2019 ASHS Annual Conference

Quinoa (Chenopodium quinoa Willd.) is an ancient crop with the potential to increase worldwide food security if field management strategies can be optimize to allow for profitable production. Some growers within the US report quinoa’s potential for competitive growth and tolerance to weed competition, yet weed control issues have led many larger producers to abandon the crop. Very limited herbicide options are currently available and the cost of labor and mechanical cultivation can be prohibitive. Understanding the interactions between weeds and quinoa is essential to developing an effective cropping system. This study uses a replacement series design with quinoa and three common weed species: lambsquarters (Chenopodium album L.), red root pigweed (Amaranthus retroflexus) and green foxtail (Setaria viridis) and two fertility levels (60 and 240 mg N kg soil-1) repeated in two independent runs. Over most treatment and planting ratio combinations, quinoa had greater biomass accumulation than both red root pigweed and lambsquarters. Tissue nitrogen accumulation was similar between quinoa and two weed species, foxtail and red root pigweed, but lambsquarters had greater tissue nitrogen than quinoa. Green foxtail was the most competitive weed species although results varied between trial runs, likely due to differences in ambient photoperiod. Further research into the impact of emergence rate and planting density under field conditions is required for to optimize quinoa planting recommendations.