Critical Weed Interference Periods in Quinoa (Chenopodium quinoa Willd.): Yield Loss, Dominant Species, and Management Implications in Andean Agroecosystems

Abstract

Weed competition is a major biotic constraint in quinoa (Chenopodium quinoa Willd.) cultivation, yet the timing and extent of its impact on yield remain poorly understood. This study quantified the effects of weed interference on quinoa yield and identified dominant weed species across two consecutive growing seasons in the Andean region. We evaluated eight weed management treatments (0 to 105 days after emergence, DAE) using a randomized complete block design. Dicotyledonous species dominated the weed community, including Amaranthus hybridus, Ambrosia artemisiifolia, Chenopodium album, and the monocot Echinochloa crus-galli. Weed competition caused a drastic 90% yield reduction, plummeting from 1,352.36 kg ha⁻¹ (weed-free) to 11.55 kg ha⁻¹ when weeds remained until crop maturity. We observed critical yield losses when weeds competed beyond 30 DAE, highlighting the importance of early weed control. We also found significant negative correlations between weed biomass and quinoa growth parameters (plant biomass and grain number; P < 0.05). Echinochloa crus-galli and Polygonum aviculare emerged as key competitors, their dominance shifting with seasonal climatic variations. These findings provide the first empirical basis for integrated weed management in Andean quinoa systems, emphasizing targeted control during early phenological stages to mitigate yield losses. This study advances agroecological strategies for sustainable quinoa production in weed-prone environments.