Abstract

The impact of herbicide application on the accumulation of secondary metabolites and photosynthesis as stress indicators in the quinoa (Chetwpodium guinea Willd.) crop is unknown. The objective of the present study was to evaluate the effect of two post-emergence herbicides on production, total polyphenol content, and chlorophyll fluorescence in quinoa. The experiments were conducted for two consecutive seasons using a completely randomized block design with seven treatments, including two herbicides and three commercial product rates, as well as a control without herbicide application. Production parameters, yield components, and stress indicators were evaluated. Yield was affected (P < 0.05) by herbicide application in some treatments; control and treatment with only one bentazon application varied from 1851.23 to 1235.03 kg ha(-1), respectively. Yield affected the number of grains per plant (P < 0.05); control and treatment with only one bentazon application decreased yield from 3984.60 to 2040.94 kg ha(-1), respectively. Total polyphenol content and percentage of germination in quinoa grains were not affected by stress caused by herbicide application (P > 0.05). The herbicide fomesafen did not affect the maximum quantum yield, while the herbicide bentazon had a significant effect (P < 0.05) during the application. Three sequential applications of bentazon and fomesafen in the absence of weeds were sufficient to achieve a yield that was equal (P> 0.05) to the control.