Optimizing weeding and plant density for improved quinoa yield and seed quality in fluvisol soils

The eco-friendly weed management is a significant challenge for sustainable crop production because weed interference reduces yield and quality of a crop.Thus, the study was conducted to determine the effect of the frequency of hand weeding and planting densities on weed composition and nutrient uptake, seed yield and quality of quinoa.The field experiments were established in Ha Noi and Hung Yen, Vietnam in a randomized complete block design (RCBD) with three replications.The treatments include combination of hand weeding frequencies (W0: Un-weeded; W1: Hand weeding (HW) once at 20 days after sowing (DAS); W2: HW twice at 20 and 40 DAS; and W3: HW three times at 20, 40 and 60 DAS) and planting densities (D8: 8 plants m -2 ; D10: 10 plants m -2 ; D13: 13 plants m -2 ; and D20: 20 plants m -2 , with a row distance of 50 cm and plant distances of 25, 20, 15, and 10 cm, respectively) of quinoa.The results showed that HW significantly reduced weed infestation, enhanced nutrient uptake of quinoa, and ultimately increased yield and quality of quinoa compared to un-weeded plot.The highest actual seed yield was recorded with HW twice or three times in both sites.On the other hand, planting density (PD) significantly reduced the weed composition and thus, enhanced nutrient uptake, yield and yield components of quinoa, and seed protein content in both sites.The optimal PD that effectively suppressed weeds and maximized quinoa yield and improved its seed quality was at 8-10 plant m -2 .This study suggests that the HW done at 20 and 40 DAS combined with PD of quinoa at 8-10 plant m -2 is the most efficient weed control strategy to improve quinoa production in fluvisol regions of Vietnam.