Sordariomycetes enrichment may indicate other community shifts that are ultimately the cause for enhanced fruit quality. Endophytes in the Hypocreales class, which was enriched in dry farm fields, are known to increase drought resistance and decrease pest pressure in their hosts, though none of the specific species known to exhibit this behavior were enriched in dry farm soils. On the other hand, Nectriaceae, the family that contains the Fusarium genus, was found to be enriched, though similarly no known pathogenic species were enriched in dry farm soils.Our study explored dry farm management practices and their influence on soil nutrient and fungal community dynamics in 7 fields throughout the Central Coast region of California, allowing us to explore patterns across a wide range of management styles, soil types, and climatic conditions. Though we were able to sample from a large swath of contexts in which tomatoes are dry farmed, we are also aware that conditions will vary year to year, especially as climates change and farmers can no longer rely on “typical” weather conditions in the region. While we are confident in the patterns we observed and the recommendations below, racks industries we also encourage further study across multiple years to better understand the full scope of the decision space in which dry farm growers are acting.
Given the scope of our current findings, we outline several management and policy implications for dry farmers and dry farming. Though we aim these implications towards the context of dry farm tomatoes in coastal California, we expect that they are likely to generalize to other dry farm crops grown in other regions with Mediterranean climates. First, given the expense and possibility that it is detrimental to fruit quality, we do not advise AMF inoculation for dry farm tomato growers. Second, we note the importance of nutrients below 60cm and the complexities of subsurface fertility management, and we recommend experimentation with organic amendments and deeply rooted cover crops that may be able to deliver nutrient sources that persist at depth, as well as planning several seasons in advance to build nutrients deeper in the soil profile. Finally, given our finding that dry farm soils develop a fungal signature that increases over time and its association with improved fruit quality, we encourage farmers to experiment with rotations that include only dry farm crops and even consider setting aside a field to be dry farmed in perpetuity. However, fully dry farmed rotations currently do not exist, likely due to a lack of commercially viable options for crops to include in a dry farm rotation. In order to experiment with potential dry farm rotations, as well as cover crops that can best scavenge excess nitrates and soil management regimes that can increase soil fertility at depth, farmers must be given both research support and a safety net for their own on-farm experimentation. Funding to mitigate the inherent risk in farmers’ management explorations will be key in further developing high-functioning dry farm management systems. Expanding land access to farmers who are committed to exploring dry farm management can additionally benefit these explorations.
Dry farm tomato systems on the Central Coast point to key management principles that can both help current growers flourish and provide guidance for how irrigation can be dramatically decreased in a variety of contexts without harming farmer livelihoods. In these systems, managing nutrients at depth–at least below 30cm and ideally below 60cm–is necessary to influence outcomes in fields where surface soils dry down quickly after transplant. Fostering locally-adapted soil microbial communities that are primed for water scarcity can improve fruit quality. Farmers can otherwise manage nutrients to maximize either yields or quality, giving latitude to match local field conditions to desired markets. As water scarcity intensifies in California agriculture and around the globe, dry farm management systems are positioned to play an important role in water conservation. Understanding and implementing dry farm best management practices will not only benefit fields under strict dry farm management, but will provide an increasingly robust and adaptable example for how farms can continue to function and thrive while drastically reducing water inputs.Unlike other forms of dryland farming , in this region dry farm tomatoes are grown over a summer season where there is a near guarantee of no rainfall. Farmers plant tomatoes into moisture from winter rains, counting on soils to hold on to enough water to support the crops over the course of the entire dry summer and fall. While some farmers irrigate 1-3 times in the first month after transplant, severe water restriction is what gives the fruits their intense flavor, and farmers trade water cuts that lower yields for price premiums that consumers are more than willing to pay for higher quality fruits. Beyond Bay Area consumer’s enthusiasm for high-quality local produce, dry farm tomatoes also trace their origins to a richer food culture of justice-oriented and farmer-centric food distribution in the region.
