Testing Northeastern North American Native and Introduced Plants as Cover Crops in an Organic Vineyard

Abstract

Cover crops have potential to provide ecosystem services including nitrogen fixation, erosion control, water retention and infiltration, buffering climate variability, and beneficial insect attraction. The objective of my thesis was to examine the potential performance of diverse cover crop species in an organic vineyard. The first component of this study aimed at testing northeastern North American native cover crop species, including Dalea purpurea, Rudbeckia hirta, Glycyrrhiza lepidota, Asclepias tuberosa, Echinacea purpurea, and Symphyotrichum ericoides. In the greenhouse, plants grown in monoculture were compared to those grown in polyculture with all the other species. The performance measurements were based on emergence, flowering, dry biomass, fresh biomass, plant moisture content, root:shoot ratio, and relative interaction index. R. hirta had a significantly higher dry shoot and root weight when grown in polyculture, as opposed to monoculture. D. purpurea also had significantly higher dry root weight in polyculture rather than in monoculture. S. ericoides and G. lepidota had significantly higher dry shoot and root weight in monoculture than in a polyculture. A. tuberosa had the largest root biomass in monoculture, while E. purpurea had the largest root biomass in the individual treatment. The second component aimed to determine the efficacy of two cover crop species (Lobularia maritima and Trifolium incarnatum) in vineyard field conditions. The plants were seeded under the vine rows, and plots were sampled along those seeded rows for each species. One vegetation survey was completed, and two insect surveys. Vegetation was measured as percent cover in the sample plots, and insects were collected on yellow sticky traps. L. maritima abundance was positively correlated with spontaneous plant species abundance, and T. incarnatum abundance was negatively correlated with spontaneous plant species abundance. The presence of the L. maritima was weakly associated with an increase in parasitoids, while T. incarnatum was weakly associated with predatory insects. Where there were more parasitoids, there were fewer leafhoppers. My results suggest a potential of these various species to provide important ecosystem services such as pest control in organic vineyards. Understanding the interactions among cover crop species, their influence on vines and the entire ecosystem requires further studies.