Amidst an increasingly industrialized food system, farmers and activists the world over have advocated and struggled to move agricultural production towards diversified farming systems. Agroecology–a form of agriculture based in small-scale, thought-intensive, diversified farming systems and the socio-political movements necessary to defend them and advocate for their wider adoption–has emerged as a combination of science, practice, and movement that can lead farming systems towards ecological, economic, and social sustainability. As climate, economic, and political injustices accelerate in the food system, transitions towards agroecology are increasingly urgent; however, these transitions have been slow to gain traction in dominant political and economic regimes. The current era of climate change is creating shocks that open windows for food systems transition, forcing farmers, researchers, and policy makers to consider new approaches to farming and food production. My own work has focused on water scarcity, which is perhaps the most salient climate shock in California where my home institution is located, and a key agricultural concern across the nation and globe. In California, the 2020–2022 drought caused the estimated loss of 15,000 jobs and $3 billion in agricultural output, and followed a similarly devastating drought in 2011- 2016, calling attention to an urgent need to address future water scarcity in the state. Meanwhile, 60% of US farms experienced drought in 2012, rolling grow tables with extreme drought in the Midwestern US causing price spikes and yield declines, followed by extensive flooding in 2019.
In response, local, state, and national advocacy groups and policymakers have begun to call for and implement policy with the intention of making farm systems more resilient to water shortages. For example, the Sustainable Groundwater Management Act in California now calls for groundwater basin water budgets to be balanced by 2042; however, there is considerable debate surrounding how to achieve such a goal. Given the complexities of the systems in which these policies operate, implementation can be difficult, and even the best-intended policies can act to either create or curtail opportunities for transitions towards agroecology. In my own work, I have seen climate-motivated policies in the US–in this case the bio-fuel mandate–lead farmers in the Midwest towards degradative soil practices, while farmers in California respond to water scarcity by growing the tastiest tomatoes chefs have ever encountered. As farmers navigate a complex web of physical, biological, political, and economic environments, they arrive at a wide array of outcomes that reflect both a unique local context and influences that act on entire regions and nations. Yet current economic and political structures have overwhelmingly led US farmers to make choices that have moved agricultural towards the inputintensive, large-scale production that now defines the country’s dominant agriculture. First, what are the farming practices that actually improve farms’ capacity to adapt to water scarcity without jeopardizing farmer livelihoods? And second, can policies support an agroecological transition towards these practices that does not allow their cooptation towards an industrial agriculture–and conversely, what policies are leading our country towards input-intensive industrialized systems even in the face of changing climates?
These questions play out in many ways across different agricultural landscapes, and I do not begin to tackle them in their entirety. Instead this dissertation explores both of these questions in two distinct systems: large-scale corn-based rotations in the US Midwest, and tomato dry farming in small-scale, diversified operations on the northern edge of California’s Central Coast region. In my attempts to answer these questions, I have tried to use the tools at my disposal to center farmers and their experience, wisdom, and intimate knowledge of the lands they work. From participatory research, to farmer interviews, to simply trying to understand farmers as complex actors in complex systems, my work has led me to see farmers as adept scientists, and I hope to honor and complement their skills with a few of my own. Given farmers’ limited access to time and resources, I have used mapping, lab analyses, field data collection, and statistics to help farmers answer the questions they find most pressing and garner the policy support needed to let diversified farming systems thrive. I begin in my first chapter, Biophysical and policy factors predict simplified crop rotations in the US Midwest, by asking what policy and environmental factors push farmers towards diversifying vs. simplifying their crop rotations in the US Midwest. After the 2012 drought, there is more reason than ever to shift this historically homogenized, highly input intensive agricultural region towards more complex rotations, which promote soil health and stabilize yields in times of environmental stress including drought. However, while soil health benefits give farmers every reason to explore complex rotations, there has been a continued trend towards rotation simplification in the region over the past century.
