This work aimed to analyze the competitive effect of Cyperus esculentus on the initial development of irrigated rice. The field experiment was carried out at the Experimental Station of the University of Tocantins, in Formoso do Araguaia-TO. The statistical design used was a 4 x 5 factorial scheme with four replications in randomized blocks. The treatments consisted of four densities of C. esculentus (25, 50, 100, 200 plants m-2 and a clean check) and five periods of coexistence with rice (15, 25, 35, 45, 60 days after emergence). At the end of each period, dry matter, leaf area, number of tillers and rice yield were evaluated. C. esculentus presented higher irrigated rice yield reduction starting from 25 days of coexistence with the crop. Two hundred plants of C. esculentus m-2 coexisting for a period of 35 days reduced yield to 20.11%, representing 17.4 sacs ha-1. Dry matter, leaf area and number of tillers per rice plant were affected by the weeds in all the coexistence periods, with the leaf area being the most affected crop parameter.
interference; Cyperus; competition period
