield in a given space: basil (Ocimum basilicum), parsley (Petroselinum crispum), cucumber (Cucumis sativus);
iii) Beneficial and companion intercropping: basil (Ocimum basilicum), parsley (Petroselinum crispum), zucchini (Cucurbita pepo), cucumber (Cucumis sativus), marigold (Tagetes erecta), chamomile (Matricaria recutita), calendula (Calendula officinalis);
These three polycultures are chosen to represent a diversity in the possible combinations with tomato, both ecologically and considering agricultural intentions.
Methods
I will establish a control treatment with tomato plants grown in monoculture. There will be three experimental treatments, consisting of the beneficial intercropping (B), companion intercropping (C), and combination beneficial and companion intercropping (BC). Each treatment will have 3 replicated 10 x 6 foot (3.048 x 1.829 meters) double row plots of tomatoes in different sections of the farm. For each plot, I will collect data on their microclimatic conditions - temperature, humidity, radiation (measured using a HOBO portable data logger), elevation (measured with an altimeter), and sunlight exposure. For the tomato plants of all treatments, I will measure insect herbivory levels (frequency and magnitude of damage). Additionally, I will use exclosures to avoid vertebrate damage, which may create significant heterogeneity across the treatments. Evidently, it would be of interest to examine the relationship between the intercropping treatments and the impact of vertebrates, however this would require doubling the number of plots and necessary funding. This is an aspect that warrants further work, and I would be interested in conducting a follow up study in the future.
The study period will last three months, from July to September. At the onset of the study, tomatoes will be acquired from the store and tested for nutrient content, flavor profile, and soil health metrics from the farms that the tomato seeds originated from. Seeds will then be extracted from these exact tomatoes and planted in each of the control and experimental intercropping treatments. Within the study period, environmental and human health metrics will be collected using the methods described in the following table.
Table 1. Environmental and Human Health Metrics Table. Categorized measurements of interest which will be measured in each of the treatments at the frequency and with the methods indicated. Note that some methods are derived from the literature and others from Dirzo and Peay lab protocols.
Category
Metric
Frequency of Measurement
Methods
Environmental Health
Bird Biodiversity
Daily
I will identify, to the species level, the birds that interact (pause motion over the plot) with the crops in the treatments. These surveys will be conducted in the morning, with anticipated maximum bird activity. Each count will last 15 minutes (protocol of the Dirzo Lab).
Pollinator Biodiversity
Daily
I will use floral observation plots to measure the pollinator biodiversity, focusing on the tomato plant and other flowering plants if applicable. Each flower will be observed for 10 minutes and pollinators identified to the major taxonomic and morphospecies level (O’Connor, 2019).
Fungal Biodiversity
Weekly
I will conduct eDNA sequencing and analysis to quantify the fungal and bacterial biodiversity with each soil sample (Hage-Ahmed et al., 2013, protocol of the Peay Lab). In addition, I will collect root samples from the plants to measure arbuscular mycorrhizal fungi colonization.
Bacterial Biodiversity
Weekly
Soil health
Weekly
I will collect soil samples to measure water retention (an indicator for drought resilience), soil aggregation, and nutrient content.
Environmental and Human Health
Temperature
Daily
I will measure temperature and air quality each day using a HOBO portable data logger. These measurements will be taken from the center of the treatments.
Air Quality
Daily
Crop health
Daily
I will measure plant functional traits of the tomato plants each day: height, color, leaf traits (Reeves et al. 2013) and the impacts of herbivory, measured by the number of tomato leaves bearing insect damage. For a sub-sample of plants, I will estimate leaf area eaten by insects (protocol of the Dirzo Lab).
Human Health
Edible Yield
1x
I will use the Land Equivalent Ratio (LER) as a metric of the yield advantage due to the polyculture treatments, as it has been well utilized in the literature and provides insights to the benefits of growing multiple crops together (Mead and Wiley, 1980).