I therefore explored how policy was reshaping this system, asking how top-down policy pressures combine with biophysical conditions to create fine-scale simplification patterns that threaten the quality and long-term productivity of the United States’ most fertile soils. Given the availability of public, spatially explicit data, I developed a novel indicator of crop rotational complexity and applied it to 1.5 million fields across the US Midwest, using bootstrapped linear mixed models to regress field-level rotational complexity against biophysical and policy-driven factors. The second and third chapters explore water resiliency in California, using tomato dry farming in the Central Coast region as a case study. Dry farming–a management system that relies on diversified farming practices to build soil water holding capacity and fertility–allows farmers to grow crops with little to no irrigation and has quickly garnered interest from farmers and policymakers as an alternative to the irrigation-intensive farming that is nearly ubiquitous in the rest of the state. While dry farming is an ancient practice with rich histories in many regions, perhaps most notably the Hopi people in Northeast Arizona, vegetable dry farming emerged more recently in California, with growers first marketing dry farm tomatoes as such in the Central Coast region in the early 1980’s. In a lineage that likely traces back to Italian and Spanish growers, dry farming on the Central Coast relies on winter rains to store water in soils that plants can then access throughout California’s rain free summers, allowing farmers to grow produce with little to no external water inputs. While this system holds great interest and promise for farmers in California, no peer-reviewed research has been published to date on vegetable dry farming in the state. In my second chapter, Deep nutrients and fungal communities support tomato fruit yield and quality in dry farm management systems, I collaborated with farmers to identify and answer key management questions in the dry farm community. This participatory-based process allowed me to build relationships with farmers and begin to coalesce a community of practice that farmers were excited to connect to. As advocacy groups begin to shine a light on dry farming as a potential key to California’s water resilient future, flood drain table it felt crucial to engage with the farmers who champion this system to collectively come to a deeper understanding of how dry farming functions and the farming practices that can best support its success. Growers were primarily concerned with fruit yield and quality, with fruit quality being of particular interest due to the quality-based price premiums that farmers rely on when growing in a region with some of the highest agricultural land values in the nation. Managing soils to promote quality and yields presents a unique challenge in dry farm systems, as the surface soils that farmers typically target for fertility management in irrigated systems dry down quickly to a point where roots will likely have difficulty accessing nutrients and water. As deficit irrigation and drought change microbial community composition in agricultural and natural systems, farmers were also interested in how dry farm management might shift fungal communities, and if that in turn would improve tomato harvest outcomes. Beyond general shifts in fungal communities, farmers were specifically curious about arbuscular mycorrhizal fungi inoculants, which are increasingly available from commercial sellers. Recent research has shown that AMF can help plants tolerate water stress, and that inoculation can improve harvest outcomes in some agricultural systems.
Farmers therefore wanted to test commercial AMF inoculants’ potential benefits in the dry farm context.It is difficult to imagine what this dissertation would have looked like without the collaboration, mentorship, and friendship of my advisor, Timothy Bowles. Working with Tim has been one of the greatest joys, privileges, and teachers of my career, and his influence can be seen in every corner of the ideas and approaches in these pages. Tim’s example is one I want to follow wherever I go, whether it be his drive to include justice and equity in conversations of science, his thoughtful and generous approach to any collaboration, or his commitment to honoring family, friends, art, and his own well being alongside the demands of an academic lifestyle. My thanks also go to Todd Dawson and Eoin Brodie, who generously served on my committee, leant me all sorts of fun field and lab equipment, invited me to lab meetings, and provided valuable gut checks all along the research process. Todd’s enthusiasm for understanding plant-AMF symbioses has been contagious, and I so appreciate our conversations and the excitement they breathed back into me when I was mired in research logistics. Eoin continues to surprise me with his ability to glance at my results and understand them better than I do, and my work is certainly better for it. Little of this research would have been possible without Jim Leap. As far as I’m aware, Jim knows every dry farmer in the state of California, and he connected me to nearly every farmer I worked with. I’m honored to consider him a friend and a mentor, and delighted every time I get to visit his farm. Jim is limitless in his capacity to teach and learn about diversified farm management, and also in his ability to guide me towards joy in this work. Of course literally none of the dry farm work in this dissertation would have been possible without the brilliant farmers I was able to collaborate with. Though of course I won’t out them all here for privacy reasons, I hope they know that they are both the reason I do this work, and the reason I can do this work. Of all the farms I have gotten to connect to over the course of my dissertation, I want to give Brisa Ranch an extra dose of gratitude. Verónica Mazariegos-Anastassiou, Cole Mazariegos Anastassiou, and Claire Woodard have taught me what agroecology can look like, and their farm has been the inspiration for much of the research I have done in this PhD. It was always such a gift to stop by after a long field day and remember what this work is all about. Rose Curley, Alex Dhond, Melanie Rodríguez, Javier Matta, and Bethany Andoko were at my side for the work that has built the foundation of my research. Amidst sample collection and analysis that at times seemed interminable, you kept me afloat with your careful diligence and enthusiasm, and allowed me to grow with you as we explored our way through the research process. My gratitude also goes to the many other undergraduates whose work made this research possible: Karly Ortega, Grace Santos, Yordi Gil-Santos, Amiri Taylor, Moe Sumino, Gisel De La Cerda, and Joey Mann. Also at my side throughout this work were the members of the Berkeley Agroecology Lab: Cole Rainey, Kenzo Esquivel, Miguel Ochoa, Paige Stanley, Aidee Guzman, Ansel Klein, HannahWaterhouse, Janina Dierks, Franz Bender, Maria Mooshammer, Khondoker Dastogeer, Jennifer Thompson, Kait Libbey, and Kangogo Sogomo have created a community that I could rely on, learn from, and grow with. From before day one, Cole has shown up for me as a friend, sounding board, teacher, and mood-lifter, and I can say beyond a shadow of a doubt that the trajectory of my career is better for their influence. Kenzo is a joy to work, cook, organize, and make music with, and his friendship has buoyed me along this ride. Ben Goldstein, though not technically part of the lab, holds a similar place in my heart, and has become an invaluable colleague as well as friend.