From the Black Panther Party’s Free Breakfast Program to strong community support for worker-owned and consumer food cooperatives , the Bay Area has become a hub of alternative values-based supply chains in a country largely dominated by an industrialized food system . Following this tradition, dry farm tomatoes originally found their footing in the United States in the Central Coast region 30 miles south of the Bay. In the 1970’s and 1980’s, innovative growers in small-scale cooperatives and teaching farms adapted an Italian and Spanish legacy of vegetable dry farming to the region’s Mediterranean climate, maritime influence, and high-clay soils . While these environmental features were necessary to grow tomatoes under dry farm management, the movement that sparked the reemergence of local farmer’s markets in the 1980’s also provided the access to direct to-consumer marketing that small farms needed to win consumer attention and loyalty, allowing farmers to both grow and sell this niche product. With their origins in local food distribution networks and local adaptations to a unique climate, dry farm tomatoes are now a signature of small, diversified, organic farms on the Central Coast and are a feature of many such operations’ business models. To this point, dry farming has largely followed its initial course and is only practiced at a small scale in the region, both in terms of geographic scope, and farm size. Dry farming may therefore be to playing a role in an agroecological transition in the region, buoying small-scale, thought-intensive management styles with access to a steady income source and consumer base. However, with recent droughts and water shortages in California, dry farming has recently begun to take a more prominent role in social and policy visions for the future of the state’s agricultural system. From the Sustainable Groundwater Management Act to emergency orders in drought years, farmers, researchers, policymakers, and the general public have become acutely aware of California’s currently unsustainable agricultural water use and the economic ramifications of water shortages . As an option that holds promise for maintaining farmer livelihoods while dramatically cutting water use, vertical growing systems journalists and policy groups have touted dry farming as an important system to target for significant expansion . Farmers have been considering how to use dry farming to adapt to drier futures for decades, lighting the way for researchers and policymakers’ more recent interest. However, up to this point, farmers’ thoughts and knowledge about dry farming have not been clearly elicited or formally incorporated into conversations about the future of the practice. Grounding conversations about future expansion of the practice in the knowledge of those who are most intimately familiar with its implementation is essential. At this moment of enthusiasm for dry farming, we look to practitioners to better understand the current state of dry farming on the Central Coast and its potential for expansion across California, along with the benefits and harms that expansion may carry.
We interviewed ten dry farmers, representing over half of the commercial dry farm tomato operations on the Central Coast, in order to collaboratively answer two central research questions. First, what business and land stewardship practices characterize successful tomato dry farming on California’s Central Coast? And second, what is the potential for dry farming to expand beyond its current adoption while maintaining its identity as a diversified practice that benefits small-scale operations? The majority of these farmers were part of an ongoing participatory research project in which field data were collected to better understand soil fungal communities and nutrient management in dry farm systems . These interviews were extensions of conversations and relationships fostered with farmers throughout the research process. We synthesized farmer insights into nine key themes that broadly describe how dry farming is currently practiced on the Central Coast, its potential to expand in scope , and the opportunities that farmers see as particularly provident for the practice. We also used the constraints identified by farmers to map areas most likely to be suitable for future dry farming. At this juncture of a high-functioning, low-water management system and urgent political interest in decreasing agricultural water use–in California and across the globe–we conclude by asking how dry farming can be a model for developing systems that decrease water use, and also how dry farming itself may be scaled out to other small-scale, thought-intensive operations without jeopardizing these same farms’ ability to continue profitably growing dry farm produce.Interviews were done with farmers who have commercial operations in California’s northern Central Coast region , as well as one farm with operations in Marin and Sonoma counties. Ranges of coastal mountains govern both climate and land use, trapping cool, moist air, and concentrating farming operations in valleys with fertile, alluvial soils. The Central Coast is known for its agricultural production–particularly berries, lettuce, and artichokes–that thrive in its fertile soils and mild climates that allow for year-round cultivation. Agricultural revenue in the region totals over $8 billion annually , making it a larger agricultural producer than most countries. This intensive production has led to both high land values and environmental degradation–largely in the form of water contamination–that shape both farmer decision-making and policy interventions . Within this landscape, farms often operate at industrial scales, though many small farms persist. Though cropland is consolidated into fewer, large operations , many smaller farms have found niches selling to local markets.After building relationships over the course of a year-long participatory field research process with eight tomato dry farmers , we conducted semistructured interviews with all farmers involved in that study. We interviewed two additional dry farmers who were not involved in the field project–one whose farm is in Sonoma County , and one whose farm could not participate in the field study due to extensive fire damage–for a total of ten farmers representing eight operations. Interviews were done in person , over the phone , and on Zoom in winter and fall 2022. Because there is no official record of tomato dry farmers in the Central Coast region, we used a snowball approach to identify farms that might be candidates for inclusion, asking each interviewee what other dry farm operations they knew of in the area. We can identify two dry farm tomato growers in the region who were not interviewed in this study, and we estimate that our interview subjects represented 50-75% of commercial dry farm tomato operations on California’s Central Coast. Interviews lasted 1-2 hours and focused on dry farm management practices, environmental constraints, support, water/land access, and economics . Interviews were recorded and transcribed, then analyzed through an interactive process of open, axial, and selective coding . Data were grouped into three overarching categories , with key themes in each category. In order to identify areas that might be suitable for future tomato dry farm management, we used farmer-described constraints to make a suitability map using publicly available datasets. We first compiled the environmental constraints on tomato dry farming described in each interview , which fell into three main categories: precipitation, temperature, and soil texture. We limited our analysis to California as the region these farmers are most familiar with to avoid extrapolating constraints beyond the context in which they were given. We used PRISM 30-year climate normals to characterize California’s temperature and precipitation . We used the average constraint named by the farmers; however, because these normals are a 30 year average and will stray significantly from these averages in individual years, particularly in the case of precipitation, we expect that we overestimate the extent of suitable areas.