Nutrient Breakdown
1x
I will measure the nutrient content of the tomatoes according to the Nutritional Quality Index (NQI), breaking down the results into the top 3 macronutrients, vitamins, and minerals (Hansen et al. 1976).
Tomato Color
1x
I will conduct the color and lycopene quantification with the protocol of (Jarquín-Enríquez et al. 2013).
Expected Outcomes
Ultimately, the research will provide data on a combination of both environmental and human health metrics, in order to assess the implications of moving away from a traditional monoculture and examine the ecological and human health implications of shifting towards tomato polyculture. I hypothesize that i) treatment B will have significant increases in overall biodiversity (birds, pollinators, and AMF colonization), but will come at a slight trade off with crop yield and nutrient metrics, ii) treatment C will have slightly lower increases in biodiversity with greater benefits of increased overall edible yield, iii) treatment BC will see lower increases overall but a net synergy between environmental and human health outcomes. The findings from this study have implications for further incorporating polyculture techniques into small scale agriculture, particularly in providing insights into which specific methodologies (companion or beneficial intercropping) are most relevant for various goals of agriculture.
D. Roles in Project
My main role in the project will be coordination knowledge between local farmers and chefs, academic advisors, and my personal expertise to develop and implement the research design. I will be involved in all aspects of the project, from ideation, to data collection, to analysis, to communication of the results. I will be working on the project full time over the summer with Chef Lan Thai. In addition, I will be responsible for allocating any grant funding between research tasks. I am responsible for ensuring reciprocity and co-management of this project alongside my partners in this community-based research with Neu Mune Farm.
My field collaborator is Chef Lan Thai, owner of Neu Mune Farm. She will be involved in the entirety of the research, from ideation, data collection, analysis, to communication, and bring in her expertise as a Chef and a Farmer. Some specific areas with her guidance include advising the crop selection of the polyculture treatments, coordination with other farmers in the area, and advising on the nutritional quality assessments of the crops.
My readers for this project are Dr. Rodolfo Dirzo and Dr. Kabir Peay. These individuals will help me in ensuring the research scoping and methods are rigorous and in line with the state of the field of agroecology. Additionally they are each experts in ecology and plant-microbial symbiosis, respectively, which will be crucial support for my research.
E. References
Andrews, D. J., and A. H. Kassam. 1976. “The Importance of Multiple Cropping in Increasing World Food Supplies.” In Multiple Cropping, 1–10. John Wiley & Sons, Ltd. https://doi.org/10.2134/asaspecpub27.c1.
Bona, Elisa, Simone Cantamessa, Nadia Massa, Paola Manassero, Francesco Marsano, Andrea Copetta, Guido Lingua, Giovanni D’Agostino, Elisa Gamalero, and Graziella Berta. 2017. “Arbuscular Mycorrhizal Fungi and Plant Growth-Promoting Pseudomonads Improve Yield, Quality and Nutritional Value of Tomato: A Field Study.” Mycorrhiza 27 (1): 1–11. https://doi.org/10.1007/s00572-016-0727-y.
Brooker, Rob W., Alison E. Bennett, Wen-Feng Cong, Tim J. Daniell, Timothy S. George, Paul D. Hallett, Cathy Hawes, et al. 2015. “Improving Intercropping: A Synthesis of Research in Agronomy, Plant Physiology and Ecology.” New Phytologist 206 (1): 107–17. https://doi.org/10.1111/nph.13132.
Dorais, Martine, David L. Ehret, and Athanasios P. Papadopoulos. 2008. “Tomato (Solanum Lycopersicum) Health Components: From the Seed to the Consumer.” Phytochemistry Reviews 7 (2): 231–50. https://doi.org/10.1007/s11101-007-9085-x.
