Nitrogen Management and Virus Incidence on Cut Flower Production of Dahlia

Abstract

Cut flower production, particularly of dahlia, has a strong profit potential for small farms. This study evaluated the field response of dahlia ‘Café au Lait’ to nitrogen (N) rates and implemented routine testing for common viruses. Yield was measured over a three-year field trial with five N application rates: 0, 56, 112, 168, and 224 kg N·ha−1 (0, 50, 100, 150, 200 lb N·A−1) in North Logan, Utah (USDA Hardiness Zones 5). A grower-participant study was also conducted in Northern Utah (USDA Hardiness Zones 5 – 7) to understand cultural practices and challenges. Application of 168 and 224 kg N·ha−1 (150 and 200 lb N·A−1) produced the greatest yields of stems per plant, while 168 kg N·ha−1 (150 lb N·A−1) was the most economically efficient from partial economic budgets. Viruses were highly prevalent in stock, resulting in cull rates of nearly 50% in 2019 and 2020. After sourcing lab-cultured stock in 2021, 0% of plants were culled, indicating a strong need for management of viruses in dahlia. Soil survey results from the grower-participant study revealed widespread levels of elevated macronutrients and salinity that increased annually and correlated with decreasing yield across farms. This study helps determine optimal N rates, increase awareness of virus management, as well as supporting fertility outreach with small growers to promote soil sustainability. Species used in this study: Dahlia, Dahlia pinnata ‘Café au Lait’.