Potatoes are an important global food crop typically produced in high-input systems in temperate zones. Growers that have access to compost may use it to improve soil health and increase tuber yields, but compost may also impact microbial communities, weed competition, weed seed fecundity, mortality, and dormancy. Potatoes were grown in field plots amended with 0, 4, or 8 t carbon (C) ha-1 of compost during the summer under weed-free conditions, and in competition with common lambsquarters (CHEAL), giant foxtail (SETFA), and hairy nightshade (SOLSA). In the fall, one hundred seeds of each weed species from each of the composted field plots were buried to a 5-cm depth in the weed-free plots of each compost rate to measure mortality. Seed bags were removed 9 months after burial. Compost did not increase biomass, seed production, initial seed viability, or seed dormancy of any weed species. SETFA and SOLSA at five plants per meter of row reduced potato yield 20%; CHEAL reduced yield by 45%. Potato yield increased 5-15% in compost compared to non-compost treatments possibly due to elevated soil potassium levels. Burial environment did not affect seed survival within a species. As the compost rate in the maternal environment increased, seed mortality of SOLSA decreased, SETFA increased, and CHEAL was unchanged. Seed dormancy was unaffected by maternal and burial environment. Arbuscular mycorrhizal fungi (AMF) inoculum did not affect growth of potato, CHEAL, SETFA, or SOLSA in the greenhouse. Nutrient concentration in above-ground plant biomass varied by species, and was not affected by AMF inoculum. Nutrient use efficiency may affect weed competitiveness in nutrient-limited potato production systems.
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