Fonteyne, Simon, José B. Castillo Caamal, Santiago Lopez-Ridaura, Jelle Van Loon, Juan Espidio Balbuena, Leodegario Osorio Alcalá, Fermin Martínez Hernández, Sylvanus Odjo, and Nele Verhulst. 2023. “Review of Agronomic Research on the Milpa, the Traditional Polyculture System of Mesoamerica.” Frontiers in Agronomy 5. https://www.frontiersin.org/articles/10.3389/fagro.2023.1115490.
Hage-Ahmed, Karin, Johannes Krammer, and Siegrid Steinkellner. 2013. “The Intercropping Partner Affects Arbuscular Mycorrhizal Fungi and Fusarium Oxysporum f. Sp. Lycopersici Interactions in Tomato.” Mycorrhiza 23 (7): 543–50. https://doi.org/10.1007/s00572-013-0495-x.
Hart, Miranda, David L. Ehret, Angelika Krumbein, Connie Leung, Susan Murch, Christina Turi, and Philipp Franken. 2015. “Inoculation with Arbuscular Mycorrhizal Fungi Improves the Nutritional Value of Tomatoes.” Mycorrhiza 25 (5): 359–76. https://doi.org/10.1007/s00572-014-0617-0.
Iverson, Aaron L., Linda E. Marín, Katherine K. Ennis, David J. Gonthier, Benjamin T. Connor-Barrie, Jane L. Remfert, Bradley J. Cardinale, and Ivette Perfecto. 2014. “REVIEW: Do Polycultures Promote Win-Wins or Trade-Offs in Agricultural Ecosystem Services? A Meta-Analysis.” Journal of Applied Ecology 51 (6): 1593–1602. https://doi.org/10.1111/1365-2664.12334.
Jarquín-Enríquez, L., E. M. Mercado-Silva, J. L. Maldonado, and J. Lopez-Baltazar. 2013. “Lycopene Content and Color Index of Tomatoes Are Affected by the Greenhouse Cover.” Scientia Horticulturae 155 (May): 43–48. https://doi.org/10.1016/j.scienta.2013.03.004.
O’Connor, Rory S., William E. Kunin, Michael P. D. Garratt, Simon G. Potts, Helen E. Roy, Christopher Andrews, Catherine M. Jones, et al. 2019. “Monitoring Insect Pollinators and Flower Visitation: The Effectiveness and Feasibility of Different Survey Methods.” Methods in Ecology and Evolution 10 (12): 2129–40. https://doi.org/10.1111/2041-210X.13292.
Pozo, Alejandro del, Nidia Brunel-Saldias, Alejandra Engler, Samuel Ortega-Farias, Cesar Acevedo-Opazo, Gustavo A. Lobos, Roberto Jara-Rojas, and Marco A. Molina-Montenegro. 2019. “Climate Change Impacts and Adaptation Strategies of Agriculture in Mediterranean-Climate Regions (MCRs).” Sustainability 11 (10): 2769. https://doi.org/10.3390/su11102769.
R. G. Hansen, B. W. Wyse, and A. W. Sorenson. 1979. Nutritional Quality Index of Foods. Connecticut: AVI Publishing Company, Inc.
Reeves, J., Z. Cheng, J. Kovach, M. D. Kleinhenz, and P. S. Grewal. 2014. “Quantifying Soil Health and Tomato Crop Productivity in Urban Community and Market Gardens.” Urban Ecosystems 17 (1): 221–38. https://doi.org/10.1007/s11252-013-0308-1.
“Vuon – Ao – Chuong – The Traditional Vietnamese Farm.” 2008. October 24, 2008. https://www.permaculturenews.org/2008/10/04/vuon-ao-chuong-the-traditional-vietnamese-farm/.
Yarime, Masaru, Gregory Trencher, Takashi Mino, Roland W. Scholz, Lennart Olsson, Barry Ness, Niki Frantzeskaki, and Jan Rotmans. 2012. “Establishing Sustainability Science in Higher Education Institutions: Towards an Integration of Academic Development, Institutionalization, and Stakeholder Collaborations.” Sustainability Science 7 (1): 101–13. https://doi.org/10.1007/s11625-012-0157-5.