Dry farming for resilience: productivity and physiological drivers of organic common bean production

Abstract Water scarce agricultural regions are increasingly challenged to find practices and systems that reduce water use. One such approach is dry farming: the cultivation of drought-adapted crop varieties without irrigation but relying on residual soil moisture following seedling establishment. Organic growers are increasingly adopting dry farming systems due to declining water availability, more frequent droughts, and their potential to enhance yield quality and consumer interest, yet little research has examined how dry-farmed crops physiologically respond to low water inputs, limiting understanding of how to maximize yield and crop quality in these systems. This study examined the physiological drivers of common bean ( Phaseolus vulgaris L.) productivity under dry farming, using irrigation as a control, by comparing two adapted varieties (Black Bean and Hopi Bean) with a standard variety (French Green Bean). Two field trials were conducted on California’s Central Coast in 2024 and 2025 to assess dry biomass, marketable yield, relative bean anthocyanin pigmentation and phenotype, water potential, stomatal conductance, root morphological traits, rhizobial symbiosis, and soil inorganic nitrogen dynamics. The Black Bean and Hopi Bean varieties demonstrated greater resilience under dry farming. In these varieties, marketable yields declined by approximately 79% in 2024 and 35% in 2025 relative to full irrigation, reflecting seasonal variability. However, relative anthocyanin content and Hopi Bean seed coat striations increased under dry-farmed conditions, potentially bolstering both nutritional value and visual appearance. Water potential, stomatal conductance, root anatomical traits, and maintenance of symbiotic nitrogen fixation were strongly driven by varietal-specific strategies, while reduced irrigation inputs were associated with greater nitrate availability in surface soil layers. These findings highlight the importance of informed cultivation practices and irrigation management. Under certain conditions, dry farming may reduce inputs while minimizing production losses and enhancing yield quality. Further research should evaluate its feasibility across diverse climates, soil types, and varieties to advance organic common bean production.