Intraspecific variation in germination response to ammonium nitrate of Powell amaranth (Amaranthus powellii) seeds originating from organic vs. conventional vegetable farms

Abstract

Abstract The primary objectives of this research were (1) to characterize intraspecific variation in Powell amaranth seed germination and emergence response to nitrogen fertilization, and (2) to evaluate whether germination and emergence characteristics varied between seeds from populations originating on organic vs. conventional vegetable farms. We hypothesized that nonherbicide–based weed management and use of slower-releasing forms of N on organic farms may have selected for seeds with lower dormancy and lower germination sensitivity to N fertilization than seeds from conventional farms. Seeds were collected from five conventional and five organic vegetable farms in central New York State. A second generation of seeds, produced under common greenhouse conditions and stored for at least 3 mo at 5 C was tested for both germination in petri dishes and emergence in the field under multiple rates of ammonium nitrate (NH4NO3). Both seed germination and emergence were greater for seeds originating from organi...