Light restriction associated with halosulfuron methyl application efficiently reduces the number and mass of tubers of Cyperus rotundus L.

This study evaluated the effect of light availability in the culture environment and the application of a post emergence herbicide, halosulfuron methyl, on the management of Cyperus rotundus . The experiment was arranged in a 2 × 6 factorial design; the first factor was two levels of light availability: photosynthetically active radiation at 1180.4 and 411.6 µmols m -2 s -1 , and the second factor was halosulfuron methyl doses from 28.13 to 140.62 g ha -1 . Photosynthetic efficiency, biomass allocation, accumulation of starch in tubers, and percentage control of C. rotundus were evaluated from 7 to 28 days after herbicide application. Doses greater than 70.30 g ha -1 of halosulfuron methyl were efficient to control C. rotundus , regardless of light availability. However, C. rotundus was managed faster under full sunlight than under shading. The efficiency of the photosystem, starch accumulation, and biomass formation decreased with increasing doses of halosulfuron methyl. In a shaded environment, a dose of 28.13 g ha -1 was sufficient to reduce 96.74% of the dry mass and 91.33% of the number of C. rotundus tubers. The decrease in light intensity associated with the use of halosulfuron methyl represents a promising practice for the control of C. rotundus .